Cheap Dual Battery Setup

[darren]

Hi all
Well after having my Navara for a few months now, I have been pondering where in heck to put the 2nd battery (2010 ST) and they say they can only do them under the front drivers seat (external - dont; like that idea) or in the ute back. I go camping and have a winch on the front, so I would only need a dual battery on odd occassions, so I reckon I have come up with a cheap fix. You can buy spare battery boxes from camping stores $16 - $160 depending on what you want. The more expensive ones have the outlets for running 12v stuff, more robust and cary handles etc. So I am currently wiring proper battery thickness wires through the tray, hooked to my main battery and ending in an 175 amp Anderson plug tucked away in the ute back. When I go Camping or 4x4 I can grab the battery pack out of the shed plug it into the Anderson plug so it gets direct charge from my battery / alternator. The 2 fridges can run off the 12v ports fitted into the battery box, should I stop for a small break, I can unclick the Anderson plug leaving the fridges running on the battery without lowering the charge in the main battery. Or should I get stuck and need the winch (and for some reason can't run the engine) same deal, I can unclick it and have it as a spare battery for restarting if I have a flat. I reckon this in theory is a great cheap option considering I would only want 2 batteries on my trips, it then leaves my tub totally free for cargo during normal city driving. I am tryin the cheap $16 box and will fit a few 12v outlets to it and try it out. At least it will prevent theft of my spare battery, and just keep the tray empty.

Anyone see any probs with what I am doing, or any advice would be good.

some other "eyes' may see a prob that I can't think of.

 

[Biscuits]

Are you putting in anything to stop surges blowing up your electrics?

Diodes? Solenoid? Electronic Isolators?

Might be worth looking into to stop any harm being done.

 

[WoodyD40]

I would also consider an isolation switch somewhere, so that you only need to isolate the rear battery if stopped for a period of time and running fridges etc ...

also would mean that you wont have a live connection in the back when u dont have the battery installed but still driving (ie empty tub)

I would put in a nice heavy duty relay with the isolation switch so there is plenty of grunt coming back through for when u want to use the winch. (ie 400 amp)

 

[Old.Tony]

I agree with Woody and Biscuits. The system needs protection.

As an absolute minimum, you need to fuse all power coming OFF the battery on the positive lead. If there's a lead running to the rear of the vehicle, it MUST have a fuse in it - a stick jammed up under the vehicle while you're offroading can easily cause the insulator on the wire to be pierced, contact the chassis and boom, primary battery is toast, possibly the alternator and ECU as well.

You may also consider a heavy duty isolator switch like this one from Jaycar.

 

[darren]

Are you putting in anything to stop surges blowing up your electrics?

Diodes? Solenoid? Electronic Isolators?

Might be worth looking into to stop any harm being done.

Are you refering to vehicle management electrics ? as I will only be running fridges and maybe a worklight (fluro 12v one) I was going to hook it onto the same point they are running the winch off looks like some form of inline fuse

 

[darren]

Thanks guys, I will look at an isolation switch or some sort of fuse scenario, the larger more expensive box's are fitted with an isolation switch, but I will go with an isolation switch at the main battery end (to turn off power along the cable until I need it - thanks Tony) and a fuse near the isolation switch.

 

[WoodyD40]

speaking of isolation switch's ...

looks like i will need to replace the one for my Winch ... It did not work yesterday when i wanted to winch myself out of a stuck situation.

i ended up backing up and having another go with a different approach (thanks Aido) and did not need the winch after all (thankfully).

 

[Old.Tony]

Woody, that link I posted above is the exact isolation switch I have on my winch.

It's rubber cap is in place, and the terminals - securely fastened - are totally bound up by rescue tape to ensure that nothing gets in and damages the contacts.

 

[digbyj]

So... That's everything but the battery?
What should we be looking at? Deep cycle/heavy duty? There's a bloke on eBay selling these secondhand ones that were for back up power in telecommunications towers and reckons they'd be great. Should I start a new thread sorry?
Cheers

 

[UncySpam]

Make yourself up an isolator isolator... a bit of heavy gauge wire with alligator clips (or bolt eye clips if they work in the situation) so that you can bypass around a failed isolator...

 

[WoodyD40]

Woody, that link I posted above is the exact isolation switch I have on my winch.

It's rubber cap is in place, and the terminals - securely fastened - are totally bound up by rescue tape to ensure that nothing gets in and damages the contacts.

Look the goods Tony - for 18 bucks plus postage i guess u cant go wrong.

If i cant get mine replaced under warrantee, then i'll order the above mentioned switch.

EDIT:
I just realised there IS a store near me ... cool !!!

 

[Old.Tony]

So... That's everything but the battery?
What should we be looking at? Deep cycle/heavy duty? There's a bloke on eBay selling these secondhand ones that were for back up power in telecommunications towers and reckons they'd be great. Should I start a new thread sorry?
Cheers

It really depends what you're going to do with the battery.

If you have every intention of draining the life out of it then a starter battery will be killed very quickly. They don't tolerate deep discharges - no lead-acid battery does, really, but starter batteries are particularly susceptible to cell warping.

Deep cycle batteries have thicker plates and can handle the discharge better, but being a straight lead-acid battery, they don't like being discharged over 50% - and the reason is sulphation, which destroys the batteries over time as sulphates form crystals that fall to the bottom of the cells and short the plates out.

AGM (Absorbed Glass Mat) batteries are similar, but hold their electrolyte in a mass of glass fibres between the cells. It's quite effective, but again it's still a lead acid battery so discharging below 50% is not good for its longevity.

Deep Cycle Gel batteries are less tolerant different beasts. You can supposedly discharge them to just 20% of their capacity (my Century 100Ah Gel claims this on the sticker) but I still like to keep mine above 50%. The problem with gels is the charging rate - they can be destroyed if you charge them at above 14.4V (consider this a MAXIMUM). Car alternators can develop up to 14.7V and that will destroy a gel battery.

So - it really doesn't matter WHAT battery you get. You'll pay a lot more $ for the deep cycle batteries, but in reality you'll get good service out of a starter battery as long as you maintain its fluid levels and don't overcharge it (or undercharge it).

What's the BEST way to charge a battery? Get an inverter, and from its 240V outlet, drive a CTek charger to charge the battery. It's a damn fine charger, and if you find your battery capacity reduced a bit, get the charger into "Recondition" mode and watch the life come back into your battery.

 

[Biscuits]

When are the Super Atificial Intelligence Space Travel batteries going to be available from the CSIRO. With internet as fast as thiers they should be able to achieve a battery capable of near light speed space travel and 100 year half life and never need recharging.

Be just what you would need to run the fridge. Wouldn't have to worry about pesky isolations either.

 

[digbyj]

Hey Tony
Thanks for all that info mate,
Yeah that blokes batteries were gel ones, they sound interesting if I can monitor the charge voltage.
I'll look into it a big more with the aid of your advice.
Cheers mate.

 

[reel-sensation]

No one is mentioning circuit breakers for protection. I have a SurePower battery isolator and all their wiring diagrams show a circuit breaker before the second battery.

Alan

 

[Old.Tony]

You are absolutely right - we talked about fuses, but didn't mention breakers.

I'm not sure they make breakers larger than 30A - I have 30A thermal resettable breakers in mine, located about 20mm from the battery (electrically, about 100mm from the battery post).

But Darren said:

So I am currently wiring proper battery thickness wires through the tray, hooked to my main battery and ending in an 175 amp Anderson plug tucked away in the ute back.

and that's more than a 30A breaker can handle, so I went the fuse route.

If you know a source for higher capacity breakers (100A, even 150A or 200A) then let us know, because I'm sure some of us could find them useful!

 

[Red Dog]

My second battery is in the tub connected via anderson plug to the main battery. I have a fuse link under the bonnet as well as an automatic fuse in the aux battery box.
My aux battery is usually always connected. However when stopped overnight with the fridge running I just pull the anderson plug and the aux takes does all the work. when its time to move on its simply just a case of plugging in the anderson and letting the alternator recharge the system.
I have in the past used an isolator (redarc) but paid the price when it got stuck and failed to dissconnect during an extended stay. So have decided to keep it simple this time.

 

[Old.Tony]

If we're describing what we're currently doing in our tubs: I've got a 30A thermal breaker off the battery into a ignition-on relay, 6mm cables running down into the tub into an inverter, the 240V outlet runs the Engel fridge and a battery charger that charges a 50A deep cycle which also powers the Engel.

There's no chance the items in the tub can drain the main battery. When mobile, the Engel automatically draws from 240V so the battery is unloaded and receives a full 100% charge from a decent charger.

Mine's more expensive to set up - $80 300W (1000W surge) modified sine wave inverter (Jaycar), $160 charger (although I'd now exclusively get CTek, which would make it about $250) on top of the other stuff you'd normally use.

 

[terryc]

hust my 2c, but considering that the biggest size deep discharge battery I have is 125amphr (C) and the recommended maximum charge/discharge rate is 12.5amps (C/10)for a reasonable long life, I would think that even if you went for double the charging rate(C/20), that a 30A breaker would be okay.

 

[Leprechaun]

When are the Super Atificial Intelligence Space Travel batteries going to be available from the CSIRO. With internet as fast as thiers they should be able to achieve a battery capable of near light speed space travel and 100 year half life and never need recharging.

Be just what you would need to run the fridge. Wouldn't have to worry about pesky isolations either.

CSIRO- Constant State of Internal Re-Organisation.