Surprisingly short battery balancing period

[gwatuk]

I've just done the first full charge (8% to 100%) for our new car.
Surprisingly the battery's balancing took only 8 minutes.
Perhaps this is an indication of how beneficial a long slow charge is?
(This was with a granny charger.)

The other unexpected thing was that on the first drive the regenerative braking was not working - presumably because the battery was full so there was nowhere for the recovered power to go.

 

[djngolf]

How do you tell if it's done the battery balancing? Does it show up somewhere?

 

[dsimpkins]

The other unexpected thing was that on the first drive the regenerative braking was not working - presumably because the battery was full so there was nowhere for the recovered power to go.

Correct, you should get a message on dash displayed to that effect. Once battery is 95% or below, full regen is available again.

 

[djngolf]

Ok thanks, I'll watch out for that, got to change to 100% this Sunday night.

 

[Martinonline]

@gwatuk, how did you determine that the balancing had completed? My Trophy often went down to zero indicated received power but then jumped back up again. I have only had a short balancing if I had balanced shortly before.

 

[wattmatters]

Surprisingly the battery's balancing took only 8 minutes.
Perhaps this is an indication of how beneficial a long slow charge is?

I've seen similar 5-10 minute low power activity when using a 7 kW charger although mine is an NMC not a LiFePO4 battery. The balancing process for each is (or should be) different due to the different charge voltage curves of each chemistry.

 

[Rolfe]

My car has always balanced for about 35 minutes no matter how recently it had previously balanced, and it was almost always charged on a granny charger. I now have a Zappi, but I haven't yet charged to 100% on that with mains power as I'm trying to maximise my use of solar. What I have noticed is that when charging on solar it often doesn't do the full 30-35 minutes balance, if there is a hiccup in solar generation during that time. And sod's law, there often is. The best I've seen is 15 minutes and a couple of times no balance at all. It's as if the Zappi on eco+ doesn't rate the continuing supply of about 20 watts to the car as any sort of priority.

If it doesn't balance next time I get to 100% I'm going to take it out to do the bottle-bank run - about two miles - then bring it home and put it on the granny charger just to get back up to 100% and balance, taking the power from the home battery. Probably only take an hour.

 

[wattmatters]

I'm probably due a full charge soon:

 

[Rolfe]

Where are you seeing that information?

 

[wattmatters]

Where are you seeing that information?

It's a Home Assistant sensor I created using data from the SAIC API integration. When the SOC reaches 100% it resets to zero days, incrementing the counter each day thereafter.

 

[Rolfe]

Clever!

 

[gwatuk]

How do you tell if it's done the battery balancing? Does it show up somewhere?

@djngolf and @Martinonline I have a device that measures the ac current going into the charger (a Shelly EM). That's where the graph above comes from. You can see there are power spikes after the main charge has finished - while the balancing takes place.
I think it's been mentioned here that the car and the app continue to say that the car is still charging even after it has reached 100% and that only changes when the balancing has finished. Maybe one of the experts could confirm this.

 

[gwatuk]

Correct, you should get a message on dash displayed to that effect. Once battery is 95% or below, full regen is available again.

Well for me that's a compelling reason not to regularly charge the car to 100%. I really like how the regen braking works, and of course it's good to recover the energy to the battery rather than heating the brake discs ?

 

[Rolfe]

On the other hand you have an SR so you should be going to 100% and balancing at least once a week according to the manual. And honestly, how long does it actually take to get back down under 95%?

 

[Rolfe]

My car has always balanced for about 35 minutes no matter how recently it had previously balanced, and it was almost always charged on a granny charger. I now have a Zappi, but I haven't yet charged to 100% on that with mains power as I'm trying to maximise my use of solar. What I have noticed is that when charging on solar it often doesn't do the full 30-35 minutes balance, if there is a hiccup in solar generation during that time. And sod's law, there often is. The best I've seen is 15 minutes and a couple of times no balance at all. It's as if the Zappi on eco+ doesn't rate the continuing supply of about 20 watts to the car as any sort of priority.

If it doesn't balance next time I get to 100% I'm going to take it out to do the bottle-bank run - about two miles - then bring it home and put it on the granny charger just to get back up to 100% and balance, taking the power from the home battery. Probably only take an hour.

Today the car reached 100% on the solar excess while the sun was doing the business. It seemed to me to balance for about 25 minutes before shutting off. OK, but on mains electricity it invariably balances for 5 to 10 minutes longer than this. Dunno quite what's going on.

 

[DannySB1]

Could anyone tell me if 11kwh charging is classed as slow or fast? I charge my MG4 weekly at my place of work and as I understand it the charger itself is 22kwh capable, but I think the cable I have only supports up to 11kwh when calculating time to charge.

If I charged to 100% on 11kwh would my car balance? Still one of the things I haven't quite nailed in my head yet

 

[Martinonline]

According to the manual it should. See image below.

 

[dsimpkins]

Could anyone tell me if 11kwh charging is classed as slow or fast? I charge my MG4 weekly at my place of work and as I understand it the charger itself is 22kwh capable, but I think the cable I have only supports up to 11kwh when calculating time to charge.

If I charged to 100% on 11kwh would my car balance? Still one of the things I haven't quite nailed in my head

It's slow charging. Limiting factor is not the cable, but the onboard charger. Once you account for losses, your 11kW is likely more 9.6kW charging rate. That's the maximum I've seen charging on 22kW charger at work, and yes, it will do a balancing charge.

 

[DannySB1]

It's slow charging. Limiting factor is not the cable, but the onboard charger. Once you account for losses, your 11kW is likely more 9.6kW charging rate. That's the maximum I've seen charging on 22kW charger at work, and yes, it will do a balancing charge.

That's great, thanks for the info. I'll do that this week in that case!

 

[dsimpkins]

I mostly charge at work, rarely charge at home. If it wasn't doing a balance charge when set to 100% I would have had a warning on the dash by now. I've also seen it register 100% on car, but still drawing tiny amount of current on the charger at work (balancing)