How to tell when charging is complete?

[Rolfe]

I've noticed this a few times. I've got the car (SR) on the granny charger (to top up after using the nearby rapid charger to get to 89%), and it can't seem to make up its mind when it's done.

Originally the finish time was going to be about 21.18 - it varied slightly as charging progressed. However, when I checked on the app about ten past nine it was already showing 100%. I left it in case it wanted to balance charge. Eventually the time it had been noting as the finish time came, but the app never recorded charging as being finished. Instead, every time I ask for an update, it moves the "finish time" to the time it actually is when I ask. We're now at 21.43 and it's still doing it.

Obviously it has 100% charge. I don't know if it's doing a balance charge or if it's simply finished and this is a bug in the app. If it's the former I don't want to stop it, but if it's actually done I'll go into the garage and unplug the charger.

I'm just going to unplug it I think, this has gone on long enough. But, any thoughts?

 

[PristDean]

I've set mine this evening to charge to 100% as I going on a long trip tomorrow morning. It's currently at 97% but I have set the window of charge to be 4 hrs at 7kw/h in anticipation that it may do a balanced charge. My first !
To me, it does sound like your battery is attempting a balance charge. Others may be able to add to this though.

 

[Archev]

There’s a target voltage for a fully charged and balanced battery- I’m not sure what that will be for your 4 but someone will be along with the number soon which you can check on the dashboard.
But I think you’ll be grand as is.

 

[Archev]

I've noticed this a few times. I've got the car (SR) on the granny charger (to top up after using the nearby rapid charger to get to 89%), and it can't seem to make up its mind when it's done.

Originally the finish time was going to be about 21.18 - it varied slightly as charging progressed. However, when I checked on the app about ten past nine it was already showing 100%. I left it in case it wanted to balance charge. Eventually the time it had been noting as the finish time came, but the app never recorded charging as being finished. Instead, every time I ask for an update, it moves the "finish time" to the time it actually is when I ask. We're now at 21.43 and it's still doing it.

Obviously it has 100% charge. I don't know if it's doing a balance charge or if it's simply finished and this is a bug in the app. If it's the former I don't want to stop it, but if it's actually done I'll go into the garage and unplug the charger.

I'm just going to unplug it I think, this has gone on long enough. But, any thoughts?

I think I’m correct in saying the time needed for a full and balanced battery charge is up to the car system. It goes through all the cells checking and slowly topping them up until it’s confident they’re all as near equal as possible. So you can’t really determine how long it’ll take to do that - just give the car a while (maybe 2 or three hours ?) after reaching 100% and it’ll be about there.
It’s a clever wee machine really

 

[Tight Git]

You can tell when it's doing the balance charge as the figure in the bottom right of the charge management screen will drop from around 1.8kw to 0.02kw or similar.

When you start the charge on the granny it cannot calculate the finish time as the balance charge can take a good while.

Think you are seeing what mine does...

 

[Rolfe]

I last charged the car a week ago, and on that occasion I think I finally got to the point where the app showed a "finish time" that didn't update as my phone's clock ticked on. However, it never showed that charging had finished, it still gave me the option to "finish charging". I think it's the app, really, but it's hard to be sure. I presume it did all the balancing it wanted to do on that occasion, so if I stopped it in mid-balance this time I don't suppose it will mind.

I know it's not really necessary, but since it wasn't quite dark I wanted to go out and unplug the granny charger. I wouldn't do that if it was finishing in the middle of the night, obviously.

I'll bear all these comments in mind and check when this happens again. I need it full again by Tuesday morning as I'm off on a road trip, so that will be a chance to watch it.

 

[Archev]

I last charged the car a week ago, and on that occasion I think I finally got to the point where the app showed a "finish time" that didn't update as my phone's clock ticked on. However, it never showed that charging had finished, it still gave me the option to "finish charging". I think it's the app, really, but it's hard to be sure. I presume it did all the balancing it wanted to do on that occasion, so if I stopped it in mid-balance this time I don't suppose it will mind.

I know it's not really necessary, but since it wasn't quite dark I wanted to go out and unplug the granny charger. I wouldn't do that if it was finishing in the middle of the night, obviously.

I'll bear all these comments in mind and check when this happens again. I need it full again by Tuesday morning as I'm off on a road trip, so that will be a chance to watch it.

Sounds like you’ve got it stuffed with as much as it wants . Now all you need do is drive and have a grand trip.

 

[Rolfe]

Well, he had his fast-food meal of rapid-charge electrons, followed by a leisurely dessert on the granny charger, so he doesn't have much to complain about.

When it gets cold and wet I may be less keen on this régime of take car to rapid charger, walk home (5 min), get on with life, walk back in time to stop the charge before I run into penalty-points time, pay less than £10, then come home to do the last 10-20% on the granny charger, but right now it suits me fine.

 

[richlove]

Well, he had his fast-food meal of rapid-charge electrons, followed by a leisurely dessert on the granny charger, so he doesn't have much to complain about.

When it gets cold and wet I may be less keen on this régime of take car to rapid charger, walk home (5 min), get on with life, walk back in time to stop the charge before I run into penalty-points time, pay less than £10, then come home to do the last 10-20% on the granny charger, but right now it suits me fine.

I've experienced similar, Rolfe, and also been a little unsure whether it's definitively finished.

Out of interest, why aren't you charging overnight with the granny, is it more expensive than using the rapid charger?

 

[Rolfe]

There's not much in it. 31p per unit on my home system (I don't have a variable tariff) and 30p per unit on the rapid charger. So there's actually a marginal saving using the rapid charger.

I'm still learning the best way of managing the charging. Basically I have a granny charger at home and the rapid charger 400 yards away which is so similar in price that the cost isn't an issue. Giving the car a session on the rapid charger is quite satisfying somehow, seeing the green bar advance so fast. Then I have to stop the charging because the village charge-point is time limited (there is only one, and it's the only one for miles around), and I can take the car home and top it up on the granny, which will let it balance if it wants to.

Of course, a couple of five-minute strolls in spring is pleasant. A couple of five-minute strolls in driving rain is likely to be less appealling.

Yesterday afternoon I started on the tidying of the garage, now that my old car has been taken away. I've now got the granny charger plugged in to a power point that is literally 1.5 metres from the car's charging port, which is a lot better than trailing the granny's lead out of the garage door to the car parked outside. It's all inside protected from the rain, too.

I suppose it will depend on how soon I need the car fully charged. If I come back in the evening with a low battery and need the car again in the morning for another lengthy trip it will have to be the rapid charger, weather or not. Otherwise it will probably depend on my whim.

I see there is a Tesla parked outside a mid-terrace house only about 100 yards from the charge-point. Whoever owns that car has no opportunity for home charging at all and is presumably relying on the charge-point for all his home charging needs. It does have a type 2 connector so I suppose he can use that to balance-charge once he has filled up on the CCS, although he'll have to wait 90 minutes between visits to the charge-point.

My next door neighbours also have a Tesla, but they have a garage like mine, and also a massive solar panel array on their south-facing roof!

 

[FiferMG4]

I've set mine this evening to charge to 100% as I going on a long trip tomorrow morning. It's currently at 97% but I have set the window of charge to be 4 hrs at 7kw/h in anticipation that it may do a balanced charge. My first !
To me, it does sound like your battery is attempting a balance charge. Others may be able to add to this though.

I charged the car to 100% yesterday (my once a month full charge for battery health on my SE Long Range) and as you can see from the Zappi screenshot, it was charging on solar during the day (between 1.4 kW ~ 3.4kW), then I switched it to draw from the grid (7.4kW) and it then trickle charged (around 100 watts) for about two and a half hours, until the Zappi told me the charge was over with a big tick on the app. So, it would seem the battery needed a further two and a half hours to perform the balance.

Is everyone finding this to be about the typical time it takes to do a balance charge?

 

[tsedge]

I charged the car to 100% yesterday (my once a month full charge for battery health on my SE Long Range) and as you can see from the Zappi screenshot, it was charging on solar during the day (between 1.4 kW ~ 3.4kW), then I switched it to draw from the grid (7.4kW) and it then trickle charged (around 100 watts) for about two and a half hours, until the Zappi told me the charge was over with a big tick on the app. So, it would seem the battery needed a further two and a half hours to perform the balance.

Is everyone finding this to be about the typical time it takes to do a balance charge?
View attachment 17495

I believe it varies a lot, depending on what the BMS decides that it needs.

 

[Rolfe]

I've been keeping an eye on the app sometimes to see how long it's taking for this. (Yes, I have now realised that's what it's doing when it seems to keep going even after it's reached its nominal finishing time. It's usually drawing 0.02 KW at this point.) It's often about half an hour. What has intrigued me is that it does it every single time. I don't think I have once seen it stop charging completely as soon as the battery is full.

 

[FiferMG4]

Interesting, so it’s perfectly normal for this to happen. I’m glad I didn’t decide to disconnect the Zappi as for about five minutes the car wasn’t drawing any power and then I noticed the trickle starting up again and it was like that for the next two hours.

 

[Rolfe]

I don't suppose it would have done any serious harm. However, if the car wants to balance charge then it will need to do it some time, and best just let it get on with it.

After the good people on this forum explained to me what was going on when I posted the OP, I've just been letting the car do it, and I think half an hour to 45 minutes is its usual. It's usually only drawing about 20 watts during that time. Of course, as it's an SR, it gets to charge to 100% all the time, so it may need less time to balance when it's doing it frequently.

Last week I used a type 2 charger very close to my friend's house to charge, three evenings in a row. I was watching the app because it was my intention to fetch the car back to my friend's driveway once it was finished. Every time, about 30 to 40 minutes on 20 watts, then done. It has surprised me that this invariably happens. I've not yet seen a charge where the car decides it's done the minute it gets to 100%.

 

[tsedge]

Thinking about it, the LFP SR may actually balance more than the NMC LR because it is much more difficult for it to keep track of the cell voltage so it probably needs to do it more often.

 

[Rolfe]

That could be it.

 

[FiferMG4]

I don't suppose it would have done any serious harm. However, if the car wants to balance charge then it will need to do it some time, and best just let it get on with it.

After the good people on this forum explained to me what was going on when I posted the OP, I've just been letting the car do it, and I think half an hour to 45 minutes is its usual. It's usually only drawing about 20 watts during that time. Of course, as it's an SR, it gets to charge to 100% all the time, so it may need less time to balance when it's doing it frequently.

Last week I used a type 2 charger very close to my friend's house to charge, three evenings in a row. I was watching the app because it was my intention to fetch the car back to my friend's driveway once it was finished. Every time, about 30 to 40 minutes on 20 watts, then done. It has surprised me that this invariably happens. I've not yet seen a charge where the car decides it's done the minute it gets to 100%.

I think you may be right. I’m only doing the 100% charge once a month and as I don’t do many long journeys, 80% is just fine for my daily needs.

 

[Rolfe]

Sounds perfect. I just let my SR charge to 100% and do its thing. The only downside is that I lose regenerative braking for a little while after I first set off. Fortunately I do not live on the top of a hill.

 

[FiferMG4]

Sounds perfect. I just let my SR charge to 100% and do its thing. The only downside is that I lose regenerative braking for a little while after I first set off. Fortunately I do not live on the top of a hill.

Yeah, that’s always a strange feeling, though it makes it easy to coast when you take your foot off the accelerator pedal. I tend to find the regen braking comes back around the 97% mark, how about you, Rolfe?