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Renogy Smart 100Ah Pouch Cell Heating

Coldcanuck

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Sep 20, 2021
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Curious as to what everyone's thoughts are on heating the Renogy 100Ah smart batteries. As you can see from the picture below of a teardown, Renogy is using pouch cells stacked on top of each other. In the photo below, the right side is the bottom of the battery pack when installed in the case. Building a heating pad solution to keep the unit above 32f, would one be safe to heat from the bottom using pad heaters and a plate or should one consider trying to heat from the sides with minimal concentration at the bottom? The pads I purchased are 3" x 13" pulling around 7 watts @ 12vdc, they get quite warm and after learning that Renogy uses pouch cells I am starting to feel a little leery. If heating from the bottom up, all the energy will be concentrated on the lower most pouch and need to travel up through the pouches (right through to left in the photo below).

Any input would be appreciated!

link to referenced teardown if curious: Renogy 100Ah Smart Tear Down
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Depending on where you're mounting it. You could just put it on the side on an angle but at 7.38" x 11.38" there might be some overhang wrap around which shouldn't hurt anything. On the floor where there mounted put some insulation or make an enclosure for the battery. It just depends on where it/ they'll be mounted.
 
Thanks for the reply. I am going to build it into an ~R10 box using 2” of XPS top, bottom and sides. Just concerned about heating from the bottom with the pouch cells, kinda wishing I waited and got the newer batteries with prismatic cells even though the cycle-count is lower. You suggest that heating from the sides is the way to go? I can trim the heat mats down by a few inches, the element is only about 8” long IIRC. I was thinking of putting two on either side and 1 at the bottom. Delta T for this could be 40°c at times assuming -30c ambient in Canada from time to time…
 
If you're going to make box and doing it with the xps I would only put it on the side (1) it will tranfer the heat. I would almost think better than just on the bottom because of the pouch cells. I wouldn't let pouch cells worry you.

Having the ability to see cell temps would be best but I don’t think yours has that. The cells will stay warmer than ambient temps. I don't use heating pads, in this thread I started awhile explains what I'm doing.
https://diysolarforum.com/threads/12v-heating-pad.2468/

I'm boondocking in SD and over the past few days the daytime temps were 40-43f, nighttime 24-32f. Lowest cell temp come morning (06:00) was 39f, I can see all individual 20 cell temps. When the nighttime temps start getting to 15f and daytime 30f or so then I might throw a small heater in there to warm everything up some but this was only needed 3 times in 5+ years.
 
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@Sojourner1 Thank you for your insight. Looks like a really nice setup you have there. Maybe I will put some more thought into the heat pad controller, a PID to maintain a set temp would probably be the best idea. That way I need not worry so much about deep frying the bottom most pouch while waiting for the heat to propagate up through the rest.

You are correct, the Renogy only has what appears to be ambient case sensors at the top beside the BMS. Interestingly enough, it appears to have a redundant sensor as noted in the teardown video, not sure how it uses both sensors, perhaps uses average between the two but maybe just a failsafe. I'd like to stick a sensor inside the case at the top of the cells but not ready to void the warranty just yet.

I like the heat mats that were referenced in your thread, would take longer to warm the cells at only 8 watts but less direct heat onto the face of the first pouch. If insulated tightly, the approximately 27BTU should be sufficient combined with charge/discharge thermal generation.
 
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