New EG4, best operating temp

[putney]

Hi all, first time post. I've searched and didn't see an answer.


So I received my Signature Solar EG4 48v battery. Temps in my area have dipped from mid 30s to 5°. I built and insulated box (rack) using 1.5" polyiso for insulation. I've basically duplicated my well house setup using a Thermo-cube, light bulb and remote thermometer to keep the temp above freezing. The cube turns on at 35° off at 45° (actual is 36°-55°). My question is, "Is it good enough to just be above freezing"? I also have a inline thermometer that i can use to set to any temp with any differential and thought about using that. Best operating range? I appreciate your input. Thanks

Amazon.com

Amazon.com

 

[offgriddave]

Maybe replace the heated light with a heated blanket, under a board directly under the battery, and put some styrofoam insulation directly on top, above? Instead of using 1500 watts (guess) use only 60-70 watts and direct contact.

nice rack but you want some cross members? that battery is probably 140lb?

Haven't received my EG4 LL yet, it went to California and tracking hasn't been updated in a week

 

[putney]

The light runs for 2 minutes tops when triggered and currently pulling from the grid. My solar setup is used to power my greenhouse the GW5000es is just enough at the moment. No problem with the battery weight in this box...and it's temporary. I have an enclosed steel rack from my recording studio days but it's about 2 hours away. I'll pick it up and replace this box. I had to throw up a few panels and tie things together to test my components. I'll tidy up when it's warmer.

My original question was about the optimal temp for the battery. The manual list a broad temp range...I want to get the most out of these cells

 

[offgriddave]

The thermal mass of the battery might take a lot to warm up. The heat light is heating up the switch, but perhaps it isn't going into the battery. With a heat pad directly under it and using the weight of the battery on top of a board, it would ensure the heat goes up into the battery where you want it to go. Otherwise, it might just slip out the sides and give you a false sense of security because the switch doesn't have that much thermal mass.

I don't know how many BTU it would take to heat 140 pounds of lithium phosphate, from 31f to 45f, but it might actually be a lot. I'd double down on the solution

Or you could put some chicks in there... sell chicken in the summer when they're at market size. lol

I believe (check the specs) the charge rate is the temperature must be above 31f
But if you are just discharging, that's the other number (-4f in your picture). You can discharge all the way to -4f (it appears from your picture) but must be at 31f to charge.

 

[putney]

Thermal mass also takes a minute to cool off so the massless switch acts to provide heat before it's needed. The two minute burn actually last 1 or more hours before re-tripping. The battery mass never sees 31° though the box might...... chicks coming in the spring!

The specs are attached above, but it seems that a constant might offer better life than swinging from -4° to 131°

 

[bigal0228]

I basically set up the same thing using a rack mount from SigSolar and covered the exterior of that with 3/4" polyiso, foil side facing in, including the door, ordered two heating pads (designed for use with an RV water tank) which have built in switching for temps between 45 and 65, connected those to a 12 volt lawn mower battery, and placed a standard 500/750/1500 watt space heater in as an extra precaution. All the cables are sealed in using spray foam. The solar room itself is inside of a purpose-built shed and the small interior solar room is also insulated using the same polyiso sheets. We've had temps down to -30F so far this winter and while I've had to run the small space heater a few mornings to get the batteries back up above 32F to charge, I can do that in 20 minutes or so. The heater is set on 750 watts and draws directly from the inverter power. The batteries have never gone into a low temp shutdown and I've never had to worry about power. We've only had around 15% sunny days here so I DO use a bit of propane running the generator to keep them charged up, but when the sun is out, the batteries will charge fully (from 50% SOC) in a few hours. (I have 3 for a little over 15KwH.) I also invested in the 48V 18Amp charger and am going to order the new 100 Amp charger when it arrives to lower my propane usage until I get more panels. I currently have 12 445 Watt Canadian Solar Bi-facials and want at least 8 more and 3 more batteries to round out my system. I copied Will's Split Phase EX6500 dual inverter setup.