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Discussion Starter · #1 · (Edited)
I finally had my home charger installed yesterday and I have a question for the experienced EV crowd. With the new battery chemistry, are you charging to 100% or still 80% for regular charging (not road trips)? I seem to remember someone mentioning the GM said 100% was fine with the new battery chemistry.

Edit: I found this on another forum:
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100% is fine, but usually the sweet spot is 50-70%, so 80% probably would be best for normal use keeps you in that middle range.

"excessive DC fast charging" isn't the same as charging up to 100% capacity - that is more so touching on degradation due to the heat/stress of super fast charging.

I'll probably do around 80% still for daily use, 100% for long road trips if needed, and won't be DC charging unless on a road trip which is probably about 5-10% of time at most for us.
 

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I charge my Mach E to 80% and my Bolt to 88% (hilltop reserve). There is no need for full range when driving around town. Despite what GM claims, it is better not to charge to 100% unless you are taking a trip.

An interesting note about the Bolt. After GM started telling people to not charge the old batteries beyond 90%, then implemented an 80% software limit, no more fires occurred. So even with my new battery in the Bolt, I rarely charge it to 100%.
 

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80% daily, bump it up to 100% for starting road trips, but make sue you have at least one 100% charge to balance the cells, mine had never been charged to 100% until I did.. When I got it at the dealer it had 10 miles and 78% charge. The dealer had done it wrong, they were supposed to charge it to 100% before delivery in 1 constant charge.


On a road trip, plan for about 150-175 miles between DC chargers , charge to 65% and move on...
 

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Just to add a technical point. One thing that degrades battery life is dendrite growth, and dendrite growth is accelerated when the battery is at 100%. If you want to understand dendrites, just google it. It is one of the main reasons not to always charge to 100%.
I think this is mostly true, but needs a lot of * * * * and explanations. Charging to 100% does not guarantee dendrite growth or degradation. I want to get Andy Oury of GM on a podcast to talk about this, because there is almost more misinformation then legit information floating around on this subject. Stay tuned...
 

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So I will be new to this charging stuff once I get my Hummer, so sorry for the dumb question…but based on what I’ve read it sounds like a pretty simple setting either on the charger itself or on the charging app to just set the max charge to 80%. Am I correct or is it a setting in the vehicle?
 

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So I will be new to this charging stuff once I get my Hummer, so sorry for the dumb question…but based on what I’ve read it sounds like a pretty simple setting either on the charger itself or on the charging app to just set the max charge to 80%. Am I correct or is it a setting in the vehicle?
You can set the max charge setting in the vehicle.
 

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So I will be new to this charging stuff once I get my Hummer, so sorry for the dumb question…but based on what I’ve read it sounds like a pretty simple setting either on the charger itself or on the charging app to just set the max charge to 80%. Am I correct or is it a setting in the vehicle?
I set mine inside the truck to 100%, let it charge fully and balance, then set it down to 80% for the next charge. I think its good for an EV to once a year or so run it down to below 10% and then fully charge back to 100% to rebalance the cells. Elon Musk has said to do this every couple months, but I have not seen the need to do it that often.
 

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I set mine inside the truck to 100%, let it charge fully and balance, then set it down to 80% for the next charge. I think its good for an EV to once a year or so run it down to below 10% and then fully charge back to 100% to rebalance the cells. Elon Musk has said to do this every couple months, but I have not seen the need to do it that often.
There is no technical reason that batteries have to be at 100% to be balanced, they simply need to be at a steady state voltage. The BMS should be able to balance the cells and then make small charging adjustments at any target charge setting.
 

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Hummer range really is fantastic, I just wish they would come out and say if charging to ‘100%’ is okay. If they padded it to account for that and 100% is actually only 90ish percent it’d be great to keep it fully charged.
I agree, I was keeping mine at 100% until I read that you should keep (general electric cars, not the hummer specifically) them below 80% so I let it fall. It would be nice to have a concrete direct statement that we should keep them below 80 or that it does not matter. I would also like to know if DC fast charging is bad for the batteries or not because I have been doing a bit of it at a free charger near work.
 

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There is no technical reason that batteries have to be at 100% to be balanced, they simply need to be at a steady state voltage. The BMS should be able to balance the cells and then make small charging adjustments at any target charge setting.
They won't be top balanced though. Top balancing puts the most energy into the pack.
 

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Hummer range really is fantastic, I just wish they would come out and say if charging to ‘100%’ is okay. If they padded it to account for that and 100% is actually only 90ish percent it’d be great to keep it fully charged.
GM did say best to go 80% daily, 100% for road trips, but informally the top battery engineer said "charge it however you want"

Batteries do not like to sit at a high or low state of charge, leaving it sit at low SOC is just as bad as high SOC
 

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Hummer range really is fantastic, I just wish they would come out and say if charging to ‘100%’ is okay. If they padded it to account for that and 100% is actually only 90ish percent it’d be great to keep it fully charged.
The hummer pack likely has just a couple % cushion at the top at most and 3-4% at the bottom. 212 kWh usable out of 220 kWh totAl doesn’t leave a lot of room. The Ultium NMCA chemistry is new to the EV industry, though, and we should pay attention to what GM says and not our past experiences. It appears to allow substantial regen recharge power back to the pack even when “full“ and not reduce accel power to “turtle“ when near zero SOC. And GM’s Battery Chief Tim Grewe has repeatedly said it is designed to “charge to 100% whenever you want”. Looks to me GM has engineered this pack to give the owner maximum freedom to both drive and charge as they need to with minimal restrictions.
 

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It appears to allow substantial regen recharge power back to the pack even when “full“
The Bolt does this as well now with the new battery and latest software, and my Mach E has always had regen even at 100%. But it is with different chemistries. GM used to tell Bolt owners it was fine to charge to 100% everyday, right up until the time the fires started to happen.

No matter what the exact chemical formula, L-Ion batteries are better off not being at the top or bottom of SoC for long periods, just like Tom said. Both of my current EVs can get >200 miles at lower SoC, and that works just fine around town. I also keep them plugged in at home, it helps with the battery conditioning and uses the wall power for that.

Telling people they can charge any way they want is a good marketing message. :)
 
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