Smart EQ 12V Battery Trickle Charging Question

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Aveline_Vallen

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Hi everyone, I used a Deltran Battery Tender to trickle charge the 12V battery in my 2018 Smart EQ Fortwo since I wasn’t driving it for a week. The charger moved through bulk mode (up to 85%) quickly but has been stuck in absorption mode (85–100%) for over three days.

The battery is less than a year old and worked fine during a recent test. I’ve charged other car batteries before, and they usually finish within a day. Could the Smart EQ’s system be limiting the charge to protect the battery?

Has anyone else experienced this, or should I just disconnect it when it’s stuck in absorption mode? Any advice would be appreciated!
 
I've noticed similar behavior with my EV and a "smart" charger. It seems these chargers can get confused by the way EVs manage their 12V batteries. They're designed for traditional cars, where the battery is a simple storage unit. With EVs, the 12V battery is more of a secondary system, often topped up by the main battery. This fluctuating voltage might be throwing off the smart charger's algorithms.

You can buy something like this battery monitor on Amazon could be a great tool to diagnose the issue. It can provide real-time data on voltage, current, and state of charge, helping you pinpoint the problem. By monitoring the battery's behavior, you can determine if it's the battery itself, the charging system, or something else causing the problem.
 
It’s possible the system is limiting the charge to protect the battery. You could disconnect the charger and monitor the battery’s condition.
 
Sorry, I'm a bit lost here. It seems like there’s some confusion between the HV battery charging system and the 12V system. Your trickle charger might not be related to the HV battery, other than both trying to charge the 12V battery at the same time. I think BMS is linked to the HV battery and doesn’t affect the 12V system.
 
EVs use a DC-to-DC converter, which charges the 12V intermittently. That leads to tripping up some trickle chargers. If the battery’s fine, I wouldn’t stress. Maybe try a battery monitor to check the voltage, or just let the car handle it.
 

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