A variation on the very nice design in the video (thanks!): I used boxes and 1.5” thick high density foam caps (upper and lower) that batteries were shipped in. Four 1.5” high density open cell foam pieces (not as good R but readily available and easy to cut with scissors. Amazon Six 1.5" foam for tool box $20). Each cut .25” taller and longer than exact fit dimension for better sealing. Above is assembled with no tape for ease of assembly/disassembly when heaters are not used. Of course, the cardboard box is not the most durable product. I will not use these much at all but took additional steps for durability, which I doubt was required. I likely will just place the heaters between the foam and not tape/attach.
Very well done in so many ways! You are saving me so much time and avoiding mistakes. One thought: the heating board maybe directly over the battery temperature sensor, which may heat the sensor area much more than much of the battery. The sensor maybe located about 1/3 from top and on one of two middle battery cells, along long side. I found location on mine using a radiant heater and blocking parts of battery face, while watching BT app temperature. Using four heaters in series keeps the maximum temperature nicely down (great job) and slowly heat battery, allowing temperatures to even out. I am not sure that this causes any issues. I am concerned that battery sensor will tell BMS that battery is warm enough when parts are not. I have not placed my heaters yet but am considering lowering the heater and moving sensor side heater a little bit away from sensor. Other thought is to insulate part of this heater (battery side) directly over sensor.
@@TimCompton-q8n Well thought out! It never occurred to me to investigate where exactly the temperature sensor was located. It’s easy enough to relocate the heater pads, which I’ll do before next winter. And I’ll update the blog as well, giving you credit for the idea. Thanks!
Why not place heaters on bottom and temp sensors on top of battery? My thought is that the heat would mor efferently rise up through the batteries. (I keep seeing everyone place heaters on the side with no explanation.) I am looking to so this shortly in my rig here in CO. I like your video. This is the one I keep referring back to.
@@andrewgronquist2523 Putting the heater under the battery seems like a good idea. I’d still suggest keeping the temp sensors on the side of the battery, however. I have no quantitative evidence to support this, but it seems like this would better measure the temperature of the battery mass than it would on the top. Please keep us posted on how it works in those cold Colorado nights.
Heat on sides or bottom will transfer heat equally well because conductive heat is not affected by gravity. There is some gap between sides of battery and case so a small amount of convection occurs. Once one part of battery is warm most of the battery is near the same temperature especially since there are not a lot of watts involved (very slow heating) so heat is equalized well. Lithium conducts heat extremely well. Putting heaters on bottom places weight on them and possibly some movement so reliability could be less. BMS is on top of battery so placing heaters above it possibly would not transfer heat as well to battery (likely would work) and I am not as comfortable applying heat directly above BMS for durability reasons. Most of this is speculation on my part, though. I will be using batteries in very cold conditions in January or February. If anything interesting occurs I'll try to check back in. Some of use will be in Colorado and New Mexico. Last year it was in the teens...
I would place the heater under the battery simply because you stand the greatest opportunity for direct battery cell contact. I doubt the cells are even touching the case on the sides but the bms might be. You would need to open the battery to see
Are you sure you need Normally Closed temperature switches? Wouldn't you want the circuit to be normally open umtil the temperature reaches 5c or lower?
@@El_Rudo It’s a little confusing, but you want the normally closed version. A normally open switch will turn the heater on whenever the temperature goes above 40 degrees - the opposite of what we want.
@@JustALittleFurther thanks for your response. Yes, the NO/NC concept is doing my head in when it comes to these temperature switches. Even asking AI like Gemini and GPT I am getting different answers depending how I phrase the question. I just wanted to make sure before ordering because It almost ordered the NO version. So if I wanted to go belt with suspenders for safety, could I also put in say a 20c NO temperature switch, like someone else mentioned in the comments? My intention would be to shut the whole thing down if the external battery temperature hit 20c. I am going to have a master physical switch to turn the circuit on when the temperature during the day gets to below 10c.
Nice vid. I just tried this with the pads underneath and thin sheet metal on top to spread heat out. Didn't seem to work. The pads are fine without the thermal switch (get really hot)...but hardly anything with the switch installed. So what i dont get is how its meant to heat up if it comes on at ~5°c then turn off at ~5c too ?
@@charleswillard775 The heaters have some hysteresis. They don’t heat up or cool off immediately. When the batteries reach 5C, the switch turns the heater off, but it takes a while for the heating pad to cool down, and the temperature keeps rising for awhile. The reverse happens when the temp drops below 5C… it takes awhile for the pad to heat up again, so the temperature of the battery continues to drop. Hope this helps, and glad you liked the video.
Battery will rarely be right at 5C and will be below 5C when heaters are warming it up (staying on non stop) and heaters always off when above 5C. When battery is around 5C it will cycle on/off to keep it around 5C, which is great.
Based on tests, I am not concerned about four heaters in series negatively affecting battery temperature sensor. As far as four 25W heaters wired in series/two per battery: Heaters kept battery above 32F while in 15F freezer for two days using power from power supply 12.8V. Insulation a little higher R-10 (repurposed material, not a recommendation for better insulation). Batteries were not in use, which generates some heat. Surface temperature between heater and battery 123F-comfortable for battery ABS housing durability. Wiring 1, or 2, 3 in series generate higher temperatures (be careful!), while just one generates highest. Five in series would generate lower temperature so not recommended. If more heat is desired using in sets of four in series might be wise, i.e. four with each battery. This would heat batteries less slow. Heating with two could take a day or two if heating from 20F to 32F. General information: • One heater provides 25W 2A @12V. Two in parallel 50W 4A. Two heaters in series provide 12.5W 1A TOTAL (counterintuitive for most). Four is series 25/4= 6.3W total, so while using two of the sent on a single battery 6.3/2=3W .5A total for two heaters per battery. Calculated and measured.
It was working great while we were in colder areas. We’re back in Vegas now, so it’s not cold enough to come on anymore, so I’ve switched to summer mode, and removed the insulation.
Author used Senasys snap disc: with close 35F, open 45F, +/-5F tolerances. Other options, purchased directly from Senasys (no free shipping), are close at 40 and 50F. I am not recommending a change. I tried one higher temperature disc (needs to be higher to allow controller to control temperature) and INKBIRD ITC-1000F--Adjustable Temperature Controller (Amazon). This is not as clean a design and more effort to use--has more wires/connections, have to set desired temperature (a little clunky), if power is lost controller turns off (settings saved), where to place/mount controller... I suspect two discs (like author's design) are more durable/reliable than controller. Anderson Power Pole connector work well for removeable connections.
Excellent video and explanation! Easy to follow and implement! It will make my winter camping so much better!!! That you!
@@caver6292 Hey, thanks for the great feedback! Glad it helped… David
A variation on the very nice design in the video (thanks!):
I used boxes and 1.5” thick high density foam caps (upper and lower) that batteries were shipped in. Four 1.5” high density open cell foam pieces (not as good R but readily available and easy to cut with scissors. Amazon Six 1.5" foam for tool box $20). Each cut .25” taller and longer than exact fit dimension for better sealing.
Above is assembled with no tape for ease of assembly/disassembly when heaters are not used. Of course, the cardboard box is not the most durable product. I will not use these much at all but took additional steps for durability, which I doubt was required. I likely will just place the heaters between the foam and not tape/attach.
@@TimCompton-q8n Hi Tim, sounds like a nice, easy way to accomplish it. Thanks
Very well done in so many ways! You are saving me so much time and avoiding mistakes. One thought: the heating board maybe directly over the battery temperature sensor, which may heat the sensor area much more than much of the battery. The sensor maybe located about 1/3 from top and on one of two middle battery cells, along long side. I found location on mine using a radiant heater and blocking parts of battery face, while watching BT app temperature. Using four heaters in series keeps the maximum temperature nicely down (great job) and slowly heat battery, allowing temperatures to even out. I am not sure that this causes any issues. I am concerned that battery sensor will tell BMS that battery is warm enough when parts are not.
I have not placed my heaters yet but am considering lowering the heater and moving sensor side heater a little bit away from sensor. Other thought is to insulate part of this heater (battery side) directly over sensor.
@@TimCompton-q8n Well thought out! It never occurred to me to investigate where exactly the temperature sensor was located. It’s easy enough to relocate the heater pads, which I’ll do before next winter. And I’ll update the blog as well, giving you credit for the idea. Thanks!
Why not place heaters on bottom and temp sensors on top of battery? My thought is that the heat would mor efferently rise up through the batteries. (I keep seeing everyone place heaters on the side with no explanation.) I am looking to so this shortly in my rig here in CO. I like your video. This is the one I keep referring back to.
@@andrewgronquist2523 Putting the heater under the battery seems like a good idea. I’d still suggest keeping the temp sensors on the side of the battery, however. I have no quantitative evidence to support this, but it seems like this would better measure the temperature of the battery mass than it would on the top. Please keep us posted on how it works in those cold Colorado nights.
Heat on sides or bottom will transfer heat equally well because conductive heat is not affected by gravity. There is some gap between sides of battery and case so a small amount of convection occurs. Once one part of battery is warm most of the battery is near the same temperature especially since there are not a lot of watts involved (very slow heating) so heat is equalized well. Lithium conducts heat extremely well.
Putting heaters on bottom places weight on them and possibly some movement so reliability could be less. BMS is on top of battery so placing heaters above it possibly would not transfer heat as well to battery (likely would work) and I am not as comfortable applying heat directly above BMS for durability reasons. Most of this is speculation on my part, though.
I will be using batteries in very cold conditions in January or February. If anything interesting occurs I'll try to check back in. Some of use will be in Colorado and New Mexico. Last year it was in the teens...
@@TimCompton-q8n A very thoughtful reply as always, Tim. Thanks
I would place the heater under the battery simply because you stand the greatest opportunity for direct battery cell contact. I doubt the cells are even touching the case on the sides but the bms might be. You would need to open the battery to see
Are you sure you need Normally Closed temperature switches? Wouldn't you want the circuit to be normally open umtil the temperature reaches 5c or lower?
@@El_Rudo It’s a little confusing, but you want the normally closed version. A normally open switch will turn the heater on whenever the temperature goes above 40 degrees - the opposite of what we want.
@@JustALittleFurther thanks for your response. Yes, the NO/NC concept is doing my head in when it comes to these temperature switches. Even asking AI like Gemini and GPT I am getting different answers depending how I phrase the question. I just wanted to make sure before ordering because It almost ordered the NO version. So if I wanted to go belt with suspenders for safety, could I also put in say a 20c NO temperature switch, like someone else mentioned in the comments? My intention would be to shut the whole thing down if the external battery temperature hit 20c. I am going to have a master physical switch to turn the circuit on when the temperature during the day gets to below 10c.
Nice vid. I just tried this with the pads underneath and thin sheet metal on top to spread heat out. Didn't seem to work. The pads are fine without the thermal switch (get really hot)...but hardly anything with the switch installed. So what i dont get is how its meant to heat up if it comes on at ~5°c then turn off at ~5c too ?
@@charleswillard775 The heaters have some hysteresis. They don’t heat up or cool off immediately. When the batteries reach 5C, the switch turns the heater off, but it takes a while for the heating pad to cool down, and the temperature keeps rising for awhile. The reverse happens when the temp drops below 5C… it takes awhile for the pad to heat up again, so the temperature of the battery continues to drop. Hope this helps, and glad you liked the video.
@JustALittleFurther thanks for the explanation
Battery will rarely be right at 5C and will be below 5C when heaters are warming it up (staying on non stop) and heaters always off when above 5C. When battery is around 5C it will cycle on/off to keep it around 5C, which is great.
A well done video. Nice presentation👌
Glad you enjoyed it and thanks for the feedback!
Based on tests, I am not concerned about four heaters in series negatively affecting battery temperature sensor.
As far as four 25W heaters wired in series/two per battery:
Heaters kept battery above 32F while in 15F freezer for two days using power from power supply 12.8V. Insulation a little higher R-10 (repurposed material, not a recommendation for better insulation). Batteries were not in use, which generates some heat.
Surface temperature between heater and battery 123F-comfortable for battery ABS housing durability. Wiring 1, or 2, 3 in series generate higher temperatures (be careful!), while just one generates highest. Five in series would generate lower temperature so not recommended.
If more heat is desired using in sets of four in series might be wise, i.e. four with each battery. This would heat batteries less slow. Heating with two could take a day or two if heating from 20F to 32F.
General information:
• One heater provides 25W 2A @12V. Two in parallel 50W 4A. Two heaters in series provide 12.5W 1A TOTAL (counterintuitive for most). Four is series 25/4= 6.3W total, so while using two of the sent on a single battery 6.3/2=3W .5A total for two heaters per battery. Calculated and measured.
Hows it working for you so far
It was working great while we were in colder areas. We’re back in Vegas now, so it’s not cold enough to come on anymore, so I’ve switched to summer mode, and removed the insulation.
@@JustALittleFurther I got all the supplies you recommended. I'll install it all in the fall. Thanks for the great advice
Author used Senasys snap disc: with close 35F, open 45F, +/-5F tolerances. Other options, purchased directly from Senasys (no free shipping), are close at 40 and 50F. I am not recommending a change.
I tried one higher temperature disc (needs to be higher to allow controller to control temperature) and INKBIRD ITC-1000F--Adjustable Temperature Controller (Amazon). This is not as clean a design and more effort to use--has more wires/connections, have to set desired temperature (a little clunky), if power is lost controller turns off (settings saved), where to place/mount controller... I suspect two discs (like author's design) are more durable/reliable than controller.
Anderson Power Pole connector work well for removeable connections.