somewhereinusa
Solar Enthusiast
Looks interesting, was able to find the same thing in US. About $10. Saw one complaint that said it didn't get warm enough. Don't think I would want to power any heating element from a usb port.
LiFePO4 heating pad for cold temperatures
- Thread starter Will Prowse
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somewhereinusa
Solar Enthusiast
You are correct, I'm waiting on some parts from China to try building my own. It's not going to be flexible though.
brassmonkey001
New Member
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No, I'd cut the end off and connect it in a more robust fashion.
brassmonkey001
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Freezing point i.e. 32F or 0C although I wouldn't take that as an absolute, I'd want to add in a safety margin e.g. 41F or 5C.
No, it can't be too hard, I wouldn't have thought.
eddie1261
Solar Enthusiast
Typically here in Northeast Ohio we see a stretch of 10-12 days where the temps are below zero. I hope to make my trip during that cold snap. It cost me an RV battery 2 years ago because it wasn't until the 3rd night of -9 to -12 that I thought to put the trickle charger on it.
The Ruixu is something like 14x10 and if I got 2 that fit around the perimeter I could then also put a thermal blanket on the top of it to hold the heat in. That would protect it on 5 of 6 faces. With the warming pad on low that should keep it warm but not hot.
Very interested to see if anybody can make a 12V pad though. For the science of it. In my case I have a spare 12v plug right on the control board to plug it into and with the one for the fridge, that I don't need when it's cold, I have 2 of them available.
The Ruixu is something like 14x10 and if I got 2 that fit around the perimeter I could then also put a thermal blanket on the top of it to hold the heat in. That would protect it on 5 of 6 faces. With the warming pad on low that should keep it warm but not hot.
Very interested to see if anybody can make a 12V pad though. For the science of it. In my case I have a spare 12v plug right on the control board to plug it into and with the one for the fridge, that I don't need when it's cold, I have 2 of them available.
offgriddle
"FOREVER BEGINNING"
Hmm 2 amps per hour is not much, (it's too much current draw for me at my present, meager ability to generate and store amperage but fortunately my batteries are in an insulated box in a six foot deep root cellar blocked from any wind movement), but if someone can spare 24 amps per day for battery heating then it's fine.
eddie1261
Solar Enthusiast
Can't get it in the US though, so 1/7th of us can't get it.
somewhereinusa
Solar Enthusiast
Amazon US
Duokon 5V2A USB Electric Cloth Heater Pad
Available, although it looks like it ship from China by the shipping time. You can also get them on ebay but, they all ship from China.
Bob B
Emperor Of Solar
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Some inexpensive ones here .... but not much info for specifications. https://www.ebay.com/itm/Red-9x5-Wa...omatic-Thermostat-for-RV-Camper-/173730225434
This, of course, assumes you have power in the first place!
Could a person use heating cable wrapped around the batteries. It normally keeps things at 35-40F and they often have a thermostat in them so it doesn't run all the time, it will run only when needed. It's used to keep pipes from freezing. Why anyone would install water supply pipes in an outside wall in Michigan is beyond me, but they did at my old house. How this passed inspection is also beyond me.
There are also bare Chinesium heater pads that run off 12v but I would not use those for expensive batteries. What about an electric blanket? Reptile heater stone? I'm just swingin' wild here!
There are also bare Chinesium heater pads that run off 12v but I would not use those for expensive batteries. What about an electric blanket? Reptile heater stone? I'm just swingin' wild here!
45C is 113F. Probably too hot for a battery.
brassmonkey001
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Yes, that's why it would need a controller to switch on when it drops below 10°C and off again when the batteries reach 15°C or thereabouts.
Dang that tape is kind of cool. I just upgraded my heat setup using a 3d printer silicone heat pad + aluminum 1/4" plate as a raised floor (minutes ago)-initial test in progress. Turns out there isn't a lot to be had in the USA &/ ETA < 6wks in the 12v flavor and with acceptable wattage/size. I ended up with a 120w 12v 120x120mm w/ thermistor.
The previous setup was an incubator heater (12v 100w and 60mm fan, measured high 92w @ 13.34v on Victron BMV) and never got used in the wild. Not that it didn't work - it passed all tests (sitting on my patio in 20*F) - but fan crapping out was a concern and I wanted to control both the fan and its heating element separately. Even got PID control working on the heating element but I disliked the thought of fan failure, relay sticking on, more wires in an increasingly cramped enclosure, yadaya.
Anyway, on to the new...
A microcontroller paired with a 3d printer heat bed module MOSFET operates the heat pad at the perfect temperature (as measured by the incorporated thermistor) so the floor will never really deviate from the setting. Once it's up to temperature it only requires a trickle of wattage to maintain in open air tests (maintain 120*F in 66*F ambient, still air..) , so I'm hoping this will be a tiny amount of draw once I throw it in the truck and the box it'll reside in is all sealed up, just trying to maintain like 47*F
Heat pad $16 (or pick anything with better dimensions for your build, or a full wrap, or something from the slow boat)
Some serious aluminum $27
A 3.3v suitable initial switching MOSFET module $9
One of the two of this 2pk of 3d printer heat bed modules, so $5.50
A $5 arduino nano clone, or a $19 particle photon, or a ESP8266/esp32 dev module for $8, whatever
Some jumper wires from a many-hundred pack
A breadboard
This is a 12 watt heater without incorporated thermistor. I ended up ordering two of these, advertised as bee colony warmers or something. Could have made them work but weren't adhesive backed and were less durable than the one in the parts list that I ultimately used. These seem like the standard fare silicone heaters that you'd get from China, and they heated well. Shoo, I might have been able to get by with a single 12w pad... but I wanted to be sure, and I liked the durability and 3m backing of *
^ the aluminum doesn't really have a hot spot even operating the pad at 90w. Maiden test capped at 50w. But still, added a strip of silicone from a cheap 3pk of silicone baking sheets from amazon. It's nice and nonskid, thin, transfers heat well, felt like the right thing to do after drinking a lot of beer and looking in to a stupid box for 3 hours with my hands on my hips like a dingaling.
^the same cell holding strategy as in the initial incubator fan heater. You can see why this wasn't really a great solution when the heat was blasting from the opposite side of the can, hitting a wooden wall, trying to maintain a hunk of cells.
loaded... more insulation has been shoved around certain places, cells have been locked in place from movement in any direction, ceiling on top of the whole shebang with BMS and other crap mounted on it...
I'm going over the top with this project but for simple insanely consistent heating... give DIY control some thought. Plug some wires in to numbered holes, connect some positive and negative wires to screw terminals, copy paste 20 lines of code and press play. Aluminum is biggest expense. My hope is that this heats slowly from the bottom so I don't get the BMS or Victron BMV prematurely enabling charge because... heat rises and stuff.
Edit: it's been like 2 hours running the plate at a maintained 78.5*F and is requiring about 8 watts to do this, installed, cells atop it. Starting temp was 67*F combined avg between BMS' onboard temperature reading and its separate probe. In that 2 hours time I've reached 71.6*F combined. This is not a fast heating solution so if I ever program it to shut off it'll be right after sundown, turning on many hours before sunrise. If I can leave it on permanently I'm just going to do that.. and I have a feeling I probably can. Low and slow works for me.
A mildly interesting observation is that it was taking like 0-4w to maintain 120*F in 66*F ambient, open air, plate just sitting on that wooden donut on my coffee table. That was reached in 2 minutes according to thermistor reading, and plate was warm-warm after a few additional minutes of soaking. Guessing the cells and all the materials are sucking heat off the plate which is requiring more to maintain
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eddie1261
Solar Enthusiast
Does cold come into play at the same temp for lithium as it does for lead acid? We are staring to see mid 30s overnight here and I don't know when I need to start caring about cold for my Ruixu lithium. It's in the 50s all day with bright sun so I don't want to take the battery out of my trailer yet. I know if we get those awful temps below zero that my battery will be inside with me where it doesn't get below 66. I just don't know where the line is. I assume when it is sustained temps at or below freezing may be a good gauge.
somewhereinusa
Solar Enthusiast
Lithium batteries don't like to be CHARGED at or below freezing.
It is indeed an ammo can, 30mm. Not 30 cal. It's giant and incredibly heavy. Still, my total project weight for 200 usable amp hours with an abundance of monitoring, microcontrollers, onboard LTE, etcetc is about the same as a naked 90ah marine deep cycle lead acid
I have a small vent cut that you can see in one of the pictures, where there's an absence of insulating wall. That's where the Victron MPPT goes, and you're right, overheating is a concern. There currently isn't an intake which would logically be placed down low, and I probably won't install one until spring though I have the parts. 40mm Noctua fan and a classy looking two piece grille that includes a filter between the two. My thought was to obviously not run the fan in the winter and install some insulating silver stuff that I used for the walls as the filter. Then when it's warm out remove that blocker and run via PWM speed control. I discovered last night that the fan can't be dimmed to 0%, it's minimum is always 30%. Means another relay to install and more fuss to deal with... later. Anyway, when done, it should force air out directly behind the charger. I know it all sounds puny but it's not like I have an inverter in there.
I really just wanted to flush mount MPPT to the ammo can. The back of it is metal and they say there should be air flow behind it, which I've achieved by elevating it half an inch off the wall (not pictured, of course).. but I would have used thermal paste and stuck it directly on the bare metal of the can for giant heatsink effect. Sadly there's like a 1/36th of an inch lip between the metal backing of the controller which would have required a pond of thermal paste. Later thought about cutting a rectangle of my 1/4" aluminum plate to fit.. but ultimately I have no idea how effective this would have been and didn't want to do anything irreversible or messy.
ianganderton
Auckland, NZ
Just watched Will’s ‘New Tesla’ vidéo and saw at the end the cheap heat pad mentioned. The problem of hot spots was also mentioned.
The easy & simple way to prevent hot spots with any of these mats is to mount them on a sheet of aluminium (or other material with good heat conductivity). This would smooth out any lumps and bumps in the heat produced in the pad.
The thicker the aluminium plate the smoother the heat output will be.
This has me thinking. I wonder how complicated and effective it would be to use an aluminium frame to thermally connect all the batteries to heat and/or cooling sources? Heat pad on one side of the bank, finned heat sink with fan on the other?
The easy & simple way to prevent hot spots with any of these mats is to mount them on a sheet of aluminium (or other material with good heat conductivity). This would smooth out any lumps and bumps in the heat produced in the pad.
The thicker the aluminium plate the smoother the heat output will be.
This has me thinking. I wonder how complicated and effective it would be to use an aluminium frame to thermally connect all the batteries to heat and/or cooling sources? Heat pad on one side of the bank, finned heat sink with fan on the other?
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