Community Forums

johnfdavid · 08-20-2021, 04:36 PM

I have a Coachman motorhome that is 4 years old. I always keep it plugged into a power source. When I am either plugged in or driving, I have a full 12 volt charge. Soon after unplugging, my charge drops to nothing. I'm guessing this means I need a new marine battery, but does anyone have a suggestion on something I should check before replacing the battery. Thank you.
John

Roy-c · 08-20-2021, 05:10 PM

Have the battery load tested. ( After charging ) It will either fail or you have a electrical draw in the system. causing it to go dead. ( if it has been drawn down to dead several times it is also toast )

chunker · 08-21-2021, 05:45 AM

Charging just means the battery was supplied with electricity, but it doesn't mean the battery did anything with it. Like a glass you are filling with water, if it has a hole in it, no water will remain. Are the batteries flooded cell? When was there last time you checked the water in them? Is there corrosion on the battery connectors? A load test is not putting a voltmeter on the terminals so make sure you did a real load test.

Persistent · 08-21-2021, 07:41 AM

Choosing An RV Battery
https://www.irv2.com/forums/download...do=file&id=231
This is a good article, but its recommendations against “Marine Batteries” does not apply to “Marine AGM batteries”.

Battery University https://batteryuniversity.com/articles

How does the Lead Acid Battery Work?
https://batteryuniversity.com/articl...d-battery-work

How do battery chargers work
https://batteryuniversity.com/articl...-chargers-work

How to Charge and When to Charge?
https://batteryuniversity.com/articl...when-to-charge

johnfdavid · 08-23-2021, 05:27 PM

I will check those things and I appreciate your help.
John

rikadoo · 08-23-2021, 07:02 PM

So depending on how long your rig is plugged in if your charger is a consistant say 14 volts it could be there is no water left in the cells. My house batterys are A wet style, after a couple months i have to add water. Overcharging batteries are just as bad as undercharging in many ways. If you continue to leave the rig plugged in it would be good to check that the charger not “cooking” the cells using a voltmeter .