CTEK Battery Charger for Re-Charging Two 12V Trailer Batteries

Question:

I hooked both my 2 12 V RV batteries together using regular battery connection cables + on + and - on -. Then I attached the trailers cables that runs from the trailers electric box to one of the batteries. I tried to charge them together with the battery charger and neither charged more than 60...even though my battery charger showed that the charge was complete after several hours....neither will charge together more than 60 when I run the truck engine...what am I doing wrong? When I remove the cables connecting the batteries the batteries will charge 100 separately? Thanks!

asked by: Paul L

Expert Reply:

While you can wire two batteries' outputs in parallel when you're using them, when charging batteries it is always best to do each one individually. Shore-power chargers like the CTEK # CTEK56353 are the only way to fully re-charge a depleted battery.

The +12V power circuit in your 7-way trailer wiring can deliver a worthwhile maintenance-level charge to the fully-charged batteries on your trailer to keep them topped off but that circuit simply doesn't have the current required to re-charge a depleted battery, let alone two of them.

expert reply by: Adam R