Building a Portable Battery Box

Neil - how much is the Arrid Twin Charge - there's not much info on their website.

Mike DiD
The Arid Twin Charge costs $299 I got mine mail order from "The 12V Shop", in WA, you could try their web site for info. - www.12volt.com.au.
I fitted mine with a decent plug/socket arrangement so I can use it in the car to charge the second battery when using a fridge etc or relocate it to the caravan to charge the caravan batteries.
Regards
Neil

Shane,

A 600CCA cranking battery will draw anything up to about 30amps at while the vehicle is running (14.2 volts). The total circuit must be capable of handling this sort of current and more. It is also nice to not have the battery connected while cranking the vehicle, so a self-resetting circuit breaker would be necessary. You may also want to consider what would happen if any of the wiring should short-circuit - I use fusible links at each battery.

And finally if you're planning on storing a wet cell battery inside the vehicle, consider what may happen in a prang. Firstly, how is it secured, and what happens to the leaking sulphuric acid in a rollover. Wouldn't want it leaking on someone trapped in the vehicle.

Sorry to be a pessimist, but theres good reasons why an auto-electrician wouldn't consider doing what you've planned.

Cheers
phil

Shane,

If you're taking advice from an Auto Elec who gets around with 3 unsecured wet cells in the back of his car, I would suggest seeking advice elsewhere.

That is simply dangerous. He is taking enormous risks and the fact that he hasn't had significant problems so far is good luck, nothing else.

Anyway, your life, your choice.

Cheers,

Jim.

All the auto elects I spoke to about setting up dual battery would not touch putting a battery in the cabin, whether it gel cell or wet. Against the law they told me. Good chance of blowing up they also mentioned. It only emmits gas when charging or discharging so simply transporting is a whole lot safer as long as it is tied down well.

Still legal to charge an AGM within the cabin I believe although this will probably change as they can give of some gas when boiling as mentioned by some one above.

Don't charge your wet cell within the vehicle cabin no matter what your auto elec told you. He has got rocks in his head. Remember also a hiace has a fairly large cabin area and the gas will dilute in the air significantly more than even say a 4 x 4 wagon. Don't know the maths on dilution, maybe someone else does.

good luck.

Hi Shane,

Its good that you've come on the forum to sort this out. There are very good reasons why no one else would do what you're doing.

>> For a starter the battery is protected by fuse's in the box.

Normally we don't put fuses between two batteries, because when they blow, the second battery will no longer get charged and you'll completely flatten the battery. Usually use a self-resetting circuit breaker, or fusible links to protect against short-circuit. Also many fuse holders have resistance of their own, and corrode.

>> The battery will have a Diode/Fuse & also a switch to stop the battery current flowing back to the socket.

The diode will be a problem - it will reduce the charging voltage by 0.7 volt, so charging will be twice as slow; secondly, the diode will most likely not handle the recharging current that wants to go to the second battery so will most like go poof.

>> The battery will be well placed & secure.

What stops the battery acid dripping out in a rollover? Thats one reason why SLA batteries are safer inside a vehicle.

>> Most batteries draw high current but can still be charged by a small 4 AMP battery charger, so I don't know what your on about.

hehehehe Thats OK. When you apply 14.2 volts to a 600cca battery it will take current (recharge). That initial current will be as high as 30amps, so can easily blow fuses or exceed the rating of your switch. An alternator recharges a battery stacks faster than a 4amp charger because it can maintain the 14.2 volts. Its very hard to get a 4amp charger to deliver more than 2.5amps.

>> And it was an Auto Electrician that gave me the idea.

I'm dumbfounded. He likes living on the edge.

>> When I asked him about the hydrogen from charging, he said, well they have been in the back for 5 years & I'm still here.

In scientific terms this is a "series of one". Will never prove a thing.

Best of luck, keep listening, it sounds like you're getting there.

Cheers
phil

Jimbo,
Am now half way through putting in a dual battery setup in the front with a Redarc Solinoid so this should keep the dogs at bay. The battery box will still be used, but only as I stated before & charged by the genset.

Thanks for all your advice. It would appear to me that the safest way out of using my wet cell is to charge it at home on a charger, use it at the destination & charge it with the gen set when needed.

Mozza,

Unfortuneately the place where I'm going will have no 240V power & I need to have the fridge going for at least 6 hrs while away from the campsite. I don't wish to leave the fridge in the back of the vehicle during this time. Later on at night I can charge the battery back up with the genset, while still running the fridge from it via a 240v/24vdc transformer. (To all those that are going to say what about the thieves, it's a cattle & sheep property & even if the fridge was taken he wouldn't carry it far with that much lead in his a--se). I may end up putting in a dual battery system just to be safe & as you say I could make up a lead as a backup should I have genset problems.

just out of curiousity... why do you need a battery backup when you can run it off your genny ?

Mozza,

I don't want to run a genset 24 hours a day, & the thing would probably run out of fuel before I returned. It's a Bunnings Special 2 stroke 850 watt & I don't know how reliable they are.( besides, can't have hot beer, frig the food, can always get a bit of underground or above mutton).

Shane,

I suggest you get a mutilmeter and check the voltage output from your gennie. I checked a Bunnings job I had for a while (actually had two) and it was around 19 volts. This will knacker your battery.

I did however hook up a 30 amp battery charger to the 240 volt outlet and it worked fine. If you're going to charge your batt from one of these cheap gennies I would recommend the 240 volt outlet through a battery charger. For it to be effective you're going to need to buy a large capacity charger and they're not cheap.

Running an $80, 6 amp job (which is not likely to give more than a constant 4 amps) is not going to give you a lot of charge from 6 hours running the gennie.

Cheers,

Jim.

Jimbo,
I have a multimeter & you are right in regards to the output, but thats to a no load situation & drops to 14.7v when connected to the battery.

Shane,

14.7 may be still a little too high. It will probably get higher as the load drawn from the battery drops.

Jim.