perjantai 15. tammikuuta 2016

Heating my EVs

I'm sure I've covered the heating in both of my EVs, the cars at least, in previous posts, but I though I'd write a new one about them and how they've been doing.

As you may or may not know, I heat both of the cars with ethanol. In Finland it's easy to get locally produced bioethanol, which is made from biowaste, so it's basically free energy in the sense that it only requires a little work to make a burnable liquid from it. It doesn't add to the carbon burden on our climate, because it's not something stored underground and pumped into the air. It's already here and it's just recycled into something useful.

The C-Zero obviously has a electric liquid heater already, but it's not very powerful and yet it consumes a lot of power. It can take up to 5 kW and when you consider that the car only has a 16 kWh (nominal) battery, you can see that it will easily eat up a third of the pack capacity in an hour. To make matters worse, any used EV will not have it's full capacity left, like mine which only has about 14 kWh left, so it's even worse. And it doesn't even really get your toes warm even if you have it on full blast. It'll keep you a alive, for a short moment, but that's about it.

The heater I have in the C-Zero is a Binar 5B from Autoterm:

It's made in Russia and meant for Siberian winters. I'm not sure if they've completely managed to hit that target or is it because I've been using ethanol only, but so far in the 15 months I've had it, I've had to replace he glow plug twice and I'm just about to replace the fuel pump. It may be that especially in the most harsh winter conditions we've had here I might have been better off using gasoline. I had left the car sitting outside for three weeks during the holidays and when I got back the fuel pump wouldn't work anymore. Ok, it had come down to -25˚C, so it wasn't exactly sunny, but still. I was a little disappointed. Why I've had to replace the glow plug twice, I have no idea. I do think that the ethanol is not as flammable as gasoline (I couldn't get a bonfire started with ethanol), so maybe that's it.

In any case, Autoterm has a 2-year guarantee on their products and they've come through nicely. I've got new plugs from them and a new fuel pump just arrived today for free, so it's mostly only been the annoyance of the heater being broken and having to fix it. Then again having to fix stuff is something I've known to have taken pleasure in.

In the Xsara I'm burning the same bioethanol, but with a different heater, a german product called Webasto Thermo Top E. This one I got from a junk yard for 150€, so it was very affordable. Actually the first one I got didn't work at all, but they let me just swap it for another, which did work right away. The fuel pump didn't come with the burner, so I had to buy it separate from ebay, which added about 50€ to the cost. The burner is also a gasoline model and this manufacturer doesn't guarantee it to work with ethanol, unlike Binar, but I just tried it and haven't had any problems with it.

Actually this burner has been the most reliable of the two. Even though it had seen some heavy use for several years and the pump was a used one too, there has been zero problems with this one. It's also smaller than the Binar and the water pump is right there at the device. It has sort of made me regret that I didn't try to look for a used Webasto for the C-Zero as well, but then again it sort of made sense to use a new part in a newish vehicle. I also might not have been able to find another for such a good price. Usually they ask Binar-like prices for even used Webasto brand burners and the spare parts are expensive as well.

The Binar does have a couple of other things going for it as well. It has a display (in the picture) which shows the "coolant" temperature, so you know what's happening. It's also more powerful than the Webasto, 5 kW vs. 4 kW. The Binar hasn't had a problem getting up to 70-80 ˚C in any weather, whereas I think the Webasto might not have been quite powerful enough in the coldest days. On the other hand it doesn't show the temperatures so it's a bit more based on a gut feeling and it's the only method of heat in the Xsara as well. Additionally, the coolant pipes in the Xsara were quite long and exposed, so I just added some insulation on them the other day, which might also make a difference. I could also test if gasoline would improve it's heat output. In any case when it's not been terribly cold it has been more than enough.

One thing you need to keep in mind with these heaters is that they're not going to keep the coolant at a set temperature at all times. They will cycle so that first they will run on full blast to get the coolant to 70-80˚C and then go to a low power mode and restart the full power if the liquid temperature goes down to 40-50˚C. So they heat output is not going to be exactly the same at all times.

The way the heat works in the C-Zero (and all i-MiEV based cars) is that when you have the temperature knob on hot (or previously had it on hot before setting it to neutral) it will blast all the heat it gets from the heat exchanger. It will not mix any cold air into it. So you need to regulate the hot airflow with fan speed if you have a burner. The idea originally has been that the knob's heat setting directly controls the coolant target temperature of the car's own electric heater. If you turn the temperature knob to cold and either keep it there or turn to neutral without going on hot, it will only put out cold air into the cabin and no heat from the heat exchanger. Also the car's original coolant pump only runs when the knob is on the hot area. The burners I have also have their own pump, so they don't need that car's pump to be running, but it's something to keep in mind. I haven't had any problems with having two coolant pumps in the system running independently.

What I generally do is that on a really cold morning I keep the temperature knob on neutral (having had it on hot previously thus keeping the air going through the heat exchanger) and only start the ethanol burner. Once it's up to temperature, I may switch the temperature knob to one step into hot, just to make both coolant pumps run. It's not strictly necessary though. If the burner is stopped (manually or by it's timer) I can then leave the know on 1st heat step, let the car's pump circulate the still hot liquid to get the most of it's heat into the cabin and perhaps let the electric heater to keep the liquid lukewarm once it's cooled down. Sometimes I might also immediately have both on, with the heat on 1st step, to get some heat into the cabin as soon as possible, but still leaving most of the heavy heating for the burner.

Update: The heaters will burn about 0,5 to 1 liter of ethanol per hour.

3 kommenttia:

  1. Brilliant info :-) Just got a c-zero ...

    Have you disabled the PTCheater - or will it not turn on when you enable both pumps ??

    Also have you installed a timer and a relay so the burner can start the fan in the car ??

    1. The heater will not turn on at all if you have the heater control set to neutral. It will direct air through the heat exhanger though, if you had it on red previously. It also won't turn on if the "coolant" is hotter than it thinks it needs to be on the chosen setting. So you can keep the heat knob in the first click of the red zone if you like. This will also run the pump in the car if your burner doesn't have one. I haven't had a problem with having two pumps running simultaneously.

      I didn't bother with the fan control, even though the burner had wiring for it. I just used a separate eletric heater to heat the car and had the burner pre-heat the "coolant" so I'd get hot air as soon as I'd start the car.