shotgun_banjo

My c300 is in storage and I noticed that it is draining the battery. Everytime I use a volt meter it registers less than 11.5v and car is having a hard time cranking. If I manage to get it running for 20 minutes it will charge back to 12.6ish volts without load. I think there is something draining the battery. Any recommendations? I have a battery maintainer attached to it and the charger keeps getting an error that it cannot maintain the voltage as there is load being applied to the battery. Tested 2 chargers and same result. Is it best to unplug the cable from the battery instead for long term storage? I rather not do that as it will be a hassle taking off the housing above the battery and unhooking the cable. One other thing. The battery is just 1 year old.

NZ-Merc

Have you tried a Ctek charger, I have a 5 amp Ctek with the accessory extension lead just for maintaining my fleet.

I had been having trouble another maintainer not putting in enough voltage for My A180 with the stop start and the battery was always partly flat.

A good quality charger should be the answer, and like you I don’t think disconnecting the battery is necessary.

edgalang

There will always be a load. If there isn't, keyless access wouldn't be able to work. Also, I know for a fact that power to the overhead console remains on for at least 30 minutes if you exit the car without locking it (regardless if the lights are on or off). I know this because that is currently where my capacitor-based dashcam is wired to.

shotgun_banjo

Tried again with another charger (same brand) and this time it fully changered the battery and went to maintenance mode. The moment I opened the door voltage dropped as the electronics of the car pulled power from the battery then it took 1 hour again to go back to maintenance mode. So I guess you really need to get a trickle charger for the car if you wont be driving it for months unless you unplug the battery. I tried using the solar panel battery maintainer but it does not have enough juice to compensate with the power draw of the car's electronics.

NZ-Merc

Hi,
Good to hear you have been having success.
If you are thinking of or going to replaced the charger this is what I recommend based on my own experiences with smart chargers some just are not up to the task for new cars, they make out fully charged but the battery is not.

https://smartercharger.com/products/...multi-us-3300/
https://smartercharger.com/products/...tension-cable/

Regards,
Dave.