Stopping charging of coach battery while on shore power

[komac]

Using the suggestions from this forum, I went to the MH with my volt meter yesterday. (Without shore power, I had left the coach batteries connected to see whether any parasitic drain from the radio, etc. would take the charge on my batteries down significantly.) I first checked my battery monitor and found that the batteries were about 75% charged. Then I checked them with my volt meter and found them at about 12.1 volts. I plugged into shore power and checked them immediately after. At first I was surprised because the batteries were now reading nearly 15 volts and my inside monitor was reading 100% charged. About half an hour later, the batteries were reading slightly more than 14 volts. I came back about two hours later and the batteries were standing at slightly less than 13 volts. So I'm guessing that my on-board charging system is working fine and shouldn't overcharge my batteries. I'm going to keep my volt meter in the coach and check the batteries occasionally when I'm camping and on shore power. Thanks again to all of you who gave me some really good suggestions. Komac

[Wanabee FTer]

Originally Posted by komac

My inside battery disconnect switches operate relays which are supposed to disconnect the batteries, but my coach (house) battery disconnect switch will not allow a battery disconnect when I'm on shore power. (I don't know why.)

Komac,
Put a volt meter on your batteries, then press disconnect on your chassis remote battery cut off switch. Note the readings before and after. You should see appx 13.6 volts slowly go down to battery voltage appx 12.6 volts. On my coach the battery light stays on when using shore power, but the remote disconnect actually works! The reason the chassis light stays on is because the monitor is tied into the coaches electrical system before the shut off solenoid for the battery, so the convertor power keeps the light on.

PS
When your batteries are fully charged you should be getting a rested voltage reading of appx 12.6 volts. The battery state of charge indicator inside the RV will show a full charge whenever it is connected to shore power wether the batteries are low or not.

[scoutmstr]

I bought one of these to know what voltage coach battery is at plus it'll tell you what voltage the battery is being charged on shore power plus an adjustable alarm setting for low battery.voltminder.com

[komac]

You're right, John! My battery disconnect switch still showed a light when I turned it off, leading me to believe that the battery wasn't being disconnected when I am on shore power. However, when I checked the charging rate with the battery disconnect switch on and off, the voltage dropped when the disconnect switch was off, even though the disconnect light remained on! That was a welcome sight. It would have been nice if my owner's manual had included that information. Thanks again to all who have helped me. Now I can and will share this information with others with the same concerns. Komac