Are micro-top-ups okay if they don't take the SOC above 80%?

I want to pick the brains of the battery super-nerds out there!

I know that having a battery at 100%, driving a few miles, and then topping up again, is basically battery battery! I know that leaving a car for a long period with less than 20% is also not good. However, I also know that battery life is often quoted in cycles.

But that got me thinking - is all charging okay as long as the you don't leave your battery in the top and bottom 20% (even if you are, say, just topping up from 77% to 80%) or is it better to wait until the battery depletes further before topping up in one go? So, are micro-top-ups okay if they don't take the SOC above 80%?

This thread in the MG4 subforum chews around a lot of these issues.

Rolfe said:

This thread in the MG4 subforum chews aroung a lot of these issues.

Charging battery to full on regular basis or allow it to go down to 5 percent before topping up

Hi, I am new to the EV driving and charging. Will be collecting my MG4 Long Range next week. I got a home charger fitted and waiting for the car. I have a rather long commute to work about 120 mile both ways, on average 3m per kWh I expect about 40 kWh consumption each day. Should I plug in...

www.mgevs.com

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Thanks. I hadn't seen that until after I'd posted. I'll take a look.

People with solar panels tend to do small top ups when the sun shines. The Zappi and other such chargers are designed to do this, so if it was a problem, I doubt they would want warranty claims from battery manufacturers claiming they had ruined the battery.

Grazing for electrons, i.e. getting what you can, wherever you can is a common way to charge, especially for those without home charging.

Gomev said:

Grazing for electrons, i.e. getting what you can, wherever you can is a common way to charge, especially for those without home charging.

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Very true . As one of those unable to install a home charger , I top up as often as possible ( not always to 100%) , 45% is the lowest I've let my battery drop to

A-B-C as Bjorn says. Always Be Charging.

I don’t see an issue with it as stated above some chargers Zappi for an example like I own, are designed to harvest excess solar and feed it to your EV, I think the golden rule and what I attempt to do that is to do a full charge on an a/c charger to balance the battery cells MG recommend every 5/6 weeks and to remember this must be an A/C charge as you can’t balance on D/C so use a wallbox 7 kw or even the granny box and cable you got with the car of course that will take much longer and then when you have done this to drive the car for several miles after to bring the SOC back down to somewhere below 80% ish battery is happy anywhere from around 30-80%
Les

That really only applies to the LR battery though. The SR is reputed to be perfectly happy going to 100% and staying there, and indeed there seems to be no way of setting it to charge to a lower level. If you don't want to go to 100% you have to step in in real time and stop the charge. (Unless you can set your wall box to do that for you.)

I know people prosyletise about treating the SR battery the same way as the LR, but the actual difference you're likely to see in a battery treated like that compared to one that simply charged up fully every time seems to me to be pretty negligible within the likely life of the car. I also note that my SR balances every single time I charge it. I have never once seen it go from charging to nothing, always there's around half an hour of maybe 20 watts being pulled after 100% charge is reached.

I just let mine do what it likes overnight on the granny charger every time the SoC drops below whatever I think is wise to have in hand for anticipated and unanticipted use, and I've never seen a convincing argument for doing otherwise. It's what my dealer told me to do, it's what MG sets the app to do (maybe it would be more convenient for it to have the app the same for the SR and the LR, but no, they've taken the trouble to remove the 80% limit for the SR), and I don't see the problem.

Actually, I charged overnight on Monday night, the car reached 100% about two o'clock on Tuesday afternoon, and it hasn't turned a wheel since. Am I worried? No.

So, it seems the consensus is 'grazing' is totally fine up to 80%, and take it up to 100% to balance every month or so before a journey that will bring it back to 20-80% zone (but don't get overly worried as modern BMS's do a good job anyway) - which is what we do - happy days.

My next project is getting a set up that means we only use excess solar and, when necessary, cheap rate lecky.

Tiny Tim said:

I want to pick the brains of the battery super-nerds out there!

I know that having a battery at 100%, driving a few miles, and then topping up again, is basically battery battery! I know that leaving a car for a long period with less than 20% is also not good. However, I also know that battery life is often quoted in cycles.

But that got me thinking - is all charging okay as long as the you don't leave your battery in the top and bottom 20% (even if you are, say, just topping up from 77% to 80%) or is it better to wait until the battery depletes further before topping up in one go? So, are micro-top-ups okay if they don't take the SOC above 80%?

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It doesn't matter whether you top-up in little fragments or big chunks, as you say so long as you steer clear of the extremes it is all the same to the battery.

Don't fear 100% charges on NMC, use them when you need to, it won't kill it. Just don't leave it at 100% for long periods.

I charge my car daily to 100% using works free charger (large solar array) initially I was going out and regularly stopping it at 80% at first but after some research concluded the biggest issues is leaving it at 100% or below 20%. It's now been 15 months and 18,000 miles, SoH is still 100%. My daily commute is 70 miles and I may have a last minute need to do a 70 mile round trip to a relative so I prefer to keep my car in a 'ready' state, leaving work at 100% generally means arriving home at 80-85% so it's never up there for long.

The other, somewhat less ethical, viewpoint is that if it's leased, the vehicle won't be yours by the time it's degraded to a point of being noticeable.

Im a firm believer the BMS should be taking care of the battery and I should be able to use the vehicle and graze free/cheap electricity as and when I can.

I would have thought that if you're charging at work then driving home the same day you should have no issues at all as the car isn't sitting at 100% for an extended period. I completely agree with you.

The need to keep a reasonable range in the car is important for most people, I think. Who knows what might come up at a moment's notice? Why on earth would I let the battery run down even to 20% in the normal scheme of things when it's sitting all night next to its charger cable? It's bonkers. (I hadn't intended to go anywhere yesterday, but then a tweet about a one-off Event Cinema performance had me scrambling into action. If the car had been sitting at 20% I'd have felt like a right plonker. The cinema I usually go to is 40 miles away.)

I have an SR and it's not even possible to stop the charge before 100% unless you intervene personally. That might mean waking up at four in the morning to get out your phone to stop the charge on the app! Not for me. So it gets charged to 100% every time and indeed they tell us the SR is absolutely fine doing that.

Last time I charged I just let it do its thing and balance at 100%. I then started to feel a bit guilty about not using the car for the next four days, despite having read somewhere that LFP batteries don't mind this in the slightest. But honestly, I can't be doing with all this faffing around. If a number of short trips get the car down to near 50% I'll just plug in the charger and charge. If I'm looking at a longer trip then I'll plug in and charge the day before. End of.

And since it seems to be agreed that the LPF battery is likely to last well beyond the lifetime of the car no matter what I do to it, I'm trying to get less concerned about all this.

Rolfe said:

I would have thought that if you're charging at work then driving home the same day you should have no issues at all as the car isn't sitting at 100% for an extended period. I completely agree with you.

The need to keep a reasonable range in the car is important for most people, I think. Who knows what might come up at a moment's notice? Why on earth would I let the battery run down even to 20% in the normal scheme of things when it's sitting all night next to its charger cable? It's bonkers. (I hadn't intended to go anywhere yesterday, but then a tweet about a one-off Event Cinema performance had me scrambling into action. If the car had been sitting at 20% I'd have felt like a right plonker. The cinema I usually go to is 40 miles away.)

I have an SR and it's not even possible to stop the charge before 100% unless you intervene personally. That might mean waking up at four in the morning to get out your phone to stop the charge on the app! Not for me. So it gets charged to 100% every time and indeed they tell us the SR is absolutely fine doing that.

Last time I charged I just let it do its thing and balance at 100%. I then started to feel a bit guilty about not using the car for the next four days, despite having read somewhere that LFP batteries don't mind this in the slightest. But honestly, I can't be doing with all this faffing around. If a number of short trips get the car down to near 50% I'll just plug in the charger and charge. If I'm looking at a longer trip then I'll plug in and charge the day before. End of.

And since it seems to be agreed that the LPF battery is likely to last well beyond the lifetime of the car no matter what I do to it, I'm trying to get less concerned about all this.

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Hi again Rolfe I can only but agree with the vast majority of what you have written above even the feeling of guilt when leaving it fully charged for 4 days not to often I would hope, true the LFP fitted in the SR should not come to much harm so your right to not be over concerned about it.
Now nobody wants to be Losing any beauty sleep myself included so in your ISMART App for the MG4 your correct you can’t set the amount of charge and then have it stop (we are talking MG4 SESR here before the owners of the LR and Trophy dive in) but Rolfe, in the app you can set a start and stop time see my pictures below which are from my wife’s MG4 SESR app on her Iphone.


So click on Charging Management and that will take you to the next page below


You will note here it says 80% just ignore that for the moment,
Click on Scheduled Charging that’s takes to the timer page next picture, and then in the top right Toggle Scheduled Charging which will go green then enter a start and end time and save it, don’t worry about the battery heating setting just ignore that, now back one page and you will see in my next picture the 80% has changed to 100% as you can’t control the percentage on the SESR so you need to Estimate the time needed to get where you want to be, and set the stop time which will stop the charge and jobs done (example on a granny charger around 2.4kws it would need around 5 hours for 10% to go in and 50-80% around 15 hours )so now you can continue with your beauty sleep.

Now when you plug in it will start the charger right away so set the starting time for around the same time as you plug in it will not control or delay the starting time as far as I know, but it will stop the charge and when it does the green light on the granny will be flashing as it is waiting for the car to charge again.

So below I have st an example for you to see once you have set the start and finish times

Once that’s done it will then ask for you password

So insert that and then you will get a little car doing a dance for a moment or two and then that will go of and the next screen will say success right at the bottom middle

So Rolfe if you do only want to charge to a set % this is how you can do it on the MG4 SESR hope this might help it may need a bit of practice and patience but it does work I have tried it on a 7kw but I will at some point but I bet it’s the same as the car is controlling the off time not the charging point.
Les.

Thank you very much for going to all that trouble. I understand now. That really is a very clever work-round.

Shouldn't be necessary, of course, but it most of the work-rounds we're dreaming up shouldn't be necessary, and at least we're beating the software into submission.

EDIT to my post at #14 I have treid charging both the MG4 SESR and MG5 Trophy with the wall charger Zappi in my case and both can be stopped by using the timer in the app
So Granny or Wallbox you can decide how much you need to charge for to get where you want to be.
Les

I was thinking, with the granny charger, start the charge and then see when the app thinks it's going to finish. I don't know whether one could then simply add a command to stop an hour earlier to that, or whether it would be necessary to stop it all completely then start again with the time limit set, but no doubt some experimentation would reveal the answer.

Hi Rolfe as S before once you plug in the charger. It will start to charge you divide for how long by setting the stop time in the app

Just one othe thing be sure to switch off the timer toggle in the app in my 5th picture down to cancel any timer settings. Other wise you may have an issue charging outside the set time so toggle on to use timing toggle off for everything else
Les

Thanks! I hope I still remember that, or remember where to find the advice, when it's cold enough to need pre-heating in the morning!