Auxiliary battery + separator advice, please

[tb2]

Hello there,

not exactly an "overland vehicle", but still my main means of travelling is a Citroen BX. As we sleep in the car and use it just like a caravan, I'd like to equip it with a second battery in such a way that the engine will always start the next morning, even if we've used auxiliary devices (like the radio or a fridge) all through the night.

During my stay in australia I owned a Landcruised with this kind of setup but that was three years ago and I don't know how it worked.

What kind of devices and cabling to I need for this? I found a few instruction manuals that are made for people that already have a dual-battery setup and just need the separator. But I'm a bit confused regarding that, because these plans usually involve a separation of electric circuits, apparently. For example these two:

That separation between "main loads" and "auxiliary loads" I don't understand. Isn't it possible to have a setup with a single electric circuit, but just one battery powering it unless you're turning the key to the diesel-preglow and starting positions, where the second battery will kick in?

Thanks for any help provided!

greetings from Switzerland
Tim

http://www.expeditionportal.com/forum/showthread.php?t=6112

 

[spencyg]

Your proposed system is basically what I've done with my rig. To simplify the explaination significantly, my head lights, running lights, starter, and glow plugs are all connected to the stock starting battery(s) as they would be from the manufacturer. I have a 1/0 electrical cable running from the positive terminal of the front starter bank to the isolator solenoid for the rear bank. The rear bank positive terminal is then hooked to the other side of the isolator solenoid. When I turn my starter key to "on", the isolation solenoid is activated, joining the front and rear banks together as though they were just a single group of batteries. When I turn the key off, the rear bank is no longer connected to the front bank, and any electricity removed from the rear bank won't also be removed from the front bank. So basically, once you've got your isolator circuit established, you just hook all of the items which you'll be using when the vehicle is not running to the rear bank, so when you use them, you won't drain the starter batteries.

Of course this is overly simplified as there is overcurrent protection, bus bars for distribution, etc, but when you boil it down to the basic bits, this is what you get.

Hope that helps.

 

[tb2]

Mhh, that's not really what I meant.

In your setup, you still have two circuits, one being the front bank, and the other being the stuff you connect at the back. What I meant was that everything is connected to one battery (let's say the front bank), even the starter and everything, but only if the ignition is turned, the second battery also provides power. As such, you could just use everything as normal, and even drain the battery completely, but when turning the key, the other battery will provide power to everything as well, and as such to the starter and make starting possible, even with the "main bank" battery drained.

Is that impossible?

 

[spencyg]

Basically you just want the second battery as an on-demand jumper. I don't think that is a good idea. Starter batteries are built different than deep cycle, and you want your "house" bank to be a deep cycle battery. If you keep drawing down your starter battery, it will be destroyed within weeks. On the flip side, Deep Cycle batteries don't provide enough "fast" power to be an effective starting battery. There are hybrid units out there, but they are basically a compromise of each type and don't do either particularly well.

While you're hooking up your camping goodies, it will be just as easy to connect them to the house battery instead of the starting battery.

Hope that clarifies.

 

[keezer37]

http://www.hellroaring.com/4wheel.php

These folks show various setups. I don't know if I'd run a pure backup setup if you're running accessories all night off the primary. But I do stand by Odyssey AMG batteries that crank and deep cycle. I've had one as a backup for about three years.
I use a backup only setup but do not run stuff all night and the primary battery is an inexpensive cranking battery. So if it dies it doesn't hurt the wallet so much.

If you're not familiar with dual battery setups, be patient. You will come up with question after question along the way.

 

[tb2]

Ahh, brilliant. I didn't even know there is such a thing as a deep cycle battery.

Thanks, that gives me a good start for reading into it.

 

[dzzz]

Just remember that spency considers all battery technology suspect that was not available at the time his van was built ("AV" - after van)

The hybrid batteries we talk about in this forum work great for both starting and deep discharge. 1200 cca, 100 ah storage @ 20 hrs, 400 deep discharges.

It doesn't take much CCA to start a modern gas engine. I wouldn't use a regular starting battery at all in an expedition/camping type vehicle - for either starting or house.

 

[phatman]

a bit of info on batteries:

starting batteries are good for just that, starting. if you drain them past 50% they start loosing capacity quickly.

Deep cycle batteries are for accessories. you can drain them down to 20% before you real start to hurt them. they can be discharged to 20% about 200 time before they are shot for good. they tend not to have as many CCA.this don't mean you can't use them for starting.

AGM (Absorbed Glass Mat) are batteries like optima, odyssey, and DieHard platinum are sealed and "maintenance free" (meaning you don't add water.) these are better for harsh environments because the matting keeps them from shorting internal. odyssey (Diehard Platinum) claim you can use there battery for starting and deep cycle. they also claim 400 deep cycles till you have a battery in need of replacement. the major down side is cost and the fact they take special charger/maintainers to fully charge them which also can be costly.

that being said check out the Sears dieHard Platinum. this is an odyssey battery minus about $100 to $150. they get great review all over the place. and if you let the car sit around for weeks at a time then pick up a Batteryminder 12248 charger. this will maintain the battery for many years. if you drive it most of the time then i suggest getting a Batterminder 12118 (cheaper), and plug it in for a week here and there to desulfate the the battery and keep it in good condition. i know it seems pricey but if you get 8-10 years out of a battery then it's paid for. as far as a isolator i plan to get a Hellroaring system. the fact that it has no moving part to break is appealing to me.

 

[spencyg]

Just remember that spency considers all battery technology suspect that was not available at the time his van was built ("AV" - after van)

This is a true statement. "Tried and True". A very useful motto and life mantra.

 

[ntsqd]

Further, if a battery is claimed to be both a starting battery and a deep cycle battery then it does neither very well. Perhaps well enough for most applications, but it will never equal a true starting battery or a true deep cycle battery.

 

[phatman]

Further, if a battery is claimed to be both a starting battery and a deep cycle battery then it does neither very well. Perhaps well enough for most applications, but it will never equal a true starting battery or a true deep cycle battery.

why do you say that? i ask because the i was looking at the Specs for a Sears DieHard pm 1 (same as the odyssey 2150) and it seem it has more CCA then most starting batteries. futhermore they claim of 400 deep cycles is twice the others i've reseached. is there somthing i'm missing?

 

[saburai]

why do you say that? i ask because the i was looking at the Specs for a Sears DieHard pm 1 (same as the odyssey 2150) and it seem it has more CCA then most starting batteries. futhermore they claim of 400 deep cycles is twice the others i've reseached. is there somthing i'm missing?

+1

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