Bought a 2017 Bolt EV

[JSH]

Some updates on life with a 2017 Bolt.

Tires:
I switched back to summer tires last week since the winter tires were to the wear bars. My efficiency dropped from 4.8 miles/kWh to a steady 4.0. Some of that is error from the winter tires being undersized but most of it is due to wider, stickier, and MUCH better tires. That puts me back to EPA range and efficiency.

Low 12V battery = no shifting
I ran into a new problem - my car would not charge when I pulled up to the DC charger AND it would not shift from park to drive to allow me to leave the charger. A bit of time with Google says a low 12V battery will cause that. I walked over to the shop for a multi-meter and confirmed the 12V battery was low at 12.15 V. So I charged it a bit and got home OK. The 12V battery is AGM and costs $200.

EDIT: Google tells me 12V power is required to move the shift solenoid and to close the battery contactors to allow charging.

GM's HVAC design engineer need to be fired:
The Bolt's HVAC is even stupider than I thought. I had the OBD scanner hooked up to record some DC charge curves so I decided to monitor what the AC does on my way home from work. With the A/C set to more than 70F the car RUNS THE HEATER to get that magical auto temp instead of just dialing back on the AC compressor speed to reduce cooling or cycle the A/C on and off as required. No doubt that works fine with an ICE vehicle where the heat is a waste product but running the electric heater in an EV at the same time as the A/C is just plain stupid


I'll post some charge curves shortly. Likely my last DC charging experiments as the DC chargers near work now have a paywall instead of being free. The pricing is a very fair $0.15 per kWh but free is still better. Back to the 3 kW AC chargers for me.

[freebeard]

With the A/C set to more than 70F the car RUNS THE HEATER to get that magical auto temp instead of just dialing back on the AC compressor speed to reduce cooling or cycle the A/C on and off as required.

[redpoint5]

Originally Posted by JSH

Some updates on life with a 2017 Bolt.
GM's HVAC design engineer need to be fired:
The Bolt's HVAC is even stupider than I thought. I had the OBD scanner hooked up to record some DC charge curves so I decided to monitor what the AC does on my way home from work. With the A/C set to more than 70F the car RUNS THE HEATER to get that magical auto temp instead of just dialing back on the AC compressor speed to reduce cooling or cycle the A/C on and off as required. No doubt that works fine with an ICE vehicle where the heat is a waste product but running the electric heater in an EV at the same time as the A/C is just plain stupid

Curious how certain you are that it was the cabin heaters coming on, as I have not heard this mentioned before, and that's kind of a big deal.

I know the battery heater is likely to turn on if battery temp is below about 70 degrees. Could it have been that?

The other silly thing about the Bolt is it uses resistive heating elements for hot air, but still utilizes a liquid heat exchanger (heater core). Instead of just warming the air directly and getting instant heat, they added complexity. Heater cores are the bane of HVAC, just ask Xist.

[rmay635703]

Originally Posted by redpoint5

Curious how certain you are that it was the cabin heaters coming on, as I have not heard this mentioned before, and that's kind of a big deal.

I know the battery heater is likely to turn on if battery temp is below about 70 degrees. Could it have been that?

The other silly thing about the Bolt is it uses resistive heating elements for hot air, but still utilizes a liquid heat exchanger (heater core). Instead of just warming the air directly and getting instant heat, they added complexity. Heater cores are the bane of HVAC, just ask Xist.

This is similar to the volt, especially if auto defog is enabled, it’s very humid and eco or comfort is selected.

Hard to disable without running fans and keeping the temp down

[JSH]

Originally Posted by redpoint5

Curious how certain you are that it was the cabin heaters coming on, as I have not heard this mentioned before, and that's kind of a big deal.

100% certain. Cabin Heat and Battery Heat are two different PIDs and I monitor both.


Update on the battery.
It is a 140R / H4 group AGM battery that is hard to find and expensive. I finally found one at O'Reilly's for $250. Costco, Interstate Batteries, NAPA, Auto Zone, and Advanced Auto did not have one in stock or don't even stock it at all. My local Chevy dealership had 3 in stock - for $335 each.

The Chevy Volt's larger H5 AGM battery is $185 but it would have taken a lot of work to make it fit under the hood of the Bolt.

[redpoint5]

I probably would have routed the battery cables into the cabin and run my own LiFeP4 battery. Startup amperage has to be low, and only draws from the battery long enough to get the DC/DC converter going.

Even if sticking with a lead acid battery, I'd just get whatever is cheap and fits in the space.

[JSH]

You would likely spend more on cables to reroute the battery than what you save on the battery cost. The stock battery cables are good size copper cables - if it was safe to use smaller cables I'm sure they would - copper is EXPENSIVE.

Interstate Battery did have a regular 140R group flooded lead-acid battery but it was $210. I can't see saving $40 to go with the regular wet cell to only then have the car undercharge the battery because AGM batteries bulk charge at 13.7 V while flooded batteries charge at 14.5 V.

[JSH]

Below is the charge curve for my Bolt. When I charged it was about 80F and the car was at 20% SOC. I was charging on a 75 kW DC charger. The car jumped right up to 50 kW and pretty much stayed there until 50% SOC and then it started to taper. In 30 minutes I gained 40% SOC and 100 miles of range.

The thermal management is a bit odd to me. Even though the battery temp started at 82F the battery heater came on and the battery pump went to 90% until the battery reached 88F. Then the battery heater turned off and the pump dropped to 55%. Battery temp stayed in the high 80's F until 54% SOC and then the A/C turned on and the pump jumped back to 90%. The A/C cooled the battery down to 55F and then turned off. The pump went back to 55% and the temp started rising again until it got back to the high 80's F and then the cycle repeated: Turn on A/C, cool to 55F, turn off A/C, let temp climb to high 80's, repeat.

The last 10% of SOC is quite inefficient and the last 1% is even worse. Even after the screen reached 100% it was still charged for 10 minutes as the RAW SOC was still climbing another 1%.

[rmay635703]

I bought the agm for my volt at Sam’s because the battery failed in the lot, lol luck.

I can buy $35 sealed recon batteries with the vent tube in almost any size.

What’s rather pathetic is on the Volt they spec a small dry cell starting battery but the car can easily use a rather large amount of capacity.

Realistically the Volt should have a 150ahr deep cycle considering how high its phantom draw is under certain circumstances.

A passenger killed my battery by running the radio a half hour.

My old suburban you could get 8 hours of radio use and still start.

[ME_Andy]

We are enjoying our 2024 Bolt a lot, in fact thinking about buying a second one. Thanks for the HVAC info. Are you excited about the new Bolt announcement?

I think GM ought to stop announcing more models and get on with production.