battery bank for weekend use yurt in western maine?

[chrisdag]

Preface: We are in the process of completing our 20ft White Mountain Yurt up in Western Maine. The yurt itself is more of a mental health project and excuse to do something fun and "hands-on" outdoors vs. a full-time home for us -- it will mainly see use on weekends year-round as we also have a kit built log home on the same land. Pictures of the build are in my gallery.

Was very excited and looking forward to geeking out building the off-grid power and battery bank infrastructure to drive some LED lighting and maybe a fan for the wood stove. But ...

The infrequent use scenario has me convinced that my dreams of a battery bank are impractical and/or impossible due to temperature reasons.

When idly looking at various battery options it looks like most of them are not designed to handle very cold temperatures (ie deep western main winters where the batteries may go unused for a week or more at a time ...). Because I don't plan to live there full time I can't promise that there will be any sort of constant temperature.

If I can't sensibly maintain batteries in a cold environment I may have to resort to a grid-tie 20amp circuit run underground and/or one of those small and quiet camping generators.

Anyone have any advice, guidance or tips for battery use in a new england winter? We do have good

insulation

all around but I can imagine the indoor temperatures will drop below freezing pretty often when we are not around and running the wood stove.

Is a battery bank impractical for this scenario?

[Jafo]

Originally Posted by chrisdag

.

The infrequent use scenario has me convinced that my dreams of a battery bank are impractical and/or impossible due to temperature reasons.

Not sure why you believe that. I have my camping yurt up in the Adirondacks here in Herkimer County NY where it regularly falls to -30+ in the winter time and cold has never been an issue with my deep cell batteries. If you get a good MPPT charge controller, it will compensate for temperature. The controller will keep your batteries full and not overcharge the bank.

I snowshoe up here all the time in the winter and enjoy fully charged batteries from the same bank I have used for the last 2.5 years.

[chrisdag]

Thanks! Do you mind if I ask what type of batteries you are using? Flooded? Sealed? AGM?

Suspect I've been looking wrongly at integrated battery/charger/controller products all of which had poor operating temperature ranges in their tech specs that convinced me I could not use them in a mostly unheated outdoor-ish structure.

I'll look now just at the basic building blocks - batteries, chargers and inverters ...

[Jafo]

I am using flooded for the main yurt, sealed for the bath yurt (Runs shower pump). Here is a post of my recent setup:

http://www.yurtforum.com/forums/powe...power-632.html

[elewis33]

Originally Posted by chrisdag

The infrequent use scenario has me convinced that my dreams of a battery bank are impractical and/or impossible due to temperature reasons.

When idly looking at various battery options it looks like most of them are not designed to handle very cold temperatures (ie deep western main winters where the batteries may go unused for a week or more at a time ...). Because I don't plan to live there full time I can't promise that there will be any sort of constant temperature.

I have the same concern, as I'm building now where it can be very cold in winter and very hot in the summer. These kinds of extremes don't seem to play well with batteries. But I'm learning as I go.

Seeing some good stuff down below. Be back soon...

[elewis33]

Originally Posted by Jafo

Not sure why you believe that. I have my camping yurt up in the Adirondacks here in Herkimer County NY where it regularly falls to -30+ in the winter time and cold has never been an issue with my deep cell batteries. If you get a good MPPT charge controller, it will compensate for temperature. The controller will keep your batteries full and not overcharge the bank.

I snowshoe up here all the time in the winter and enjoy fully charged batteries from the same bank I have used for the last 2.5 years.

This is really good to know. but I'm just noticing that this thread is really really old. Not that the information isn't still reasonably good. It's just that technology for charge controllers and such have changed quite a bit in 5 years.

So flooded lead acid should still be a reasonable option, but they also come with some concerns. I see that you're still here on the forums so perhaps you can answer a few questions?

• Where did you locate your batteries?
• Did you do anything to try to keep them warmish?
• How did you vent them?
• What other components did you have in your system, besides a charge controller and panels?
• What voltage did you run your system at? 12v? 24v?

[Jafo]

If you keep your batteries charged at 100%, then even the coldest temps should not bother them. The mistake I see people make is they go to their weekend cabin, run the batteries down to 50% and then leave. The batteries at this point will now freeze at a much higher temperature. Once they freeze, they're done.

I have learned this from experience which is why I have a small generator (think Harbor Freight 2 stroke, $80 generator) and a 24v marine battery charger for when I visit my yurt in the winter. When I wake up on the morning of my last day there, unless I am expecting full sun (which charges my bank in about 45 minutes), I will run the generator & charge the batteries until I am ready to leave.

[elewis33]

Originally Posted by Jafo

If you keep your batteries charged at 100%, then even the coldest temps should not bother them. The mistake I see people make is they go to their weekend cabin, run the batteries down to 50% and then leave. The batteries at this point will now freeze at a much higher temperature. Once they freeze, they're done.

I have learned this from experience which is why I have a small generator (think Harbor Freight 2 stroke, $80 generator) and a 24v marine battery charger for when I visit my yurt in the winter. When I wake up on the morning of my last day there, unless I am expecting full sun (which charges my bank in about 45 minutes), I will run the generator & charge the batteries until I am ready to leave.

Good stuff. So from a system design point of view do you have some sort of disconnect between your panels and charge controller, and you're shutting off charging while you're not there?

Also, do you have any feedback on my other questions?

[Jafo]

Originally Posted by elewis33

Good stuff. So from a system design point of view do you have some sort of disconnect between your panels and charge controller, and you're shutting off charging while you're not there?

Also, do you have any feedback on my other questions?

No. I leave them connected. The charge controller will turn itself off once it detects the battery bank is full. As for your other questions:

• Where did you locate your batteries?

The are inside, next to my inverter.

• Did you do anything to try to keep them warmish?

No. They are inside so they are as warm as anything else.

• How did you vent them?

I don't. They are AGM batteries but even when I had flooded batteries, we are talking about two batteries here, not 20. And we are talking about a yurt, not an airtight closet. Yurts breathe rather well and I doubt you would ever be in any real danger. Besides, with the proper controller, your batteries really shouldn't be gassing at all.

• What other components did you have in your system, besides a charge controller and panels?

Backup generator, battery charger, battery bank fuses, ground rods and wiring, 12v step downs and inverter.

• What voltage did you run your system at? 12v? 24v?

24v.

[skihuckster]

If you need your batteries outdoors and you're worried about temps you can bury them in a battery box and put some pieces of foam board on top. That will vent well enough and the batteries won't get too cold. Same system is used on septic tank covers.

For battery voltage you get what you get with batteries, and most are "12V", but you can wire them in parallel to get 24V or 48V. The advantage of wiring to get higher voltage is that you don't need as large of wires (save $ on copper).

Like other posts have said, technology is good these days. A charge controller is the critical piece, wired so that you don't over charge or over drain your cells.

My batteries (AGM) are in a box outdoors and I use a charge controller. My other electrical components like inverter as well. So far the only issue I've had is that my main battery disconnect (marine battery disconnect) keeps getting brittle and breaking. At least it's a $10 part.

Which reminds me...I have a friend in WY that has an old ranch truck that he only runs spring through fall. He kept having issues with the battery being dead after each winter and he thought it was the cold. Then he started removing the battery cables in the fall and reconnecting in the spring. Problem solved. He must have had some parasitic losses. So a disconnect switch for long times away is a good investment.

And if it hasn't been said yet...if you go for it and a battery fails, how much are you out? As experiments in building materials go, this is a good one to tinker with. Better than a structure fail.