Electrical question - Aux battery setup

Submitted: Friday, Mar 29, 2019 at 21:34
ThreadID: 138082 Views:1811 Replies:5 FollowUps:11
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Hi all
Got an electrical question for the buffs. My set up (it was in the car when I bought it) - 2013 Prado Diesel
- standard man battery from RACQ
- 80AmpHr AGM Aux battery under the bonnet
- Projecta DC/DC charger also under the bonnet to charge the 2nd battery
- ABR Sidewinder Isolator switch
- ABR sidewinder battery monitor in the cabin (it has a "Link" switch to join the two batteries together in an emergency)
Question is - what do you think would be the result of not driving the car for about a week with that Link switch turned on?
I went out to the car yesterday and the main battery was as dead as a door nail but once we got it started it took charge really well and the alternator is charging well. I left nothing turned on in the car.
cheers
Suitcase
Prado SX and a little van

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Reply By: Allan B (Sunshine Coast) - Friday, Mar 29, 2019 at 22:46

Friday, Mar 29, 2019 at 22:46
.
At a guess, I would think that the "ABR Link Switch" activates the "ABR Isolator" which in fact contains two hefty relays being used to "join the two batteries together".
The coil currents of the relays in that isolator would be enough to discharge the battery if left on continuously for about a week.
Cheers
Allan

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Follow Up By: Pepper - Saturday, Mar 30, 2019 at 06:59

Saturday, Mar 30, 2019 at 06:59
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.
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Follow Up By: Athol W1 - Saturday, Mar 30, 2019 at 08:40

Saturday, Mar 30, 2019 at 08:40
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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Follow Up By: Allan B (Sunshine Coast) - Saturday, Mar 30, 2019 at 08:46

Saturday, Mar 30, 2019 at 08:46
.
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?
Cheers
Allan

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Follow Up By: Pepper - Saturday, Mar 30, 2019 at 08:56

Saturday, Mar 30, 2019 at 08:56
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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Follow Up By: Allan B (Sunshine Coast) - Saturday, Mar 30, 2019 at 08:57

Saturday, Mar 30, 2019 at 08:57
.
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.
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Allan

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Follow Up By: Pepper - Saturday, Mar 30, 2019 at 09:00

Saturday, Mar 30, 2019 at 09:00
Alan a further thought , could it be that the dc dc charger is using power from the start battery when the vehicle is parked ??
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Follow Up By: Athol W1 - Saturday, Mar 30, 2019 at 09:25

Saturday, Mar 30, 2019 at 09:25
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
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Follow Up By: Athol W1 - Saturday, Mar 30, 2019 at 09:35

Saturday, Mar 30, 2019 at 09:35
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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Reply By: Allan B (Sunshine Coast) - Saturday, Mar 30, 2019 at 10:13

Saturday, Mar 30, 2019 at 10:13
.
As usual, this is descending into much irrelevance and confusion.

Suitcase asked...... "Question is - what do you think would be the result of not driving the car for about a week with that Link switch turned on?"

I answered that in the first response. Then he is getting a lot of confusing expressions of how everybody else's system is constructed.

It seems likely that his system was OK for the previous owner and has been OK for him until he left the "Link Switch" on for a week.

Surely the only answer to Suitcase is "Do not leave the Link switch on unattended" and.... "It may be a good idea to wire the Link switch via the ignition circuit as per the ABR diagram below."



Cheers
Allan

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Reply By: Rangiephil - Saturday, Mar 30, 2019 at 10:14

Saturday, Mar 30, 2019 at 10:14
I have an ABR sidewinder VSR on my car with the dash control..

The unusual thing with them is that they cut at12.4 volts not the usual 12.7.
The relays remain closed until both batteries are at 12.4.
I find my primary battery loses voltage to under 12.4 quite quickly maybe 3 days.
I then find the primary battery loses voltage much more slowly.
AnswerID: 624707

Follow Up By: Allan B (Sunshine Coast) - Saturday, Mar 30, 2019 at 10:27

Saturday, Mar 30, 2019 at 10:27
.
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.
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Allan

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Reply By: HKB Electronics - Saturday, Mar 30, 2019 at 10:22

Saturday, Mar 30, 2019 at 10:22
Suitcase,

Can you please clarify, by writing you can link the batteries together this tends to indicate you have a VSR installed between the main and auxiliary batteries, if this is the case then the DCDC charger will effectively be bypassed and just consuming power with no benefit?


You indicated that only the cranking battery has gone flat, this would tend to indicate that the two batteries were not linked else they both would have run down. I would be looking for a parasitic drain on the main battery, could possibly be caused by the DCDC charger. Also you didn't leave your keys in the ignition by any chance?


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Reply By: Member - Suitcase (QLD) - Saturday, Mar 30, 2019 at 11:05

Saturday, Mar 30, 2019 at 11:05
Jeez - leave a thread unattended for 12 hours and look what happens. :-)

So... It looks like I have an ABR DBi-140 isolator and an ABR Dual battery monitor 12V with Link switch.

I'm afraid I didn't check both of the batteries when I found the main battery flat - I just measured the main battery and it showed something like 8V (but don't quote me or tell me that that could not be because I am not sure).

In the ensuing couple of hours I also cannot be sure about the state of the isolator and the Projecta charger. I do know that after I had gone for a drive I had 13+ volts showing in each battery.

The next morning the main battery was showing 12.9V and the aux battery 13.7 (ish) and the charger showed that it was on float charge.

Last night I noticed that the main battery was at 12.7V and the charger changed to standby.

Does all this sound reasonable?

This morning I went out and everything is the same as last night. I flicked the link switch on and the isolator led came on - Lo and behold.

So … could it be - as Allan first suggested and my battery monitor is not connected to ignition - and maybe not even to accessories.

Everything seems consistent. With the link switched off and batteries fully charged, the charged stayed on float until the main battery dropped below its minimum input voltage at which time it changed to stand by - it's still showing that this morning.

Short story - I believe Allan's diagnosis might have been correct. The autoelectrician is going to check things this morning. If something is awry I'll probably pull the aux battery out rather than spend money fixing stuff. I probably only use the damned thing twice a year and I can use my little Waeco battery then anyway - it will run my fridge overnight if I really need it.

cheers and thanks everyone
Kevin
Suitcase
Prado SX and a little van

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AnswerID: 624709

Follow Up By: Member - Suitcase (QLD) - Saturday, Mar 30, 2019 at 11:11

Saturday, Mar 30, 2019 at 11:11
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!
Suitcase
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Follow Up By: Allan B (Sunshine Coast) - Saturday, Mar 30, 2019 at 11:17

Saturday, Mar 30, 2019 at 11:17
.

"ta da" indeed Kev.

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Allan

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