Battery Depletion before Recharging

[JerryBob]

Being new to this forum I am not sure if you have discussed this yet. If you have could you tell me where. Is it better for longer battery life to recharge the battery when it has used most of it's energy or should you keep it topped up? I have an 80 mile EV and can't wait to have extended range. I am currently recharging every 2nd or 3rd day. It's possible I may have a 2 Bolt family soon and it would make sharing a single home charger easier to manage if the charge cycle is less often.

 

[Anonymous]

Always
Be
Charging

 

[LeftieBiker]

Don't keep the battery full most of the time. If you can recharge every few days without running too low on charge, that is better for the pack.

 

[Anonymous]

Don't keep the battery full most of the time. If you can recharge every few days without running too low on charge, that is better for the pack.

Really? So you drive your Bolt EV every day, yet, you do not plug it in every night?

This is contrary to my practice.

I have heard some people using the "hilltop reserve" to charge only up to 85%, but I have never seen a recommendation to NOT plug in!

Do you have a source for this recommendation, which you claim is "better for the pack?"

 

[GetOffYourGas]

Always
Be
Charging

This is the easiest solution for the user. For many, it was necessary for 80-mile EVs. It wasn't necessary for the OP with his 80-mile EV, and will be less necessary with a 240-mile EV.

Plenty of sources indicate that Lithium batteries prefer lower states of charge. I have read/heard that the ideal is somewhere between 20-40%. From that, it would be ideal to charge to about 40%, and not charge again until it's down to 20%. But what's the difference in life between doing that and always charging to full? Nobody knows.

My MO for a Bolt would be to use the Hilltop Reserve, and plug in whenever it's convenient. I would only go to full right before a long trip (>150 miles). That seems like a good balance of being gentle on the battery and convenience to me personally.

 

[michael]

It is well documented that mid range charge states are better than high charge states in terms of battery life.

Better, for example, to run it between 40 and 60% rather than 80 to 100%. or even 70 to 90% (with hilltop)


How much better? Hard to say. But always be charging, no. That's the worst practice for battery life.

And yes, to agree with GetOffYourGas, there is good reason to believe that lower is even better than mid. But whenever I have made that point I get pushback, so I refrain from making that assertion.

 

[Anonymous]

But always be charging, no. That's the worst practice for battery life.

And yes, to agree with GetOffYourGas, there is good reason to believe that lower is even better than mid. But whenever I have made that point I get pushback, so I refrain from making that assertion.

So you do NOT plug in your Volts every night?

 

[LeftieBiker]

Has coffee been bothering you lately? ;-) The Volt is programmed to keep the pack well below 100% actual SOC, so plugging it in every night isn't a big deal - although that too would benefit from a lower average SOC. The Bolt likely charges the pack higher, because they wanted to have the most range in class. Hilltop Mode is likely a perfectly adequate compromise, but to agree with GOYG, if they don't need all that range, then it's better for the battery to only charge fully occasionally, and to not charge every day.

 

[boltage]

The conventional wisdom is that battery life is reduced if:

a. There are more charging cycles.
b. The battery is kept or charged at high states of charge more of the time.

So driving until it gets "low" (where "low" is below what you want for the next day of driving plus a buffer against range anxiety) and then charging to hilltop reserve level is likely to lead to longer battery life than topping it off to full every day even if you drive only a little that day.

Obviously, you may have to recharge every day if the car has only enough for one day of typical driving. Also, those who do not have overnight charging at home may have to charge based on availability of other charging stations (e.g. work, public).

 

[Anonymous]

Here is MY thinking: your mileage may vary!

In 2013, I leased a Chevy Volt because I wanted a pure EV and 80-100 miles did not cut it for me; a Tesla S was just too much money to spend and I could "play" pure EV with the Volt for 3 years while I waited for the Bolt EV to come out.

Now, I have my Bolt EV lease and it is costing me a $10,000 premium over what my Volt cost me, but it is exactly what I want!

If I get the sudden itch to drive to Northern California (which has happened frequently in my 12,400 miles so far), I can drive up to Paso Robles (196 miles) to a DCFC and if for some reason it is not functioning, I can go another 30 miles to San Luis Obispo and charge there for the remainder of my trip!

But according to you guys, I have to stop somewhere first and "top off" so that I can make it to Paso Robles, because I am not supposed to keep my battery fully charged! Every such trip will take an extra 30-60 minutes!

Thanks, but NO thanks!

As a leasee, I have the legal obligation to operate the vehicle according to specifications. I have reviewed the manual and see no specific instructions warning me NOT to keep the Bolt EV always plugged in when it is parked in my garage!

Hence: Always Be Charging!

I also note that after almost 8 months and 12, 400 miles, my Mileage Gauge is showing larger mileage available after full charges than when it was new.

 

[LeftieBiker]

But according to you guys, I have to stop somewhere first and "top off" so that I can make it to Paso Robles, because I am not supposed to keep my battery fully charged! Every such trip will take an extra 30-60 minutes!

That isn't what we are saying, and if I might suggest de-caf...? It really cuts down on those exclamation points! ;-)

What we are saying is that if you don't need more than half of the car's range, you should consider only charging back to Full when you drop to roughly half a charge. This is better for the car. If you are leasing and still don't need all that range, feel free to charge to 100%. I'm sure the next driver of your car won't mind if it has 20 or more fewer miles of available range...

 

[Anonymous]

But according to you guys, I have to stop somewhere first and "top off" so that I can make it to Paso Robles, because I am not supposed to keep my battery fully charged! Every such trip will take an extra 30-60 minutes!

That isn't what we are saying, and if I might suggest de-caf...? It really cuts down on those exclamation points! ;-)

I don't know your age, but an exclamation mark was the "original emoticon!" Are you equally offended by commas, quotation marks and semi-colons?

What we are saying is that if you don't need more than half of the car's range, you should consider only charging back to Full when you drop to roughly half a charge. This is better for the car. If you are leasing and still don't need all that range, feel free to charge to 100%. I'm sure the next driver of your car won't mind if it has 20 or more fewer miles of available range...

This last paragraph makes little or no sense, with or without caffeine!

So, you are doing to all this effort to save 20 miles of range 3 to 5 to 8 years from now?

Since coffee seems to be making the rounds in your replies to me, and you seem to know it all; let me ask you:

What is the reduction in percentage content of caffeine from regular coffee to de-caf coffee?

 

[LeftieBiker]

I'm not a coffee drinker, have no problem with punctuation when used properly and sparingly, and I charge my Leaf to 80% to preserve my current range.

Now imagine the above as:

I'm not a coffee drinker! I have no problem with punctuation when used properly and sparingly! I charge my Leaf to 80% to preserve my current range!

Doesn't the second version bring to mind "Tweak" from South Park? Except for him not drinking coffee, of course.

 

[Anonymous]

I'm not a coffee drinker, have no problem with punctuation when used properly and sparingly, and I charge my Leaf to 80% to preserve my current range.

Now imagine the above as:

I'm not a coffee drinker! I have no problem with punctuation when used properly and sparingly! I charge my Leaf to 80% to preserve my current range!

Doesn't the second version bring to mind "Tweak" from South Park? Except for him not drinking coffee, of course.

I think you're overly sensitive, rude and suffer from entitlement! I am starting to understand your age group now...

Your first post referencing coffee was following mine using only a question mark...

Stay focused. It is real easy for us to go back and check these things you know; they are right here printed on these pages LOL. This is not exactly Harvard/Yale quality debate team stuff here dude.

Tweak that!

And you're giving charging advice to a Bolt EV owner when you own a Leaf, which has one-third the capacity and a whole completely different set of issues and considerations!?! Sheesh!!! No wonder you are so worried about 20 miles of range!!!! (4 exclamation marks), and how much coffee I must be drinking...

 

[LeftieBiker]

Your first post referencing coffee was following mine using only a question mark...

You do understand that "de-caf" is coffee, right? There were six exclamation points in the post before that reference, which is why I suggested de-caf. But hey, who's counting? Anyway, your Bolt uses a lithium pack, as does my Leaf. If you want to believe that 'Be Always Charging!' is the way to go, I really don't care. But please don't suggest that as a definitive answer to someone who genuinely cares about their own battery pack's longevity. Last word from me to you on this.

 

[GetOffYourGas]

The conventional wisdom is that battery life is reduced if:

a. There are more charging cycles.
b. The battery is kept or charged at high states of charge more of the time.

So driving until it gets "low" (where "low" is below what you want for the next day of driving plus a buffer against range anxiety) and then charging to hilltop reserve level is likely to lead to longer battery life than topping it off to full every day even if you drive only a little that day.

Obviously, you may have to recharge every day if the car has only enough for one day of typical driving. Also, those who do not have overnight charging at home may have to charge based on availability of other charging stations (e.g. work, public).

Not exactly. Not all charging cycles are the same. In fact, a full charge cycle is more than twice as hard on the battery as two half-cycles. Frequent small charges have been found to be the way to go.

That said, the difference isn't huge. We are talking about single-digit percentage points over 10 years. So again, my suggestion is to charge using Hilltop Mode whenever convenient, and then top off before a long trip.

But according to you guys, I have to stop somewhere first and "top off" so that I can make it to Paso Robles, because I am not supposed to keep my battery fully charged! Every such trip will take an extra 30-60 minutes!

Thanks, but NO thanks!

I'm not sure who is saying that - it certainly wasn't me.

My MO for a Bolt would be to use the Hilltop Reserve, and plug in whenever it's convenient. I would only go to full right before a long trip (>150 miles). That seems like a good balance of being gentle on the battery and convenience to me personally.

You threw out the extra variable of an impromptu trip. If you are likely to do that, then feel free to charge to 100%. For me, I would know ahead of time any time I'm going more than 150 miles in a day. Part of having a family is giving up these impromptu journeys. Everyone's situation is different.

And to be clear, I trust GM's engineering team did a decent job of protecting the Bolt's battery. It should easily last 10-12 years while providing 200+ miles per charge. I would want to treat it like it's going to last more like 15-20. (Dates and degradation are obviously unknown, this is just my own WAG).

 

[SeanNelson]

...Frequent small charges have been found to be the way to go.

That said, the difference isn't huge. We are talking about single-digit percentage points over 10 years. So again, my suggestion is to charge using Hilltop Mode whenever convenient, and then top off before a long trip.

This is really the key - yes, there may be a difference, but it's not a huge difference. Some people get quite passionate about that small difference and others just say "meh!". Neither approach is wrong, IMHO.

 

[cranial1963]

I think this is a great topic.
With a normal gas powered car, the big concern for someone like me who is a buyer with a long commute is how long
the engine and transmission will last. You try to keep up on the maintenance schedule: tune-ups, oil and filter changes,
the cooling system, and all the other stuff to extend the life of the car as long as possible.

Moving to a Bolt, the focus is now is mostly all on the battery, and while the number of components to worry about
has been greatly reduced, maintaining that one component is new and mysterious.

I have dealt with lithium-ion batteries in my laptop and cell phone, and from what I understand the battery in the
Bolt is of the same type, so what advice I have heard for extending the battery life for a laptop or mobile phone should
also apply to the Bolt. (I did some quick research, and my guess is that the battery in the Bolt is equivalent to approx. 8,000
iPhone 7 batteries!)

I have a friend who works for a car company that makes EVs (not GM) and his advice closely matches the tips I found on
this website (2011):
http://www.plugincars.com/eight-tips-extend-battery-life-your-electric-car-107938.html

Here is a summary:
1. Avoid full charging when you can
2. Avoid deep discharging your battery pack
3. Minimize use of DC quick charge

But the best part is the conclusion, and I quote:
"These tips can extend the life of an electric car’s batteries, but I’d like to make it clear that most are
not absolutely necessary. With modern plug-in vehicles, you can simply plug them in anytime and drive it
any way that you see fit and you should still have batteries that perform well in 10 years. The manufacturers
already build in precautions so you cannot overcharge, over-discharge, or over heat. These are the biggest
impacts to lifespan. Still, the tips can help wring a few more cycles out of your pack—and show you how to
enjoy your EV while maximizing battery lifespan.

You can choose to be a battery-babier or a battery-abuser. That's up to you. For many of these tips, there is
not extensive data that demonstrates exactly how much more life you can get."

So to the original poster, we could basically say: it doesn't really matter. Choose your charging/discharging
levels based on convenience, personal schedule, conserving electricity costs, or anythings else other than
worrying about battery life.

 

[boltage]

I have dealt with lithium-ion batteries in my laptop and cell phone, and from what I understand the battery in the
Bolt is of the same type, so what advice I have heard for extending the battery life for a laptop or mobile phone should
also apply to the Bolt. (I did some quick research, and my guess is that the battery in the Bolt is equivalent to approx. 8,000
iPhone 7 batteries!)

If EV batteries had the same lifetime as cell phone batteries (months before the capacity loss becomes noticeably annoying), no one would want an EV. Of course, in smart phones, cell phone batteries are often sized to be just enough for a day's use, or often less, so they get drained to low levels frequently and require recharging or topping off to 100% daily or more often. I.e. lots of charge cycles to 100% and lots of deep discharges, which is probably a severe use case for the battery.

 

[michael]

But always be charging, no. That's the worst practice for battery life.

And yes, to agree with GetOffYourGas, there is good reason to believe that lower is even better than mid. But whenever I have made that point I get pushback, so I refrain from making that assertion.

So you do NOT plug in your Volts every night?

Of course I do, because the battery size is so limited that it is absolutely necessary for me to fully charge them, both every night and every day at work.

If my Volt battery fades, it doesn't matter since I have the engine to fall back on. If the Bolt (or any EV) battery fades, it's a concern.

If I know I'm not going to use the car for a few days, I don't charge it until the night before I will need it.