Battery heater pad question.

[Tomthumb62]

correct. same but different.

in retrospect i probably should have used the polyimide type like this:
DONGKER 12V Polyimide Heating Film, 25W PI Polyimide Heater Plate 100mmx100mm Polyimide Flexible Adhesive Heater https://a.co/d/3b2V37d

you might be interested in this purpose made silicon for the DIY cell build:
SUNFUN

What makes the polymide ones better than silicone?

 

[12vDC]

What makes the polymide ones better than silicone?

i do not have a satisfactory scientific explanation other than to say for my installation/application i believe there would be better heat transfer without the silicon.

 

[Horsefly]

in retrospect i probably should have used the polyimide type like this:
DONGKER 12V Polyimide Heating Film, 25W PI Polyimide Heater Plate 100mmx100mm Polyimide Flexible Adhesive Heater https://a.co/d/3b2V37d

Before building my two insulated / heated battery box builds I tested out several of the silicone and polymide heating pad / strips. The polymide got way too hot, way too fast. For my two batteries (8S 24V) I ended up using (in each) 2 x 12V 12W silicone pads, taped to the bottom of an aluminum plate (see here). Once tested in subfreezing conditions, the system kept the batteries between 50°F and 60°F, expending between 3.0Ah and 4.0Ah from the 24V battery for every 24 hours. I've got graphs posted over in my build thread.

 

[12vDC]

Before building my two insulated / heated battery box builds I tested out several of the silicone and polymide heating pad / strips. The polymide got way too hot, way too fast. For my two batteries (8S 24V) I ended up using (in each) 2 x 12V 12W silicone pads, taped to the bottom of an aluminum plate (see here). Once tested in subfreezing conditions, the system kept the batteries between 50°F and 60°F, expending between 3.0Ah and 4.0Ah from the 24V battery. I've got graphs posted over in my build thread.

same. my silicone pads are taped to the underside of the aluminum plate which have standoff feet.

regarding heat power i think i chose correctly with the 7.5W pads x2 for each battery. i tried them in series but after 30mins they didnt get hot enough at the higher voltage (in free air).

so maybe im okay with the silicone over the polyimide. it was tough trying to find the right kind, power spec, size, quality, etc. and relating to the OP query on Facon tank pads.

 

[Sanwizard]

Thanks for your responses.

To be clear, I have not set up or tested anything here yet. I just re-watched Will's video. He uses a thin aluminum sheet to attach the heating pad to. The aluminum sheet I would use is a bit thicker. As I say above, about 0.025 [in] thick.

All this is about the explicit instructions on the heater pad, do not to stick the heating pad to a metal surface. I am trying to understand why they would state that?

I guess I will try the aluminum sheet first and see if that works. If it doesn't, I will try some Mica. Wish me luck.

I did what Will did, and it worked well. I used heat resistant tape on the aluminum though to assure no shorts to the cells.

Post in thread 'LiFePO4 heating pad for cold temperatures' https://diysolarforum.com/threads/lifepo4-heating-pad-for-cold-temperatures.5/post-924381

 

[gotbeans]

You don’t need pads .. insulate your batterybox ( mine is 2 inches on 6 sides… ) .. I live in a cold mtn area… the heat from the batteries working at a reasonable load plus the inverter will keep it pretty warm in the enclosed area…
if things get really cold put a 50 watt light bulb and a small whisper fan circulating the heat and you will be fine ..Im in the second winter of doing this … works great…
everyone’s set up is different… all areas are different … everyone’s engineering skills are different You gotta self figure your need and answer…

i kept it in the 40s inside over a few days last year when it was -16 below F outside for two days…with a 50 watt bulb. Safe , easy ,it works….

insulation and keeping the battery’s working is the key….sry , no offense meant to pad sellers.
J.

Really depends where you are and where your batteries are to not use any heating at all.
I have 8 inches of rock wool / mineral wool insulation (which I'd recommend everyone since it won't catch fire, ever)
Still need 20watt pad under it all to heat it. I just use a plastic lizard heater that was $5 or something.
I prefer the lizard pad which draws 23.8 watts (rated at the 20 stated above) to the light bulb method. but lights work too. Incandescent is getting rarer and rarer though. Used to use a 300 watt one for my pump house for pool back in 1990s lol

 

[JRH]

Really depends where you are and where your batteries are to not use any heating at all.
I have 8 inches of rock wool / mineral wool insulation (which I'd recommend everyone since it won't catch fire, ever)
Still need 20watt pad under it all to heat it. I just use a plastic lizard heater that was $5 or something.
I prefer the lizard pad which draws 23.8 watts (rated at the 20 stated above) to the light bulb method. but lights work too. Incandescent is getting rarer and rarer though. Used to use a 300 watt one for my pump house for pool back in 1990s lol

4000 ft ele on a mountain..it’s 29 outside now…will be colder about dawn.. the system and batts is at 56 degrees…im only drawing 2.28 amps at 24v according to the BMV unit using 61 watts. That will get me through the nite …simply Running the multi+ and a couple of lights some other low draw gizmos , and a small Walmart fan…

the system is almost off and it will stay around 50 all night with no other heat than what the Victron stuff and batteries produce …the fan keeps the temps evened out inside.

yes, each set up is different, every ones build is unique…very little is universal …but for my system I have learned how much I need to ” work “ the system to generate the heat I need to warm the batt bank.
if it we’re getting a lot colder I simply use more energy , which make the components generate more heat…if I hook up a 20amp load on the batts for some use I need anyway ( a small space heater for the shed or floodlights near the RV..it will keep things warm down to about 10F outside…30 amps even more heat…40;amps an ass load more…
now if it was daytime sunny and 0F… and charging at 50 to 100 amps and using a good load too , it would be 60 inside the trailer.. maybe 70 …..???
it’s not perfect , but it’s free heat.. , and works for my set up…
if it ever gets really cold -25F or somthing or I need help to heat stuff , I will simply put a small 400 watt space heater inside to cycle off and on at about 50 degrees ..or a small btu Mr buddy propane heater…

there’s always a way to rig up what ya need if ya have a lot of random resources laying around…no biggie…
it always good to have multiple layers of back up..

J.

 

[gotbeans]

Yea that's a good temp. My CO ranch doesn't have lifepo4 yet (looking at going straight to sodium ion actually) I only have them in AR
It's 9k ft there and at 11 degrees right now haha, I'm not there though.
I'm keeping my lifepo4 down here at 75-80 degrees which seems the "optimal" temperature.
Meant the stuff mostly for OP though, unfortunately he's pretty much gone from the looks of it, sad nobody ever responded until a year later lol