Lithium auxiliary battery and cold weather charging

jimbob394

Adventurist
Hey guys,

I have a rather particular question that I'm just trying to feel out as I want to develop a product and possibly bring it to market if it makes sense.

I currently have a lithium auxiliary battery mounted in the bed of my truck (which has a topper on it). I live in Colorado and winter is coming up, so its going to get cold. I'm sure everyone knows that you can't charge lithium batteries when the battery temp is 32 degrees F and below. So since I can't use engine heat to keep the battery warm and a battery doesn't generate much heat by itself to warm itself up from use (even if I have it wrapped in a thermal wrap), I'm looking to develop a thermostatically controlled DC powered battery heater.

So this leads me to my question for everyone:

I'm curious how many people use a lithium battery as their auxiliary/house battery and have it mounted somewhere that isn't temperature controlled and live in a colder climate that can get below 32 degrees F.
Also, if you were in my situation, what would you do to heat your battery up so it can charge in cold weather and maintain near its rated capacity? Or if you have any product recommendations that would work - it has to be DC powered, not AC.

Thanks,

Jimmy
 
Is plugging it into a charger when you're at home an option? In California it's less of an issue because we can use solar to keep the battery heated. But I would say if you have a sizeable panel up top, take some measurements for a day when it's rainy or cloudy or snowy. something as much as 25 watt hours might be enough to keep things above freezing if it's properly insulated.
 
Is plugging it into a charger when you're at home an option? In California it's less of an issue because we can use solar to keep the battery heated. But I would say if you have a sizeable panel up top, take some measurements for a day when it's rainy or cloudy or snowy. something as much as 25 watt hours might be enough to keep things above freezing if it's properly insulated.

Kalieaire,

Plugging it into a charger at home isn't an option in this situation. I'm particularly talking about boondocking during winter or using the battery when its cold out. The battery also is in a hard to get to place and I'd like to keep it wired up all the time.

I'm not sure your solar option would work because lets say the battery is already below 32 degrees, it wouldn't be able to charge, but would still be able to discharge until 14 degrees F (my battery in particular).
 
Perhaps a 12v silicone battery pad heater with a temp regulator hooked up to solar.

https://www.amazon.com/Waterproof-Silicone-Flexible-Heating-60MM/dp/B010B2A3KI

Hey Greg,

I've been looking at these as well as Polyimide style heaters, but I just can't seem to find the size I want. These might be the only option though, and I'll just have to suck it up and using something smaller, but who knows they may be enough heat.

I have a pair of motorcycle grip warmers that I never installed on my dual sport, so I may try to test those first to see if that's enough wattage.

I'll have to look into the different sizes available for the silicone heaters.

Thanks for the suggestion!
 
Kalieaire,

Plugging it into a charger at home isn't an option in this situation. I'm particularly talking about boondocking during winter or using the battery when its cold out. The battery also is in a hard to get to place and I'd like to keep it wired up all the time.

I'm not sure your solar option would work because lets say the battery is already below 32 degrees, it wouldn't be able to charge, but would still be able to discharge until 14 degrees F (my battery in particular).

Well the goal is to keep it at a standard operating temperature.

For example. YMMV, but a 100w panel could get about maybe 320 watt hours on a clear December day in Maine. On a 10watt heater like Greg mentioned.. twice.. and me inferring it previously, it could put in enough heat. Your battery in a box in winter trying to keep warm is basically a jug of water with a slow leak. Obviously if you're heating it up more than it's leaking heat, it'll stay within operating temperature.

The question comes down to how long do storms last between cloudy days? If the heater is running at 10w burning 240watt hours a day and you have a 100 amp hour battery at 12v, you have 5 days of storage. If you drive your vehicle, then your battery can charge during dark hours too replenishing your reserves.
 
Maybe way over complicating things, but you could do a diesel fired heater for the engine coolant and run a loop into the battery box as well.

Boondocking with a camper? Can you run a heat duct to it?
 
Maybe way over complicating things, but you could do a diesel fired heater for the engine coolant and run a loop into the battery box as well.

Boondocking with a camper? Can you run a heat duct to it?

Java230,

No camper on my truck, it's just a topper from ARE - so no insulation, unfortunately. Your heater idea sounds like more than I could tackle lol. I'm good with electronics, but not sure I'd be comfortable messing with the coolant loop.
 
Java230,

No camper on my truck, it's just a topper from ARE - so no insulation, unfortunately. Your heater idea sounds like more than I could tackle lol. I'm good with electronics, but not sure I'd be comfortable messing with the coolant loop.

They are really pretty simple, but understand the not wanting to deal with the coolant, but if its the rig in your avatar it would like warm coolant too ;)

Im going to agree with the others and say a small 12V heat pad, insulated box and a solar panel will be the easiest route then. Not so good on snowy days, but you can run the truck as needed also.
 
I went ahead and bought two 12v 20w silicone heating pads. My plan is to create an insulating battery wrap with these wired inside the wrap. I have heavy duty vinyl material, thinsulate, these heating pads, and nylon webbing so that it can be adjustable to different battery sizes. I'm modeling it after a product from Hotstart, except this will be 12v and not 120v.

https://www.hotstart.com/assets/ProductImages/f25ed7255f/HOTSTART-UL-Battery-Wrap.jpg

For the wiring part - I'm going to be using a W1209 12v thermostat (https://www.amazon.com/Generic-Temperature-Control-Thermostat-Thermometer/dp/B00Q6WQJ2O ). Its going to have a battery terminal temp probe and be connected to two power sources - the ignition for when the truck is running and solar for when I'm camped.

The thermostat will have upper and lower temperature bounds, so if the battery reads lets say 35 degrees, the thermostat will kick on the heating pads utilizing one of the two power sources until it reaches a set temp such as 77 degrees, where it will then shut off. This way the heater is always keeping the battery within its charging temperature range.

My set up is a bit unique - I have a Cargoglide tray in the bed of my truck so the only space I can fit the battery is between the tray and the interior side wall of the bed. This leaves juts about zero room for a box or anything else, so that is why I'm creating this wrap.

If you all have any ideas that you think would help, let me know!


Thanks!
 

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The best insulation will have the following two properties:
  • Radiant Barrier (Reflective)
  • Prevents air circulation
So 2 layers of Mylar with LDPE (Low Density Polyurethane) foam. LDPE is closed cell packaging material you might see electronics inside. This material is good because it's pliable (to a degree), lightweight, and has small bubbles which inhibit convection.

When you're designing a thermal isolation system, it's very basic to identify potential losses.

  • Conduction, how heat is transferred by touching something
  • Convection, how heat is transferred by the flow of air
  • Radiation, how heat is transferred by infrared radiation, and to a lesser degree, visible light.
Radiation is controlled by the radiant barrier
Conduction and Convection are controlled by the LDPE insulation.

You don't need a crap ton, but you need to be efficient in its build so that it addresses each of the methods of heat transfer. If you can get your hands on Aerogel, definitely use that. I think it has an R-Value of 10 at 1" thickness. LPDE is like 6.25. Vacuum insulated panels, ~30-50, great, probably way too much for what you wanna do. Also keep in mind, when you USE or CHARGE your battery, the internal resistance and the change in chemistry will release energy as well. And so well that it might be even more efficient than a heating panel.
 
The best insulation will have the following two properties:
  • Radiant Barrier (Reflective)
  • Prevents air circulation
So 2 layers of Mylar with LDPE (Low Density Polyurethane) foam. LDPE is closed cell packaging material you might see electronics inside. This material is good because it's pliable (to a degree), lightweight, and has small bubbles which inhibit convection.

When you're designing a thermal isolation system, it's very basic to identify potential losses.

  • Conduction, how heat is transferred by touching something
  • Convection, how heat is transferred by the flow of air
  • Radiation, how heat is transferred by infrared radiation, and to a lesser degree, visible light.
Radiation is controlled by the radiant barrier
Conduction and Convection are controlled by the LDPE insulation.

You don't need a crap ton, but you need to be efficient in its build so that it addresses each of the methods of heat transfer. If you can get your hands on Aerogel, definitely use that. I think it has an R-Value of 10 at 1" thickness. LPDE is like 6.25. Vacuum insulated panels, ~30-50, great, probably way too much for what you wanna do. Also keep in mind, when you USE or CHARGE your battery, the internal resistance and the change in chemistry will release energy as well. And so well that it might be even more efficient than a heating panel.

Thanks Kalieaire for the great info!
 
That looks pretty cool! Only bad thing is that I have a quite large non standard battery size - it's the Renogy 170Ah lithium battery that is 14" x 6" x 10.6". Plus, I have it mounted and hooked up to an electrical panel I built already lol. But that is a really cool product/idea. Wish I saw that before I had set up everything!
 
There's a Group 31 version of it and that's close to the size of the Renology. Good chance it would fit.

Something to bookmark for later if you get the itch or have a need to reorganize.
 
I mean, if it needs to be sealed, pretend you're making a fish tank w/ plexi or similar plastic, add insulation, drill in holes, blind tap them, and put a cover on top.
 
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