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Advise on new dual battery setup 

 

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 Post subject: Advise on new dual battery setup
Posted: Tue Jan 07, 2014 12:17 am 
Getting Side Ways
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Hey guys, sorry been an eventful few months.... Got the Gq, 93 tb42e, 5 speed lsd, airbags, power everything... Including a dual battery system.
Currently its running an isolator that seems to be triggered just before start and both battery's are reading 14.4v while running engine and around 13 on idle on main. For some reason ( Im new to this) the aux battery only reads 2-3v when the isolator is off. I want to be able to either run the aux battery at 13 odd all the time, or atleast on when accessory is on. If I just ran the isolator trigger to the accessory feed, will this fix my low aux battery voltage on accessory? If so, whats the downfalls? Ive read up as much as I can on the net and have read about voltage sensitive relays, would this be a better idea as I can get one off the net ( Narva) for around $50 new. The isolator I have now is a cylinder shape, + feed in and out, a little earth and I take it to be the trigger bolted to the front.
advise would be appreciated as the batteries cost me $400+ ( taken from mq before scrapping). Maybe Id like to run a fridge in the future, but mainly the aux system would power 2 amps and maybe some other crap with a lighter socket in the back.
Cheers lads and Ill get some pictures up soon
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 Post subject: Re: Advise on new dual battery setup
Posted: Tue Jan 07, 2014 8:19 am 
Getting Side Ways
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Hi,

You may have a bad earth connection, or a dead battery. Or maybe even the isolater, so test the battery first. The battery that has 3 volts is the one that I mean. Charge it up with a seperate charger and see what you get. If it takes a good charge and will run a load then there is an earth or isolater problem. Dont let it stay flat, as this will ruin it. Post back what you find.

 

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 Post subject: Re: Advise on new dual battery setup
Posted: Wed Jan 08, 2014 7:05 am 
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I agree with previous reply - check the battery, if you are getting 14 + volts while the engine is running then the system is working OK the problem must be the battery, check fluid levels. I have seen batteries with low fluid not be able to hold a charge, as with previous reply after checking fluid level fully charge battery with a battery charger and then check what the volts are, if the fluid levels are very low it might take a couple of days to get the battery back up to fully charged if it ever comes back, I think you might be up for a new battery.
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 Post subject: Re: Advise on new dual battery setup
Posted: Wed Jan 08, 2014 8:31 am 
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Can nearly bet that any 12v lead acid that drops below 9-10 volts is useless... Once you get below this level the battery internally fails and will never be the same again... That's just a characteristic of all lead acid batteries...

When you measure 3 volts is that on top of battery directly? Or are you measuring from the isolator to the ground or one terminal to the ground? You need to prove the batteries by measuring directly at the battery terminals, this rules out bad connections in the battery diagnosis...

Voltage sensitive relays are the lazy way of doing it... They mean you hook up power in and out and earth and don't need to try and find a trigger wire... They connect the batteries when the car is running (above 13.5v maybe) and disconnect it as soon as it stalls irrespective of key position... They work fine... For my dual batteries in my Ed I used a solid state relay and a high power diode block and get all the possibilities... Pretty sure I have some photos up in my build thread...

Let us know how you go with your stuff but...

Cheers,
Tim

 

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 Post subject: Re: Advise on new dual battery setup
Posted: Sat Jan 11, 2014 11:56 pm 
Getting Side Ways
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Sorry for the late reply, and the culprit was??? Dead a** battery. She was 6v completely removed. Suspect on the wire setup and solenoid too, and with no cash thanks to the bearded red wearing a**hole, Ive just yanked the lot out. Threw away the isolator, kept the wires and turfed the battery. Really, it was only running a trailer brake controller and a fag lighter in the back. I still like the idea of dual batteries, so advise on a good setup would be good.
Ive kept the tray in place and will wait till I have the cash for a deep cycle battery to fit. Solenoid, I read the voltage sensitive ones will allow you to drain the aux battery and will make sure the main does not go below around 12.5v. Is this right? If so, it make sense to use one for a basic bloke like me. Mainly, I just want to run my stereo without worrying about flattening the battery. The aux battery will run 2x amps ( maybe 50a max) + deck (10a max), the cig lighter in the back for maybe a fridge and thats it. Ill run the 130w spots off the main and leave the rest stock.
Thoughts?
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 Post subject: Re: Advise on new dual battery setup
Posted: Sun Jan 12, 2014 8:13 am 
Getting Side Ways
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Hi,

A deep cycle is good if you run it down using a fridge, but do you have a winch ? I set up a 2nd battery with an isolator so if I flatten it winching, and if I stall I have the main battery to start. I also had a manual isolator with a " tab " I can remove if I wanted to take the battery out to run the electric outboard. I have a switch with a light I can see when the 2nd battery is isolated, so if I run it down I can start with the fresh battery and then connect it when the engine is going.

Deep cycle dont like big loads, and the batteries that do dont like being flattened. When you buy another, choose one that will match your needs. I dont like " automatic " controls, I would rather have things do what I want.

Another common mistake is with the " grey import " 24 volt 4X's. When they are 24 volts the batteries have to be replaced as a matching pair, and everything has to run from both. Many people run 12 volt driving lights for example off one battery, and they will always be replacing batteries.

 

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 Post subject: Re: Advise on new dual battery setup
Posted: Sun Jan 12, 2014 9:17 am 
Getting Side Ways
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Voltage sensitive relay is the way to roll.
Also twin volts gauges.
I run a Baintech in the Mav and have had no issues with it.
They work by leaving the batteries isolated from each other until the main crank battery reaches 13.8V. Then the relay closes and brings the auxiliary battery in for charging.
When you turn the car off they stay in parallel until the battery voltage on the main drops to 12.8V. Then they automatically disconnect and isolate. So you can use the aux battery for the stereo etc and still be able to start the truck.
Also they have a contact that you connect to and put a push button on the dash. If you loose a main crank battery you hit the override button and you can start the car off the aux battery.
They are a pretty good fool proof unit.
Deep cycles don't charge properly off an alternator. They only will take a low amount of current and they take hours to charge.
I charge my deep cycle off the charger in the Mav every month or so.
I have used my winch before with both batteries in and the deep cycle has survived it.

Ultimately the best setup is a DC-DC charger which is what I will be using this build. They are about $300 from Jaycar.
No matter what just don't get an Optima battery. they are s**t nowdays.
Look at the CAT batteries. Dual purpose , made for the rough world of earth moving and really cheap.
They have funny sizes but you need to figure out.

 

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 Post subject: Re: Advise on new dual battery setup
Posted: Mon Jan 13, 2014 12:25 am 
Getting Side Ways
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cheers Matt... but according to the jaycar cat the dc to dc is actually $229 lol. Good looking unit. I noticed jaycar have an isolator that has what your saying for me (mb-3680). Kind of like an adjustable vsr with the added bonus of drawing from both if needs be to start the car. Exactly what i wanted. Cheers for the steer in the right direction.
Hey, i flogged the mq off but kept a few things. Your not interested in those 16" rims i cleaned up for the mq with perelli tyres or the mq's rear bar ( steel with spare wheel swinging carrier)? Reckon with a tailgate the rear bar would look great, cant use it on my gq due to barn doors
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