Can't Trickle/ Maintain Batteries- 2023 S580

You must be charging the 12 V battery, no way to charge the 48 V battery. It should not make any difference if the car is a mild hybrid or not (or a PHEV like mine).
Just to be sure, you had your car in sleep state, no consumers active?
It seems like a stretch to me too, to use a 12V 5 amp trickle charger and convert it to 48V and then charge the 48V battery "sufficiently" and then trickle charge it. What I read about Lithium batteries is they do not need to be kept fully charged. Perhaps say, a 50% charge is sufficient. But a charger is sold for this purpose including BMW & Audi.
This car does not have a sleep state but do I lock-it which is suppose to use a minimal amount of battery power.

There is no way to charge the 48 V battery from the 12 V battery (when the car is parked, no need when it is driven). Now I'm confused about what did you actually try to charge and how, if not the 12 V battery?
I did not mean to refer to the real deep sleep state that these new cars have but the normal sleep when the car is parked, ignition off and doors closed. That would be the normal low power state where a 4 to 5 amp Ctek should be able to fully charge the 12 V battery.
Some Mercedes cars have a 12 V lithium battery. I believe your Ctek must be a suitable model for those cars. Mine is not intended for 12 V lithium batteries.
Yes, the charger is compatible with my batteries. Maybe it needs 50-60 hours or more before it steps down to a trickle charge but I hate to overcharge the batteries and Ctek tells me 24 hours should be sufficient. But a lot going on for a little 6 amp charger maintaining two battery and voltage systems.
Thanks
I too got a "critical'' battery message and driving it for a time charged the battery sufficiently for it to go away. I had previously sat in the car without the motor running for maybe an hour playing the radio and tweaking/ learning the various functions of my recently purchased car. Two things I have learned, is with all the electronics running this car, the 12V battery does not hold a charge very long without the motor running. And driving the car charges the 12V battery much easier and faster than anything else, that is through the 48V ISG. And I'm questioning if I can get a trickle charger that will protect my batteries for extended periods of time.
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Again, my problem is after 40+ hours of charging by my new MB 5 Amp Charger for both Lead Acid & Lithium batteries (made by Ctek) and on my new 2023 S580, it never stepped the charging rate down to "trickle/ maintenance" and continued at the higher charging rates of Bulk/ Absorption. Ctek tells me it should have stepped down at least by 24 hours of charging and suggesting it may be over charging the batteries, which is more of a concern than under charging batteries.
Since I tried two different chargers that didn't step down after considerable time, I think it has more to do with the 48V/ 12V ISG two battery electrical systems than the charger. Why don't you try it before you leave and see if it steps down or not. I would love any input regarding if your trickle chargers are stepping down the charging rate or not in these MHEV's type cars.
So one can not trickle charge the 48V battery from the charging posts when leaving the car for an extended period of time, only the 12V. I can't imagine you could leave the ignition on for months.

The 48 V lithium battery has zero load during long term parking. Only internal leakage makes it lose charge and that is very insignificant. How many months would the car need to withstand? We have many big machines that sleep off-season, 5 to 6 months. Even a standard VRLA battery keeps enough current (these do not have any load from remote door locks or alarm systems etc.).
I had had an unfortunate event when my almost new house bank batteries (on our boat) were over charged by my inverter/ charger, and it cost me $13k to replace them. In this case the batteries actually started melting besides being ruined. If they were Lithium like the 48V, they may have exploded if they shorted out. Although I question if a small amp trickle charger could actually melt batteries, but it could ruin them. That is why the automatic chargers step the charging rate down, not to save on the electric bill.





Buy an appropriately power rated 7 day timer... plug the charger to it
Set it to timer(charge) for a few hours once a week OR 30 minutes a day
OR
Whatever charging set up you feel comfortable with
With this setup the possibilities are endless
You may have to have a charger that has buttons as opposed to Digital controls ( clueless here)... Which in my case I do have... So when I set the charge to trickle 5, 10, 30, jump, it is a button setting so applying wall power immediately activates whatever setting I have on the charger
I personally have had a manual setting charger for 20 years... trickle setting Has served me perfectly while being on travel for many months at a time..
Last edited by kafklatsch; Jan 7, 2023 at 11:41 AM.
"Thank you for contacting the Premier Luxury Department. In regards to proper charging of your vehicle for longterm battery preservation information can also be found on page 196 of your owner's manual. If leaving the vehicle idle for extended periods, park the vehicle with the high-voltage battery condition of charge at between 30% and 50%. Do not keep the high-voltage battery continuously connected to power supply equipment. If leaving the vehicle idle for extended periods of time avoid, if possible, high ambient temperatures. Check the high-voltage battery's condition of charge every six weeks (page 208). Charge the high-voltage battery if the condition of charge is below 20%. Do not disconnect the 12 V battery even if the vehicle is left idle for an extended period. Otherwise, the condition of the vehicle's high-voltage battery cannot be monitored."

If you are going to be away for 4 months, I'm afraid the 12 V battery will run completely flat. Not sure about the 223 idle current but older models consumed some 80 mA if they had an alarm system (40 mA without alarm). The 223 has all the on-line connectivity "half active", the idle current must be higher than 80 mA. But calculate 4 months times 30 days times 24 hours times 80 mA and you'll get a ridiculously high Ah figure (please check, I had to calculate 3 times and still feel it is surprisingly high).
It would be better to unplug the 12 V battery ground rather than leave the car for 4 months without any charging. The 48 V lithium battery would survive if it had decent SOC at start, no consumption on that battery when the car is parked.
I find it odd that your trickle charger does not reach the final state, perhaps it just assumes a lower idle current on the car than the 223 has. Don't know if it is a good idea then to have the trickle charger connected all the time but the timer proposal sounds much better than leaving the car as it is. The very minimum I would do is activate the deep sleep mode but I'm afraid even that is not good enough. The timer approach needs a proper charger, easy to test. Some chargers even stop charging after any mains loss (I had one for a 12 V car battery providing power for a GPS base, it died frequently for a flat battery). Ctek would be fine, I'm sure many others are.




