Charge every night or every other?

[PowerWall]

Hello, I have a Gen2 17 Volt. During the warmer months I can get 2 daily commutes in with a full charge. Is it better for the battery pack to charge each night when there is still about 50% of the charge remaining, or do it every other night after depleting the battery? In winter I deplete about 70% of a full charge.

Here is some background to share. I use a Clipper Creek LCS-30 240 charger which takes about 4 hours from empty to full. We have solar and net meter in part because our house is 100% electric and have only had 2 utility bills (this winter because of extreme cold) since March of 2013 when our array went online.
I have about 17K miles on my Volt acquired Christmas eve 2016. According to the OnStar app 87.5% of those miles were electric, so they were free. It shows that only 2090 miles were gas powered. Life time fuel costs about $150. The gas miles would be my vacation drives.

 

[Francisco]

Greetings. Personally, I charge/top it off as soon as I park it in the garage. This way it is ready for an unexpected longer drive. Need to charge anyway. From North Central New Mexico - Bueno Bye. Francisco.

 

[Joseph Yaroch]

Keep in mind the following, from the owner's manual:
This section explains the process
for charging the high voltage battery.
Do not allow the vehicle to remain in
temperature extremes for long
periods without being driven or
plugged in. It is recommended that
the vehicle be plugged in when
temperatures are below 0 °C (32 °F)
and above 32 °C (90 °F) to
maximize high voltage battery life.

I live in New Mexico where it is often over 90 degrees, so my policy is to keep the car plugged in most of the time it is in the garage.

 

[Francisco]

Greetings Joseph:
I am currently in Questa, but also have a house at Ventana Ranch, in Albuquerque. I am greatful for an attached garage at each location because outside temperature can be at extreme ends of the thermometer. All vehicles, electric or not should be started up and driven from time to time. This includes riding mowers and motorcycle in winter. You are correct in your response. We need to protect our investment. Okay, Bueno Bye. Hey it's CHILE time.
Respectfully
Francisco

 

[Roland]

We adopted the habit of plugging ours in as soon as we get home, regardless of what reserve may be left. Since the car sits more than it goes, it would be too easy to forget to plug it in other than when we first park it. So we made that our habit. Using a gas station next week is going to be strange...haven't been to one of those since last May!

 

[Wizard of ahs]

If you're not driving it, plug it in

 

[larrenz]

Do you guys top it off every night to about 90% only?

 

[Roland]

Do you guys top it off every night to about 90% only?

I don't think that's an option on the Volt...at least on Gen1s. I charge to 100%, 100% of the time.

 

[PrivatePilot]

I don't think that's an option on the Volt...at least on Gen1s. I charge to 100%, 100% of the time.

Not necessarily. The Volt is engineered so that the battery is never actually at a 100% SOC, nor is it ever depleted to 0% - the Gen1's for example never go below ~20%, and never go above ~90%. The margins are a little smaller on Gen2's, but there is still buffer on both ends. This was designed this way to aid in battery longevity as a battery at 100% adds stress, and a battery depleted to near 0% does as well.

The GM engineers realized this and designed the car so that those scenarios never really happen, even when the end user may *think* they are.

Accordingly, one never needs to worry about "overcharging" the Volt nor stressing the battery by leaving it plugged in all the time, which is the recommended course of action no matter how much or little charge you consumed, or need the next day. The other benefit of leaving it plugged in is that the thermal management system can heat or cool the battery as necessary to both aid in capacity, but in extreme temperatures, keep it cool and again, ensure longevity.

Just leave it plugged in whenever you're home. A.B.C. - "Always Be Charging".

 

[Pushmi-Pullyu]

The Volt is engineered so that the battery is never actually at a 100% SOC, nor is it ever depleted to 0% - the Gen1's for example never go below ~20%, and never go above ~90%.

He meant what the car's instrument panel reports as 100%. No EV maker allows the battery pack to actually charge to 100% of the battery cells' nameplate capacity, to avoid premature aging. Ditto for driving the car until the battery is actually exhausted to 0%, even if the instrument panel reads 0%.

 

[Pushmi-Pullyu]

Is it better for the battery pack to charge each night when there is still about 50% of the charge remaining, or do it every other night after depleting the battery? In winter I deplete about 70% of a full charge.

Let me first explain the theory of maximizing battery life, then I'll explain why that probably isn't applicable here.

In theory, you should try to maintain an average battery charge of 50%. For example, if your daily drive uses 50% of a full charge, then you should try to charge to 75% and discharge to 25%, meaning that ideally you should hit 25% just as you return home for the night. Similarly, if you were to use let's say 70% of the battery's full capacity, then you'd want to charge to 85% and discharge to 15%. That's the theory.

The problem is, as has already been pointed out in comments above, GM has engineered the car to reserve a certain percentage of the battery capacity; a part that is not accessible to you. GM isn't going to tell you how much that is, and unfortunately the car isn't programmed to tell you if it's lost capacity over time. So, how could you know what an actual 50% charge is? You can't. All you can tell is what the car's instrument panel says is a 50% charge... but most likely isn't.

So, for practical purposes, you should charge the car whenever you return home and it's below 80% charge. If it's 80% or above, then for maximum battery life it would be best not to charge it... unless you plan a drive the next day which will test the car's EV range, in which of course you should go ahead and charge it to what the car says is "100%".

Or... as several people have already commented above, it may be best to simply plug it in every time you park it wherever the charger is, to make sure you get into the habit and don't forget. It depends on the individual. If you really can train yourself to check the charge level before plugging in every time, then never charging when it's above 80% may work for you. But if you're like most of us, the best habit would be simply to put it on the charger every time.

If you're really concerned with battery life, then drive the car gently, and don't drive with a lead foot. (If it was a different plug-in EV, I'd add "Never use DC fast charging", but so far as I can tell, the Volt isn't built to do that at all.)

Frankly, for the average driver, you shouldn't need to worry about battery life. Unless you're going to be using the car in a way that strains the battery pack more than it's designed for, it should last as long as you'd want to keep the car.

Sorry we can't give you a more definitive answer than "it depends". But the good news is that very few people have reported any problem with the Volt's battery pack. I understand a very few have reported reduced maximum power in older Volts which have been driven long distances or have otherwise been abused, and that does indicate reduced maximum capacity.

Bottom line: Odds are very high that you won't need to worry about "babying" the battery, so long as you don't abuse the car.

​

 

[Roland]

Frankly, if you look at the history of the Chevy Volt battery, you will read that even after 300,000 miles these batteries are operating with virtually no descernable loss over time. And it's not due to the expert operation and care by the end user. Most of us end up learning on the fly, what works best for us, since experts are few and far between. This morning I got an email from the dealer where I purchased my Volt, congratulating me on my 1 year anniversary of owning it. It also offered to answer any questions I might have on my Volt. That gave me a chuckle since at my last visit it was painfully obvious that I already knew more about the car than they did. These cars are designed by GM so us dummies can just drive them and plug them in every evening when our day is done and not worry about it anymore than that. If the indicator says you'll get 38 miles, you will probably get somewhere close to that if you are not lead footing it. If you're hyper-mile-ing you could get more than what the indicator is showing You don't have to worry about micro managing the charge level, they did all that for you in the programming. Just charge and go...right past the gas stations!

 

[PrivatePilot]

No EV maker allows the battery pack to actually charge to 100% of the battery cells' nameplate capacity

The buffers vary greatly between manufacturers on the top and bottom side of SOC. The 2017 Kia Soul EV for example (my sister owns one) only holds a 5% buffer on the top side and 10% on the bottom. Our Volts hold 21-22% on the bottom and 10% on the top, and if you somehow get it down to 16% the car goes into limp mode and the engine will roar at max RPM to quickly recover it back to what GM thought (at the time) was a "Safe" bottom SOC.

He meant what the car's instrument panel reports as 100%.

Just posting it for public knowledge of any others reading the thread, such as the OP perhaps. It's a very common misconception that zero on the GOM means the battery is actually at 0%SOC, and a full GOM means the battery is at 100%SOC. This is the underlying thinking behind why many people question (IE, this thread) if it's safe to leave their EV plugged in all the time, etc.

GM has engineered the car to reserve a certain percentage of the battery capacity; a part that is not accessible to you. GM isn't going to tell you how much that is

The buffer numbers are generally easily visible using an OBD2 diagnostic app that shows the BMS SOC vs the GOM/Display SOC. Torque, programmed with the correct PID's (For example) will show you all sorts of normally "hidden" info. I use the MyGreenVolt app on my Volt that shows me all sorts of data about traction power usage, temps from a variety of locations (including the battery), true and displayed SOC, etc etc etc.

and unfortunately the car isn't programmed to tell you if it's lost capacity over time.

Again, consumer level OBD apps can get you this information on most EV's - some even have a PID specifically for tracking the usable SOC, IE the loss of usable capacity. Some EV's like the Leaf will even display their degradation level right on the dashboard for the savvy end user, or potential used car buyer.

 

[Pushmi-Pullyu]

Some EV's like the Leaf will even display their degradation level right on the dashboard for the savvy end user, or potential used car buyer.

Aargh! Right you are, my bad for posting a false meme.

Kudos to Nissan for engineering the Leaf to display a gauge that shows the capacity of the battery... altho the gauge displays "bars" which shows loss in segments, not the precise amount; and not all bars represent the same amount of loss. So that is also a bit of a "guess-o-meter", altho for a different reason.

And a curse upon used car dealers who reset that gauge on Leafs which have permanently lost bars, to make it look like they not lost any. This is similar to the scam for resetting an odometer, but unfortunately this one isn't against the law, so used car dealers can do it with impunity. (◣_◢)

Are there other plug-in EVs which have a similar gauge? The Leaf is the only one I've read about which has that.

The buffer numbers are generally easily visible using an OBD2 diagnostic app that shows the BMS SOC vs the GOM/Display SOC.

Wow! This is all news to me. I've seen long detailed arguments from electrical engineering experts about whether this or that method of measuring an EV's battery pack capacity is accurate or not, and under what circumstances... since, for example, maximum capacity varies a bit by temperature.

If you've got some sort of meter that shows you directly what the SOC is, and you can use that to accurately measure the "bottom" and "top" buffers, then that's a remarkable improvement over what I've seen discussed before!

Is this a new type of meter?

​

 

[PrivatePilot]

A $10 OBD2 bluetooth reader and your smartphone (or in the case of iPhones, you need a $20 WiFi version of the reader instead, but that's another story) and a configurable OBD scantool app (Torque Pro for the Android Crowd, and I use one called "OBD Fusion" on my iPhone) will get you the relevant data. If you install the custom PID's into the related apps you can then usually have a nicely displayed "dashboard" that shows SOH, SOC, etc etc.

Here's one for the Kia Soul EV using Torque Pro programmed with the related custom PID's showing a TON of info that isn't normally visible to the end user, but gives the geeky or data hungry people like me access to all sorts of extra info.

Here's the Volt version (that I use) called "MyGreenVolt".

There's many custom written apps specific to certain make/models... Leaf owners have one called "LeafSpy" for example.

Great write up about how to do this in this thread below...this is specific to the Kia Soul EV's, but some Googling can turn up related data for other makes/models.

http://www.mykiasoulev.com/forum/viewtopic.php?f=6&t=471&sid=2bcf41a9601e99cb6ced4d1c5550cf81

 

[Roland]

Hey, that's pretty neat! I just downloaded the MyGreenVolt app for my android, now all I need is that blue toothed dongle thingy! I can see I'm about to get real nerdy...

 

[Roland]

My daughter just purchased an '18 Clarity. Anyone know if they make a similar app for the Clarity plug-in?