Your correct. I don't know where this balance charging at anything less than 100% came from. Eon Musk recently used this analogy. Think if the battery as a large car park. When the gate opens cars flow in and fill up the spaces at a near constant rate. As the car park nears capacity and cars have to search longer for spaces then the rate at which spaces are filled decreases. When there are only a few spaces left it takes cars a very long time to search for and find empty spaces to fill until 100% capacity is reached.
I have struggled with this theory of balancing below 100% SOC myself on my car at least.
So, I have decided to investigate this a little more on our ZS EV LR with the NMC battery chemistry.
Yes of course other MG models maybe different, I do fully understand this.
The object here was to try and catch the balance cycle commencing at SOC % ( state of charge levels percentages ) lower than 100%.
For anybody who may find this subject of any interest, here is my very recent findings (16/01/24).
I set the charging level to complete at 80% because my day time tariff is 40p/kw and my off rate rate is only 5p/kw in the early hours of the morning.
Conducting this test in day light hours to monitor the situation is therefore expensive.
So, prior to this test starting, my SOC level of the pack was at 69%.
My home energy meter is displaying an electric energy consumption of between 250 & 400 Watts is being used by the house ( fridge freezer etc ) no other high demand being used.
I plugged the car into our 7 kw wall box at 12.40pm ( after lunch ).
Instantly the home energy meter jumps to 7.4 Kw's and the I.smart App is displaying that the car is accepting 6.41 Kw's so all is fine.
Here is the updated results, set out in the following sequence.
Precise Time of day of each check up on progress.
Battery SOC / percentage check at each stage.
The updated predicted range at each stage.
Energy meter consumption figures ( house ).
Level of energy being accepted by the car.
Predicted time when completed.
13.10pm / 76% / 186 Miles / 7.40 kw's / 6.41 Kw's / 13.44pm.
13.28pm / 79% / 196 Miles / 7.56 kw's / 6.58 kw's / 13.39pm.
13.36pm / 80% / 198 Miles / 7.65 kw's / 6.41 kw's / 13.40pm.
13.40pm / 80% / 199 Miles / 7.50 kw's / 6.43 kw's / 13.43pm.
13.44pm / 80% / 201Miles / 641 Watts / 3.67 kw's / 13.46pm.
Wall box has now returned to the standby state condition and home energy meter is only displaying 417 Watts of power being used by the rest of the house.
The results above would strongly suggest two options here.
1) Either the battery was already in a very good state of balance, given that the balance cycle only appeared to last about 4 minutes or even LESS.
But then I have to question this theory, because the car was pulling a strong, almost 7 kw's and then dropped over a cliff's edge rapidly down to 641 Watts, then quickly stopped the charge altogether.
I would expect to see a must more gradual ramp down in power being drawn by the car myself, prior to a balance cycle commencing.
Our previous ZS EV ( Gen1 ) with NMC chemistry would gradually step down from it's max 7 kw's, firstly down to 3.5 kw's at about 97% SOC then when nearing 100% it step down to about 950 Watts , then 500 Watts, then 300 Watts / 175 Watts then after short time, return the wall box to the standby state.
2 ) Or, as I suspected no balance cycle had taken place, when the charge level was set to 80% SOC.
I was tempted slightly to conduct the test again, by setting the SOC level to 90% this time, but charging in the day light hours proves to be expensive.
Other MG models fitted with NMC or LPF batteries may have a different charging protocol and balance cycle process of course.
Models with LFP packs ( like the ZS EV standard range ) charge to 100% SOC only, so a balance cycle is therefore called for at every charge session on a A/C supply.
LFP batteries are noted to struggle predicting the remaining range if charged below a level of 100%.
Tesla Bjorn has pointed this out on many of his long EV test drives.
