BEV No Heat, Again...

[eNate]

Leaving work last night, 47° outside, 100% charged with the Level 1 EVSE still connected, and pre-conditioning / climitazation all set up just like it is every night.

Only this time, freezing cold car, and the heat never came on during the 20+ minute drive home.

I mention it's the BEV because the heat pump is in the mix.

I had an unconnected series of these no-heat events last fall. I took the car in to BMW for a few different issues, this being one. They were non-specific in how they addressed it -- "software update" I believe -- and the heating problem hasn't presented itself since then.

Any other BEV owners experienced this?

 

[alohart]

2014 BEV here. The cabin temperature has never dropped below the climate control set point temperature, so the heat pump heating mode has never turned on. In our climate, I don't expect to ever need cabin heat, so I have no experience with cabin heating.

Because the heat pump uses the A/C compressor and the compressor is loud enough to be heard outside an i3, I would confirm that the compressor is running when cabin heat is needed but not being provided. If the compressor is on, a valve that changes the heat pump system from cooling to heating might be stuck. I would use a OBD scanner that understands BMW diagnostic trouble codes (DTC's) to look for DTC's that might explain the problem.

Good luck!

 

[eNate]

Hmmm, interesting. I'll have to listen for that when it IS working, as a point of comparison.

Where I'm unclear is when the system uses the heat pump vs. when it selects resistive heating. Do you happen to know if the heat pump is the default choice, or what set points cause it to kick in?

This afternoon leaving for work, it appeared everything was working normally again. If I recall correctly from my problem with this last year, it only presented itself at night.

 

[alohart]

Where I'm unclear is when the system uses the heat pump vs. when it selects resistive heating. Do you happen to know if the heat pump is the default choice, or what set points cause it to kick in?

In the I01 Heating and AC Systems Training Manual:

"From an ambient temperature of -10 °C / 14 °F and a mean set-point value of the heating and air-conditioning system (22 °C / 71 °F in automatic function) an interior air temperature control without the additional heating is realized by the electric heating. The heat pump is no longer operated below -10 °C / 14 °F."

Might be a poor translation from German. My interpretation is that the heat pump provides all cabin heating above -10 °C / 14 °F with resistive heating providing all heat below -10 °C / 14 °F.

 

[eNate]

Good info there, Art.

Tonight it worked, only difference is it was a few degrees warmer outside. Just the blower was operating, not the compressor, so it appears maybe resistive heat is the source for precon?

 

[alohart]

Tonight it worked, only difference is it was a few degrees warmer outside. Just the blower was operating, not the compressor, so it appears maybe resistive heat is the source for precon?

Hmm, maybe when a BEV is plugged in to an EVSE, resistive heating rather than the heat pump is used for cabin preconditioning. Others will know.

 

[eNate]

This is where it gets confusing. Because when it's warm and precon needs to cool the car, obviously it runs the AC compressor (and I can hear it, different from just the blower).

So if the heat pump is more efficient than the toaster oven, I'm not sure where the logical disconnect is.

In any case, I should schedule a service appointment now, expecting this is going to happen again.

 

[jadnashuanh]

FWIW, I've seen the i3 pull more than 20A at 240vac during a precondition with departure time set. IOW, the OUC is not large enough to keep the battery full when you select that option. The battery heater is 1Kw, and I'd guess the cabin heater is larger, then throw in the fans and it adds up.

 

[eNate]

Whoa, 20A is crazy! Wow. I've seen 3kW cited as a max consumption for precon in a interview with a BMW engineer. That would be closer to 12A @ 240V.

In any event, I always charge at 120v @ work, and 99% of the time the preconditioning works dandy, cabin & battery.

Shoot... I need to check whether my battery is being warmed up properly on those occasions when my cabin heat doesn't kick on. I can't imagine they're related, but worth investigating.

 

[3pete]

Based on the noises in my driveway last winter, the heat pump/ compressor is indeed used for cabin heating.

And yes, I can also confirm preconditioning will pull 20+amps for a bit while getting going! It does ramp down from there once it gets going, but definitely more than the OUC can handle.

 

[eNate]

Sure, but 20A at 120v is half 20A at 240v.

 

[jadnashuanh]

Sure, but 20A at 120v is half 20A at 240v.

True, but do you know of any 20A/120vac EVSEs? Mine is 240vac, and I saw 20A when preconditioning while a departure time was set.

 

[eNate]

Jim, no, my point being that 20A at 120v is a 2400W power draw which is clearly a charge deficit for any L1 setup, but that you mentioned you recorded 20A at 240v being consumed, which to me seems like an insane amount of consumption for preconditioning. Again, the figure I recall from the interview with the BMW engineer was a maximum of 3,000W or maybe 3,500W.

 

[jadnashuanh]

The amount of power surprised me. I do not think the meter is wrong, as it shows about 30A (my normal acv=247) when charging the battery shortly after starting up. This case, the battery was full, but it was in the middle of a departure time, well, in the segment of the program when it finally turns the HVAC on in addition to the battery heater. Now, it is possible that it started out using battery power before it turned the EVSE back on to both top the batteries up and perform the conditioning. That could account for the higher level. I didn't watch it for long, so it may have been at that level for only a short time.

But, I agree, the 10A, 120vac device included with the USA vehicles (and probably elsewhere that have 120vac as the nominal receptacle) cannot keep up and you'll likely not depart with a full battery. But, because it's warmer, it may be somewhat of a tossup...you'll certainly be more comfortable when you get in!

 

[3pete]

Now, it is possible that it started out using battery power before it turned the EVSE back on to both top the batteries up and perform the conditioning. That could account for the higher level. I didn't watch it for long, so it may have been at that level for only a short time.

I think you might be on to something here. If I recall correctly, I saw a peak around 26 amps (at ~240v) one day I was actively monitoring the Juicebox app when preconditioning started. It ramps down pretty quickly, but I don't recall exactly how fast or where exactly it 'settles' for preconditioning.

Once it gets colder here, I'll do a test and share my findings...

 

[frictioncircle]

Shoot... I need to check whether my battery is being warmed up properly on those occasions when my cabin heat doesn't kick on. I can't imagine they're related, but worth investigating.

I've found that bottoms of the rear cupholders get warm as the battery is used.

And on the few times I've preconditioned with a set departure time on a cold morning, the cupholders are similarly toasty.

 

[3pete]

For whatever it's worth, I had a chance to capture the consumption for preconditioning this week because we had a cold night and I actually had a place to go in the morning. I set the departure time for 9:30 am.

The ~1kW battery warmer kicked on from 6:30 to 7:15 which used just under 1kWh.
The preconditioning started at 9am and went up to 6 or 7 kW for five-ish minutes before coming down to 4~5 kW for 10 minutes or so then ramping down to 2kW for the rest.

 

[alohart]

The preconditioning started at 9am and went up to 6 or 7 kW for five-ish minutes before coming down to 4~5 kW for 10 minutes or so then ramping down to 2kW for the rest.

If yours is a REx, I assume that the cabin preconditioning consumption would have been considerably less for the heat pump in a BEV, unless a BEV also uses the electric resistance elements for cabin preconditioning. I don't see any reason why it would, though.

 

[jadnashuanh]

FWIW, during the summer, I had a situation where mine was not cooling well, if at all. The compressor was working fine, but a couple of valves were sticking. It could easily stuck the other way so it can't provide heat, as it's the same pump. They replaced the valves...parts and labor ended up about $1k.

 

[3pete]

The preconditioning started at 9am and went up to 6 or 7 kW for five-ish minutes before coming down to 4~5 kW for 10 minutes or so then ramping down to 2kW for the rest.

If yours is a REx, I assume that the cabin preconditioning consumption would have been considerably less for the heat pump in a BEV, unless a BEV also uses the electric resistance elements for cabin preconditioning. I don't see any reason why it would, though.

Mine's a BEV. The consumption certainly surprised me when I first saw it. At 6+ kW, I felt I needed to time my departures to only run preconditioning for a few minutes to "take the edge off" of the cold to not waste electricity on warming a car in my driveway, then one day I let it run for a while and saw the quick drop to 4-5 then further drop to ~2. I'm ok with a half hour at those levels to get into a nice, warm car in the winter. Still, I'm not really sure why the spike is so high at the beginning. That's why I think Jim's point about sending some juice to the battery for a bit might have some veracity to it. Maybe the i3 kicks on the climate control and pulls from the battery for a minute before the battery says "hey EVSE, give me some more juice here."?