Battery bank idea?

[sdwarf36]

So-since I built my bus before I discovered this site, there are things i've learned i need to improve on. I have 2 deep cycle batteries and a (crappy) 2000w inverter mounted in the bottom of a hutch. It tells me its gone to 10.5v way sooner than I think it should + shuts down.
I was under the bus ( ) yesterday looking at the condition of my steps-which aren't very good-and started thinking-what if I fab up the steps and combine them with a battery box? I could make the 2nd of the 2 steps flip up as an access lid-or something similar. I was thinking 3 6v golf cart batteries. I have tons of room between the steps + the frame I could use. The rest of the underside of the bus is getting used up quickly-drivers side has my veggie oil tank + filters from the start of the box to the rear wheels-and I have an underframe box that will mounted on the passenger side taking up most of that side.
Thoughts welcome-its just in the crazy idea stage atm.

[chev49]

i thimk that the main thing would be to be sure you have access to service the batteries. for example, on my thomas yesterday, when i wanted to spray the engine battery bank down with the acid eliminator stuff, the slides were stuck from sitting all winter, and i had to mess around for 20 min freeing them up and greasing them.
so always make sure you can easily get to any battery for service - water.
second, if you use only three golf cart batteries you would have to hook 2 in paralell as you need multiples of 12v, so i would use 4.
just a few thoughts...

[roach711]

As Chev49 said, for compatability with your 12v system you'll need to hook up your 6v battery pairs in series to get 12 volts.

Three 6v batteries hooked in series will give you 18 volts nominal and about 20 volts actual. That will almost certainly cause problems with your bus electrical system which expects no more than 14.8 volts or so from the charging system. Your alternator and/or coach charging system wouldn't fully charge the 18v battery pack which will kill it relatively quickly. Three 6v batteries cabled in parallel gives you only 6 volts. Neither setup plays well with a 12v system.

My coach batteries will be two 6v, 225 amp batteries cabled together in series to get 12 volts, then cabled in parallel with the chassis batteries. Wiring batteries in series means hooking one positive post to one negative post which gives me in effect one 12v, 225 amp battery. If I cabled them in parallel (positive to positive, negative to negative) I'd get in effect one 6v 450 amp battery. Cabling in series multiplies the voltage and cabling in parallel multiplies the amp-hour capacity.

Letting your batteries drain down to 10.5v is a pretty deep discharge and will kill them quickly. If memory serves, a golf cart deep cycle battery is good for 30 or 40 deep cycles. A fully charged 12v bat. will show 12.7 volts and to avoid deep cycling it should not be discharged below 50% or about 12.1v. If you don't deep cycle a battery pack it should last quite a long time.

I do like your idea of using the stair well as a battery box. Very creative.

[jkindt]

Originally Posted by sdwarf36

...It tells me its gone to 10.5v way sooner than I think it should + shuts down...
...I was thinking 3 6v golf cart batteries...

Do yourself a favour and learn as much as you can about batteries, voltages, capacities, venting, and anything else to do with setting up a battery bank before you even buy a single battery for your project. There are many threads in these forums that deal with many of the issues involved. Use the search function and sit back and learn a lot.

[sdwarf36]

Well 2 batteries it will be. Even number of 6v batteries always made sense in my mind-coulda swore i saw someone with 3 in a post not long ago. (those were gonna be the next questions. )

[lornaschinske]

If you only have room for 3 batteries, why don't you use the 12v deep cycle marine batteries. We have room in our battery bay for 4 batteries all total. That's one for starting (yes, we start our bus on a single battery... we used a single battery to crank the 8v71in the Eagle coach for several years as well with no problems) and 3 for the house bank. 6v batteries are too tall to get into the existing battery bay and we aren't going to rebuild it. The Class C has a single house battery (12v) and it has been powering the lights & water pump since 2006. Since golf cart batts are only supposed to last 5 to 7 years, then I figure the 6 years the 12v deep cycle battery (from Wal-Mart) is currently at is pretty much equal and cost way less than 2 golf cart batteries of the same amperage. We most definitely DO NOT take care of the thing. Old rather basic converter in the Class C keeps the silly thing charged up. Lights power directly off the house battery as does the water pump (when we aren't hooked to city water). Since we don't plan on running a whole lot of stuff of the battery (lights on inverter, 12vDC water pump, 12vDC heat exchanger fans/12vDC circulating pump) we feel we don't need to invest double the $$ into a pile of batteries for the bus. I may add a TV & DVD player to the inverter load. Don't know yet. But the inverter I already have will handle that. And so will 3 batteries (it would only be for a couple hours while skooliedocking in a parking lot).

You may want to read Phred's Poop Sheets on Batteries.

[jkindt]

Originally Posted by lornaschinske

...You may want to read Phred's Poop Sheets on Batteries...

Good link, I keep forgetting about that site. It explains the 12V side of things well.

[roach711]

Originally Posted by sdwarf36

Well 2 batteries it will be. Even number of 6v batteries always made sense in my mind-coulda swore i saw someone with 3 in a post not long ago. (those were gonna be the next questions. )

You can hook up any number of 12v batteries (in parallel) but 6v batts. need to be used in pairs in a 12v system.

Off topic - Did you ever get your chassis air conditioning sorted out? I pulled my rear AC and found that I had no condenser coil in the engine compartment. Looked for some DIY AC hose parts but only found places that would make custom hoses. I've got plenty of hose but no ends.

[sdwarf36]

I'll have a good chance to look things over-I am 1/2 way thru an engine swap. When I get to that stuff to be bolted up, gonna look harder.