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Discussion Starter · #1 ·
In an effort to make my van more reliable in cold climates I'm considering adding a battery heater. I have 2 Renogy LFP 100Ah batteries under the drivers seat. I often leave my van for several weeks and the interior of the van drops below 32 deg F which activates the battery's BMS system and locks them out from charging. Im thinking about adding a small heater below them to keep them warm enough to charge. Here is what I ordered https://smile.amazon.com/gp/product/B077VLB1KK/ref=ppx_yo_dt_b_asin_image_o03_s00?ie=UTF8&psc=1. The plan would be to place this under the two batteries maybe with an aluminum plate above it to distribute heat and insulate the sides and top. I would power it off the batteries themselves and while parked I would make sure it was plugged into shore power or I may be able to just power it off the solar system as long as they don't get covered in snow. Has anyone attempted this? I do have the new style Espar gas heater that would also work but would eventually run out of gas. It uses about a gallon a day of fuel when it is really cold out. The van is insulated with wool on the walls and 2" polyiso under 3/4" plywood on the floor.
 

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I like that it has a built-in thermostatic control.
Not crazy about the power consumption. If the solar panels are covered with snow for 2 weeks, wouldn't it drain the batteries?
 

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Discussion Starter · #3 ·
I like that it has a built-in thermostatic control.
Not crazy about the power consumption. If the solar panels are covered with snow for 2 weeks, wouldn't it drain the batteries?
If I insulate it well, I don't think it would be on for a long period. Not sure about how long I can float with it and no sun. I will likely just plug it into shore power.
 

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2014, 138WB, High Roof, Gas, SW MT
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Hi,
If you could insulate the batteries, it would take very little heat to keep them above freezing.

For example, if the batteries are roughly a 1 ft cube with 6 sqft of heat loss area, and you could insulate all the way around with 1 inch poliso (R6), and the outside temp was 10F and you kept the battery cube at 35 F, then the heat loss would be (6 sqft)(35F - 10F) / (R6) = 25 BTU/hr, which is equivalent to 7 watts, or a continuous 0.6 amps. So, 15 amp-hrs for a full day at 10F. If you could do 2 inch polyiso, the power use would be cut in half.

The only down side I see to the insulation is that if you put a heavy load on the battery and it heats up, then it will be harder for it to lose the heat and it will get hotter. Don't know enough about Li batteries to know if this could be an issue?

If you can insulate around the battery, I think a smaller heater would be better.

If you are limited on where insulation can be applied, you want it for sure below the heater.

Is there some way you could put the heater on a timer such that it would turn on a few hours before you plan to get back to the van?

Gary
 

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2017 159, w/dual sliders. SF Bay area
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I like the idea, but I think the range is too much. It doesn't cut out until 68F. I'd look at a little DIY with something like this where you can set the on and off points.


and some 12v heating pad.
 

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I just read a bunch of the reviews.
I have a formula for reviews.
I factor in the most common denominator and the stupid human factor.
If every single review says it's junk and doesn't work, it's safe to say it's junk.
What I saw was that it works fine , but the instructions are bad on how to wire it. Seems like the folks with experience/knowledge of electronics were able to figure out the wiring and programming on their own and then said it worked great. If it was a $40-100 unit, it should be idiot-proof.
But people buy a $15 piece of equip and then complain. That's people.
Anyway, not sure if I need one yet, just saving it for future reference. When you pull it up, other similar units pop up to thumb through.
 

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2017 2500 HiTop 159 Cargo Van white.
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Why would you need to charge them if it is in storage? Just disconnect and leave them alone. They discharge so little that they should be ready to go even if stored for months at a time.
 

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MMXVI - L2H2 in Indiana
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Why would you need to charge them if it is in storage? Just disconnect and leave them alone. They discharge so little that they should be ready to go even if stored for months at a time.
When I read the OP I thought he's looking for a solution to a non-existing problem.
 

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Discussion Starter · #13 ·
Its not easy to pull the batteries out and store them in a heated area and the van is parked for a week or more frequently. Just looking for an easy way to keep them from freezing. I like the $15 thermostat and will likely use it with a smaller heater if I can find one. I can also set an alarm using that device to warm me if they get too hot. Thanks for all the help!
 

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Its not easy to pull the batteries out and store them in a heated area and the van is parked for a week or more frequently. Just looking for an easy way to keep them from freezing. I like the $15 thermostat and will likely use it with a smaller heater if I can find one. I can also set an alarm using that device to warm me if they get too hot. Thanks for all the help!
I agree with you. Since the biggest risk is over heating, it might be worth considering a second thermostat that will kick off if the heater turns on too much.
 

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What's the problem with the BMS shutting off the charger? If you aren't in the van, shouldn't all the loads be off? Lithium doesn't need to be fully charge (in fact if you aren't using the battery for long periods of time it's better to keep them at a lower state of charge). You'd be better off just disconnecting your battery when not in use.

Before my upgrades, I used one of these to turn off my solar charger when below freezing:


You could use this with a normal heating pad or the one you purchased. The relays are good for 10 amps however personally I would never use power just to heat the battery just so I can charge the battery. It doesn't make sense to me. If you are in the van, you are probably heating the van so the batteries should stay above freezing. My option was to just disable the charger. However since your issue is the BMS shutting off the battery I don't see the issue with that unless the battery doesn't turn back on?

Another thing to think about would be a malfunctioning heater pad. Like gary stated, NO batteries like too much heat. This was another reason why I opted to not go down this path. If you do insulate the batterybox, a MUCH smaller heating pad will work just to heat the space inside the box.
 

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2016 136WB low roof diesel, converted to an RV by Sportsmobile, TX
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Or you could run your heating pad directly off the charging power - if there is no charging power, there is no need for heat. If there is charging power, it can run the heater and what's left over can charge the batteries.
 

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The concern is charging frozen batteries, not the batteries freezing or even using the batteries when frozen. It’s a big difference. If you are leaving the van for a while, I’d say best to just disconnect them (can wire a switch to do this). When you get back in and start using the van, you are likely going to warm it back up before you need to start charging.
 

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Remember to switch off the solar at sunrise on those freezing days too.
Yes, if the van is sitting for a long time and getting completely cold, you need to disconnect everything!

FWIW, I'm limiting my comments to the times you are leaving the van sitting for a long time. If you are using it, the risk of the batteries freezing is minimal. We were camping down to about -10º and it was never an issue because we either had heat running or, if we didn't, the electrical system was still running (fan, fridge, random loads, the vampire draw of the inverter, etc.) and easily keeping itself sufficiently warm because all our components were in the same box.
 

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What's the problem with the BMS shutting off the charger? If you aren't in the van, shouldn't all the loads be off? Lithium doesn't need to be fully charge (in fact if you aren't using the battery for long periods of time it's better to keep them at a lower state of charge). You'd be better off just disconnecting your battery when not in use.

Before my upgrades, I used one of these to turn off my solar charger when below freezing:
There are two views about using a BMS (battery management system) to turn the charger on and off based on battery temperature:
1) One view is that a single sensor is just fine for running a control system and no back up is needed
2) Another view is that the BMS is there as an "emergency backup" in case the normal controllers such a charger, temp control, etc fail to perform correctly

At this very moment, Boeing has a whole bunch of 737s parked in a big lot because of just one instance of thinking in terms of (1)

Similarly, there are two views about the power system being on vs off when parked at an airport.

I may or may not turn off the inverter, but in general, my electrical system is designed to be turned on - and stay on.
 
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