Battery Management

[DNAinaGoodWay]

Yes! Went here: http://gm-volt.com/forum/forum.php#/topics/276041?page=2&_k=zlf686

Found this:

 

[Pigwich]

The Volt has a bazillion PIDs that don't apply to a purely electric vehicle. Does anybody here want to start a Google Sheets with all of the Bolt applicable PIDs? When I did the generic dump-to-Torque of all the Volt PIDs, I think Torque went in to slow Slow SLOW reading all the non-applicable PIDs, at least on the Spark EV. Maybe after I cook this pizza I will start this project?

 

[Nagorak]

I've thought more about the concept of only charging to 50%, but in that case I don't see why you'd bother with a Bolt. The whole point of the Bolt is that it has a large enough battery, so you don't have to worry about running out. If you artificially make the car into a low range EV, then why bother? You could just get an Ioniq instead and save yourself a lot of money, which you could use to rent a car when you needed the range. After all, it's not like you'd have the range in a pinch anyway, if you're never charging beyond 50%.

If EVs are going to be successful, then they need to be able to be driven like a normal car, without bending over backwards to try to baby the battery. Maybe we're not there yet in terms of technology, but in that case I'd prefer to lease and turn the car in at the end, so the battery longevity is someone else's problem.

 

[sgt1372]

If EVs are going to be successful, then they need to be able to be driven like a normal car, without bending over backwards to try to baby the battery. Maybe we're not there yet in terms of technology, but in that case I'd prefer to lease and turn the car in at the end, so the battery longevity is someone else's problem.

Totally agree. I leased my Bolt for a variety of reasons but battery degradation was one of them.

It's the same reason I would not buy a used Prius or any other hybrid or EV. Battery replacement is expensive. You have no way of knowing how well or badly the battery was treated and you don't want to be left holding the bag.

 

[phil0909]

If EVs are going to be successful, then they need to be able to be driven like a normal car, without bending over backwards to try to baby the battery.

Yes. Life is far to short to spend it painstakingly managing a car battery. I use hilltop reserve charging to charge to 87% daily, and set the timer to complete charging just before my commute. It's all automatic, and I just never worry about it. Gives me enough juice for the day, and should be reasonably gentle on the battery, If the battery degrades, well, that's a shame and I'll buy a different car next time.

 

[LeftieBiker]

I've thought more about the concept of only charging to 50%, but in that case I don't see why you'd bother with a Bolt. The whole point of the Bolt is that it has a large enough battery, so you don't have to worry about running out. If you artificially make the car into a low range EV, then why bother? You could just get an IONIQ instead and save yourself a lot of money, which you could use to rent a car when you needed the range. After all, it's not like you'd have the range in a pinch anyway, if you're never charging beyond 50%.

This looks to me like a straw man argument. Who exactly suggested always charging to only 50%? And if you got an Ioniq, presumably you'd also charge that to 50%, leaving the range at...62 miles. The point some of us are making is that it you don't need 200 miles of range, you don't need to keep the car fully charged, and that will in turn help the battery life. If you know you'll need it all, then by all means, charge it all the way. Otherwise, 87% - NOT 50% - seems sensible.

 

[devbolt]

If EVs are going to be successful, then they need to be able to be driven like a normal car, without bending over backwards to try to baby the battery. Maybe we're not there yet in terms of technology, but in that case I'd prefer to lease and turn the car in at the end, so the battery longevity is someone else's problem.

Totally agree. I leased my Bolt for a variety of reasons but battery degradation was one of them.

It's the same reason I would not buy a used Prius or any other hybrid or EV. Battery replacement is expensive. You have no way of knowing how well or badly the battery was treated and you don't want to be left holding the bag.

It's easy enough pull the battery health status from a Prius to give you an idea of whether the battery is likely to die. Age of the car is also a decent indicator. A new battery installed is about $3200. Which is about the same price you'd spend on an automatic transmission rebuild in a traditional car. You can get used or rebuilt packs for much less than $3200, too. If you are risk averse to buying a hybrid because of unknown treatment of the battery, are you also averse to buying a used car with a traditional automatic transmission? You have no way of knowing how the automatic transmission was treated.

 

[Nagorak]

I've thought more about the concept of only charging to 50%, but in that case I don't see why you'd bother with a Bolt. The whole point of the Bolt is that it has a large enough battery, so you don't have to worry about running out. If you artificially make the car into a low range EV, then why bother? You could just get an IONIQ instead and save yourself a lot of money, which you could use to rent a car when you needed the range. After all, it's not like you'd have the range in a pinch anyway, if you're never charging beyond 50%.

This looks to me like a straw man argument. Who exactly suggested always charging to only 50%? And if you got an Ioniq, presumably you'd also charge that to 50%, leaving the range at...62 miles. The point some of us are making is that it you don't need 200 miles of range, you don't need to keep the car fully charged, and that will in turn help the battery life. If you know you'll need it all, then by all means, charge it all the way. Otherwise, 87% - NOT 50% - seems sensible.

I feel like reading the other replies it's definitely suggested that only charging halfway is best for battery longevity and even hilltop mode is considered potentially risky. I considered that possibility (charging only halfway), but after thinking about it more, I felt like if I were going to do that regularly, it suggests I should consider a short range EV instead because I clearly don't need the range.

With a low range EV there's really no question about charging to full or at least 80%, because below that point you have no range at all. But a smaller battery means you pay less up front, and replacing the battery later also won't set you back as much.

Setting hilltop mode does seem like something almost everyone should do.

 

[sgt1372]

If EVs are going to be successful, then they need to be able to be driven like a normal car, without bending over backwards to try to baby the battery. Maybe we're not there yet in terms of technology, but in that case I'd prefer to lease and turn the car in at the end, so the battery longevity is someone else's problem.

Totally agree. I leased my Bolt for a variety of reasons but battery degradation was one of them.

It's the same reason I would not buy a used Prius or any other hybrid or EV. Battery replacement is expensive. You have no way of knowing how well or badly the battery was treated and you don't want to be left holding the bag.

If you are risk averse to buying a hybrid because of unknown treatment of the battery, are you also averse to buying a used car with a traditional automatic transmission? You have no way of knowing how the automatic transmission was treated.

An EV/hybrid battery is not the same as a transmission.

You can probably tell if a battery is degrading but not by means of a test drive. I suppose there are tests that can be done to provide info on the max charge capacity of a battery BUT when a battery dies, it just dies and renders the entire car inoperable.

When a tranny is failing or causing problems you can easily determine that in a test drive and can still operate the car. You have some kind of warning and you can fix it -- usually for less than $1k. Not so if your battery dies. When it goes out, the car is totally useless.

I've owned/leased 2 Priuses -- both new -- and got rid of them after 3-4 years. No problems doing that. Yes, a hybrid battery can be replaced for around $3-4k but that 's still not cheap and an EV battery is a lot more expensive than that.

An EV battery costs MUCH MORE than one for a Prius. The cost for replacing a Tesla battery after the 8 year warranty lapses is $10k (60kwh) and $12k (85kwh).

Do you want to get caught holding the bag for that? Not me!

 

[SeanNelson]

I feel like reading the other replies it's definitely suggested that only charging halfway is best for battery longevity and even hilltop mode is considered potentially risky.

What's missing from the discussion is "how risky". For example, the battery might be reduced to:

60% of original capacity after 10 years of regularly charging to 100%, or
80% of original capacity after 10 years of regularly charging to 90%, or
85% of original capacity after 10 years of regularly charging to 75%, or
90% of original capacity after 10 years of regularly charging to 50%

Now these are completely speculative figures, but the point is that the degradation between normal charging to 90% vs. 100% is far greater than the difference between normal charging of 80% vs 90%, and so on down the line.

So the while the risk factor decreases as you reduce the maximum state of charge, it decreases the most rapidly with only small reductions in maximum state of charge.

Therefore, the question becomes: is it worth the hassle of only charging to 50% each day in order to have (according to the above speculative figures) an extra 20 to 25 miles of range after 10 years?

That's what you have to ask yourself.

Personally, I think that just using hilltop reserve mode under normal circumstances is completely reasonable.

 

[michael]

I feel like reading the other replies it's definitely suggested that only charging halfway is best for battery longevity and even hilltop mode is considered potentially risky. I considered that possibility (charging only halfway), but after thinking about it more, I felt like if I were going to do that regularly, it suggests I should consider a short range EV instead because I clearly don't need the range.

With a low range EV there's really no question about charging to full or at least 80%, because below that point you have no range at all. But a smaller battery means you pay less up front, and replacing the battery later also won't set you back as much.

Setting hilltop mode does seem like something almost everyone should do.

No. A large battery being treated "gently" is far better than a small battery being pushed hard. Plus you have the option to go long distances when needed.

 

[michael]

I feel like reading the other replies it's definitely suggested that only charging halfway is best for battery longevity and even hilltop mode is considered potentially risky.

What's missing from the discussion is "how risky". For example, the battery might be reduced to:

60% of original capacity after 10 years of regularly charging to 100%, or
80% of original capacity after 10 years of regularly charging to 90%, or
85% of original capacity after 10 years of regularly charging to 75%, or
90% of original capacity after 10 years of regularly charging to 50%

Now these are completely speculative figures, but the point is that the degradation between normal charging to 90% vs. 100% is far greater than the difference between normal charging of 80% vs 90%, and so on down the line.

So the while the risk factor decreases as you reduce the maximum state of charge, it decreases the most rapidly with only small reductions in maximum state of charge.

Therefore, the question becomes: is it worth the hassle of only charging to 50% each day in order to have (according to the above speculative figures) an extra 20 to 25 miles of range after 10 years?

That's what you have to ask yourself.

Personally, I think that just using hilltop reserve mode under normal circumstances is completely reasonable.

As the battery fades, you need to push it harder and harder. Take care of it and it will take care of you.

It's not a lot of trouble to limit the charge. You don't need to do it religiously, just as often as practical. Use your charge time so that most days it doesn't reach the hilltop limit before you are ready to leave for your morning commute.

Yes, GM should have made it easier by providing a slider like Tesla does. But they didn't so it's up to you and me.

With a typical 6 kW EVSE, the car will charge about 10% hour. So set the thing to charge to 40% immediately upon plug in, and set the charge timer to complete (90%, hilltop) maybe two hours after your normal departure. See what is the status at your departure and adjust the completion time as necessary to get whatever is your target. If you don't go to work one day, fine, that one day it will go to completion. If you leave an hour early, you will be only 10% less than usual.

In my opinion, not much trouble.

 

[LeftieBiker]

Nagorak wrote:
I feel like reading the other replies it's definitely suggested that only charging halfway is best for battery longevity and even hilltop mode is considered potentially risky.

I "feel like reading the other replies" that no such thing was suggested.

 

[Nagorak]

Nagorak wrote:
I feel like reading the other replies it's definitely suggested that only charging halfway is best for battery longevity and even hilltop mode is considered potentially risky.

I "feel like reading the other replies" that no such thing was suggested.

See below.

From the standpoint of battery life, I would much rather run between 20-60 rather than 50-90. On the other hand, it depends on how much or little reserve makes you comfortable.

Your car is a $20,000 battery on wheels. You don't want to wait a few years to see how they are holding up. You should use the best possible practice from the beginning.

I agree, hilltop as a normal practice. I would try to stop charging before it reaches 90% as often as practical.

I'm not sure what the big deal is about discussing this?

To be honest I'm sort of on the fence about it. Just charging to 90% would be easiest and part of me is thinking that's all I stood be expected to do. On the other hand maintaining as much battery life as possible did make sense. Provided the price comes down to the level I'm looking for (we're getting there), I'll probably try keeping the battery at moderate charge to start with. It would be an interesting experiment, if nothing else.

 

[LeftieBiker]

The quote from Michael has him writing first that he'd "much rather run" a 20-60% SOC range, then concluding that 87% is fine as normal practice. 60% is actually 20% more than 50%.Taking the smallest, weakest statement from a bunch of them and then running with that as prevailing opinion is another form of the Strawman Argument. The only real difference of opinion here is the "charge to 100% all the time" crowd, vs the "charge to 100% only when needed" crowd. I'm guessing most people will just happily use Hilltop mode.

 

[peteblair]

Until Chevy gives us a way to select charging capacity (beyond hilltop mode) I will just be using that. I am not all that concerned about charging to 90% as compared to 60%. Sure 60% max SOC should give overall less battery fade but to me it isn't such a significant difference that I am going to obsess about it. Plus it is useful having 90% of the range available when needed. Yesterday I hadn't planned on doing anything and I ended up driving 150 miles and I didn't really have time to stop and recharge. So having the 90% available worked great for me. Had I been metering it to 60% I would have needed to charge.

 

[michael]

The quote from Michael has him writing first that he'd "much rather run" a 20-60% SOC range, then concluding that 87% is fine as normal practice. 60% is actually 20% more than 50%.Taking the smallest, weakest statement from a bunch of them and then running with that as prevailing opinion is another form of the Strawman Argument. The only real difference of opinion here is the "charge to 100% all the time" crowd, vs the "charge to 100% only when needed" crowd. I'm guessing most people will just happily use Hilltop mode.

You misunderstood what I said., although I agree it was ambiguous. What I said was to set hilltop mode as standard practice as opposed to full charge mode. I did not intend that to mean that charging to tat level was ok in my opinion

I will avoid charging beyond what I need whenever practical.

 

[gpsman]

Two things:

It is reasonable to expect the "guess o meter" to drift from reality over time if you "Always" keep the battery in the middle. I don't care how great the battery management software is. It only really, truly, knows what the battery state of charge is at the absolute bottom or absolute top.

I'll assume the BMS software is very good.
Assume the error is at most 0.5% error per day.

After 10 days your SOC meter might be 5% off.
It will display 60% full when really it is 55%.

After 100 days you could be a whopping 50% off!
(Worst case scenario, but you get my point.)

Thus, I believe, it is a good idea to charge to 100% at least once per month. THIS will recalibrate the guess o meter and your SOC and range remaining will be more reliable. The longer the interval between full charges, the less reliable the guess o meter becomes.

I also think it is healthy for balancing low cells.
It is impossible for all cells in a multi cell pack age, charge, and discharge at exactly the same rate.

Lastly, I only charge to 100% using the 120 VAC cord that comes with the car. I do not have access to 240 VAC and I only DCFC when away from home (about 3 times a month). Surely charging to 100% at 8 or 12 amps (~1 kw rate) will not put heat or stress on the battery as I approach 100%. What do you all think about the "gentleness" of charging to 100% with the trickle charge only? I think this would be benedicial for once a month battery calibration and balanancing while putting the least stress on the battery.

 

[WetEV]

It only really, truly, knows what the battery state of charge is at the absolute bottom or absolute top.

Err.. no. Knowing the no load voltage and temperature gives state of charge. Nothing special about top or bottom.

Thus, I believe, it is a good idea to charge to 100% at least once per month.
I also think it is healthy for balancing low cells.
It is impossible for all cells in a multi cell pack age, charge, and discharge at exactly the same rate.

A good idea to charge to 100% on a weekly or monthly schedule, but for the second reason and not the first. The balancing of cells is usually done near 100%, or "top balanced". You might gain range by having the cells better balanced: how much depends on how the car balances cells.

Lastly, I only charge to 100% using the 120 VAC cord that comes with the car. I do not have access to 240 VAC and I only DCFC when away from home (about 3 times a month). Surely charging to 100% at 8 or 12 amps (~1 kw rate) will not put heat or stress on the battery as I approach 100%. What do you all think about the "gentleness" of charging to 100% with the trickle charge only? I think this would be benedicial for once a month battery calibration and balanancing while putting the least stress on the battery.

8A is 960W, of which a few hundred will be used by pumps, fans and electronics. Some may be needed for cooling or heating...And pack conditioning might have a large impact at higher or lower temperatures. Net rate might be near 400W to 600W, less if pack conditioning. 12A is 1440W, leading to a charging rate of near 900W to 1.1kW, again less if pack conditioning needed. The "gentleness" of the charge is the "C" rate, or the charge rate divided by the capacity. 65kW/60kWh = C rate over 1, which is a "fast charge", and is somewhat harder on the battery. 0.4kW/60kWh = C rate of 0.0067, which is slow enough to again be slightly harder on the battery. A C rate near 0.1 to 0.05 is about ideal, or 6kW to 3kW. Which is what you get with a 240V charging station...

The reason why a low C rate seems to be mostly that the battery is at a higher state of charge for longer while getting to 100%. The effect is small, and probably not observable in real cars. Fast charge is worse, and faster capacity loss is observable. 3 fast charges a month isn't very much, I wouldn't worry about that. But you might have a problem in the heat of summer with charge rate on 120V, especially if limited to 8A.

 

[cyaopec]

So is this really only a 100,000 mile battery? I drive 100.5 miles per day. Using my 2013 Volt as a gauge I would use roughly 28.5 kWh of electricity per day. (The first half of my commute is down hill and only uses 7.7 kWh in the Volt). So I would be putting five hundred miles per week on the battery. Granted, the battery would only be discharged roughly 50% at the end of each day. But would two 100 mile runs in a row be equal to a single discharge of two hundred miles? I guess I'm wondering if total miles on the battery is more of a factor than the number of deep discharges. With my Volt battery fade isn't an issue because you'll just use more of the engine as the battery fades. But I'm concerned people with long commutes may end up with a battery that's less useful after 100k miles than your typical Japanese 4 cylinder engine in a Civic or Corolla. I could tolerate a 15% fade around 200k miles. But the 40% figure cited in the manual would be a deal killer.