Dual battery setup - how/what to wire off aux battery

[El_Freddo]

G'day all,

I've had a dual battery setup to add to the subi for some time now. Last weekend I busted it out to see what needed to be done. I've pretty much got my layout planned and just have to install the system. I've got two main questions:

1) the dual battery kit comes with a spike protection unit - there's nothing to say if it should be mounted in cab or under the bonnet and there's not enough wire to get to the battery if mounted in the cab. Where would be the best place for this to be mounted? I'm looking at in the cab.

2) After the setup is installed do you play around with the wiring so that the engine running system + lights, indicators etc are run from the original battery and everything else from the auxiliary via a relay that's triggered by the accessories on the ignition? What have others done?

Any input from those who have set up their dual battery system would be great as I'm keen to get this sorted for a little more reliability when camping and listening to music for long periods of time...

Cheers

Bennie

[maxxair]

Bennie, illd keep the original as is, and continue hooking extras (stezza, inverter ect to it.) then with the second one, have it charge up as you drive along, but only use it to start the engine. do you have a switch for the dual setup?? how does it operate??? tht is the important part, isolating one battery, so when you run one flat the other has full charge. if u get what im saying. i havent done it yet, myself.

[Matt]

Check out these. It is what i have had in my ute for around 5 years and it works great

http://redarc.com.au/products-and-servi ... -start-sbi

1. It should go between the relay and the second battery on the positive side.

I have run my accessories with a relay from the second battery triggered by the accessory wire.

[Wraith]

i second what matt has said. That redarc product will sort out all your issues. I have them in my L's. Never ever had a drama running a fridge, or even power tools!!! And never had a flat battery.

Well worth the coin. I picked up mine off Ebay new for $90.00

My 2 cents

[thatsgoodsquishy]

The more rewiring you do the less reliability you will have. Just hook up any extra work/camping lights, inverters etc to the second batt. I would add a feed from the second batt to a switch on dash to power the stereo when the ignition/acc is off if ya want to listen to tunes. Make sure you switch if off before turning the ignition/acc on or it will try to recharge the second batt through it, and that may be fire starting bad:razz:. You could add an ignition/acc triggered relay to cut the second feed to make sure this cant happen.
This is all assuming you have an automatic isolation system:D

[El_Freddo]

Thanks matt, I've already got the kit, just have to install it!

I have run my accessories with a relay from the second battery triggered by the accessory wire.

This is what I was thinking of doing, to show it I've drawn up this diagram to show it:



Can anyone see a problem in there or have a thought on the setup? I know I haven't got the numbers for the appropriate terminals on the relay but that doesn't matter as I can work that out later. What amp rated relay should I go for?

Wraith, since the EJ conversion and the wiring loom swap I've had one flat battery - due to the interior light being left on for 5 days. While in the US it sat for 2 weeks without a flat battery on my return.

Thatsgoodsquishy, I think that's a bit of a contradiction - don't mess with the wiring due to un-reliability, then hook up a switch that could potentially start a fire if the user is un-aware of it being left on when the aux battery is flat. Thanks for the idea (I do mean it in a non sarcastic way) but I think I'll have a go at the above diagram if I've drawn it properly

Cheers

Bennie

[thatsgoodsquishy]

No dramas Only issue i could see with your setup is that the relay will be drawing from your starter battery. I like the idea of no draw at all from the starter batt, but the relay isn't gunna draw much. But if you forget about it, it will be sitting there nawing away your starter batt slowly.

[El_Freddo]

No dramas Only issue i could see with your setup is that the relay will be drawing from your starter battery. I like the idea of no draw at all from the starter batt, but the relay isn't gunna draw much. But if you forget about it, it will be sitting there nawing away your starter batt slowly.

Yeah I'm aware of that, it shouldn't be an issue. But if it is I could wire in an ON/OFF/ON switch - wired to be ACC/OFF/AUX power sources to trigger the relay. It wouldn't be hard to incorporate or add later. The Accessories on the ignition would only be used for the CD player, heavier accessories such as a fridge would be wired directly to the AUX battery as you've already suggested - fused of course!

Cheers

Bennie

[thatsgoodsquishy]

OK, here is my new plan. Variation on your system, run the original acc feed into the normally closed terminal of a nc/com/no relay and the feed to the accessories out of the com terminal. Then a feed from the second batt into the normally open terminal and a switch powered from the second batt to energise the relay. Day to day no change in operation, turn the keys off and then flick the switch and radio/cig lighter/etc are powered from the second batt with no draw at all from the starter batt. No way for the charge to flow from one batt to the other either so no fire risk:D

EDIT: Yep your idea above would be best of both worlds Fully auto plus off and manual mode, total control, i like:mrgreen:

[El_Freddo]

Yep your idea above would be best of both worlds Fully auto plus off and manual mode, total control, i like:mrgreen:

Now just have to fit it, I know how I'm going to do that, just gotta find a battery to fit where my spare tyre used to be, it needs to be shorter in height to fit under the bonnet...

Cheers

Bennie

[El_Freddo]

Yep your idea above would be best of both worlds Fully auto plus off and manual mode, total control

Here's the updated wiring diagram incorporating the switch we were just talking about. I'm going to need a switch board at the rate I'm going!



Cheers

Bennie

[thatsgoodsquishy]

Yep i like it, switch it to Aux and zero draw from starter battery.:D

[Barry1956]

Bennie,
I am a dunce when it comes to 'electrickery', 12 volt or otherwise, but can thoroughly recommend the electricity section of the 'myswag' forum, http://myswag.org/forum/ , A few of the (mostly) blokes on that forum really know there stuff, and would readily advise on what you are doing. And its always easier to sort these things in advance.
(Myswag is also compulsory reading for all Jayco owners, even 80s ones like yours. )

Basic things I'd suggest are :
* A minimum of 6 gauge wire between the two batteries - to minimise voltage drop while charging.
* When stopped / camping run your fridge, lights etc from the Aux. battery.
* Make sure you have a low voltage cut out on the Aux. battery, so you don't flatten the starter battery.
* Get a deep cycle battery as your Aux. battery, if you want it for running stuff in camp.
* If you want the Aux. battery for both running stuff and as starter back-up, you could use a 'Marine battery'.
* Above all, to maintain battery life, DO NOT DISCHARGE BELOW 50% of the State of Charge.

Hope that is useful.

[El_Freddo]

Bennie,
I am a dunce when it comes to 'electrickery', 12 volt or otherwise, but can thoroughly recommend the electricity section of the 'myswag' forum, http://myswag.org/forum/ , A few of the (mostly) blokes on that forum really know there stuff, and would readily advise on what you are doing. And its always easier to sort these things in advance.
(Myswag is also compulsory reading for all Jayco owners, even 80s ones like yours. )

Basic things I'd suggest are :
* A minimum of 6 gauge wire between the two batteries - to minimise voltage drop while charging.
* When stopped / camping run your fridge, lights etc from the Aux. battery.
* Make sure you have a low voltage cut out on the Aux. battery, so you don't flatten the starter battery.
* Get a deep cycle battery as your Aux. battery, if you want it for running stuff in camp.
* If you want the Aux. battery for both running stuff and as starter back-up, you could use a 'Marine battery'.
* Above all, to maintain battery life, DO NOT DISCHARGE BELOW 50% of the State of Charge.

Hope that is useful.

Yep not bad Barry!

The dual battery kit came with the battery wiring - its a projecta kit - 85 amp which should do me just fine.

When the ignition is in the off position, the soleniod automatically disconnects the auxiliary battery from the starting battery. If the auxiliary battery is flat I need to turn the switch off so that the isolating solenoid doesn't connect the two when I'm trying to start the motor. Should be simple enough.

All other accessories such as the fridge etc will be wired from the auxiliary battery. The standard battery will be there for just engine starting/running

No cutout needed if the auxiliary battery goes flat - the isolating solenoid does that. And a lead acid battery should be fine to go quite flat without problems, for now I want to keep cost down - a lead acid is cheaper than a decent deep cycle battery. A mate of mine bought a deep cycle battery off the net for $500, it weighs a tonne!

I'll have to check out that forum sometime, I'll hold off so I don't get distracted with other things I'm doing. That second setup I've posted should do the job

Cheers

Bennie

[twilightprotege]

i was going to use one of those redarc things on my car. from what i can gather, just have the starter motor on the main battery - every thing else, and i mean everything else off the other battery.