# Heating The Batteries In Winter?



## Ethos Electric Vehicles (Sep 24, 2012)

In our vehicles we convert we provide a warm water loop at the bottom of the battery box with a digital thermostat built in. When charging it can be heated automatically with the hot water heater we install in our conversions and if needed it can be heated while underway but we provide enough insulation that we have not had much need while underway. But you can also go the inexpensive way and use a under tank heater from a reptile pet store but be careful, they cannot have anything resting on them or they may short out.


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## tomofreno (Mar 3, 2009)

the gas wizard said:


> *has anyone ever tried to preheat the batteries while charging them in the winter to get better range. i was thinking of putting a nitrous blanket around each battery to keep it warm. ......any ideas?????*


 Do a search. A number of posts on this site. I used the Farnum heater pads from kta-ev.


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## dtbaker (Jan 5, 2008)

or variable output wire (can use either AC or DC!) from heatline.com


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## kickngas (Feb 3, 2011)

How hot can the electrolyte get before the cells begin to degrade or otherwise become damaged? I have heard 110 degrees was a high end cut off temp.


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## rwaudio (May 22, 2008)

I have my EMW 10kW charger in my insulated battery box with the cells and it got below 0C last night (we had snow!!! blah!!!) but the battery box was 20C this morning, so between the heating of the cells as they charge and the waste heat from the charger things stayed toasty. I may have to watch it in the summer time that things don't get TOO hot.


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## Zak650 (Sep 20, 2008)

Is there a problem using regular old water pipe heat tape used to keep your pipes from freezing? It's got a built in thermostat/relay just to keep things moderately warm.


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## dtbaker (Jan 5, 2008)

Zak650 said:


> Is there a problem using regular old water pipe heat tape used to keep your pipes from freezing? It's got a built in thermostat/relay just to keep things moderately warm.



typical pipe tape relay only works with AC and will fry when used w/ typical pack voltage DC, and cord will overheat/melt/burn if you have any overlaps. 

much safer product is from heatline.com self-regulating (variable resistance) line that will work w/ either AC or DC


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## mizlplix (May 1, 2011)

Insulate the battery boxes well. It works both ways, summer and winter.

OK, crazy maybe...

Put a hand held hair dryer into a hole in the battery box with a vent at the other. It comes on when charging. They run on AC or DC, the pack or the 120VAC charger input. My son uses one as a windshield defroster in winter.

In summer, switch off the heating coils and just blow air through the box to cool the cells being charged.

I use a marine bilge pump blower to cool mine.

Miz


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## Antoine (Nov 2, 2020)

Are insulated battery boxes ok for the summer? If I switch off the heating pads during the summer, won't the batteries still get hot in the summer with all that insulation?


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## dtbaker (Jan 5, 2008)

mixlplix use of a hairdryer is not a bad approach.... I would say it REALLY depends on your local temps, and whether you typically charge in a garage or outside. The closer the batteries are to 70 F, the better. anywhere 60-90F won't have much effect in capacity.

If you store/charge the vehicle outside, and temps drop below freezing, you may have problems.

In my case personally, EV parked/charged in my garage never drops below 60 in the winter, and on snowey/cold winter days I usually don't drive it, so I decided NOT to insulate or heat battery boxes. I have more concern with summer heat which commonly hits 85-90 on summer days; not a problem unless car is parked in the sun all day and the engine bay and trunk can hit 120F.


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## Antoine (Nov 2, 2020)

I live in Ottawa, where it can get as cold as -22°f on the coldest days. I pretty much have to insulate and heat up my batteries. I am just wondering if the insulation is going cause the batteries to overheat in the summer when driving aggressively?


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## dtbaker (Jan 5, 2008)

aha, now I understand your question a little better. 
Good news for you is that the resistance in lithium batteries is very low... and even with 'aggressive' driving, you are not likely to be under heavy loads for minutes... more likely just 10-30 seconds between stoplights, right?! I drive my eMiata pretty hard, commonly accelerating pulling 800-900amps, but only for maybe 10 seconds; my battery boxes are not ventilated, and I've reached back and felt the battery bus bars after some 'acceleration events', and they are barely warm. I don't think air cooling vents would dump much heat off the battery cases anyway... so I have had decent durability not worrying at all about ventilation/cooling battery boxes even with regular 5c-10c accelerations.

If you were racing, with higher 'duty cycle' full on, or have an AC motor with regen pumping energy back in... THEN I'd consider cooling an issue, but also encourage fluid cooled heat sinks, not just convective air cooling.


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## brian_ (Feb 7, 2017)

Antoine said:


> Are insulated battery boxes ok for the summer? If I switch off the heating pads during the summer, won't the batteries still get hot in the summer with all that insulation?


Yes. But depending on your climate, that might not be an issue. I would be concerned about hard driving on a hot summer day in Ottawa, but as Dan suggested, it might be okay.


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## Antoine (Nov 2, 2020)

Ah okay thanks a lot for the info!


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