Hey Guest, welcome to ChevyBolt.org. We encourage you to register to engage in conversations about your Bolt.

Several Curious Charging Questions

1331 Views 5 Replies 5 Participants Last post by avery_larry, Dec 21, 2021

Jim McCall

Discussion Starter · Dec 21, 2021

1) If you have hilltop reserve on to limit your max charge to 90%, how does cold weather change the equation? For instance San Francisco is having some cold weather, and the mileage estimate is going down from around 212 to 180. If my charging session is complete in the morning, is the battery still charged to 90%? I was wondering whether the lower number suggests that maybe I might disable Hilltop. In truly cold climates much more extreme than San Francisco, I wonder how much more the maximum range is reduced.

2) I have the feeling that my 30 amp home charger slows down the number of miles per hour of charge, but I haven't actually tested it. I was wondering if this generally happens and if so, what exactly happening? Either the rate is slowing and it is actually not using as much power, or it is using the same amount of power but I am getting fewer miles per KWH. If the latter is true, then one might have incentive to plug the nozzle earlier.

Save

1 - 6 of 6 Posts

Dark-Fx

· #2 · Dec 21, 2021

Jim McCall said:
1) If you have hilltop reserve on to limit your max charge to 90%, how does cold weather change the equation? For instance San Francisco is having some cold weather, and the mileage estimate is going down from around 212 to 180. If my charging session is complete in the morning, is the battery still charged to 90%? I was wondering whether the lower number suggests that maybe I might disable Hilltop. In truly cold climates much more extreme than San Francisco, I wonder how much more the maximum range is reduced.

2) I have the feeling that my 30 amp home charger slows down the number of miles per hour of charge, but I haven't actually tested it. I was wondering if this generally happens and if so, what exactly happening? Either the rate is slowing and it is actually not using as much power, or it is using the same amount of power but I am getting fewer miles per KWH. If the latter is true, then one might have incentive to plug the nozzle earlier.

1) This was my record last winter season at the recall 95% charge limit. It was -16 F out and had been sub-zero the whole week before:

Font Speedometer Vehicle Audio equipment Gadget

I wouldn't disable hilltop unless you actually need the range.

2) The Bolt will use some extra energy from the wall to heat the pack up if it's cold out. I'm guessing what you're actually trying to say is because your efficiency is reduced when it's cold out, you're noticing that you don't get as many miles for the same charge time. This is because the Bolt isn't showing you the amount of energy that goes into the battery, but the estimated range based off your recent efficiency. Energy storage is still occurring at close to the same rate.

See less See more

Save

TheCyberKnight

· #3 · Dec 21, 2021

Jim McCall said:
1) If you have hilltop reserve on to limit your max charge to 90%, how does cold weather change the equation? For instance San Francisco is having some cold weather, and the mileage estimate is going down from around 212 to 180. If my charging session is complete in the morning, is the battery still charged to 90%? I was wondering whether the lower number suggests that maybe I might disable Hilltop. In truly cold climates much more extreme than San Francisco, I wonder how much more the maximum range is reduced.

2) I have the feeling that my 30 amp home charger slows down the number of miles per hour of charge, but I haven't actually tested it. I was wondering if this generally happens and if so, what exactly happening? Either the rate is slowing and it is actually not using as much power, or it is using the same amount of power but I am getting fewer miles per KWH. If the latter is true, then one might have incentive to plug the nozzle earlier.

As my tag indicates, I'm in Canada.
I can tell you that cold (and very cold) weather have close to no effect in the charging time using a 32 A charger.
The charging process seems to generate enough heat in the battery to avoid using the conditioning system.

Meanwhile, after a battery is fully charged and remains plugged-in, the car may sporadically use about 2 kW to 2.5 kW to condition the battery. The frequency and duration are related to the temperature. But, it usually does not occur above 0 C.

Save

ARob

· #4 · Dec 21, 2021

Jim McCall said:
1) If you have hilltop reserve on to limit your max charge to 90%, how does cold weather change the equation? For instance San Francisco is having some cold weather, and the mileage estimate is going down from around 212 to 180. If my charging session is complete in the morning, is the battery still charged to 90%? I was wondering whether the lower number suggests that maybe I might disable Hilltop. In truly cold climates much more extreme than San Francisco, I wonder how much more the maximum range is reduced.

2) I have the feeling that my 30 amp home charger slows down the number of miles per hour of charge, but I haven't actually tested it. I was wondering if this generally happens and if so, what exactly happening? Either the rate is slowing and it is actually not using as much power, or it is using the same amount of power but I am getting fewer miles per KWH. If the latter is true, then one might have incentive to plug the nozzle earlier.

Don't confuse State of Charge (SoC) and range estimates. Charging to 90% (HTR) results in a 90% SoC regardless of temps. The range estimate is based on recent driving efficiency which drops in colder weather due to a variety of factors. So range estimates will tend to drop in colder times, rise in warmer times. The "sweet spot" is roughly human temperature preferences, 60-80F.

Charging times in colder weather is mainly impacted when it gets cold enough (<30F or so) to require battery conditioning which consumes some of the energy to heat (or in summer, cool) the pack. Otherwise, the pack will charge to full or target levels in roughly the same time. But again, the miles per hour charge rate is a factor of recent efficiency. So, it may feel like fewer miles per hour.

To illustrate, consider recent efficiency of 4 vs 5 mi/kWh efficiency. At 30A charging speeds (7.2kW), you will add roughly 7 kWh of energy per hour or 7*4=28 miles if recent efficiency was 4mi/kWh. If recent efficiency was 5 mi/kWh, that same hour of charging would tend to boost range by 7*5 or 35 miles. It is not that precise as the range estimates are based on a variety of factors which seem to include the EPA rated efficiency of ~4mi/kWh and average efficiency over hundreds or thousands of miles.

See less See more

Save

Reactions: 1

Jim McCall

Discussion Starter · #5 · Dec 21, 2021

Dark-Fx said:
1) This was my record last winter season at the recall 95% charge limit. It was -16 F out and had been sub-zero the whole week before:
View attachment 39333
I wouldn't disable hilltop unless you actually need the range.

2) The Bolt will use some extra energy from the wall to heat the pack up if it's cold out. I'm guessing what you're actually trying to say is because your efficiency is reduced when it's cold out, you're noticing that you don't get as many miles for the same charge time. This is because the Bolt isn't showing you the amount of energy that goes into the battery, but the estimated range based off your recent efficiency. Energy storage is still occurring at close to the same rate.

Wow - down to 107 miles range at -16F! That is really interesting to read for comparison. I know we're "soft" in San Francisco...

Save

avery_larry

· #6 · Dec 21, 2021 (Edited)

Batteries actually have less capacity in cold temperatures. This is partially, but not fully, offset by battery conditioning (keeps the battery warm). Lots of charts and articles if you search lithium batteries capacity temperature chart.
Effect of temperature on Li-ion battery capacity. | Download Scientific Diagram (researchgate.net)
Cold air is significantly more dense, increasing the air resistance. At 0 F air is around 15% more dense than at 70 F.
Heating takes a lot of energy.
This is why when people ask me how far I can drive on a charge, I tell them 250 miles in the summer, 150 miles in the winter.

Save

Reactions: 5

1 - 6 of 6 Posts

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.

Top Contributors this Month