Low temps and our batteries

[FFMan]

Here in the UK we have a little cold spell, it was -7.5 this morning. I did put the car in the garage but it was probably still 0c.

What can one expect in lower temps and should i modify my charge behaviour ?

My 21kwh pack charges from a granny charger overnight so its not fast charging but is it ok to charge at sub-zero at all ?

In terms of capacity, what can i expect from the cells in these cold temps. I know lead acid could drop as much as 30% due to cold.

Should i discharge slower by asking less of the pack ?

[johu]

My 21kwh pack charges from a granny charger overnight so its not fast charging but is it ok to charge at sub-zero at all ?

That is C/10. If it's NMC cells you can charge at that rate down to roughly -15°C. LFP I'm not sure.

Should i discharge slower by asking less of the pack ?

By doing that you loose less energy to heating the pack up

[arber333]

What can one expect in lower temps and should i modify my charge behaviour ?

Four years back i had to go to Frankfurt for a meeting by airplane. I had to leave Mazda on the airport for several days outside. It hasnt snowed at the time but temps droped to -3 or -4. So when i came back it was about -1 and it was evening 10pm. I had to get home about 50km away. I still had 70% SOC in my car, that should be 120km.
At first driving the local roads was not a problem so much. I saw somewhat low voltage across all cells. However when i drove on highway ramp voltage droped suddenly and i lost traction due to BMS while ON the ramp. Not cool! I had to nurture the car for like 20km at about 70km/h for cells to heat up internaly. Then i could drive at 110km/h.
But stil when i arrived home i was close to empty! I havent measured the charge going into the car but i kept it low through the night.

[Jacobsmess]

I was reading a little bit about how Tesla's handle this if you drive to a fast charger, they preheat the battery so that it can be fast charged safely.

[DVD3500]

I am programming our cars to do a few heat cycles tonight as it is supposed to get to -11°C here. The Enyaq will be on a wall box and the Jeep Avenger will by on a "granny plug" set to maximum power (3.7 KW I think).

Probably overkill but even if I use 10 KW for each that is only 3€....

[MattsAwesomeStuff]

temps droped to -3 or -4.

I'm in a warmer part of Canada.

It was -38'C here for the last week, -50'C with the windchill.

Doesn't happen often, but, does happen.

People still drove their EVs. There's reddit threads every storm of curious people asking about how EVs handle it.

IIRC you'll get less power out of them, so, maybe trouble accelerating uphill if you didn't have battery heaters, but every EV has battery heaters so it doesn't matter. You can discharge most cells okay, recharging is where you'll need them warm first.

But, if recharging, you are plugged into a wall, and you can use that energy to heat the cells. So, it'll take a bit longer to charge, and, you'll lose a bit of range when driving. Someone who needs to recharge quickly overnight for their entire range might not start the next day back at 100%.

Most of the range loss when driving comes from the fact that you're using so much energy for heat. 6kw heat, when only using 10kw on average in stop/go traffic is a pretty huge hit to range.

...

Honestly I think the best solution for heat in an EV is to have a diesel burner under the hood. Fuels are inefficient at turning chemicals into motion, but they're still highly compact and effective at turning chemicals into heat.

I'm not a purist, if a gallon of diesel a season goes into my heater, I'm fine with that.

Was this you who told me about this a few years ago? It's starting to be time for me to look around for an appropriate under-the-hood diesel heater for cabin (and battery).

[FFMan]

yeah i was thinking about diesel heater. I have a chinese diesel heater off amazon for like £100 and its claims 8kw (feels like 5kw) but 4l of fuel burns at max for 8 hours plus we can use 'red' diesel in so tax is less. I run it in my garage and for the money to buy and run it is great.

My intention is to wire my Outlander heater so i can run up the cabin heater whilst its plugged in, which covers both home and work probably and preheat the car without burning the batteries

there are lots of active forums for CDH (chinese diesel heater) on facebook and people use them all over the place and bar a few known issues they are reliable if not a tad noisy.

[arber333]

I was using this diesel heater connected to car heater matrix. I start it with simple webasto timer and it works for about an hour, then you need to restart it.
https://www.ebay.de/itm/403085271282?ha ... BMhryZkqVj
https://www.ebay.de/itm/291538650098?ep ... R-L6xJKlYw

If you replace the main board with aftermarket one you can simply start it by a switch and it will run at 50% power indefinitely.
https://www.ebay.de/itm/165935736166?ha ... R_DLp5KlYw

Then there are several chineese air heaters. They could be mounted in the trunk and they will blow hot air from the rear. Could be remotely controled for car preheating or camping...
https://www.ebay.de/itm/355172443130?ha ... BM2PS5kqVj

[Ev8]

Personally I think diesel heaters go against the spirit of an ev! Putting a fuel tank back in! But I get the appeal I had one in my camper and the Chinese webasto copies are bloody good for the money, I have my front bmw modules sat on heated seat pads in the box and a couple of 12v ptc fan heaters in the boot with the rear modules but in all honesty they don’t make a huge difference. I have thought about ducting the main cabin heater through the front battery box and back to the boot but that might be tricky, besides I’m pretty sure this will be the last cold snap in the uk for the winter,

[Jacobsmess]

I was using this diesel heater connected to car heater matrix. I start it with simple webasto timer and it works for about an hour, then you need to restart it.

There are several models of the webasto diesel heaters that work by a simple on/off switch, no board change whatsoever. From memory I think they were used in early 2000s Chrysler's and Citroen's amongst others. They are popular in the boating community and have different switching pins depending on the manufacturer. That being said, an hour run time is probably plenty. Others are also can triggered, so given the CAN savviness here, they could probably be easily reverse engineered and implemented

[arber333]

Others are also can triggered, so given the CAN savviness here, they could probably be easily reverse engineered and implemented

The problem for CAN version is that you need to provide another CAN signal for it to operate. So you need to kmow which type of car it was made for...

@Ev8, i never said i went ev route because of anything other than power and ease of use...and some ocd . But to sacrifice range for heating... never! Talking of ev sustainability is easy when 25deg. Try -15 which was yesterday here! I think my ev will thank me for sustaining it with the help of some dino juice. I would love for it to be methanol or other natural juice. Maybe in the future...

[Jacobsmess]

Try -15 which was yesterday here! I think my ev will thank me for sustaining it with the help of some dino juice. I would love for it to be methanol or other natural juice. Maybe in the future...

Make biodiesel from waste vegetable oil then you are away from diesel altogether if that's your motivation!

[Ev8]

Yes I didn’t come into ev’s chasing the eco friendly ideals, in fact with it being -5 here a couple of days ago I have been driving around in a 2.5v6 Mazda bongo rather than trying to get my battery above freezing! But it’s only reinforced how much better I find driving electric

[arber333]

Make biodiesel from waste vegetable oil then you are away from diesel altogether if that's your motivation!

I am not sure biodiesel and webasto...there is some science there and i remember dead webasto heaters reported from using biodiesel. There was sulphur and some other mineral content mentioned. Inside webasto there is a wiremesh which is different for diesel or petrol version. This is responsible to disperse fuel into the chamber which should burn AFTER the mesh. Someone mentioned to me that most defects result from wrong combustion inside the mesh which clogs it with carbon and fuel cant mix with air correctly. I would imagine to burn biodiesel heater would need to be calibrated...

[E46Driver]

I'm in a warmer part of Canada.

It was -38'C here for the last week, -50'C with the windchill.

Doesn't happen often, but, does happen.

Personally I think diesel heaters go against the spirit of an ev! Putting a fuel tank back in! But I get the appeal I had one in my camper and the Chinese webasto copies are bloody good for the money, I have my front bmw modules sat on heated seat pads in the box and a couple of 12v ptc fan heaters in the boot with the rear modules but in all honesty they don’t make a huge difference. I have thought about ducting the main cabin heater through the front battery box and back to the boot but that might be tricky, besides I’m pretty sure this will be the last cold snap in the uk for the winter,

When its in the -38*C range, diesel heat is a welcome "feature". I'm also in that "warmer" area of Canada and I run a China knock-off of a Webasto liquid heater. I have a 4L insulated tank in the back as well as circulation pumps for the batteries. Keeps the batteries around 20*C in my insulated boxes, and I also circulate it through the heater core for cabin heat (along with electric heated seats). However, this is only used down to about -18*C. I do not drive my conversion when its any colder. I guess I'm not a "purist" EV'er. But practicality wins for me - and I can vouch for the use and practicality of diesel heat. I have not tried the bio-diesel in mine, but its good to have it as a "greener" option for the future. I can also confirm that the liquid heating version that I have, is quite noisy when its on full output. Once the liquid is warm, it reduces the burn rate and runs quieter.

[johu]

Don't think you need to bother with biodiesel. At least the german produced one has similar ghg emissions due to the farming and low spacial efficiency of crops e.g. compared to PV. Let alone plant fuels that required chopping down actual forest to grow oil plants instead.

Bio ethanol seems a truly low ghg variant. Not sure if it works in petrol heaters?

[Jacobsmess]

Don't think you need to bother with biodiesel. At least the german produced one has similar ghg emissions due to the farming and low spacial efficiency of crops e.g. compared to PV. Let alone plant fuels that required chopping down actual forest to grow oil plants instead.

Bio ethanol seems a truly low ghg variant. Not sure if it works in petrol heaters?

It depends heavily on the source, also HVO but I don't think that is very widespread or affordable. Biodiesel can be made quite cheaply from waste vegetable oil, which then makes it much more green than biodiesel produced from raw stock, in which case yes there's a lot of issues

[barracuda816]

I made good quality biodiesel for years, the heaters can work very well on it so long as you get the burn right. However unless you make it with raw oil and use additives it's no good at low temps. It starts to jell at not too low temps depending on the type of oil used.