battery drain when connected to charger?

[rocknroj]

Thanks for reading, and of course knowledgeable responses.

Does/can a battery charger discharge a connected battery when the charger is not plugged in to 120v?

Background:

Lately I have left my battery charger connected to the battery terminals while sitting unused. Leads to the motor are disconnected. Got tired of climbing in the boat to connect and disconnect the charger each time. Typically, once charged the battery was good and if hooked up a few weeks later to the charger it would only run briefly before stopping indicating to me that the battery was fully charged. I would climb in the boat and disconnect the clamps from the charger to the battery.

My new lazy habits (well mostly some sore knees) are just to leave the charger connected to the battery and plug the charger in occasionally. I have noticed the charger continuing to run like a drained battery even though nothing has been used and the leads to the boat are disconnected.

So either the charger is draining the battery or its just end of life for the battery.

So after all that.. my question.. Does/can a battery charger discharge a connected battery when the charger is not plugged in to 120v..

 

[Chris1956]

A properly working charger will not drain the battery. It has diodes, which are one way electricity valves to prevent that.

I suspect your battery is near end of the line. They usually last about 5 years.

 

[Texasmark]

Diodes have reverse leakage current usually in the Microamperes. Your internal battery normal discharge characteristic way outweighs that. I noticed for the first time...for some reason I decided to check everything...that in checking my batteries in everything, plus the new spares, they were all low in voltage except for the ones I had been using in recent days. So I got out the maintainers and solved that problem which will extend the life as keeping them topped off prolongs their life and at today's battery prices a good idea!