12V battery
- Thread starter electriceddy
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Bit of some strange battery "scheduled top up" activity yesterday (25/09/2025)
Top ups were 6:23-6:43
8:49-9-23
1045-1103
11:49-12:09
12:15-12:33
13:43-14:03
(6 times!)
The others were a combination of drives and a DC charge and drive home@12:47-13:37
First time I have seen 6 scheduled top ups in 1 day, not normal ones like displayed the 7 day graph.
Oh well, the voltage settled @ 12.72V after 14:03 top up, and things are back to normal today, resting ~12.67V.
I will keep my eye on it ,maybe the cooler weather freaked out my car
Top ups were 6:23-6:43
8:49-9-23
1045-1103
11:49-12:09
12:15-12:33
13:43-14:03
(6 times!)
The others were a combination of drives and a DC charge and drive home@12:47-13:37
First time I have seen 6 scheduled top ups in 1 day, not normal ones like displayed the 7 day graph.
Oh well, the voltage settled @ 12.72V after 14:03 top up, and things are back to normal today, resting ~12.67V.
I will keep my eye on it ,maybe the cooler weather freaked out my car
@KiwiME does a wonderful job of explaining here (better than I could write up).
The BM2 info has been pretty consistent with that explanation with every Kona EV I have owned...with the exception of the data recorded above on the 25th.
It did have me wondering if something was vampire draining or a possible update download was in progress, however things have returned to "normal" with no other indications of indifference which makes me happy once again.
After 13 months, I am still trying to figure out the 12V charging algorithm on this SX2 model, but I will add some observations... some similar to SX1 and some different.
It seems several factors come into play:
(1) Time- always once every 24 hours for ~ 45 minutes to 1 hour and usually at the same time of day.
(2) SOC traction battery and cell temp- between 50% to 83% is my usual preferred SOC. The reason 83% is when DC charging, the BMS will kick in ~82% and limit the charge to less than 1kW for 3 minutes as the BMS does the cell deviation checks etc, then returns to normal DC charging levels after that...but only when the cell temps are warm (summer), this does not happen when DC charging in cooler temps.
When the car is parked (off and asleep), regular top ups occur shortly after (usually 10 to 12 minutes), also observed is when waking up the car ( ie walking in proximity to the car w/ keys in pocket) or opening door to get something- the charge light on the dash immediately starts like it is preparing for a drive. Sometime those top ups last 45 minutes to 1 hour, other times it is only a short duration ~ 10 minutes.
Only exception I have found is when I had my subwoofer installed and the 12V battery was disconnected for a short duration. After ~ 4 days of intermittent diving and zero top ups, I DC charged to again 83% and after that everything went back to normal 12V charging characteristics.
Below a screenshot- 12/2/2026 13:47 long top up (car parked asleep) a gain short one starting 16:39. 16:51 was a DC charge and start 17:55 drive home.
13/2 2026 car was waiting for the usual timed 24H top up, but I had to get something out of the car before that happened so at 13:39 the long 45 minutes to 1 hour top up occurred. I again woke up the car at 14:07 and a short charge occurred and again at 14:23.
What ever software configurations have been applied to this system, it definitely works a lot better than SX2 and my 12V battery SOC now is @12.9V with the car asleep.
It seems several factors come into play:
(1) Time- always once every 24 hours for ~ 45 minutes to 1 hour and usually at the same time of day.
(2) SOC traction battery and cell temp- between 50% to 83% is my usual preferred SOC. The reason 83% is when DC charging, the BMS will kick in ~82% and limit the charge to less than 1kW for 3 minutes as the BMS does the cell deviation checks etc, then returns to normal DC charging levels after that...but only when the cell temps are warm (summer), this does not happen when DC charging in cooler temps.
When the car is parked (off and asleep), regular top ups occur shortly after (usually 10 to 12 minutes), also observed is when waking up the car ( ie walking in proximity to the car w/ keys in pocket) or opening door to get something- the charge light on the dash immediately starts like it is preparing for a drive. Sometime those top ups last 45 minutes to 1 hour, other times it is only a short duration ~ 10 minutes.
Only exception I have found is when I had my subwoofer installed and the 12V battery was disconnected for a short duration. After ~ 4 days of intermittent diving and zero top ups, I DC charged to again 83% and after that everything went back to normal 12V charging characteristics.
Below a screenshot- 12/2/2026 13:47 long top up (car parked asleep) a gain short one starting 16:39. 16:51 was a DC charge and start 17:55 drive home.
13/2 2026 car was waiting for the usual timed 24H top up, but I had to get something out of the car before that happened so at 13:39 the long 45 minutes to 1 hour top up occurred. I again woke up the car at 14:07 and a short charge occurred and again at 14:23.
What ever software configurations have been applied to this system, it definitely works a lot better than SX2 and my 12V battery SOC now is @12.9V with the car asleep.