Warming a 200ah LifePo4 in the car?

[uksuntimes]

As part of rebuilding my car 12v solar/power system that I use for camping, I am looking address how I install/care for the battery itself.

We don't often get below freezing here, but it does happen.

To that end, I have started looking at how I might warm my batteries. I've seen suggestions for heat pads, seed warming pads, tank warmers etc.

But alongside this, people also talk about building enclosures for the batteries, and then a wide mix of different insulation methods.

My question is, would it be suitable to use something already made as my enclosure to save a lot of extra materials and build costs.

I have discovered that there are lots of 'bags' available such as these (attached image).



Would getting one of these that fits my battery be a suitable approach? Perhaps even over sizing it, and then either adding some kind of thermal blanket or similar?

Or are there also suitable ready made 'boxes' that exist?

Or do I just have to bite the bullet and figure out how to make a box? Which then raises questions such as what materials, how to secure the battery inside etc.

I'm just starting my journey on the storage/warming side of things and the number of approaches, materials, problems and solutions is quite overwhelming.

For reference, my current battery is a 200ah Renogy with bluetooth, but no internal heating.

Ultimately I just want the simplest way to keep my battery at a good temp inside the car (seat area).

Any suggestions welcome. I will keep reading more of the posts on here that are available already as well.

 

[uksuntimes]

Though oddly, their specs suggest 0 degrees c is within charging range. But I doubt that massively.

 

[Doggydogworld]

Very slow charging at 0 C sounds feasible. Bags should work ok, but it's easier for a box to have thicker walls and use higher R-value materials. Corners and zipper areas are most vulnerable to leaking heat. I question handle strength on some of those, too, ha.

Without heating even an insulated battery will eventually reach ambient temperature. If the battery is constantly charging or discharging it will generate internal heat, but if it just sits there for long stretches you might still need a heat pad.

Insulation can lead to overheating, especially during fast charge/discharge. So you need to think about that. If you only use it once in a while you could just pull it out of the bag. But if it's in use 24x7 you need a solution that works for both cold and hot temps.

You can also just control the car's interior temp. Easy to do in an EV, less so with a combustion engine.

 

[uksuntimes]

Thank you for the considered reply and thoughts.

While I am 'away' the battery is in reasonably constant low current use for lights and 12v fridge. With solar topping up as sun allows.

The car engine is not really run though, so no heating from the car for the 2-3 days. I sometimes turn the car on to top up the battery from the alternator at about 50amps if weather isn't great, but not really any time for the car to get warm in the cabin.

Plus the cabin is generally open at the tailgate other than during sleeping. So I do feel box/bag temp regulation is going to be best.

But I also share the concerns about too hot as well.

The ideal for me would be to just have a 'bag' or suitable 'blanket' that goes over the battery when it's cold and is left off when it isn't. But that isn't particularly scientific or suitable So the investigation on options continues.

If I could find a suitable box, I'd pull the trigger on that, but finding something that fits the massive dimensions of the battery without also being impractically tall is proving tough, but I am sure not impossible. Even tool boxes are all either 2cm too small or massively oversized.

However, one thought is that I could get a box and then simply cut it down to size from the bottom. That way the lid would still work and I can just reattach a cut out of the bottom.

Sorry, this is a lot of 'thinking out loud' but I appreciate the space as it is helping me figure a plan slowly

 

[Alkaline]

Sun Fun Kits 12v Heated Jacket for Lithium Batteries. Insulated with up to 100 watts of heating. 5 Heating Modes: ECO, MEDIUM, and EXTREME along with 2 timer modes 12 Hour, and 24 Hour. 1" Thick insulation 1680 DN water proof nylon fabric.

Sun Fun Kits 12v Heated Jacket for Lithium Batteries. Insulated with up to 100 watts of heating. 5 Heating Modes: ECO, MEDIUM, and EXTREME along with 2 timer modes 12 Hour, and 24 Hour. 1" Thick insulation 1680 DN water proof nylon fabric.

www.sunfunkits.com

 

[uksuntimes]

Thank you so much for the reply.

As it happens I have just managed to FINALLY find a toolbox that will fit the massive battery while still also fitting in the vehicle

The question that remains now is, what insulation (if any) to add inside and or what heating pads. I would love any recommendations on that front

I did have to cut the front lip off the toolbox with a saw, but that took 1 minute and now the battery fits perfectly, with lid closed, including plenty of space for cable work etc.

I will also drill additional holes to ensure it is not even remotely possible to become air tight.

 

[uksuntimes]

I think someone suggested Rock Wool?

 

[SeaGal]

My insulation, albeit for a static environment, is 50mm PIR/Celotex, but don't see how that would fit in the box.

 

[SeaGal]

Yesterday am: at 07:30.... garage temp -1C; LiFePO4's 22.6C
50mm celotex and 21W of heat, on about 50% of time
(that's for a large 14.3kWh 48V 280Ah system, btw)

 

[uksuntimes]

My insulation, albeit for a static environment, is 50mm PIR/Celotex, but don't see how that would fit in the box.

Thank you. I will investigate.

I'd imagine that thinner versions (e.g. 30mm) would still be better than nothing at all. That said, I do have room around all the sides even though it doesn't look it in the photo. So perhaps I go thicker all sides, then thinner on bottom and top (but as much as can be fit).

It may even be combining it with another material (e.g. foil) could adjust the properties. (EDIT: I see that material has foil already, what I meant to say is I could add more foil layers to it)

Really appreciate the heads up on the material, will do some investigation.

 

[uksuntimes]

Yesterday am: at 07:30.... garage temp -1C; LiFePO4's 22.6C
50mm celotex and 21W of heat, on about 50% of time
(that's for a large 14.3kWh 48V 280Ah system, btw)

Do you put your warming pads outside or inside of the insulation?

My general thought was
- warming pads on the bottom of the box
- insulate the box bottom, lid and walls (attach to the box rather than the battery)
- Then place the battery inside
- That way the pads would be less likely to create any hot spots on the battery and instead work to turn the entire box into a sort of gentle heater

Either that, or use a seedling warming mat in a similar fashion. I've not yet got to how I will actually add heat/what pads etc as yet.

 

[SeaGal]

Inside. Also use an STC-1000 thermostat or similar to turn it on / off.

 

[Coydon]

I think someone suggested Rock Wool?

For what? It's tiny ceramic fibres break off easily to become airborne and will persist in the lungs as an irritant. Sheep wool would work, and could be free if you know a Shepard that doesn't have other use for their discards...

 

[SeaGal]

Sheep wool would work

Might be a bit smelly... and isn't lanolin flammable? ?

 

[OTRwSolar]

We found 24w of heat would keep a 12v 4s 200ah cell pack (OP's battery is 200ah) at 60f while exposed to ~0f. The cells were placed inside a plastic Group 24 battery box with a top attached. No insulation was used. Four 80x100mm 24w heating pads wired in series/parallel (total combined heat output of all 4 pads was 24w) were attached directly to the cells using aluminum HVAC tape. During the winter kept these cells at approx. 50 - 55f using a thermostat.

Insulation will certainly improve heating efficiency, but I'm not convinced it's mandatory to achieve satisfactory results. We didn't use insulation for this particular pack due to space constraints. Had maybe 1/8" of remaining space after shoehorning this pack inside a small outside compartment.

Someone in an earlier thread suggested using approx. 1w of heat per a kg of cell weight. I believe that's a good starting point. There's a number of variables at play, but generally speaking, I believe 1w/1kg, along with "some" insulation should be capable of maintaining cell temps above 35 - 40f with ambient temps as low as 0f. Although I've been focusing on the amount of heat, distributing the heat evenly, throughout as much of the exterior area of the cells as possible, is equally important---don't want hot-spots. Also, for situations where a heating pad may be producing excessive heat (or only high wattage pads are available), a PWM (pulse wave modulator) may be helpful in fine-tuning heat output.

 

[SeaGal]

We found 24w of heat would keep a 12v 4s 200ah cell pack (OP's battery is 200ah) at 60f while exposed to ~0f. The cells were placed inside a plastic Group 24 battery box with a top attached. No insulation was used. Four 80x100mm 24w heating pads wired in series/parallel (total combined heat output of all 4 pads was 24w) were attached directly to the cells using aluminum HVAC tape. During the winter kept these cells at approx. 50 - 55f using a thermostat.

That's great real-life feedback for the OP, who probably does have a lot of space

 

[uksuntimes]

We found 24w of heat would keep a 12v 4s 200ah cell pack (OP's battery is 200ah) at 60f while exposed to ~0f. The cells were placed inside a plastic Group 24 battery box with a top attached. No insulation was used. Four 80x100mm 24w heating pads wired in series/parallel (total combined heat output of all 4 pads was 24w) were attached directly to the cells using aluminum HVAC tape. During the winter kept these cells at approx. 50 - 55f using a thermostat.

Insulation will certainly improve heating efficiency, but I'm not convinced it's mandatory to achieve satisfactory results. We didn't use insulation for this particular pack due to space constraints. Had maybe 1/8" of remaining space after shoehorning this pack inside a small outside compartment.

Someone in an earlier thread suggested using approx. 1w of heat per a kg of cell weight. I believe that's a good starting point. There's a number of variables at play, but generally speaking, I believe 1w/1kg, along with "some" insulation should be capable of maintaining cell temps above 35 - 40f with ambient temps as low as 0f. Although I've been focusing on the amount of heat, distributing the heat evenly, throughout as much of the exterior area of the cells as possible, is equally important---don't want hot-spots. Also, for situations where a heating pad may be producing excessive heat (or only high wattage pads are available), a PWM (pulse wave modulator) may be helpful in fine-tuning heat output.

Thank you. Super useful insight and data. And relevant to my own adventure. Appreciate you taking the time to share.

 

[JRH]

For what? It's tiny ceramic fibres break off easily to become airborne and will persist in the lungs as an irritant. Sheep wool would work, and could be free if you know a Shepard that doesn't have other use for their discards...

Uhhh,,, yep……silicosis isn’t a good thing … it’s easier to develop than many think…many common day items things can cause it…

 

[suimei]

The flow of the story so far is completely consistent with my prototype. Four 100A battery packs are placed in an aluminum case and the case is kept warm by an 18W heater and a PID controller.