Redneck idea for thermal regulation for LFP

[Flunkyboi]

The fancy (costlier) batteries for outdoor use have thermal protection (high and low) and have internal parasitic heating. My first bank here are from the other side of that expense Bell curve.

I live in the South. Central-ish Alabama. My cheap Dumfume bank us 4x12v strung to a 48v bank configuration. My batteries didn't cost much to get 5kwh, but I'm concerned for them when we will get a decent cold stretch in that open solar shed. (Not long ago we had a stretch of days in the teens.) I've been studying threads here about rigging thermostatically controlled warming for my bank.

Then I recalled recommended frost line depth for this latitude. 4". That spurred the redneck engineering gene in me.

"I'll bury the batteries in the dirt floor of this shed...they'll stay a comfy 50f all year. " Direct burial would not work, but inside of a moisture barrier would. I got to thinking about potting enclosures I've seen in electrical work, but those are pretty costly. The best coffin I can figure on is a big, cheap Igloo cooler. Bury the cooler up to the hinged lid. Winter time, close the lid, summer open it.

If I want to double my storage, I'll bury another Igloo. There is room.

This might not work for you Northmen, but down here, I can't see how it would not work. What do you folks think? Critique is welcomed.

 

[pollenface]

I've hypothesised putting them in an insulated box like a big esky/ice box and submerging with electronic grade mineral oil (like an oil PC) and using a thermatic switch controlled aquarium heater.

Just wild thoughts, it doesn't get that cold where i live

 

[SeaGal]

This might not work for you Northmen, but down here, I can't see how it would not work. What do you folks think? Critique is welcomed.

Works in Alaska at 6' under - see here...

Post in thread 'Pylontech - The Right Buy for Me?'

Feb 18, 2022

It appears from what I'm reading that the Pylontech BMS is made to not simply ensure the battery is operated safely, but to also ensure it lasts long enough that you don't get to replace it while it's under the ten year warranty. Because, you know, efficiency. Apparently its BMS will limit you to 25% of the charge current to extend the life of the battery at times.

An interesting tactic if true. If they limit you to only charging or discharging 1% of the battery's actual capacity they could advertise a 1000 year warranty. Maybe we'll see that in an advertisement soon.

From what...

• AlaskanNoob

See also this posting...

Post in thread 'Homemade Low Temperature Disconnect for LiFePO4'

Dec 2, 2022

Here's my scenario in more detail. The solar system is 10 hours away in a remote cabin which includes a few bodies of water to get across. the cabin has about 60 watts worth of drain in the form of electronics (in winter setup) which allows a satellite link and and a weather station plus a half dozen ip cameras to keep an eye on the place while we are gone for winter. It rains there weeks at a time, unless it snows and so, the power that comes off of the solar panels into the battery bank are sometimes quite rare at this time of year. So to add a battery heater that wants 50 watts may...

• 32 volt boater

• 

 

[SeaGal]

Just wild thoughts, it doesn't get that cold where i live

... but if it does you have a big digger to bury them with

 

[Kornbread]

Heat also shortens life expectancy, so a way to keep them from cooking inside a cooler in the hot Alabama heat might be beneficial.

 

[Flunkyboi]

Heat also shortens life expectancy, so a way to keep them from cooking inside a cooler in the hot Alabama heat might be beneficial.

Actually, the dirt, below a certain depth, stays rather cool. I took the kids to a cavern attraction last year in July. Sweltering day. The temp immediately dropped just walking a bit in the grade down in the entry. The girls regretted not bringing a sweatshirt for the tour.

 

[Kornbread]

Actually, the dirt, below a certain depth, stays rather cool. I took the kids to a cavern attraction last year in July. Sweltering day. The temp immediately dropped just walking a bit in the grade down in the entry. The girls regretted not bringing a sweatshirt for the tour.

Yep, but the batteries cycling generates heat and with those being inside a small well insulated cooler, temps may rise considerably. Even with an open lid, a hot 100* Alabama day isn't going to cool them off any. It would be worth keeping an eye on.

 

[Flunkyboi]

I just thought of something that might work better than an insulated cooler. The ground stays at a fair constant year round. I could buy one of those stout totes they sell at Home Depot. Bury the tote to just under the rim. Dig a shallow trench around the perimeter and fill it with a batch of Quickrete, for reinforcement.

In summer, the lid will be a chunk of plywood, riddled with vent holes and window screen glued on. This will keep the batteries protected from debris, dropped wrenches and my caveman feet. It allows heat to escape.

For really cold Winter days, the stock lid replaces the warm weather lid, but it's modified. The top has plywood screwed to the plastic top. The underside has a chunk of foam insulation glued to it. That protects from crushing footfalls, dropped wrenches and cold.

 

[shadowmaker]

You don't need to bury (at least not in Alabama) batteries underground, just use ground tube ventilation (=earth air tunnel) to keep them cool in summer and warm in winter.

 

[Flunkyboi]

You don't need to bury (at least not in Alabama) batteries underground, just use ground tube ventilation (=earth air tunnel) to keep them cool in summer and warm in winter.

Care to explain this in more detail?

 

[shadowmaker]

Care to explain this in more detail?

Didn't have time to watch this video, but something like this.

 

[doing it different]

Usually any hole you dig will fill with water. Need to be on a high point, with a tile drain or sump pump.

And even if its sealed container it will float and lift if water gets around it.
Like septic tanks or cisterns, they need to be filled right away. Or it will pop out of the ground

 

[sunsurfer]

if you are using the earth to keep from freezing and to cool, temp can creep from the shallow soil coming in from the sides/surface. Some extruded polystyrene sheet buried shallow along the side and moving out at a slight downward angle can help with any temperature creep from the surrounding surface soil.

For up in the far north, how about a heat pipe? Then your batteries aren't 6' down. Only works for freeze protection.

 

[Heatpumpman]

Right now, I've got my PV setup in a larger than normal pump house (approx 8' square). All sensibilities tell me I'm playing with fire to house both my water supply and 540 Ah worth of LPo4 batteries in the same spot, but it kept the batteries warm enough to function during the winter and seems to reason that having an 80 gallon water tank (thinking of adding another) in there will provide some cooling capability, too. This summer will be an opportunity to watch the temps in there and see what happens. An insulated shed would retain the heat created by the PV equipment, is what I should of said! I live in L.A. too, Lower Alabama.

 

[Flunkyboi]

Right now, I've got my PV setup in a larger than normal pump house (approx 8' square). All sensibilities tell me I'm playing with fire to house both my water supply and 540 Ah worth of LPo4 batteries in the same spot, but it kept the batteries warm enough to function during the winter and seems to reason that having an 80 gallon water tank (thinking of adding another) in there will provide some cooling capability, too. This summer will be an opportunity to watch the temps in there and see what happens. An insulated shed would retain the heat created by the PV equipment, is what I should of said! I live in L.A. too, Lower Alabama.

Now you are spurring another idea for a straight up solar system my brother wants for one of his wells. I'm thinking cinder block enclosure and insulated roof. At this latitude, the batteries should be able to be used year round with no thermal range concern.

 

[Flunkyboi]

Didn't have time to watch this video, but something like this.

I watched it. That is cool. It's related to those "Earthship" articles I used to read about in the 80s in Mother Earth News (that was before MEN went full commie-retard)

Cool, but not applicable to my little solar shed. It's open for parking a yard tractor and ATV.

 

[Hedges]

Bury the cooler up to the hinged lid. Winter time, close the lid, summer open it.

You're putting insulation between the earth and the batteries.

Dig a hole. Place batteries in hole (maybe in non-insulating basin to avoid contact with moist earth.)
Place inverted igloo cooler over the top.

Don't want humidity, consider sealing a bag around them with desiccant inside.

If water table is a problem, make that "floats and pops out of the ground" a feature not a bug.

 

[Flunkyboi]

Heat also shortens life expectancy, so a way to keep them from cooking inside a cooler in the hot Alabama heat might be beneficial.

Alternative (seasonal) lids. One, insulated for hard, cold, the other, vented for hot weather. Plus, my shack/array is open with big doorways on three sides.

I'm about to rig up a thermostatically controlled fan system (two, cheap box fans in the rafters) for sweltering days. The roof is made of bifacials, so there is already a good bit of heat radiating down. I'll set a line current thermostat to force draft more air under the array and out the top vent if it gets over 90°. It convects nicely now, but the forced draft will be nice when the July sun is beating down and I'm working in there. I figure the forced draft might even help with panel efficiency on roasting days.

 

[Backyard]

if you are using the earth to keep from freezing and to cool, temp can creep from the shallow soil coming in from the sides/surface. Some extruded polystyrene sheet buried shallow along the side and moving out at a slight downward angle can help with any temperature creep from the surrounding surface soil.

For up in the far north, how about a heat pipe? Then your batteries aren't 6' down. Only works for freeze protection.

View attachment 292626

Heat tubes like that are only good if you want to extract heat from the bottom and move it to the top. If the bottom is colder then the top nothing will happen and the water/acetone will stay at the bottom with little to no convection

I've actually made a handful of those before. I started with a schrader valve and vacuum pump. But found a ball valve worked much better. Put water mix inside tube. Heat tube, crack open valve to release air and vapor. Close valve to retain vacuum when water mixture cools

Even just straight water worked really well. If you have a lower pressure the water will boil at a lower temperature so it works even when warm. It's always a weird feeling when you make one 6 feet long and stick the bottom in a bucket of hot water and within a dew seconds the top gets hot