12V chargers issues

Ricki1 · Dec 3, 2024

My 2 year old 2015 Smart ED is having a fit with its 12V battery. If I don't plug it in, the battery dies and can even drain the big battery.

The car's always sucking power from the 12V battery, even when it's off. A battery monitor showed it dropping way low before the big battery kicks in. Keeping the big battery plugged in helps, but the 12V battery is still a problem.

People say to use a trickle charger, but I was worried it might mess with the car's system. I found out that a small, cheap charger under 3 amps should be fine.

I tried a cheap charger, but it kept turning off. So I got a super cheap one, and it's working great! It's slowly charging the battery without any issues.

Sussystorm · Dec 3, 2024

For all of my cars, I leave the battery plugged in and use a "maintainer" rather than a trickle charger. It's wonderful that you found one that works because it appears to function nicely without interfering with the system.

Wendy · Dec 11, 2024

It sounds like the small charger under 3 amps is a great solution! Glad it's working without causing issues.

Evholic_34 · Dec 16, 2024

What can you ask for more than a happy ending with money left in your pocket? Goooood freaking job!

4enz.dzn · Dec 31, 2024

Ricki1 said:
My 2 year old 2015 Smart ED is having a fit with its 12V battery. If I don't plug it in, the battery dies and can even drain the big battery.

The car's always sucking power from the 12V battery, even when it's off. A battery monitor showed it dropping way low before the big battery kicks in. Keeping the big battery plugged in helps, but the 12V battery is still a problem.

People say to use a trickle charger, but I was worried it might mess with the car's system. I found out that a small, cheap charger under 3 amps should be fine.

I tried a cheap charger, but it kept turning off. So I got a super cheap one, and it's working great! It's slowly charging the battery without any issues.

Try using a thermal camera to find the hot spot. It might be the fuse box or the SAM.

sixlifts26 · Jan 1, 2025

Sussystorm said:
For all of my cars, I leave the battery plugged in and use a "maintainer" rather than a trickle charger. It's wonderful that you found one that works because it appears to function nicely without interfering with the system.

Yeah, the maintainers are awesome! I’ve been using it for months now without any issues.