Battery placement

bstbkr · July 2017

Hello all-I am just getting started with my off grid system and would like some feed back on my battery placement. I am concerned about the winters here and cold. I know that I will have to insulate my batteries. Would it be acceptable for me to place my batteries in the crawl space under the house? Where I would like to put them, I can stand up fully, so i don't think space confinement would be a problem.

littleharbor2 · July 2017

Flooded lead acid batteries like, and last longer in cool temps. Well maintained properly charged batteries are remarkably freeze resistant. Where are you located? If your crawl space is already vented you should be fine. Use a temperature sensor with your charge controller. If your crawl space isn't well ventilated you should provide ventilation above your batteries. If using sealed AGM batteries ventilation is less of an issue.

mcgivor · July 2017

Using the lead acid a model, capacity is reduced as temperatures drop, inversely they increase as temperatures rise, but it's a double edged sword, lower temperatures increase the life expectancy whilst higher temperatures decrease it. The happy medium, according to many manufacturers is around 20°C or 68°F, but cooler is generally considered benificial, placing in a crawl space that has some ventilation should not be a problem, always consider the deminished capacity and use a remote temperature sensor with the charger as the cooler thy get the higher the voltage to maintain them is.

Estragon · July 2017

I have mine in the crawlspace. It's enclosed and insulated, which helps moderate extreme temps in both winter and summer. Unless you're in the arctic, you likely wouldn't get much colder than here (can be sub-zero F highs for weeks at a time). The main thing is to keep them close to fully charged. At low state of charge, they can freeze. Fully charged they won't freeze until -70 or so.

The crawlspace varies in height from about 1' to 6' with about 1000sq.ft footprint. I haven't got around to ventilating yet, but the banks aren't using that much water yet so I think the risk is low given the size of the space.

BB. · July 2017

A big issue is the weight of lead acid batteries... Can be 200lbs or more for separate batteries (large AH capacity). And can go 1,000 to 2,000+ lbs for "forklift" style batteries. You want a good way of moving the batteries into/out of the space. Generally avoiding stair access.

Of course, this depends a whole bunch on the size of your battery bank (4x golf cart batteries for 400 AH @ 12 volts at 60-70 lbs each, or something much larger).

Flooded Cell lead acid batteries do vent hydrogen+oxygen, plus a little sulfuric acid mist. Venting is important, and some people are very sensitive to the sulfur smell (rotten egg). Hydrogen dissapates very easily/quickly through woo

AGM/Sealed batteries are nice. But they tend to be more expensive and sensitive to over charging (all lead acid batteries can be ruined by undercharging/deficit charging). And, one of the end of life failures of AGMs are venting of hydrogen/oxygen/electrolyte--So venting is still important.

One thing I always worry about is fire... You have lots of large/high current cables and a battery bank very capable of turning those cables red hot if there is a short circuit. Circuit Breakers/Fuses are, of course, very important for reduction of fire hazards.

And, any lead acid battery, does run the risk of fire if over charged/boiled dry (failed battery charger, batteries not checked monthly for water levels, etc.).

In terms of risk management--I like to suggest that you think about installing batteries be installed in separate "bunker" outside or next to the home so that. And a separate shed for the genset+fuel (things go wrong). I suggest a sharp axe and/or heavy set of bolt/cable cutters (wood/plastic handles, perhaps a set of googles/face shield) be handy near your battery bank so you can shut down short circuits if the worst does happen (nothing like looking a glowing red wires and you can do nothing). Also some sort of cover over the battery bank/terminals so that dropped tools and other metal stuff (kids, work bench, etc.) do not cause issue will help with safety.

Of course, many people do install their batteries in basements/under floors of cabins and such and are just fine.

-Bill

Estragon · July 2017

Mine are in a plywood box. I don't need a critter meeting its maker on the bank and ruining my day. Bill's right about heavy batteries and access. I just barely managed to get the dozen L16s in.

Vic · July 2017

Things have been fairly-well covered.

If you are planning on using Flooded batteries (ones that need water added periodically), then DO make sure that there is good access/headroom for measuring Specific Gravities (SG), and for ease of adding Distilled Water (which often requires an easy ability to look into each cell of the battery. Personally would suggest that the person maintaining Flooded batteries be able to stand erect, comfortably when measuring SGs and adding water, and doing other maintenance of the battery bank.

All of the battery banks here are in plywood boxes with a hinged lid on top. BUT, after a year of keeping the lid closed, began to run Air Conditioning (A/C) in the power rooms to keep the batteries and electronics as cool as practical. This really necessitated keeping the lid open to the room. The vent ports for each system is now flush with the ceiling, and there are two inlet ports for outside air very low in the battery boxes. There is also a fan to help stir the air in the room and around the batteries.

All of these things are tradeoffs. And perhaps, the A/C in the power rooms is a bit too OBSESSIVE, but all has been working well with these systems for a number of years ... knock on wood.

FWIW, Vic

Battery placement

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