Battery Charging: I don’t understand this

[Chuggs]

Purely a function of the bi-directional relay.

Incidentally...Lead Acid and AGM are both lead acid chemistry. Plus...the bi-directional relay we normally would find installed has no clue if you have one with caps or absorbed glass mat. It's just looking for certain parameters to be met.

Mine happens to trigger around 12.7v. The upper number may change...due to where in the charge cycle, or temp coefficient being applied to charge parameters.

 

[Chuggs]

 

[Richpatty]

As an addendum to this thread, I found that the small trickle charger panel on the roof does provide some juice to the chassis battery… Maybe too much?

It started when I noticed that the Precision circuit meter always showed both the house and chassis at about 14.3v/14.4v all day long. (We are camping currently). I initially suspected that my LiBim was stuck in the connected state and worried about boiling the chassis batteries away. I reached out to Precision Circuits (Who also makes the LiBim) and they had me cut out charging from the solar and magnum to see what the voltage would be at the LiBim. Turns out that after turning off the chargers, nothing really changed…so it was decided that the LiBim was hung and needed to be replaced.

So I went and removed the cable between the house batteries (lithium) and the LiBim to cut down the charging of the chassis batteries. Funny thing is that nothing changed. Now I was puzzled. I then went to check the voltage at the chassis battery when I realized that it was still connected to the small panel on the roof…. So I took the 7.5amp fuse out and watched the voltage drop down to 12.6 over time. I even reconnected the LiBim and it stayed at 12.6…as the LiBim is designed to do.

So…bottom line is that small panel does put out some power…enough to boil the batteries away? Not sure…but I sure didn’t like seeing my lead acid chassis batteries sitting at 14.4 all day long. Maybe it is harmless? After all, I just replaced my original chassis batteries just last year. And since my RV is stored under cover, that panel actually gets very little real use.

Anyway, sorry for the length of this post, but I figured I would pass along my experience.

Rich