Chassis Batteries Not Maintaining At Same Rate as the House

[MoJoe1003]

We have been in our new 2021 XL for two weeks tomorrow. I have noticed that while on shore power, the house batteries show 14.3 Volts, but the chassis batteries only show 12.6 Volts. In our 2018 XL, those two numbers in the Precision Plex screen stayed about the same.

Should I be concerned that the chassis batteries are not be charged properly based on these numbers?

[tomkatb]

Maybe!

Not enough information.

A fully charged wet cell battery systems that has been off the charger 4-5 hours will read about 12.6 volts.

A converter running on bulk, a rare situation, will charge at 14 volts or more for several Hours. It will require likely 24 hours of charging. But, voltage will drop to 13.4 volts after two hours from the converter.

Lithium batteries typically charge at this higher voltage. Did you add them? Change converter?

So maybe all is ok.

What I would do is charge from shore power 36 hours. Then disconnect for 4 hours and read the battery voltage at the batteries with a voltmeter.

[bclemens]

Sounds like it is working as it should.

The BIM should only connect the house and chassis batteries when it needs to.

You can read the sell sheet on the BIM to get a better understanding.

It is the "Battery isolation Manager"
https://forestriverinc.help/#/dynama...als/Electrical

[mjbenedict]

The BIM will not connect the two banks if the chassis battery is above a certain voltage. From your reading you are at near full charge on the chassis AGMs. Has to drop to ~80% charge to connect. 80% charge for lead battery is ~12.4V. No need for alarm.

[Adrian Gordon]

Originally Posted by MoJoe1003

We have been in our new 2021 XL for two weeks tomorrow. I have noticed that while on shore power, the house batteries show 14.3 Volts, but the chassis batteries only show 12.6 Volts. In our 2018 XL, those two numbers in the Precision Plex screen stayed about the same.

Should I be concerned that the chassis batteries are not be charged properly based on these numbers?Attachment 257205

The 14.3 volts you are seeing on the house batteries while on shore power is almost certainly the charging voltage, not the battery voltage.

[MoJoe1003]

Thank you all. Appreciate the input as always. Just never noticed the the two being that much different on the old unit. Must just been the randomness of when I checked it.

[Frankiejay]

Batteries charge at different rates. Automotive batts 12.6 volts indicate a fully charged battery. (Some house batts can discharge almost down to 8.5 volts.) Seems like your batteries are doing great. Safe & Happy travels

[tomkatb]

When the converter or whatever is supplying the 14. Voltage to batteries concerns me.

Voltages over 14 for very long will boil the batteries. The old chargers typically did this. Causes premature failure. Remember those batteries exploding?

I would explore the high reading. In three years I have never seen a reading over 13.5.

[Frankiejay]

The internal resistance of the battery determines the rate of charge. That's why batts are replaced/installed in pairs of the same kind. I think the Ford Motor Co sets the rate of charge at 13.8 volts. 14 volts is OK. The new type batt chargers taper off the amperage (rate) of charge as the batt/batts reach full charge. As a Retired Ford Tech, in 55 years, I've seen very few batts "boil dry. Enjoy your new rig. Safe & Happy travels