12v Battery bank in my box truck

[Neo_Ocelot]

Hello,
New to the forums and had a few questions about wiring a battery system for my large commercial box truck.

I'm going to buy batteries from Sam's club, I'll wire them to make a 12v 800 Amp Hour Capacity bank at 20 amp.

I will add solar panels and a controller later

My question is about charging the bank using the alternator, I have a Delco Remy 22SI wich puts out 150amps.
The truck has 3x big 12v starting batteries and 2 smaller unknown batteries for running the lift in back.

Is the alternator powerful enough to charge my bank as well? if so do i need a charge controller or weird wiring?

[SunEagle]

Hello Neo_Ocelot and welcome to Solar Panel Talk

I guess one question I have is how those Sam Club batteries are going to be wired to create a 12v 800Ah system. My guess is that you are taking 4 to 6 12volt batteries and wiring them in parallel.

That would be a mistake since anything more than 2 batteries in parallel can result in unbalanced charging and discharging no mater what type of charger or alternator you use.

Something that might help you is the minimum rate an FLA battery needs to be charged. That rate falls in between C/8 and C/12 where C is the battery system Ah rating. So for an 800Ah you need somewhere between 70 and 100 amps of charging. But some of that will be lost due to resistance in the wiring and batteries. That is what leads to unequal charging.

[Logan5]

Don't buy anything yet. your fixin to make a huge mistake. take your time and read, read, read. you have so much to learn, you are no where near prepared to buy, own and maintain batteries.

[Neo_Ocelot]

The batteries i'm looking at are GC2 6v Golf Cart batteries. they need to be in paired in series and in then in parallel.

there must be a solution for this unbalenced charging issue IE using Buss Bars and equal length wire.

Dumb question maybe but, Dose anyone know if an alternator will overcharge a battery?

[Logan5]

Yes, it's called wire them in series only and purchase a new inverter.

[Neo_Ocelot]

If I wired them in series only, the 6v batteries will only put out well 6v. not much use as the charging system and the load will need 12v.
That's why you pair them up.

[Logan5]

sorry did not realize you were stuck at 12 volts, you are heading for big trouble. 800 ah at 12 volts is heavy and extremely inefficient. works much better with a 24 volt truck.

[Neo_Ocelot]

Something that might help you is the minimum rate an FLA battery needs to be charged. That rate falls in between C/8 and C/12 where C is the battery system Ah rating. So for an 800Ah you need somewhere between 70 and 100 amps of charging. But some of that will be lost due to resistance in the wiring and batteries. That is what leads to unequal charging.

This is indeed a great help, thanks for that pearl.

[SunEagle]

The batteries i'm looking at are GC2 6v Golf Cart batteries. they need to be in paired in series and in then in parallel.

there must be a solution for this unbalenced charging issue IE using Buss Bars and equal length wire.

Dumb question maybe but, Dose anyone know if an alternator will overcharge a battery?

Unfortunately even the best parallel wired system ends up creating different charging paths due to small amounts of unequal resistance either in the batteries or connections. Bus bars may help but the physical properties of wire and resistance is against you.

[Neo_Ocelot]

Here is a quick wiring setup for the battery bank. Any thoughts?

[Neo_Ocelot]

Well maybe we should just forget the hole thing, since there is unbalanced charging we can't make battery banks or use solar, sorry guys close the forum. (being cynical)

but seriously I don't see an easy way around making an affordable battery bank that docent have some drawbacks but my main concern is to make it as well as I can and get some advice from people with experience.

That being said what would the proper way to setup a battery bank to charge from an alternator? do I need a controller? Diode? Shunts?

[Logan5]

If you need that kind of power, then you can only archive it with a 24 or 48 volt system. Under the circumstances I would go with 24 volts alternator and starter and a step down for the truck electronics. any money you save will cost you fuel hauling around the load of the batteries. not sure where you are going, are you trying to run an Air conditioning unit?

[Neo_Ocelot]

yes to the AC,
could you explain why I would need a higher voltage system? seems like a real pain. why not 12v?

[Mike90250]

Look at http://www.balmar.net/ for ideas on good, reliable alternator / battery isolators that will charge your batteries. Sadly, most standard vehicle alternators are not Heavy Duty that can output full power for hours on end, charging up low house batteries. In a vehicle, what you are trying to do, would suggest adding another alternator, and installing a 24V house battery and alternator, and not mess with the factory 12V system at all. Adding 6 large batteries is enough weight to cause handling problems (when you include all the other buildup in the truck) Adding 4, 6V 200Ah golf cart batteries will yield a 24V 200ah system (4800 stored watt hours, 2400 of which is safely usable) After you figure how this works for you, if not large enough, you could try LFP batteries, much smaller and lighter, but more stringent in operating voltages.

[Neo_Ocelot]

I should be more definite of my goals.
Enough power to run basic low draw stuff as well as a small AC window unit in a vary well insulated Refrigerated Box truck.

Thanks for the link ill have to check them out. I agree a separate alternator seems to be to way to go

Also can you explain why go with 24v? I know you can get by with smaller wire but is there something I'm missing here?
I've heard 24v stuff is more expensive aswell , inverters ect.

The weight shouldn't be an issue (BIG Box Truck), I have 5000 pounds of weight before i hit my GVWR and that's just what i can haul legally. the truck can haul 12000lb safely.

[Logan5]

let's just start with 1000watts at 12 volts 1000 watts is 83 amps, same watts at 48 volts is only 20 amps. Lower amps, Less heat, less loss due to resistance. smaller wire, more efficient.

[Neo_Ocelot]

I see thanks for explianing, how much power would I need to run an ac unit?

[Logan5]

a 5000 BTU AC could consume 600 to 800 watts. But it could take as much as 1200 to 1600 watts for a few seconds just to start the compressor under load.

[Mike90250]

It's better practice and lower cost wire, to place batteries in SERIES to increase VOLTAGE, instead of in parallel to increase amps. Same wattage stored & delivered. I'd suggest 48V, but that's beyond most available vehicle alternators and regulators. 24V is common, and is a step up from 12v high amp systems. Running an air conditioner will require a lot of battery. You might look into a reefer cooler unit from a truck, and use it's engine as air conditioner, or a small
genset (honda eu1000) to charge battery bank while running AC. A gallon of fuel weighs a lot less that 6 batteries

[Neo_Ocelot]

(flying high on battery power) Mike90250 (brings me crashing back to earth).
I gave it some thought and i think your right. taking the load off the battery bank and just buying fuel in the summer.

OK lets shift gears, my demands on the battery bank just dropped drastically with out the AC.
So i need to run:
12v LED strip lights (1 Amp)
12v Vent fans (1-2 Amp)
12v Pump for water (3 Amp)
Beefy Laptop has a 170watt brick (99% of the time probably only drawing less than 20watts)
Travel Ryobi Battery charger for my tools (unknown?)
Possibly a small flat screen TV (50 Watt)

Total 20 amp draw Max.

How many batteries would i need for that? Can I get by with 12v? Cable Size is no big issue, no run longer than 10ft-18ft.

[ewarnerusa]

This is looking more like typical RV loads now. 2 6V batteries, 300 watts of solar, keep the 12V system, can get by with a 300 watt inverter but I wouldn't hesitate to hook a 1000 watt one up to this system.