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(Last updated 14/12/2011)

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Table of Contents
How do I charge multi-battery banks without the loss normally associated with diode splitters and still maintain isolation between the separate battery banks…?
Why should I use an X-SPLIT or X-PORT for split charging rather than a cheap diode splitter or an 1/2/both switch..?
What are the advantages of using an X-SPLIT and X-PORT instead of a voltage controlled relay split charge system…?
How can I make sure that my batteries are fully charged … ?
What do I need to charge a two battery bank installation … ?
What do I need for a three battery bank installation … ?
What do I need for a twin alternator multi battery bank installation … ?
If my alternator is battery sensed energised what does this mean and can I use the X-SPLIT/X-PORT with the alternator … ?
Can I parallel different charging sources to the input of an X-SPLIT so that I can charge all my batteries simultaneously…?
If I replace my 1/2/both switch with an X-SPLIT or X-PORT can I still use it to parallel the batteries in case of starting problems … ?
What are the main differences between the three types of battery… ?
What are the main differences between a GEL battery and a AGM battery and why should I choose one in preference to the other… ?
What type of battery should I use … ?
Why does my battery not last as long as my calculations say it should … ?
What size of battery bank should I use … ?
What size of alternator should I be using…?
What size of Battery Charger do I need…?
How long does it take to recharge my batteries using a Battery Charger…?
What is the difference between a Quasi-Sinewave Inverter and a Pure Sinewave Inverter…?
What type & size of X-SPLIT/X-PORT charge splitter do I need …?
Why should I use a Galvanic Isolator / Cathodic Protector …?
How can I protect my batteries from being discharged to low ….?
How can I charge a 12 volt battery used for leisure circuits whilst the only charging source available is from a 24 volt alternator system ….?
How do I purchase the components or system of my choice …?
If I have an installation that does not appear as an option in the list can you help …?
NEW… How can I check that my X-SPLIT or diode split charge installation is correct…?

….NOTE:- To enable quick navigation between the relevant product pages mentioned in the answers simply click on the BLUE hyper links….

How do I charge multi battery banks with minimal loss and with maximum efficiency… ?
Standard diode splitters lose in excess of 0.8 volts (800 mVolts) at normal float currents rising to as much as 1.2 volts (worse state conditions for cheap diode splitters) for high charging currents. The X-SPLIT or X-PORT in comparison have a charge loss of less than 100 mVolts for the X-SPLIT and 300 mVolts for the X-PORT at full charging current dropping to less than 20/40 mVolts at float currents whilst the diode splitter, will still exhibit a loss of 800 mVolts. The X-SPLIT or X-PORT used as the charge splitter will provide a low loss charging system giving isolation between battery banks. Unlike mechanical charge splitting relays or 1/2/both switches which will put all batteries in parallel when operational. When the charging source is switched off this could cause a problem of discharging your engine battery if the 1/2/both switch is not switched off or the relay contacts have become welded closed when the service battery is discharged through use. Using the X-SPLIT or X-PORT means that the auxiliary service batteries can be discharged without affecting the engine start battery. For an application note on a typical X-SPLIT installation click on the blue hyper link Applications.
For more information on either the X-SPLIT or the X-PORT click on blue hyper link of the model required.

How can I make sure my batteries are fully charged … ?
When charging from an alternator to ensure your batteries are charged to maximum levels an addition of an intelligent charge regulator such as one of our X-ALT range should be used. A standard alternator will not charge much above 80% due to the operation of the alternator’s regulator. No doubt if you have such a system you may have seen the charging current start off high and then quickly drop to a low level even if the batteries are discharged. By using the X-ALT as an intelligent alternator charge controller it will over ride the early shutdown and maintain a higher charge current, which enables your batteries to be charged to a much higher level, nearly 100% in the majority of cases. Listed below are answers to how you can put together various components to obtain a high efficient charging system which will make sure batteries are fully charged.
(see question 1)

What do I need to charge a two battery bank installation … ?
To charge a two battery bank installation without problems and do it efficiently you have two choices. Option 1). A simple system with an engine start battery bank and a service battery bank. If the engine start battery is only used for engine start purposes. a single low cost sensing systen can be employed saving money. Option 2). A system which monitors both your engine and service battery with the added benefit of single point automatic temperature compensated control. This second option is useful if the engine start battery is used for additional tasks e.g. bow thruster operation.
Option 1 is a low cost option and requires an X-ALT “BUCCANEER” alternator charge controller and a two way split charger either an X-SPLIT XSP/1/2BS; or the equivalent X-PORT if the charging current is greater than 120 Amps ( refers to rating of alternator charging current e.g. 60 Amps).
Option 2 would require an X-ALT “SKIPPER” alternator charge controller and a two way split charge controller either an X-SPLIT or the equivalent X-PORT similar to option 1.

By using an X-SPLIT or X-PORT to handle the split charging, the alternator does not have to increase its output much above the selected boost charge voltage as the losses are minimal. Whilst the X-ALT will compensate for voltage losses, to achieve the same voltage levels using diode split charge devices would mean an alternator output of 15.6 volts when in boost mode and 14.8 volts in float mode, this voltage loss ( 0.8 volts) is dissipated as heat in the split charge device.
Click on the option numbers to see an application drawing applicable to each installation.
Option 1 application drawing.
Option 2 application drawing
For more information go to “BUCCANEER”
For more information go to “SKIPPER”

Why should I use an X-SPLIT for split charging rather than a cheap diode splitter or an 1/2/both switch..?
The advantages of an X-SPLIT over a diode splitter have already been mentioned, the disadvantages of 1/2/Both switch have also been illustrated. What has not been mentioned are the possible problems that can occur with battery banks being charged via diode splitters where the alternator is being controlled via an alternator charge controller. Let us assume that the auxiliary battery bank is much larger than the engine start battery or is deeply depleted then the potential voltage drop through the channel feeding the auxiliary battery bank can be much higher than that supplying the engine battery. So the alternator charge controller kicks in because it has detected a deeply discharged auxiliary battery and increases it’s output to compensate for the higher voltage drop incurred by the diode in the auxiliary circuit. However the engine start battery is not depleted so the voltage drop is normal and it can be up to 0.5 volts less than that of the auxiliary battery. This means that the engine battery is getting 0.5 volts higher charge voltage than the auxiliary battery. The boost charge voltage of the auxiliary battery for arguments sake = 14.8 volts, this means the engine battery is receiving 15.3 volts. This could lead to the engine battery being over charged and causing possible gassing problems. You may argue that if I did not have the alternator charge controller this would not happen. True; but; if the alternator was running as a stand-alone with it’s output voltage sitting at 14 volts, the engine battery would be seeing 13.2 volts whilst the auxiliary battery would be seeing anything between 0.3 and 0.5 volts less. This voltage differential would not be as high as in the previous example because there is a lower voltage the current will be lower and hence so will the voltage drop. Fine! no problem? but think how long will it take to re-charge your auxiliary battery bank under those conditions, I’ll leave you to think that one out.

What are the advantages of using an X-SPLIT instead of a voltage controlled relay split charge system….?
Most voltage controlled relays sense the voltage feed to the engine start battery and will only switch on when the sensed voltage reaches a pre-set voltage nominally 13.6 volts. If the engine is only on tick over the alternator’s output voltage may be in the proximity of this voltage threshold, so; the relay switches on and assuming that the service battery or batteries are depleted they may attempt to draw a high charging current. This causes the output voltage to drop due to the auxiliary battery taking this current and could cause the relay to switch off due to a voltage dip. The voltage again rises, the relay switches on and the cycle begins again. In worst cases the relay may chatter until the engine is speed is increased, this will cause the alternator to develop more power and eventually the power dip does not bring the voltage below it’s threshold and the relay remains energized charging the service battery. However at this point unless the alternator is producing a high current charge the service battery may be helping itself to a secondary current charge from the engine start battery as the two battery banks are no longer electrically isolated. Though this relay chatter may only be a momentary problem as most people tend to move off once the engine is running though there are some who run the engine purely for battery charging when no mains hook up or other form of auxiliary charging is available then for short time this problem can be a nuisance.
However it is not usually the engine battery that needs monitoring but the service battery, this is the battery bank that is normally depleted and is the one which needs recharging. Instead of waiting for the engine battery to be recharged before the service battery is switched into the charging circuit the X-SPLIT allows each battery bank to take what ever it wants from the charging source (i.e. the moment the alternator starts to develop a charging current). Not only does it allow the battery banks to determine their own charging needs it keeps them electrically isolated from each other preventing discharge from one battery bank into another. As the service battery is normally the bank which is depleted this bank will take the lions share of whatever charging current is available whilst the engine battery may only take a float charge. Other important factors are; the X-SPLIT is solid state, NO MOVING PARTS, no relay contacts to corrode or burn out, is an ultra low loss device and last but not least easy to install normally only the main power cables plus a small earth lead (supplied).

Can I parallel different charging sources to the input of an X-SPLIT so that I can charge all my batteries simultaneously…?
The answer is yes but a word of caution; if your main charging source is an alternator it is advisable to switch off the secondary charging system or systems prior to starting the engine. Using the secondary charging system at the same time can confuse the alternator especially if the secondary charging voltage is higher than the alternator’s charging voltage. It is possible to connect, a battery charger, a wind generator and solar cell all in parallel with an alternator without affecting the X-SPLIT (unless the total sum of the charging currents exceed the rating of the X-SPLIT). Each charging source should have its own voltage control circuit to limit the maximum charging voltage.

What do I need to charge a three battery bank installation … ?
This is similar to a previous example but in order to charge a three battery bank system from an alternator or other charging source (each battery bank can comprise of a number of batteries in parallel) you will need an X-ALT “SKIPPER/3″ alternator charge controller and a three way split charger either an X-SPLIT ” XSP**/1/3BS” or the equivalent X-PORT if the charging current is greater than 120 Amps. The “SKIPPER/3” is capable of monitoring three battery banks but does not offer the capability of temperature compensated control as in the previous example. As with the previous examples the battery banks will be charged simultaneously and will be isolated from each other. A battery charger or other auxiliary charging source can be connected in parallel with the alternator but must be disabled before the engine is started. For an application note showing how a three battery bank system can be implemented click X-SPLIT 3 battery bank installation
For more information click on the blue hyper link SKIPPER.

What do I need for a twin alternator multi battery bank installation … ?
This is similar to the previous two questions except that the X-ALT alternator charge controller required will be a “CAPTAIN”, similar in some respects to the SKIPPER but has the capability of controlling either one or two alternators simultaneously or independently and monitor up to three separate battery banks. The split charge device in this instance can either be an X-SPLIT XSP2/2BS (in the two input versions it is only available with 2 outputs) or the X-PORT XP/2/3 (which has the facility of 3 outputs). The “CAPTAIN” has as standard, single point temperature compensated control for automatic adjustment of charging voltage with respect to changes in ambient temperatures. The “CAPTAIN” can control different types of alternators and as they are controlled independently you can run on one engine/alternator without problems. For an application note showing an example how a system can be implemented click here dual alternator and multi battery bank installation.
For more information click on the blue hyper link CAPTAIN.

If my alternator is battery sensed what does this mean and can I use the X-SPLIT/X-PORT with the alternator … ?
There are two types of what are called battery sensed alternators, the main type is more commonly known as “battery sensed energized” the second type is “battery sensed controlled”.
The former type means that unlike machined sensed alternators which derive their initial start up voltage via the charge warning bulb circuitry, these alternators derive their start up voltage direct from a battery source. The problem occurs when an X-SPLIT/X-PORT or a standard diode splitter is used to split the charging output from the alternator, using such a device effectively isolates the alternator from it’s energisation source and as a result the alternator does not always start charging, when it does it is normally the result of its remnant magnetism remaining in the core. All is not lost however as the X-SPLIT and X-PORT have an additional circuit built in to provide this facility, all that is needed is a separate switched ignition feed capable of supplying at least 5 Amps. This additional feed is wired to a terminal marked “SENSE” which in turn is fed back to the alternator to provide its start up energisation voltage. In the majority of instances this simple direct feed is adequate and no problems occur, however there are instances where the installation consists of a large auxiliary battery bank or banks which get deeply discharged and this occasionally causes the 7.5 Amp protection fuse (on new versions of the X-SPLIT this fuse is built in) to blow due to the auxiliary battery bank attempting to take a high charge current via this circuit. If this problem occurs then the addition of a energisation relay will alleviate this problem. The relay is wired as shown in X-SPLIT ‘application 1’ click here for a quick link to “X-SPLIT application pages ” then select application 1. If wiring an additional relay to the circuit is not practical proposition adding high power resistor value 22 ohms between the switched ignition feed and the B+ terminal on the alternator should solvethe problem.
Alternators that fall into this category that we know of todate are-: Prestolite 110-*** range, Valeo 60 Amp (as used on Nanni engines) and Kubota Denso 40 Amp (as used on Beta Marine engines). If you know of any others drop us a line it may assist your fellow boat owners.

The “battery sensed controlled” alternator means that it has an additional control wire added which is normally wired to a battery and in most cases this would be the auxiliary battery on dual or multi battery bank installation. This added wire is used to compensate for voltage drops in the wiring and if a charge splitter is used it will compensate for the losses incurred using such a device. If an X-SPLIT/X-PORT is used the additional wire, whilst useful for eliminating wiring voltage drops. It is possible that it can be wired directly to its own output as the voltage losses caused by our split charge devices are minimal. It will come into its own if a standard diode splitter is used and it will raise the output of the alternator equivalent to the voltage loss so that the voltage at the sensed point is equal to the normal float voltage of the alternator. The output voltage of the alternator under these conditions could be as high as 15 volts. To achieve this voltage the alternator has to work much harder and as a consequence it is not as efficient.

If I replace my 1/2/both switch with an X-SPLIT can I still use it to parallel the batteries in case of starting problems … ?
The answer in simple terms is yes, simply connect the output of the X-SPLIT which feeds your engine start battery to the common terminal on your switch and then connect the output of the X-SPLIT which feeds your service battery to either terminal 1 or terminal 2. During normal use ensure the switch is off and then simply select either position 1 or position 2 (depending on how you wire the switch) to parallel the batteries. Doing this will not cause a problem to the X-SPLIT but if you have successfully started your engine always remember to switch the switch off otherwise you might discharge your engine start battery by mistake.

What are the main differences between the three types of battery… ?
There are three main types of battery in common use today. They are Lead Acid (including both flooded and sealed), Gel and Absorbed Glass Mat more commonly known as AGM.
Flooded or Wet Cells are the most common Lead Acid battery in use, they are usually not sealed and allow the user to replenish the electrolyte water as it evaporates as a result of the charging cycles. As these batteries are not sealed they will spill the corrosive liquid if tipped over or the case gets damaged. The sealed versions may be tipped over without spilling the corrosive liquid but will still spill the liquid if the case is damaged. Correct installation is also important especially for sea marine applications to prevent sea water coming into contact with the battery contents to avoid the generation of Chlorine Gas.
The Gel type of battery uses similar chemical conversion techniques but the battery is sealed for life and has a self resealing safety valve fitted to allow any excessive gas pressure to escape safely. The electrolyte is no longer a liquid but more like a paste with a thickening agent such as fumed silica to immobilize the electrolyte. This allows the battery to continue to work even if the case is cracked. As the electrolyte is no longer a pure liquid but more like a paste the battery can be inverted without spillage of the corrosive electrolyte. The down side of some types of Gel type batteries is that they require a lower charging voltage than that required for Lead Acid cells so a special charging routine is required. As the electrolyte cannot be replenished due to over charging it will terminate their life very quickly. However the Gel range that we offer (not currently available as the supplier has gone into liquidation) the charging voltage is the same as the Lead Acid & AGM range, which means our version of the Gel and AGM battery range can replace any standard Lead Acid battery without changing the charging source.
AGM batteries are the latest evolution in the manufacture of deep cycle battery technology. Instead of using an electrolyte in the form of a gel the AGM batteries uses fibreglass felt like separators (hence the name) to hold the electrolyte in place very similar to the action of a sponge. The physical bond between the separator fibres, the lead plates and the mechanics of the battery case itself makes the AGM batteries spill proof, and perhaps the most resilient battery against vibration and impact resistant of the three examples. Like the Gel batteries it will continue to function even if the case is cracked or inverted. There are advantages of Gel and AGM batteries over standard Lead Acid batteries and in simple terms are;
1) They can dispense a higher charge rate than flooded cells due to their lower Peukerts exponent. Normally Deep cycle Flooded Cells cannot deliver more than 25% of their rated amp-hour capacity in amps without seriously reducing their available capacity. The majority of Lead Acid battery manufacturers recommend a ratio of 4:1 between battery bank size and the largest load size which will be encountered. AGM and Gel batteries have a ratio of at least 3:1; a significant difference in the load factor.
2) The higher charge efficiency of AGM and Gel batteries allow you to recharge with less energy: Flooded Lead Acid batteries convert as much as 15 – 20% of the electrical charging energy into heat instead of potential power. Gel batteries approximately 10 -16%, where as AGM have the best conversion figure as they lose as little as 4%. The resulting higher efficiency of AGM can contribute to significant savings when it comes to the use of expensive renewable energy resources.
3) Virtually no gassing under normal operating use and are therefore maintenance free, which means no replenishing of distilled water, or specific gravity checks. Even though you can get sealed Lead Acid batteries that are maintenance free their performance and disadvantages are the same as standard Lead Acid batteries.
4) The standard lead acid batteries lose up to 1% per day due to self discharge where as the AGM & Gel batteries lose only 1 – 3% per month, this means that if your batteries are going to be left without any trickle charge source which may happen over winter storage or on a swinging mooring where no mains hook up is possible the obvious choice will be either the AGM or Gel type of battery.

What are the main differences between a GEL battery and a AGM battery and why should I choose one in preference to the other… ?
It is a well known fact that AGM and Gel batteries are far superior in performance to standard lead acid batteries whether they are sealed, ventilated or constructed from different materials. The AGM and GEL batteries have very similar properties as explained above. However the main difference is in the number of discharge cycles that each type can sustain.
Where the batteries are going to be continuously deep discharged and recharged the preferred option is the GEL battery. The GEL batteries performance under these conditions can be as much as 33% higher than a AGM battery however the penalty is the cost. In general the GEL batteries can be nearly 40% more expensive size for size.
Unfortunately it is not as simple as ABC and a major problem can exist with the charging of GEL batteries and it depends on the manufacture of the battery (our battery range, whether it is GEL or AGM can be used with standard alternators without modification). The problem is the recommended limitations on the float (normal) and bulk charging voltages. In some instances the standard output voltage derived from normal alternators is too high, being in the region of 14 volts. This being above the maximum specified normal operating voltage which can be as low as 13.3 volts. Continuously charging at this high voltage even over a short period of time would seriously reduce its life expectancy. Where these batteries are being used the normal method of overcoming this problem is to install and use an intelligent alternator charge controller (like our X-ALT range adjusted for such a battery) in place of the standard alternator’s regulator, there is of course the one off additional price penalty of purchasing and fitting the alternator charge regulator.
A similar problem can also occur with certain types of AGM batteries but in this instance the problem is not so severe and certain manufacturers allow standard alternators to be used without modification.
If you intend to limit the depth of discharge and the number of discharge cycles then the AGM would be the best option, more expensive then the lead acid battery but overall a better performance.
For more information on our battery range go to Batteries.

What type of battery should I use … ?
This is a matter of individual choice but the correct battery must be used for each task.
For engine starting, a proper automotive or traction style battery should be used as these batteries are designed to give the high instantaneous current required for engine start routines. Though you could use a leisure battery for engine starting due to their construction it is possible unless the data states that it can be used for dual purpose prolonged use for engine starting will shorten their life and or could damage the plates inside the battery cells.

For service / auxiliary battery banks you have a choice of three, the Lead Acid variants tend to be the least expensive but as with most things you get what you pay for. The cheaper the Lead Acid battery the lower the quality and its capability of providing good service irrespective of how it is looked after. The cheap batteries will give a limited discharge/re-charge cycle count before expiring and need replacing. As a norm both Gel and AGM batteries will provide a much higher discharge/ re-charge count and in the long run prove to be a better purchase if you regularly discharge and re-charge the battery bank. Where you are likely to leave the battery without any form of charging especially over winter then the Gel or AGM battery must be the battery type selected as standard Lead Acid batteries will self discharge by as much as 1% per day without any trickle charge.
more information go to Batteries.

Why does my battery not last as long as my calculations say it should …?
In theory the capacity of a battery should mean that; if the AHr rating was divided by the current consumption it should give a figure for how long the battery should last before it was discharged. This is all well and good theoretically but it does not quite ring true. This is because the AHr value batteries are specified at, is their Total Capacity not the true Available Capacity. Their Available Capacity depends to some extent on how quickly you attempt to charge or discharge them relative to their Total Capacity. The true Available Capacity is always less then the Total Capacity.
It is confusing but you can do a simple calculation to obtain a more precise figure if it is important.

To obtain a more realistic calculation the Peukerts equation should be used, First determine the Peukerts capacity:
I is the discharge current (usually measured in amperes)
T is the time (usually measured in hours)
n is the Peukert number/exponent
C is the theoretical storage capacity of the battery i.e. 100Amps.
Pc is the Peukerts capacity
R is discharge rating normally specified by battery manufacturers and in the majority of instances the figure quoted is 20.

If using these equations check with the manufacture for the correct figures for the rating (R) and Peukert value. As a guide the Peukert exponent for a good AGM/Gel battery would be 1.10, and for standard lead acid batteries the value would be anything from 1.3 to 1.8 or for cheap batteries as high as 2, you pay your money etc.etc.

First calculate the Peukerts capacity (Pc) using equ 1.

equ 1.
Pc = R(C/R)n
example: Consider a 100Ahr AGM battery rated @ 20Ahr with a peukert value of 1.1.
Pc = 20(100/20)1.1
Pc = 117.46
Using the value Pc obtained in equ 1 above the time for which a battery can be used can be found using equ 2.
equ 2.
T = Pc / In ;
example (assuming constant discharge rate at normal temperatures): In theory discharging at a rate of 10Ahrs should give 110/10 = 10 hours but in reality using the correct calculation you would only get: T = 117.46/101.1
T = 9.32 hours.

If you increase your charge rate to say 20Ahrs and re-calculate the time your battery will last using the same formuala, not 5 hours but only 4.35 hours which is a less than the theoretical value obtained by simply dividing 100/20.

For your interest using the same calculations as in equ 1 & 2 but for a expensive Lead Acid battery with a Peukerts figure of 1.3 will give a usage time of 8.1Hrs compared to 9.32Hrs.

Using the original formula you can calculate what size battery is needed for a given task, using the above example again but this time you want to use 20 Amps for 7 hours. The battery size would then need to be, C = T x In ; substituting figures C (size of battery) = 7 * 29.96 = 209.7Ahrs + safety margin if critical (this based on the assumption that the battery is fully charged of course). This equates to a battery bank of 22Ahrs. If the Peukerts exponent increases then of course the size of battery bank will increase, assume a Peukert value of 1.5 then the battery required would be 722Ahrs a huge difference. The Peukerts exponent also affects how readily the battery absorbs the charging current, this is why AGM & Gel batteries can be charged at a higher rate than standard lead acid batteries.Just to complicate matters as the battery ages then the Peukerts value changes and as a consequence the battery life expectancy diminishes and experience will show that the battery appears to no longer last as it did when new.

What size of battery bank should I use … ?
Option 1 is the quick way, a more involved way is explained in Option 2.
Option 1.

The quick method is to note the power requirement (in Amps) of the equipment with the highest demand, this would normally be the dc-ac inverter if one is fitted or a fridge. Note the power rating and multiply the required power by 4, e.g. 1.5Kw inverter ( @12 volts) will take approximately 125 Amps at full power, using the formula as previously mentioned the recommended battery bank for this application would be 500Ahrs. Hint…If only the power in watts is known divide the power in watts by 12 for a 12 volt system or 24 for a 24 volt system, this calculation will then give the Amps used by the equipment.

Option 2
The more complicated method is to add up your total power requirements in Amps., of all the equipment being used in the absence of any charging source. Note the time each piece of equipment is going to be used in hours. Then multiply the Amps by time (in hours), this will then give a Ahrs figure of your expected total power demand. If only the power rating in watts is known divide this figure by 12 volts for a 12 volt system or 24 volts if a 24 volt system. When you have added up the total AHrs requirement it will give a figure of the theoretical battery bank size required. If you refer to the previous question and use the equation to calculate the size of battery bank required for the type of battery in use, if the Peukert exponent is not known for your battery as a rough guide line, for standard deep cycle Lead Acid batteries use a figure of 1.35; for AGM & Gel use a figure of 1.15.
It is a proven fact that the increase in the number of cycles ( the number of times you discharge a battery to a given percentage of its total capacity) you can obtain from discharging a battery to only 70% of its capacity compared to the number of cycles if you discharge a battery to 50% of its capacity is phenomenal. This is another good reason why over sizing a battery bank is sometimes advisable rather than having a battery size just capable of providing the required power even though the ratio of 4:1 is exceeded.

What size of alternator should I use … ?
This could be considered a follow on from the previous question regarding battery bank size. A good rule of thumb is to choose a battery bank size to alternator size using a ratio of 4:1, e.g. for a battery bank size of 240Ahrs an alternator of 60 Amps should be used (minimum). Using a larger alternator will not damage the batteries by over charging on the contrary it means the alternator does not have to work so hard. By fitting an alternator charge controller such as a member of our X-ALT range the charging will be enhanced and enables the batteries to be charged back to nearly 100% compared to the 80% at best using a stand-alone alternator. Though most alternators are rated at a given Amp output rating this figure is applicable for an alternator speed (not necessarily engine speed) of 6000rpm. If the engine /alternator drive belt ratio is small e.g. 2:1 and the normal engine speed is low then the charge current will be much lower then expected. If a large battery bank is installed and is deeply discharged it will mean running the engine for hours to recharge the batteries. Under these extreme conditions even the fitting of an alternator charge controller may not help as the alternator is always producing its maximum output until the batteries start to take on a charge. This condition could damage the alternator by causing the windings to over heat due to the extremes of current demand coupled with the low rotational speed producing little or no cooling. If and when fitting a larger alternator due to your power demand out stripping the capability of your present alternator, that for every 25 Amps the alternator has to develop it will need a minimum of 1 horsepower of drive power. Ensure that your drive belt’s, mounting fixtures and engine can withstand the extra demand. If up grading an alternator a good rule of thumb is for alternators above 110 Amps twin toothed vee belts should be used and ideally powers between 90 and 105 Amps should have a toothed vee 1/2″ belt though a 3/8″ belt can be used if an intelligent alternator charge controller is used that has a slow start facility to prevent instantaneous high power torque demands. Another very important factor if you upgrade your alternator is the capacity of your electrical wiring, if in doubt always consult a qualified person who can advise on the correct size of cable for any given installation upgrade. See Alternators or Genie.

What size of Battery Charger do I need…?
When calculating the total battery charge capacity the starter battery is usually not included in any calculations as it is normally fully charged. The rule of thumb is that the battery charger should be rated at approximately 25% of the battery capacity. This figure ensures that the batteries can be charged quickly and safely. For example, consider a battery bank of 200AHr, 25% of this figure gives 50 Amps, this is the ideal rating, a smaller charger will still recharge the battery bank but will take longer. If the batteries are all Gel or AGM it is possible to increase the size of the charger as these batteries can absorb a higher charge rate than standard Lead Acid batteries.

How long does it take to recharge my batteries using a Battery Charger…?
The time it takes to recharge a battery or battery bank depends on the sort and type of battery, and how long it took it to be discharged (fast discharge as when used by inverters or slow when used on a fridge). Rule of thumb is to divide the battery capacity by the maximum charge capacity available and then add 4 hours. For example taking the figure in above question, 200Ahr battery bank and a 50 Amp charger, 200/50= 4 + 4 = 8 hours.

What type & size of X-SPLIT/X-PORT should I use … ?
The rating of an X-SPLIT or X-PORT should be based on the capability of the charging source. The rating should be the same as or greater than the source output current, e.g. if an alternator with an output of 70 Amps is used to charge two separate battery banks then an X-SPLIT or X-PORT with a rating of 90 Amps should be used, i.e. XSP90/1/2BS. The BS at the end indicates that it has an energisation circuit built in for those alternators which are battery sensed, for standard machine sensed alternators this circuit is redundant and need not be connected. For a three output battery bank change the 2 to a 3 and for a four output change the 2 to a 4. The X-PORT is not available as 4 outputs but is limited to a maximum of 3 outputs. Using an X-SPLIT or X-PORT with a rating higher than the charging current source will not be detrimental but the exact opposite, the charging loss will be reduced still further. Battery bank size does not have an affect on the X-SPLIT or X-PORT rating. If two or more charging sources are connected in parallel ensure that the total charging capacity does not exceed the X-SPLIT or X-PORT rating, this especially important if two alternators are running in parallel. If this mode of operation is required use a two input model as each input will have the correct rating using the same example as above, e.g. XSP90/2/2. A battery bank is defined as a single battery or number of batteries in parallel where each bank is dedicated to a distinct task, e.g. normal domestics or fridge etc. For more information go to X-SPLIT or X-PORT.

Why should I use a Galvanic Isolator …?
A Galvanic Isolator such as our X-PEL should be used if you are connected to shore AC power for any length of time. When connected to shore power there is a high possibility that a potential difference could exist between your boat, the shore and your neighbour’s boat. This voltage difference could cause the wasting of your Cathodic anode or other metallic extremities of your boat i.e. prop shaft etc. to waste away faster than you would like. The fitting of an Galvanic Isolator between the mains earth input and the boats earth bus bar will help to reduce or eliminate this low dc voltage difference but will still maintain your ac safety earth. By eliminating or reducing this voltage difference the wasting of your Cathodic anode or other metallic parts of your boat will be reduced. Disconnecting your boat’s earth whether it be the AC or DC earth to over come this voltage differential is a definite no-no. If a problem occurs with your AC supply shorting the live to earth aboard the boat it could cause certain parts of the boat or the water around the boat to become live causing a hazard to fellow boaters in the near vicinity or any one swimming near the boat. For more information go to X-PEL.

How can I purchase a component or a complete system … ?
All the products discussed in the FAQ pages can be ordered direct from Driftgate 2000 Ltd. Purchases can be made either by credit card or cheque. Where credit card payment is made an additional admin. charge of £2-50 will be made. Delivery is normally ex-stock either by next day registered post or by courier depending on the weight of each consignment. We will give you the carriage charge when you place an order.

How can I protect my batteries from being discharged to low ….?
To protect your batteries from being completely discharged you could split your power requirements between essential and non essential systems. Essential items would be your lighting and may be heating controls etc. and a non-essential item could be your power-hungry fridge. With the all new X-CISE and power relay you can now switch off the non essential equipment automatically when the battery voltage falls below a predetermined voltage value for a period of time without manual intervention. This would reduce the battery drain and save the remaining power for those items which are absolutely necessary. When a suitable charging source is available it would enable the unit to re-connect the non essential items automatically with no delay. The unit also allows a manual reset if the battery voltage rises above a second predetermined set point after a reset time. This rise in battery voltage may happen once the non essential items have switched off and the battery recovers. If certain individual items are then manually switched off it will allow other items deemed to be non essential but necessary to be used provided their power drain does not cause the battery voltage to discharge to the alarm level.
For more detailed information go to the X-CISE home page or to see a typical installation go to X-CISE application page.

How can I charge a 12 volt battery used for leisure circuits whilst the only charging source available is from a 24 volt alternator system ….?
The best method of achieving a suitable 12 volt charging source from a 24 volt alternator or 24 volt battery charger is to use a member of our X-TRACT family, either the XT150 or the XT300. The main difference between the two models is charging current capability. The advantages of these two models over standard voltage dropper type of converter is that the excess voltage is not lost as heat but is converted into power which means that you obtain a higher output charge current at 12 volts then the input charge current at 24 volts. When you have a depleted 12 volt battery system every scrap of charging current makes the recharge time more acceptable. The output of the X-TRACT can be changed either to a) provide a constant 12 volts output for sensitive 12 volt equipment or b) be set at 13.8 volts which is the ideal long term charging voltage for 12 volt leisure batteries. Having the charging voltage set at 13.8 volts means that the 12 volt battery is unlikely to be overcharged unless a problem with the battery occurs. To see how an X-TRACT can be used to provide the function described above click X-TRACT Application Page.

What is the difference between a Quasi-Sinewave Inverter and a Pure Sinewave Inverter …?
The main difference between the two types of inverters is the shape and form of the voltage wave form. The quasi inverter has a variable mark-space ratio square wave. The sinewave inverter as it’s name suggests, a wave form approximating to a sine wave similar to normal household mains voltage. The main disadvantage of the quasi-wave inverter is the wave form, as it has sharp rising wave form this can be reflected as noise on hi-fi systems, on televisions it causes a noise bar on the screen, when used with microwave ovens it increases the cooking time required to perform the same task as a pure sine wave inverter and last but by no means the least; any equipment which has a variable speed control incorporated will not function correctly. The main advantage is that they are generally cheaper than the sine wave equivalent and if they are intended for use with resistive types of load e.g. lighting and heating or standard types of electric power tools they would be a cost effective answer.
If the load has variable speed motor drive like modern washing machines or is a LCD flat screen television / DVD player then the sine wave inverter is the only option as they will not cause interference and will function with variable speed control devices, The disadvantages are that they are more expensive (as much as 30% or more), they tend to be larger in physical size and in some cases they can be restricted in the types of load which can be connected.

How can I check that my X-SPLIT or diode split charge installation is correct…?
How to check that a X-SPLIT charge splitter is functioning correctly utilizing the on board batteries. It applies to all versions irrespective of I/O format. It can also be used to check simple diode splitters except that the voltage measured from Input to Output will be approximately 0.800 volts – 1.00 volts. On dual input units repeat the tests for each separate Input.
For these tests you will need a digital multi meter and a 5 watt bulb suitable for the working voltage.

Disconnect all but one of the battery negative leads i.e if you have 3 separate batteries disconnect 2 of them. (this isolates the batteries from the X-SPLIT)
Remove the power lead from the Input on the X-SPLIT; this is the power cable from the alternator.
Remove all Output connections to X-SPLIT taking care not to short the only battery live terminal to earth.
Connect this live battery cable to the input of the X-SPLIT.
At this point the small red light on the X-SPLIT should be on, if this is ok proceed to instruction 6. If the small red light does not come on check the -Ve connection; this is the small spade connection. Ensure that this connection is secure and is connected to a good earth point. If this is ok check that you measure more than 12 [24] volts at the input of the X-SPLIT. If 12 [24] volts is measured then it appears the X-SPLIT is defective and it needs to be returned to our factory for checking.
Now connect the 5 watt bulb between any output terminal and 0 volts (-Ve). It is easier to start with Output 1 then 2 etc.
The bulb should light. Now measure the voltage between the Input terminal and the Output terminal where the bulb is connected. This voltage; should be very low ideally approximately 0.020 volts, if the voltage is approximately 0.600 volts or higher then the channel under test is suspect.
If test 7 is correct repeat the same test for all the other channels again similar results should be seen, i.e. a low voltage reading. If any channel indicates 0.600 volts this indicates that a problem exists with that channel and the unit should be returned for investigation.
The checks 1 – 7 check that the X-SPLIT is functioning as a charge splitter with no loss.

Where the alternator is a battery sensed energized alternator follow the next instructions. Normally if such an alternator is being used there will be a wire connected to the Sense terminal. Disconnect the lead to Sense terminal then proceed with the next instruction.
If there is a Sense terminal on the X-SPLIT and is used; connect the live battery lead to the Sense terminal. The small red light should come on. Measure and note the voltage at the sense terminal to 0 volts (-Ve), then measure the voltage at the Input terminal to 0 volts (-Ve) (this is with the battery lead still connected to the Sense terminal). On early units you will measure a differential voltage (that is a difference in the reading obtained at the Sense terminal and that measured at the Input terminal, simply subtract the Input value from the Sense value) of approximately 0.80 volts on newer units this voltage will be 0.40 volts. If the small red light does not come on or you measure a much higher voltage contact Technical Support for further assistance.
The next set of instructions is used to check if the X-SPLIT is not isolating properly. If the X-SPLIT is what we call back feeding it will allow a fully charged battery to be discharged by a discharged battery, as there is no longer isolation between the batteries.

1.Reconnect the live battery lead to the input; then reconnect another battery negative lead taking precautions not to short out the second live lead to earth.

Connect the second live battery lead to an Output terminal, again I suggest you start with Output 1 then proceed to the other outputs.
Connect the bulb to the Input terminal and 0 volts. The bulb at this stage should be on, remove the battery connection to the input terminal. The bulb should then go out. If the bulb remains on then the channel under test may be faulty and the unit be needs to be returned to us for checking. If the bulb does not remain on but goes off as soon as the input connection is removed that channel is ok, proceed to instruction 4.
Re-connect a battery lead to the input, the light should light once again, now connect the second battery lead to another output and repeat the same test as 3. The bulb in each instance should switch off immediately without a delay.
For dual input units repeat the tests 1 thru 4 connecting the battery lead to input 2 and checking each output separately.
If you are fortunate in having a dual power supply simply replace one power supply for each battery and repeat tests as above.

If I have an installation that does not appear as an option in the list above can you help …?
If you have an installation, which does conform to any of the above configurations send us an email describing the system you have or the system you would like. We will design where practical the system of your choice with details how the various component parts would fit together along with the costs involved.

Author information: [email protected]
Copyright & copy; 2004 [Ray Williams (I.Eng. FIET) @ DRIFTGATE 2000 LTD.] All rights reserved.
Revised: 19th May 2004.
2nd April 2005.
5th June 2006.
29th November 2008.
22nd July 2010
3rd October 2011
28th February 2013
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