Battery Bank Location Plan

[bloadie]

Hi, been lurking on this site for a awhile and sincerely appreciate all the information you folks have posted. It's been a big help.

I'm designing the power system 100% off-grid power system and looking for a bit of advice.  I plan to essentially wire the entire cabin in 12 VDC. The only major AC loads I will use regularly are the washing machine and the microwave. Both appliances are located close to the battery room, so I'm thinking of just plugging them directly in to outlets of a 1500 watt inverter and not have any "hard-wired" AC runs. (Using 12 gauge AC extension cords from the inverter; the type with built in circuit breakers to keep things simple is my idea right now.) This would avoid an AC circuit breaker panel

After searching the other postings on the board, the consensus is to build a power shed. However, I'm wondering if it might make more sense to use AGM batteries indoors in my case since:

? Having the batteries inside will mean shorter cable lengths and better efficiency for the DC Loads

? Battery temperature issues should not be an issue.

Of course deep cycle AGM batteries are more expensive, but I'm thinking the cost may balance out (at least to some degree) if weighed against the other issues.  I'm thinking of 6, 2volt apx 400 amp hour batteries will be the bank size.

Suggestions or comments would be appreciated.

[terry5732]

If you are using daily or so, you needn't worry to much about temperature if you simply have them inside a box of about one inch foam. Charging produces heat which will warm the box pretty good. If the comparment has a pressure relief and little extra space, gas build up shouldn't be a problem.

Of course you don't want a hydrogen accumulation inside the cabin unless it gets REALLY cold out.

[nothing to lose]

Well I don't see anything about how mild or severe of cold if any. You could probably just put an old freezer up against an outside wall, drill a couple small holes and run the cable through the wall into the house. Batteries outside, gases outside, inverter in the house. Cable length pretty close to same as if the batteries were in the cabin.

Unless your thinking of putting the batteries in the center of the cabin, the batteries up against an outside wall should not really be that much more wire than on the same wall on the inside. Do everything safe of course, but I think that's how I would do them. Either through the wall or the floor, which ever works best, but probably only a couple feet of extra wire at most?

 Old junk freezer should be free or cheap, insulated already, etc.. Could paint it to blend in and look decent if wanted also.

Might work very well, unless your cabin is high up off the ground.

[bloadie]

The freezer chest is a great idea! Cheap, low profile and practically ready built. Thanks, that idea has really got my design juices flowing in a new direction for the batteries.

Just to clarify the climate - It is not uncommon to have week+ stretches where the temp does get above 0 degrees Fairenhieght and -40F lows  are a definite possibility. (Yes, Matt Lauer is in northern Minnesota

So even in this artic climate, the advantages of keeping the batteries inside are negligible I gather from the comments.  I would be able to charge them every day if needed. With all the stuff I've read about the nuances of determining the correct full charge, I figured a constant temperature might  be beneficial, but it appears not enough to justify spending 30% more on (agm) batteries.

Another idea. If a had a 3 phase wind gennie and  built the rectifier  box so that it could be moved - I could place the rectifier in the Battery box in the winter.  This of course would mean a long run of 3 wires from the gennie instead of two (versus rectified at the tower.) But if made the batteries more efficient in the winter it might be worth it?

[bloadie]

Oops typo -- "tempature does NOT get above 0 degrees F for week+"

[nothing to lose]

Well -40 may be getting a bit low for just a freezer perhaps but it's a great ready built small shed for alot of things. It could also easily have extra insulation added inside or on the outside if needed.

 Beware of acid and fumes and sparks if you put anything near batteries of course.

Not sure if putting the rectifiers in a freezer is so good.