Need ideas on how to keep a 24V batery bank warm in the winter (6V x 4 bat)

[Silver_Is_Money]

I've seen charts that show battery banks at only 35% of rated capacity when the outside temp. hits -20 degrees F, which is about how cold it gets where I live on the coldest couple days of each winter. But in order to stay safe and keep a FLA battery bank vented I'm assuming that the vented enclosure must be located outside of the home. If that is the case, how do you keep them warm so they deliver their rated capacity (to 50% max) in the winter? Need some ideas.

[inetdog]

I've seen charts that show battery banks at only 35% of rated capacity when the outside temp. hits -20 degrees F, which is about how cold it gets where I live on the coldest couple days of each winter. But in order to stay safe and keep a FLA battery bank vented I'm assuming that the vented enclosure must be located outside of the home. If that is the case, how do you keep them warm so they deliver their rated capacity (to 50% max) in the winter? Need some ideas.

You can keep an FLA battery bank inside as long as you keep the box ventilated to the outside. The acid mist and sulfur gasses given off during end of charge and equalization are more of a concern than the hydrogen given off. Just do not seal the box without any ventilation exits from the very top where hydrogen could collect.
It actually diffuses so well that with any ventilation at all the concentration should not get dangerously high.

If you put your batteries outside and insulate them very well the normal heat from charging and discharge might keep them at a usable temperature range anyway.

[Silver_Is_Money]

If you put your batteries outside and insulate them very well the normal heat from charging and discharge might keep them at a usable temperature range anyway.

Does anyone have direct experience here?

[Sunking]

Done every day around the world, routine with outdoor cellular cell sites, not so much with Solar but a few. I have several sites in NN and AZ at altitude. Some AGM, some FLA.

When outdoors you just have to design for it. Batteries are odd things. When hot they have higher capacity but shorter lives. In cold they have lower capacity and longer lived.

-20 is not extremely cold for a battery if it is charged up. AGM is almost impossible to freeze. Trick is to select the right battery type, and adjust capacity for the temperature. -20 F is no problem for FLA assuming you can get it charged. Even less of a problem if you are only talking brief dips to -20 infrequently. Insulation will help coupled with proper charging will heat the battery, and thermal mass all help.

What you have to do is size the battery to account for the capacity loss, and up size the panel wattage to account for larger battery and short days of winter. That could bring about exceeding C/8 charging and force you to use AGM.

Completely workable, all it takes is money.

Smart money is bring the batteries inside as Dave suggested.

[Silver_Is_Money]

Smart money is bring the batteries inside as Dave suggested.

Does bringing them inside the home require going with AGM?

[inetdog]

Does bringing them inside the home require going with AGM?

Not as long as they are properly enclosed and ventilated.
And even AGMs can vent if abused, so some provision should be made for that occurrence anyway.

[Mike90250]

Does bringing them inside the home require going with AGM?

No. Because AGM can also vent, you will need a robust battery containment system for either type. So I'd just use Flooded.
The box needs to be a swimming pool to contain spilled acid, and the lid needs to direct fumes outside the dwelling.

[lkruper]

No. Because AGM can also vent, you will need a robust battery containment system for either type. So I'd just use Flooded.
The box needs to be a swimming pool to contain spilled acid, and the lid needs to direct fumes outside the dwelling.

Would you use flooded inside a van converted to rv (Class B) with the same battery containment system?

[Mike90250]

Would you use flooded inside a van converted to rv (Class B) with the same battery containment system?

Van & RV applications need battery tie downs, and in case of roll-over, a way to contain the acid I suspect. Or have it outside the occupied portion.

[Sunking]

Silver bringing FLA batteries inside is no more dangerous than having a wood/coal burning stove or fireplace in the house. Figure it out, you are smart enough.

[lkruper]

Van & RV applications need battery tie downs, and in case of roll-over, a way to contain the acid I suspect. Or have it outside the occupied portion.

Did not consider roll-over. That's a high bar! AGM's would have the same requirement?

[Sunking]

Did not consider roll-over. That's a high bar! AGM's would have the same requirement?

AGM have niche applications. They can be installed at unusual orientation like on their sides an inverted where spills cannto be tolerated. They were developed for the Aircraft military industry where extreme temps and orientation are an issue. They also have very low internal resistance so they can run very high speed heated air to start jet engines.

Also good choices for EV's. Trick is they cost big bucks. So use then where you can justify the expense.

[Mike90250]

Did not consider roll-over. That's a high bar! AGM's would have the same requirement?

Vehicle batteries have to be tied down or restrained. Bouncing down a road can bring terminals into contact with something that could short them out, or tear them loose from the cables.
Since AGM can vent under certain conditions, their box must be vented outside the inhabited space, like you would plain flooded.


But you can insulate an outdoor battery case for winter usage.

[Silver_Is_Money]

Does adding water to FLA's require that they be disconnected to any degree in order to do so?

[Sunking]

Did not consider roll-over. That's a high bar! AGM's would have the same requirement?

AGM batteries were invented for military aircraft industry. The best AGM battery made is by the company who invented them. Concorde makes a full line of AGM batteries. They make awesome RV, Wheelchair, Sun Extender, Marine, and Racing AGM batteries.