AGM coach batteries won't charge

[BobC]

A three year old MH should have a converter with a multi-stage, smart charger so I doubt that is the problem. I agree with thataway4 in that you need to have a battery or batteries in place in order to have 12V power even if connected to shore power.

Get your batteries tested by a professional and save yourself a lot of angst and time.

[jerichorick]

To all needing batteries. I just replaced my six 10 year old AGM's. I could not find a better place to buy a quality battery for a reasonable than here: https://www.bargainshore.com/
I discovered this battery and seller when doing my research. I am very pleased with the delivery time, the batteries and what I paid.
Rick Y

[tderonne]

Originally Posted by icw2gotra

Battery levels look like this on the monitor panel:
Engine off, coach plugged in, coach battery in 'disconnect' mode:
Chassis bat = 12.3v House bat = 13.2v
Unplug from shore power and the monitor panel goes dead.
Turn on engine and monitor panel levels are:
Chassis bat = 14.1v House bat = 14.1v

Seems perfectly normal to me.

With the "coach battery in 'disconnect' mode" the coach batteries are disconnected from most everything, the monitor panel and converter included. Exception being when you start the engine, it's then connected (via a solenoid) to the alternator.

[MadMaxWinny]

There IS an inherent issue with AGM batteries. The chemistry of a battery dictates its' specific charge algorithm. In the early days of AGM hitting the general market (they were used in military applications for years), they looked so much like a Gel Cell battery, many RV/boatyards set up the smart chargers for that program, which killed the AGMs in 2-5 years. Charged by their specific needs, I've had them last 12-15 years. The most common program is of course for "wet" batteries. Fortunately for us, the algorithms are SO close, the AGMs can usually get at least 10 years. If you are getting less, check the FINAL voltage of your charge (when the batteries are at 100%). If it's over about 14.2v (temperature dependent), that is the problem.

[Goodspike]

Originally Posted by MadMaxWinny

There IS an inherent issue with AGM batteries. The chemistry of a battery dictates its' specific charge algorithm. In the early days of AGM hitting the general market (they were used in military applications for years), they looked so much like a Gel Cell battery, many RV/boatyards set up the smart chargers for that program, which killed the AGMs in 2-5 years. Charged by their specific needs, I've had them last 12-15 years. The most common program is of course for "wet" batteries. Fortunately for us, the algorithms are SO close, the AGMs can usually get at least 10 years..

Why are Chevy Colorado Duramax owners reporting only about four years of life from their AGM's? Is it due to the heat from the engine?

[MadMaxWinny]

@Goodspike, no...temp is rarely the issue (but always a factor with batteries). Automotive alternators are notorious for loosey-goosey voltage regulators. They can shorten the life of any battery, but sealed (non-maintenance) batts are extremely sensitive to excessive voltage. They WILL out-gas, and there is no way to replenish them.

I good rule for anyone using sealed batteries (in any application) is to check the two most critical voltages: "charge" voltage (battery is 25-50% discharged with charge source engaged) and "finished" voltage (battery is less than 5% discharged, with source engaged). This is true for converters (AC chargers) and alternators, both.

[Goodspike]

Originally Posted by MadMaxWinny

@Goodspike, no...temp is rarely the issue (but always a factor with batteries). Automotive alternators are notorious for loosey-goosey voltage regulators.

I think the Colorado voltage regulators are pretty advanced. Once charged often no charge is applied (a 12.6 voltage) and they even know when the vehicle is coasting downhill and will increase the voltage during those events to capture the free energy.

But, if a trailer is attached the voltages could be higher to charge the remote batteries. I wonder if that is is?

[Morich]

Charging trailer batteries is always going to be a bit off the ideal just simply due to the setup of a battery in the vehicle is likely to be pretty close to fully charged and then we tie a trailer battery of a far lower state of charge on the first. Somewhat like changing out only one battery in a flashlight? One battery or the other is likely to not be getting the best charge for the longest and best life. If the trailer battery is going to get the voltage/ current to charge it best, the start battery is going to be getting too high or the other way around!
Batteries are like lots of things we do, it's all very simple until we look closer.