Battery charging shut off

[tgodrich]

I recently checked the water in my trailer batteries. One was very low. My rig sits next to my house and is always plugged in. I can switch between battery 1, battery2, both batteries, and disconnect. I normally charge one, then the other, and alternate every few weeks.
My question is... Does the charging system in the RV stop charging when the battery reaches full charge? I would think these days it should shut off on full charge. Is there a way to check if this is the case?

[Country Campers]

The converter/chargers will keep the battery "topped off" meaning it will likely be constantly charging. The problem is the situation that you describe , this is called "boiling off" where the constant charging causes the "water" in the battery to slowly evaporate. Battery maintenance is key when leaving plugged in for long periods.

Brian

[JCR GD]

... and every time you switch batteries the charger goes back into bulk charge again.

Set to both batteries (hopefully identical) and check water once in awhile and you should be fine letting the charger do it's thing.

[Jkwilson]

If the charger goes to float mode, there should not be much water loss. The float voltage is chosen to be below the gassing voltage to replace charge lost to self discharge without much water loss. The converter determines when it should be in float mode by monitoring current being drawn. In an RV, this doesn’t usually work well because there are loads on the 12V system all of the time, so the time spent at float voltage may be minimal or non-existent. To make it worse, once the electrolyte level drops, the current stays high so the charger keeps charging at higher voltage which accelerates the water loss.

My advice would be to leave the switch in the disconnect position and charge each battery about once a month for 24 hours with a quality portable charger. Only use the converter to charge when the batteries are being used or are low.

[tgodrich]

If the charger goes to float mode, there should not be much water loss. The float voltage is chosen to be below the gassing voltage to replace charge lost to self discharge without much water loss. The converter determines when it should be in float mode by monitoring current being drawn. In an RV, this doesn’t usually work well because there are loads on the 12V system all of the time, so the time spent at float voltage may be minimal or non-existent. To make it worse, once the electrolyte level drops, the current stays high so the charger keeps charging at higher voltage which accelerates the water loss.

My advice would be to leave the switch in the disconnect position and charge each battery about once a month for 24 hours with a quality portable charger. Only use the converter to charge when the batteries are being used or are low.

I like John's suggestion. I will check the water level again, and then do a 24 hour charge on each battery once a month. Since it sits next to the house, this is easy to do.
I have the age of the batteries staggered by about a year so that they do not tend to wear out at the same time. The life is not guaranteed, but in my past experience they give me about 3 good years before they begin to be less efficient at holding charge, at which point I replace them.
The float mode is what I would like the charger to go into. But with GD design, the batteries are never fully disconnected unless I put my added switch in the disconnect position, at which point the charger would be disconnected too.

As a secondary thought / question, does the charge circuit from the charger have a solo wire to the batteries, or do they gang the 12 volts together near the charger. If the wire comes directly to the batteries from the charger, and nowhere else, I should be able to move that connection to the battery side of my switch. This would allow the float mode to engage better. I would assume that the charger would not draw down the batteries when off shore power. Is that a correct assumption?
A wiring diagram from GD would be very helpful. Any idea where the charger in a 2016 303RLS would be located. I am thinking behind the fuse panel?

[Jkwilson]

Your converter is behind the short basement wall.