Electrical question - Aux battery setup

Alan i have one of these abr units between the two batteries in the engine bay of my 100 series cruiser (as standard) and the two auxillary batteries in the rear of the vehicle.

The abr unit can only link all four batteries if the ignition is switched on..it seperates the front pair from the rear pair so that you do not flatten the starting batteries ...all accessories run from the rear batteries when ignition is switched off..

My vehicle is left parked for extended periods without flattening the starting batteries.

Pepper
The issues that you may experience with your set up will only appear when your main (starting) batteries are dead flat, as you will not have the required power available to activate the ABR isolator relay.

Suitcase.
Your issue will best be overcome by the use of a spring loaded switch, naturally OFF, to activate the isolator relay.

It is my recommendation, and also the way that I normally fit them up, to use the Auxiliary battery for the power supply for the manually operated spring loaded switch that activates the isolator relay. When fitted up in this manner then the emergency situation can be accommodated AND there is no/little likelihood of all batteries being discharged to dead flat, all other things being operating normally.

Regards
Athol

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Yes Pepper, that would of course depend on Suitcase's ABR monitor being wired via the ignition switch. The evidence suggests that it may not be.
In fact, the ABR wiring diagram shows the control to be connected to the "accessory' connection. The ABR diagram for the ABR DBi-140 isolator being used with a "switch" not even associated with the ignition or accessory function.
Who knows how Suitcase's is wired.
What is your suggestion of Suitcase's problem?

Without seeing it i would be looking at the condition of the start battery first , then looking for where current is going to from the start battery when the ignition is switched off.

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Athol, It matters much not whether the control is sourced from the auxiliary battery or the cranking battery if a basic switch is used for control. If left on, both sets of batteries may discharge down to the isolator drop-out voltage.
As you say, it may be safest to use a spring-loaded or push-button switch in this role although this may be impractical if its function is to parallel the batteries whilst using a winch. Safest solution is to wire via the ignition or accessory function.

Alan a further thought , could it be that the dc dc charger is using power from the start battery when the vehicle is parked ??

Allan B

It matters not as to where the manual switch gets its power whilst it is in the OFF position as the VSR type battery isolator will stay ON until BOTH batteries have dropped to the VSR drop out voltage.

If you doubt this statement then try using a VSR when the Auxiliary battery is a Lithium battery, as these batteries maintain good voltage until they are almost completely flat. Whilst it is not recommended that a VSR be used in conjunction with Lithium it can be done provided that there is an ignition activated cut out fitted to the sensing wire of the VSR, so that the sensor is only active when the ignition is in the ON position.

By their very nature all VSR's sense the voltage on the start battery side, and whilst the VSR is in the on position then the voltage on both sides of it are equal (allowing for some small variation due to the resistance across the contacts).

As far as wanting to combine both batteries for winching purposes I would not entertain this idea. When winching you should always, as far as practicable, have the engine running so as to provide the best available power supply (batteries plus alternator), and as such then the VSR will be in the CLOSED position., and as such both batteries are then employed for the winching process.

Should it not be desirable for some reason to have the engine running then it is preferable to use the Auxiliary battery for winching, as this then allows for the engine to be started from its starting battery instead of having BOTH batteries flat, if the engine is in a suitable condition to be restarted.

I will always fit my vehicles up so that the starting battery is used just for that, starting the engine, and any additional batteries are used for all other purposes with the ABILITY to be used as an emergency starting power supply.

Regards
Athol

Suitcase.

On re-reading your post can you confirm as to exactly the role of the ABR Sidewinder Battery Isolator. Is this in any way activated by voltage, or is it purely a switch activated relay that can only manually be used to join the 2 batteries.

Should it be an automatic voltage activated switch then the fitment of the DC-DC charging system IN PARRALLEL with this relay is useless, and may cause some unusual type problems.

Also the fitment of a DC-DC charging system under the engine bay will cause this charger to overheat, and any heat that they are subject to reduces their output.

Regards
Athol

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This is irrelevant. Suitcase said that he had a "Projecta DC/DC charger" NOT a VSR.

It seems likely that his "ABR Sidewinder Isolator switch" is a basic ABR 100A solenoid to link the batteries for emergency.

BTW
Sent an email to Derek at ABR Sidewinder. He suggests that leaving the link switch on for a week will:

0.3A per hour so 24x7x0.3 = 50ah lost. If the DCDC charger is also on then the batteries may be totally flat.

ta da!

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"ta da" indeed Kev.