GM Volt Forum banner

1 - 20 of 25 Posts

·
Registered
Joined
·
22 Posts
Discussion Starter #1
Does Bolt EV have a battery buffer like in the Volt? Gen 1 Volt had a 16.5 kwh battery with roughly 10.5 kwh usable (63.6%) from 0-100%. Any mentions about this in the manual? Any daring Bolt EV owners willing to do a 100% -> 0% run and see if the usage is 60 kwh?

The reason I'm asking is I'm curious whether it's "safe" to charge to 100% and back down to 0% on a regular basis, or even occasionally. I know that Tesla's have irreplaceable damage to the battery if it reaches 0% even once, and costs $40k to replace the pack. Tesla has a software safeguard where it shuts down the car before it reaches this level, so this never happens in reality. Similarly, I've read that leaving the battery pack at 100% for an extended period is also bad, especially in the heat. In the Volts, we don't have to worry about this due to the buffer.
 

·
Registered
Joined
·
3,193 Posts
The Bolt EV will have a buffer but not like the Volt's. The Bolt EV appears to allow the use of up to ~95% of the usable capacity.

In a vehicle like the Volt the battery is going to see a higher % use on a daily basis and the cells are going to see higher proportion of charge and discharge. So having a large buffer is important for battery life. Also with that gas engine back up people will run the car to zero range on a regular basis.

Most Bolt EV's are likely to see a much lower %SOC usage on a daily basis. And very few are going to run the EV range down to zero (how many people run their gas tanks to empty before refilling in a normal ICE car)? And the much higher capacity battery will see proportionally lower charge and discharge rates. So the Bolt EV can get away with allowing the use of more battery.
 

·
Moderator
Joined
·
4,862 Posts
My recommendation for any Bolt owner that doesn't need 100% of the range 100% of the time, is to use the "Hill top Reserve" functionality to not charge that last 10%.

As Neromanceres points out, it has a bit of a buffer but not nearly as conservative as the Volt. The 60kWh number is usable energy, as far as I know. So the battery is a bit larger than that.
 

·
Banned
Joined
·
7,289 Posts
My recommendation for any Bolt owner that doesn't need 100% of the range 100% of the time, is to use the "Hill top Reserve" functionality to not charge that last 10%.

As Neromanceres points out, it has a bit of a buffer but not nearly as conservative as the Volt. The 60kWh number is usable energy, as far as I know. So the battery is a bit larger than that.
GM officials have been quoted as saying the Bolt uses "almost all" of its capacity, so the 95% usable figure is probably on the money. The Spark EV (2015/2016) also used upwards of 95%. And based off the media test drives, the usable capacity is very close to 60 kWh, if not actually 60.

If I ever can run the battery down all the way, I'll report my first hand results. I haven't even plugged in my Bolt the last 2 nights because of the ample range. :)
 

·
Registered
Joined
·
949 Posts
If I ever can run the battery down all the way, I'll report my first hand results. I haven't even plugged in my Bolt the last 2 nights because of the ample range. :)
I will probably check this during my first weekend with the car as I'm also curious - will take pics.
 

·
Registered
Joined
·
13 Posts
Best thing to set is the hilltop reserve.. It does stop the charging at around 86-89%. Also the car reports it as a full charge (for the data that it keeps in the app and on the car computer.

Like others have said, I'd probably only turn off the HTReserve if I need the distance.
 

·
Banned
Joined
·
7,289 Posts
I can also use my JuicePlug to restrict charging to whatever level I want. But the 90% level activating hilltop reserve will likely suffice for most cases. I can tell it how many kWh/battery % to charge before charging shuts off.

 

·
Registered
Joined
·
787 Posts
My recommendation for any Bolt owner that doesn't need 100% of the range 100% of the time, is to use the "Hill top Reserve" functionality to not charge that last 10%.
I probably know less than you, but do you have any data from GM to back up your recommendation? I would guess that if fully charging the Bolt battery was not recommended, GM would make the "Hill top reserve" the default setting.

Please remember, we forum members, and Moderators especially, are relied on by the public to provide accurate information. Believe it or not, many people don't even bother to read the manual and take what is typed here as gospel.
 

·
Registered
Joined
·
2,634 Posts
The car will prevent over discharge.

Also, the Bolt EV only needs to cycle the battery about 630 times to drive 150,000 miles, but the 2013 Volt would need to cycle 4000 times for the same EV miles. Point is, they have different design goals.

My understanding is the usable capacity is near 60kwh, but haven't seen a firm number on this.
 

·
Registered
Joined
·
1,489 Posts
I probably know less than you, but do you have any data from GM to back up your recommendation? I would guess that if fully charging the Bolt battery was not recommended, GM would make the "Hill top reserve" the default setting.
The problem with making it the default setting is that the EPA would then use it as the basis for its range estimate, and therefore the official range of the car would go down. This is exactly what happened to the Nissan Leaf when they provided a way to charge to less then full and made it the default. GM is unlikely to make any public pronouncement or recommendation because of that.

However it's very well known in the industry that the best way to prolong battery life is to never fully charge nor discharge it. Therefore there's no doubt that charging only to the "hilltop reserve" level will be easier on the battery than charging it right up what the car reports as 100% state of charge on a regular basis.

The big question is whether or not this will result in any sort of significant difference compared to whatever GM has allowed as the reported 100% level (which itself wouldn't be the battery's true ultimate capacity). The best anyone can say right now is that it certainly won't hurt, and it will probably be at least a wee bit better for battery longevity.
 

·
Moderator
Joined
·
8,680 Posts
Folks who are looking at the cell capacity have come up with a nominal total capacity of 64 kWh for the Bolt pack. The 60 number GM is quoting is probably the usable battery out of that total. Not a huge buffer, but maybe enough - especially for folks wise enough to use the hilltop reserve as others have described.
 

·
Registered
Joined
·
2,634 Posts
Folks who are looking at the cell capacity have come up with a nominal total capacity of 64 kWh for the Bolt pack. The 60 number GM is quoting is probably the usable battery out of that total. Not a huge buffer, but maybe enough - especially for folks wise enough to use the hilltop reserve as others have described.
Nice, that is impressive and explains the usable capacity of 60 kwh. Makes the battery even more impressive.
 

·
Premium Member
Joined
·
14,156 Posts
I probably know less than you, but do you have any data from GM to back up your recommendation? I would guess that if fully charging the Bolt battery was not recommended, GM would make the "Hill top reserve" the default setting.
I think the advice he gave is consistent with everything we know about batteries. In this case what we know is the batteries lose capacity most quickly if at full SOC and hot. They lose the least if partially discharged and cold. Now the LG cells may be different but there isn't any reason to believe this to be the case.

Other manufacturers have used options to charge the batteries to less than full SOC if the range isn't needed. It's something of a game with the EPA rated range. GM may not worry because there is a small buffer and the Bolt EV has a TMS, but you certainly can't hurt anything if you only charge to 90%. Unless you think you'll need the range the advice seems quite good.

Having said that, the Bolt EV probably top balances the cells, so it might help to occasionally top off. No idea really, but it's one of those things which would be great if GM answered.
 

·
Registered
Joined
·
261 Posts
All this discussion of hilltop reserve reminds me of the huge, gooey, delicious cinnamon rolls at the Hilltop Restaurant up in L'Anse, MI...

https://www.sweetroll.com/

Would have to take the Volt to get there, though, or stop for several hours to charge on the way in a Bolt!
 

·
Registered
Joined
·
1,890 Posts
I probably know less than you, but do you have any data from GM to back up your recommendation? I would guess that if fully charging the Bolt battery was not recommended, GM would make the "Hill top reserve" the default setting.
The problem with making it the default setting is that the EPA would then use it as the basis for its range estimate, and therefore the official range of the car would go down. This is exactly what happened to the Nissan Leaf when they provided a way to charge to less then full and made it the default. GM is unlikely to make any public pronouncement or recommendation because of that.
Tesla got around this by using a slider bar to select the charging target. You can set it to 100%, or 90%, 80%, etc. at 10% increments. (My understanding is most people do 90% for daily driving.) This gives the owner lots of flexibility to set their charging target, while also allowing the EPA to rate it based on its max range.

Idk why GM wouldn't have done a similar approach. My only guess is to dumb it down and keep it simple for the average person.
 

·
Registered
16,17 volt
Joined
·
733 Posts
I think the advice he gave is consistent with everything we know about batteries. In this case what we know is the batteries lose capacity most quickly if at full SOC and hot. They lose the least if partially discharged and cold. Now the LG cells may be different but there isn't any reason to believe this to be the case.

Other manufacturers have used options to charge the batteries to less than full SOC if the range isn't needed. It's something of a game with the EPA rated range. GM may not worry because there is a small buffer and the Bolt EV has a TMS, but you certainly can't hurt anything if you only charge to 90%. Unless you think you'll need the range the advice seems quite good.

Having said that, the Bolt EV probably top balances the cells, so it might help to occasionally top off. No idea really, but it's one of those things which would be great if GM answered.
I think the bolt batteries have a higher nickel content than the volt and handle higher temps
 

·
Banned
Joined
·
7,289 Posts
Tesla got around this by using a slider bar to select the charging target. You can set it to 100%, or 90%, 80%, etc. at 10% increments. (My understanding is most people do 90% for daily driving.) This gives the owner lots of flexibility to set their charging target, while also allowing the EPA to rate it based on its max range.

Idk why GM wouldn't have done a similar approach. My only guess is to dumb it down and keep it simple for the average person.
n00b owner: "What the hell!! My Bolt didn't charge last night!"
Dealer: "What was your charge % slider set to?"
n00b owner: "My WHAT?? Hmm.....hey, it's set to 10?!?"
 

·
Registered
Joined
·
6,464 Posts
As others have stated, I believe the capacity is closer to 64 kWh. Even when fully charged, if I turn on the car while still attached to the L2 charger, it will draw ~6 kW. So there is a potential for "topping off."

It looks like we have a number of ways to control the total SOC. Hilltop reserve is probably the easiest. I like bro1999's juicebox option. I also posted a video on how to set it if you charge at home and are taking advantage of rates. It can be customized based on your charger and goals:

 

·
Registered
Joined
·
22 Posts
Discussion Starter #20
Great responses from everyone. Here is what I've gathered so far from this thread:

1) The Bolt EV is using roughly 95% of the battery capacity, which means roughly 64 kWh total capacity. This is assuming 60 kWh usable by the end user, which we don't really know until someone does 100% -> 0% test.

2) We don't know how that extra 4 kWh is allocated. The 4 kWh could be the buffer below 0%, above 100%, or it could be split 2 kWh below 0% and 2 kWh above 100% or another mix.

3) Because of #2, we still don't know whether it's safe to charge to 100% and drop to 0% regularly. Someone brought up a good point that if it really wasn't safe to charge to 100% regularly, Chevy would've made the Hilltop Reserve feature the default setting, but they didn't. Similarly, does the manual warn against discharging to 0% regularly? If not, or if there's a large enough buffer below 0%, then it's probably okay to discharge to 0%.
 
1 - 20 of 25 Posts
Top