Charge to 100%… or not?

dsr · Jan 23, 2025

Having done a 5% to 100% charge in mid-December and a ‘normal’ charge to 100% on New Year’s Day, I find myself in an unusual situation. Basically, until Easter I have no long journeys planned; I expect to do no trips of more than 5 miles and to average well under 100 miles a month. I am aware of what the user guide says and I am also aware of postings that refer to the resilience of the car battery and not to worry. But do people feel I should…
Charge to 80% as needed (my current practice and intention);
Charge to 100% (or 90%?) monthly and continue my mini trips;
Charge to 100% monthly and go on a joy ride for an hour or so;
Something else.

Bricktop X PWR · Jan 23, 2025

Charge to 80% as per your intention.
Sounds good to me.

tommasov · Jan 23, 2025

I charge above 80% only when I need more range, but every month I charge to 100% to balance the cells

Jomarkh · Jan 23, 2025

Does your MG4 battery balance at 80% or just at 100%?

siteguru · Jan 23, 2025

Missing a monthly balance charge if the mileage use doesn't require it, isn't going to hurt anything.

Jomarkh said:
Does your MG4 battery balance at 80% or just at 100%?

Good point .. the ER uses NMC so will balance at the target SoC.

BarryH · Jan 23, 2025

siteguru said:
Good point .. the ER uses NMC so will balance at the target SoC.

Cell balancing is only started by the BMS once the SoC reaches 100% on an AC charge. It then trickle-charges the cells or banks of cells which have the lowest voltage without further charging the cells that have already reached 100%. The BMS will also to a lesser extent balance when driving at high SoC following a Balance charge. Typically, a Balance charge will be at about 300 watts after you've been charging at 7 kW.

Martinonline · Jan 23, 2025

As has been shown many times the NMC battery will be balanced at levels lower than 100%.

I am a low mileage user and will only go to > 80% when needed.

ReintjeWA · Jan 23, 2025

Just don’t let the car sit at 100% for long periods, that is apparently bad for the battery. I’d just go 80% if I were you, I currently have a similar commute and I only ever charge over 80% if I’m waiting in line somewhere and want to avoid idle fees at public chargers.

siteguru · Jan 23, 2025

BarryH said:
Cell balancing is only started by the BMS once the SoC reaches 100% on an AC charge. It then trickle-charges the cells or banks of cells which have the lowest voltage without further charging the cells that have already reached 100%. The BMS will also to a lesser extent balance when driving at high SoC following a Balance charge. Typically, a Balance charge will be at about 300 watts after you've been charging at 7 kW.

As explained by others, that only applies for the LFP battery chemistry used in the Standard Range model. The NMC chemistry used in the MG4 LR and ER will balance at whatever target state of charge you set.

Zeioth · Jan 24, 2025

On LFP batteries is actually recommended you charge them 100% (unless you are planning to not use the car for a few days).

The NMC ones it's recommended you keep them about 80% to increase its life expectancy.

It's totally ok if you charge 100% on both batteries, the issue is charging it 100% and then not using it.

salty · Jan 25, 2025

Charge my X Power approximately every 3/4 days. Using me Granny Charger, And nearly always to 100%, depending on what time I put it on charge. But mostly to 100%. Works for me.

dsr · Jan 25, 2025

salty said:
Charge my X Power approximately every 3/4 days. Using me Granny Charger, And nearly always to 100%, depending on what time I put it on charge. But mostly to 100%. Works for me.

I understand that, but I assume you are using your car regularly for reasonable length journeys. My issue is that, for the next 12 weeks, I will be doing a handful of short journeys a week totalling about 15 miles. Given that, I think I will opt for the majority view of charging to 80% as needed - and no higher.
As an aside, I have not seen a definition of a ‘long journey’, but I have worked on the basis of it being one that reduces a full battery to 80% or below.

salty · Jan 25, 2025

dsr said:
I understand that, but I assume you are using your car regularly for reasonable length journeys. My issue is that, for the next 12 weeks, I will be doing a handful of short journeys a week totalling about 15 miles. Given that, I think I will opt for the majority view of charging to 80% as needed - and no higher.
As an aside, I have not seen a definition of a ‘long journey’, but I have worked on the basis of it being one that reduces a full battery to 80% or below.

Fair enough. No right or wrong as such. Whatever works for you.

I just think, sometimes it's far to, overthought, and made much more complicated than it really is. My thinking is, when it's ready for a charge, I'll charge it, simple's. Up to 100% or 90% or whatever the length of time it's charging puts in. It's not rocket science.

BarryH · Feb 8, 2025

siteguru said:
As explained by others, that only applies for the LFP battery chemistry used in the Standard Range model. The NMC chemistry used in the MG4 LR and ER will balance at whatever target state of charge you set.

Balancing also sets the GOM range of the BMS so you are not correct in what you say. BMS will only initiate it's balancing once the 100% SoC has been reached and once it has completed the regular 7 kW charge. It then selectively trickle charges cells or groups of cells at a low range to equalise their cell voltage to the full change voltage of others in the pack to balance or equalise the cells. During this equalising phase, the car will only draw a few hundred watts as opposed to the several kW of the main charging phase. Once this is completed and the cell voltages are as close as they can to each other. Only then, can the BMS calibrate to this voltage as the new 100% SoC.

Martinonline · Feb 8, 2025

@BarryH, please explain what battery type you are referring to as it has been shown that the NMC battery in the MG4 balances at the set battery level.

Are you commenting on the act of balancing or calibrating the BMS.

Finally your profile says you do not drive an MG so please state the source of your information.

Charge to 100%… or not?

dsr

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Bricktop X PWR

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tommasov

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Jomarkh

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siteguru

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BarryH

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Martinonline

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ReintjeWA

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siteguru

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Zeioth

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salty

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dsr

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salty

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BarryH

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Martinonline

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