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Discussion Starter #1
Without needing the Hilltop Reserve which only does 90%. The solution to this requires having a JuiceBox EVSE. I found that on the web version control of your EVSE (whatever version, Pro presumably), you can have a one time "add X kWh". So a simple calculation later, I come home with 57% battery, I want to charge to 70%, the battery is 60 kWh, and my desired kWh is 42 and presently I'm 34.2, so I need to add 7.8=8kWh. Just plug that in and it will charge to 70% over night.

I put in a ticket to eMotorWerks to add the feature where you have a setting for you battery size and desired charge level, then just enter in your present and it'll take care of it. They are really responsive but if you like this feature a few more pings on it wouldn't hurt.

The more I use the JuiceBox EVSE's the more impressed I am. I have the ClipperCreek JuiceBox, and the JuiceBox pro in the car. The best made I've seen of any EVSE's and the most feature rich. Highly recommend them, if you already have a "dumb" EVSE you can get the JuicePlug to use with it, and have all the new configurability features.

Oh by the way, it also supports "load groups". So you can put two on the same circuit and they'll share the max amperage - no extra cost. The ClipperCreek has this as an expensive option.
 

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That works great, if your Juicebox is close to your internet hotspot. Unfortunately, our garage is some yards from the house, and I cannot get a reliable connection, without using a expensive range booster. I don't mind too much, as I can simply set an alarm to remind me to go out and unplug it, when it reaches the desired level. I have taken the hotspot out to the garage, and run charges long enough to see that it is consistently putting about 7.5 kW into the pack, 15 kWh...about 25%, every two hours. When I plug it in the car says when it would reach 100%, so just need simple math to know when to unplug it.
 

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Discussion Starter #3
That works great, if your Juicebox is close to your internet hotspot. Unfortunately, our garage is some yards from the house, and I cannot get a reliable connection, without using a expensive range booster.
What about having it connect to the Bolt WIFI, assuming you have a data plan? I have a JuiceBox and a JuicePlug in the car (or will momentarily) and will have them both connect to the car hotspot. Barring that you can have them connect to your phone hotspot.
 

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Since it's pretty much accepted that Hilltop Reserve (90% SOC) is safe to use on a daily basis.... why cutoff at 70% SOC?

Just asking.....
 

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Discussion Starter #5
Since it's pretty much accepted that Hilltop Reserve (90% SOC) is safe to use on a daily basis.... why cutoff at 70% SOC?

Just asking.....
Good question. A hardware engineer buddy of mine is a nut on EV's. He has a Volt presently and is a walking dictionary of EV knowledge, and his work is related to that (different field, similar application). He recommends 30%-70% for the Bolt and Li batteries in general. Elsewhere on the web I've seen 20%-80%. Batteries are black magic so it's slippery as to the 'right' thing to do. However at 70% I have a 230 mile range which is more than enough to keep a 30%-70% range, I just need a charge or two per week. So it's easy to maintain that for me (I charge up at work, keep an eye on the level, then go move when it gets to 70%). 90% is fine too, don't sweat it if that works for you.
 

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Good question. A hardware engineer buddy of mine is a nut on EV's. He has a Volt presently and is a walking dictionary of EV knowledge, and his work is related to that (different field, similar application). He recommends 30%-70% for the Bolt and Li batteries in general. Elsewhere on the web I've seen 20%-80%. Batteries are black magic so it's slippery as to the 'right' thing to do. However at 70% I have a 230 mile range which is more than enough to keep a 30%-70% range, I just need a charge or two per week. So it's easy to maintain that for me (I charge up at work, keep an eye on the level, then go move when it gets to 70%). 90% is fine too, don't sweat it if that works for you.
Real world data from multiple EVs (that have thermal battery management) so far pretty well refutes the 70% figure. A lot of this charging/discharging knowledge for Li-ion batteries is based on those that don't have thermal management and the best way to limit or control damage to Li-ion batteries without thermal management is to keep them well away from 100% or 0% SOCs.

Go check out all the data that Tesla owners have been gathering on their car batteries as it pertains to degradation. The data is collected worldwide, tracks charge cycles, discharge amounts and all the pertinent other points, you can even narrow down to certain areas and climates. Short of a few outliers the data shows Teslas batteries degrade quite slow and that you should have 85% or more of battery capacity even after a decade of use and 300,000 plus miles.

You can also look at data from Volt batteries which are much smaller and used much heavier than ours are being that most of them go through the entire battery daily and some go through it multiple times. I have a friend at work who has a 2012 Volt and he uses the full battery on his commute in, charges at work, uses the full battery on the way home. He has done that for 5 years now and is at about 135,000 miles. He has only about 10% degradation on the battery which is quite impressive for how hard he uses the thing. Just from work commutes he has done over 500 full charge cycles. He has been thinking about buying a Bolt but wants to run that Volt into the ground first.
 

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I look at it this way Professor....

100% indicated SOC is probably really only 90% actual SOC because of the built in battery protection buffer.
With that in mind 90% indicated (Hilltop Reserve) is probably closer to 80% actual SOC.

So, Hilltop Reserve gets you right at that 80% (actual) SOC sweet spot!
No need to play with things to go lower than Hilltop Reserve level.
 

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Discussion Starter #8
I look at it this way Professor....

100% indicated SOC is probably really only 90% actual SOC because of the built in battery protection buffer.
According to my buddy the Bolt has no protection reserve. The Volt does, not the Bolt. They apparently figured that people would prefer range over protection, and gave it a more sophisticated battery.
 

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I believe the Bolt has to be turned on for the car wifi to work, and I think that will go away anyway, when our trial Onstar account ends. We don't have smartphones, so our wifi hotspot is our only option.

All current lithium ion batteries prefer to be in the middle of their charge range. Any deviation from that sweet spot has some effect on longevity. Is it worth worrying about? It depends on lots of factors. We are retired, don't drive much, or very far. This is our last car. In ten years I hope to pass it on to one of our kids with ten more years of useful life. After that, I don't image anybody will be driving anything anywhere.
 

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According to my buddy the Bolt has no protection reserve.
That's not possible.... no auto manufacturer would let you run their $$$$ battery down to 0% SOC and still offer a warranty.
Bring that big battery down to 0% SOC a few times and it will be dead in under a year.

It's been suggested that the Bolt battery has up to a 10% buffer, it was estimated the Volt had a 20% buffer IIRC.
 

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I have to believe there is a buffer in the Bolt battery, exactly how much I don't know. Every EV I know of has some buffer, Tesla's have a minimum of 3% buffer, even on the 100s.

If we knew the voltage of each cell and amp hour capacity it would be simple math to know how big the Bolt battery really is. 288(cells) x 4.15v x ?aH = actual capacity. I put 4.15v in because that is the max for the cells in the Volt. I have read reports that say the aH of cells is 55. So if we use that, it gives us 65.7kWh actual capacity of the battery, that is if the 4.15v is correct as well. Of course neither the v or aH is confirmed so this is just pure speculation of course.
 

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Discussion Starter #12 (Edited)
^ That's not possible.... no auto manufacturer would let you run the $$$$ battery down to 0% SOC and still offer a warranty.
Run that big battery down to 0% SOC a few times and it will be dead in under a year.

It's been suggested that the Bolt battery has up to a 10% buffer, it was estimated the Volt had a 20% buffer IIRC.
The manual has a spec of possible 40% capacity loss within the 8 year warranty.

According to the UBS teardown
  • Cell Format: Pouch
  • Capacity: 60 kWh
  • Num Cells: 288
  • Approximately 140 kg of active cell materials (Ni, Co, Li, Mg, Graphite)
  • Therefore 210W/pouch
  • Li ion batteries have a specific power of 250-340 W/kg
  • Energy density of 100-265 W-h/kg
  • Therefore this battery has a specific power of 35kW-48kW
  • Finally an energy density of 14kWh-37kWh
The figures for Li ion are taken from Wikipedia which simply gives us an average, if accurate. This battery is specced at 60kWh, 40% higher than this calculation shows. It's a state of the art battery so probably does not fall within norms, and the Wikipedia data might be at fault. At any rate this is all ballpark, but note that there's no magic here, it's basic battery chemistry and all Li batteries from the Bolt to your flashlight are in the same ballpark in terms of performance.

Putting it together I think indicates that the Bolt is probably operating at the top end of its capacity and there is not a hidden reserve. The battery is the single most expensive component and another 10% reserve is an additional 6kWh of capacity*. That's thousands of dollars of battery just for a slush fund for keeping your battery for the long term.

Just my 2cents, like I say charge as you like and don't sweat it.

* For reference the Tesla Model 3 base battery is 50kWh (compare to 60 kWh for the Bolt), upgrading to the 75 kWh costs $9,000 for 25 kWh, or $2160 for 6 kWh. So a 10% reserve, all else being equal, is perhaps a $2k add cost to the base price of the car. Now it could be that they got 10% 'for free' with these advanced LG batteries, yet we're already at 10 kWh over the Model 3 size. Seems unlikely.
 

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This is all good info, but how is the charge interrupted when a certain level is reached or when circumstances say stop now . The manual says used the evse off switch or use the off button on the Display screen. My Bolt does not show an off button or I'm looking in all the wrong places -- help.
 

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There might be a prompt that pops up if the car is on while charging and you are sitting in it, I've not tried that yet. I terminate charge the same way ProfessorBolta does, I set my OpenEVSE to start several hours before departure time and calculate how many hours I need to charge to hit my desired charge %. Sometimes I use the "Energy Limit" on the OpenEVSE WiFi so I can pick how many kWh I want to put into the pack instead if I want to charge immediately.

I also keep the battery at a lower SOC than hilltop reserve 99% of the time, I'm usually staying in the 30-70% range as well. I'll be keeping the battery pack for other energy storage uses after the car's end of life if resale value is low, so slight effort toward managing degradation is both dead simple easy and might have further life cycle payoffs for me. If energy storage is dirt cheap in 10 years it might not matter, but I can't predict the future, so...
 

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Discussion Starter #15
I'll be keeping the battery pack for other energy storage uses after the car's end of life if resale value is low, so slight effort toward managing degradation is both dead simple easy and might have further life cycle payoffs for me. If energy storage is dirt cheap in 10 years it might not matter, but I can't predict the future, so...
Nothing is as cheap as something you've already paid for :)

If anybody figures out an 'auto off' defeat, like a sack of potatoes, this is a brilliant battery. Say worst case it loses 50%, that's still a day of full household usage of 30 kWh.
 

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I read somewhere that while the advertised battery pack size is 60 kWh, the actual battery size when adding the cells is 65.8 kWh or a 10% buffer as previously mentioned. Given how GM seems to have oversized every component in the drivetrain to prepare for a wide range of future applications, I feel safe about charging to 100% (indicated) every day.
 

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Discussion Starter #17
I read somewhere that while the advertised battery pack size is 60 kWh, the actual battery size when adding the cells is 65.8 kWh or a 10% buffer as previously mentioned. Given how GM seems to have oversized every component in the drivetrain to prepare for a wide range of future applications, I feel safe about charging to 100% (indicated) every day.
I've done a lot of searching and have seen nothing. Considering that the Bolt battery is 3X the size of the Volt, having a hidden reserve will cost 3X what it does in the Volt. At this point we have hearsay and no identified information that there is any reserve in the Bolt.
 

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Considering that the Bolt battery is 3X the size of the Volt, having a hidden reserve will cost 3X what it does in the Volt.
...IF the reserve is of the same proportion - BUT there's no reason for that to be the case. The Volt has to be engineered for a use case where it's fully charged and discharged on a daily basis (and by "fully" I mean to the limits that the software allows), because with a gas generator drivers are perfectly happy to drive beyond battery range. The Bolt is different - because of range anxiety it will hardly ever be discharged to the software limit, and therefore there's far less need to have as deep a reserve.
 
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