What problems can be caused by leaving the HV battery fully charged for several days?

emmrecs

emmrecs

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I've seen a number of posts in this forum where users have strongly advised that it is not good for the battery to be charged to 100% and the car not be driven for some days after the charge is complete. Can anyone tell me what the effect is likely to be on the battery?

(Unfortunately, I first came across the advice after I had left my car fully-charged on two occasions, once for a period of about a week or so!)

I ask the question because my pre-facelift MG5 Exclusive LR has just had its first service at my MG dealer. I read elsewhere on the forum that it is not now standard practice for the service report to include the battery State of Health so I specifically asked for this to be done; the result was 98%!

I found this figure slightly concerning, after one year and less than 6,000 miles and wanted to seek advice, especially from those users who are clearly much more knowledgeable about electricity and electronics than I could ever be!

So, could that 2% loss be attributable, at least partially, to my "ignorance" about leaving the battery fully-charged?

TIA.
 
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When I had my second service at 30K they said the SOH was at 100%. I did check it with an OBD device and it 99% so not bad.
I don't use a lot of rapid chargers and on my home EVSE charge between 80-90% and try to battery balance monthly.
The advice seems to be leave the car between 50-80% if you are not going to use it for some time but I have no idea what is does to degrade the battery if left at 100%
 
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The battery will deteriorate a little every year, the car automatically protects it from excessive deterioration by limiting the minimum and maximum charge and mainting a good temperature range. Between 0-20% and 80-100% the closer you go to full or empty the faster it deteriorates so leaving it at 100% will have contributed but there is really no way to tell since the software that manages it is proprietary.
 
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emmrecs said:
I've seen a number of posts in this forum where users have strongly advised that it is not good for the battery to be charged to 100% and the car not be driven for some days after the charge is complete. Can anyone tell me what the effect is likely to be on the battery?

(Unfortunately, I first came across the advice after I had left my car fully-charged on two occasions, once for a period of about a week or so!)
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Occasionally doing so isn't going to be a major problem, leaving it at a high SOC for weeks on end isn't that good for it but ultimately it's likely the difference will be a few % on the State of Health after several years.

I've had a couple instances where I've accidentally charged more than I intended due to either forgetting to turn off-peak only charging back on or ev.energy failing to stop the charge session at the end of the off-peak period (I have an EO mini pro that i manage with evenergy rather than the EO app)

It's also good to occasionally charge to 100% and then leave it on the charger for a few hours after it hits 100% to let the BMS do a cell balance if the BMS determines it wants to do that.
 
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Hi
I have a similar MG I have done about 10,000 miles in about 20 months
I do try to do a 100% charge every month to let the cells get balanced, you may find a bit of rebalancing could help improve SOC. ?
Mine is still at 100%. All charging has been at home on 7kw .or granny lead
General rule is charge between 20 - 80% and do a full 100% charge when you know the car is going to be used within 12 hours.( also when using fast charge try not break the 20 80 rule).
When doing the 100% BMS cell balance use either a home charger or the granny lead, remember sometimes balancing can take between 1 -5 hours, the car does all the work you can unplug everything when you know that no power is being taken by the charger.
Don`t forget Kers will not be very good until your battery drops 95-96%
 
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Because I need my car at short notice and may have to travel 250km in a day I have always charged to 100% on a granny charger only and always allowed it to balance every time I charge it. 20 months in and almost 30k driven and my battery shows 100% SOH. The BMS is very sophisticated and should look after the battery for you. Just drive it and enjoy it 😁😁
Screenshot_2023-03-08-15-30-43-49_6c3649c0e80913619d728ac7fe39c2ba.jpg
 
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Many thanks to everyone who has contributed!

I should have added that I have a Rolec Home Charger and it has been used for all my charging sessions over the year, apart from a total of six occasions when I was away from home and needed to use Rapids.

Using my Home Charger, along with the associated ev.energy app, I can see no obvious method for limiting the charge delivered to anything below 100%. Anyone using that particular app know any different? The pre-facelift does not include any settings in the car to limit time or level of charge, which I believe the facelift model does.

Because I have Solar PV I use the "Solar Charging" feature of the app (so using a mix of solar and grid) the car may be connected for anything up to 20 hours (as of now, the car is charging, using both solar and grid, to be "ready" for my standard setting, in the app, of 7am tomorrow). Because of the length of time it is connected (sometimes the app shows me that all the charging was done during daylight hours and because the charger's maximum output is 7kW) am I correct to assume that balancing is happening on each occasion? Or is balancing achieved only when using a granny charger? I think not but would be happy to be definitively told otherwise.

@Barrie I do enjoy driving it, very much! It was my first EV and I find it one of the "best" cars (whatever that may mean!) that I've ever driven. (I've never been fortunate, or rich, enough to drive anything like a BMW, Audi, Jaguar or similar marque. :) )
 
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Balancing will occur on any A/C charging once the SOC is at or near 100% and the BMS determines it's needed.
If the cells are already fairly balanced then balancing may either not be triggered or be very quick.
 
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emmrecs said:
Using my Home Charger, along with the associated ev.energy app, I can see no obvious method for limiting the charge delivered to anything below 100%. Anyone using that particular app know any different? The pre-facelift does not include any settings in the car to limit time or level of charge, which I believe the facelift model does.
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There's currently no way for the charger to know the current SOC

Ohme do it by using the car manufactures API (I think EVenergy as well perhaps) but that only works for supported cars.

Since the pre facelift 5 doesn't have a limiter in the car's settings and there's no API to get the data form there's no way i can think of to easily terminate the charge at 80%

Something plugged into the OBD2 port can query the current SOC but I'm not yet sure if it's possible to do when the car is locked without setting the alarm off which seems to be the MG's behaviour if it detects an "intrusion" into the cars systems.
 
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Briefly the consensus of opinion with regards to being kind to your HV battery, is to avoid fully charging to 100% and then leaving the battery at max charge / bursting point for days and days on end.
If you charge to 100% overnight and intend to use the car the following morning, then is okay from time to time.
In the ideal world, you would charge to 100% then start driving ASAP.
Running the car down to a very low SOC on a regular basis is regarded as more harmful for the long term health of your pack.
So given these two factors, we reach the point of view ( of trying ) to use the battery in the SOC level of between 20 to 80% region and then charging.
Not running the SOC to low, then charging back to 100% very frequently.
Of course the point has been correctly made, that trying to adhere to this 20 - 80 of practice is just not practical, for users who will be pushing the boundaries of the pack on a regular basis.
In this case you have no real options then really, regardless of the long term affects on your battery health.
If your usage case regularly necessitates an "empty to full" approach SOC then that's the way it has to be ???.
The same applies with rapid charging, I think we would all agree that the heat generated by consistent rapid charging, has proven to have a detrimental long term affect on battery health.
But if that is what you need to satisfy your demands, then so be it.
An EV with a larger battery pack will avoid this type of thing from happening of course.
 
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Lovemyev said:
Briefly the consensus of opinion with regards to being kind to your HV battery, is to avoid fully charging to 100% and then leaving the battery at max charge / bursting point for days and days on end.
If you charge to 100% overnight and intend to use the car the following morning, then is okay from time to time.
In the ideal world, you would charge to 100% then start driving ASAP.
Running the car down to a very low SOC on a regular basis is regarded as more harmful for the long term health of your pack.
So given these two factors, we reach the point of view ( of trying ) to use the battery in the SOC level of between 20 to 80% region and then charging.
Not running the SOC to low, then charging back to 100% very frequently.
Of course the point has been correctly made, that trying to adhere to this 20 - 80 of practice is just not practical, for users who will be pushing the boundaries of the pack on a regular basis.
In this case you have no real options then really, regardless of the long term affects on your battery health.
If your usage case regularly necessitates an "empty to full" approach SOC then that's the way it has to be ???.
The same applies with rapid charging, I think we would all agree that the heat generated by consistent rapid charging, has proven to have a detrimental long term affect on battery health.
But if that is what you need to satisfy your demands, then so be it.
An EV with a larger battery pack will avoid this type of thing from happening of course.
Click to expand...

Worth noting that is for NMC chemistry, some cars now are using different chemistry such as LFP (It's less energy dense so tends to be in the standard range models as opposed to long range) I believe that one doesn't mind being charged to 100% infact it may be beneficial for balancing.etc
 
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dragon2611 said:
Worth noting that is for NMC chemistry, some cars now are using different chemistry such as LFP (It's less energy dense so tends to be in the standard range models as opposed to long range) I believe that one doesn't mind being charged to 100% infact it may be beneficial for balancing.etc
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Absolutely true of course - Thanks !.
( I omitted this due to the pack chemistry used in the case of the OP's model ).
LFE battery chemistry has a harder time giving out an accurate ( predicted ) range on the GOM compared to the NMC ( cobolt element ) packs.
In the case of the ZS EV ( Gen 2 ) standard range, fitted with the LFP chemistry packs, this can been seen in the cars inability to restrict the SOC to 80%.
This is unlike the cobolt element pack chemistry used in the LR model, where the charging advice is different.
 
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emmrecs said:
Many thanks to everyone who has contributed!

I should have added that I have a Rolec Home Charger and it has been used for all my charging sessions over the year, apart from a total of six occasions when I was away from home and needed to use Rapids.

Using my Home Charger, along with the associated ev.energy app, I can see no obvious method for limiting the charge delivered to anything below 100%. Anyone using that particular app know any different? The pre-facelift does not include any settings in the car to limit time or level of charge, which I believe the facelift model does.

Because I have Solar PV I use the "Solar Charging" feature of the app (so using a mix of solar and grid) the car may be connected for anything up to 20 hours (as of now, the car is charging, using both solar and grid, to be "ready" for my standard setting, in the app, of 7am tomorrow). Because of the length of time it is connected (sometimes the app shows me that all the charging was done during daylight hours and because the charger's maximum output is 7kW) am I correct to assume that balancing is happening on each occasion? Or is balancing achieved only when using a granny charger? I think not but would be happy to be definitively told otherwise.

@Barrie I do enjoy driving it, very much! It was my first EV and I find it one of the "best" cars (whatever that may mean!) that I've ever driven. (I've never been fortunate, or rich, enough to drive anything like a BMW, Audi, Jaguar or similar marque. :) )
Click to expand...
I too have a Rolec (smart) and use the ev.energy app.

If you are on a time of day tariff such as Go, then the 4 hour period will add approx 40-45% per night, so only charge when around 50% or lower. Alternatively set the ready by time to earlier than 04:30am and it should stop then.

And remember 100% is not 100%...there is a buffer managed by the BMS to prevent you charging to 100% :)
 
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Gomev said:
And remember 100% is not 100%...there is a buffer managed by the BMS to prevent you charging to 100% :)
Click to expand...
(y)
And the warranty on the battery doesn't stipulate that you should mollycoddle it.
They just say if the SOH falls below 70% after 7 years they will repair or replace it. That means a drop of 4% SOH per year is acceptable.
 
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You would have to leave it unused at 100% for weeks rather than days to have any chance of detecting a deterioration and even then only with specialist testing.
 
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Many thanks to all who have contributed to this thread!

Having now also read of other users reporting battery SoH even lower than 98% after one year with similarly low mileage to mine, I'm now happy that my ignorance about this has not caused an unusually high deterioration in my car's battery!

👍👍
 
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emmrecs said:
Many thanks to all who have contributed to this thread!

Having now also read of other users reporting battery SoH even lower than 98% after one year with similarly low mileage to mine, I'm now happy that my ignorance about this has not caused an unusually high deterioration in my car's battery!

👍👍
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You never mentioned what the GOM said when you have fully re-charged and balanced, and reset the trips. That should give an indication of any degradation.
 
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emmrecs said:
True!

So, this morning, on 100% SoC, trip meters both reset:
ECO: 249
Normal: 237

I think that suggests everything is pretty good???
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The 98% soh suggests everything is pretty good. I can't actually remember what the normal and eco defaults are supposed to be. If no one else helpfully responds ill double check next time I balance charge. Did you have the fan at 0 as I think it changes them if you put it on.
 
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