Nedd some guidance - Replacing chassis batteries

[Greyghost]

I need some guidance from those of you that have replaced your chassis batteries in a DP with solar. Both of my chassis batteries are no longer holding a charge. They will charge up but shortly after I stop charging they discharge down to about 10VDC.

When I change the batteries, what all do I need to disconnect before changing. I plan on taking the MH off of shore power and throwing the battery switch. I'm also considering removing the battery bank completely from the MH circuit by disconnecting at the fuses to the converter, inverter and charge controller.

Am I being too cautious or should I do anything else before I start the replacement of the batteries?

[MrWizard]

My three yr old surplus AGMs , just passed a load test yesterday, using a 500 amp carbon pile tester, and a 200+ amp load per battery
Fluke meter showed immediate rebound to 12.76 ~ 12.78 on each battery
We full-time the batteries are cycled everyday
My flooded wet cell batteries did not fair as well during testing, and one was a total loss with a bad cell,
I just came from getting it replaced
I am going to buy more AGMs to replace the flooded cell batteries
Even GC batteries only last me about 30 months or less and have to be replaced as too worn out

I'm NOT a big fan of AGM batteries, 'way over-hyped, once they outgas they are DEAD. And even less of a fan of paralleling batteries. Weak cell in one battery drains the charge from the other battery. Even worse, SHORTED cell (common failure mode) can turn into an explosive matter quickly, RAPID outgassing from the charge, POWER, flowing in from the good battery.

[Greyghost]

My system uses a Morning Star SunSaver Duo charge controller that depending on the dip sw settings I can direct 90% of the solar charge to the house batteries and 10% to the chassis. Another setting allows a 50/50 split. The default settings for the charge controller were 90/10. I strongly believe that the 10% was not enough to keep the older chassis batteries charged. I changed the settings to 50/50 and now the batteries will charge but not hold the charge.

After I replace the batteries I hope to be able to do more thorough testing to see if I have some phantom drains on the chassis. At the moment I'm kind of hindered by the fact that my wife is very ill with shingles and I'll need to be able to take the coach completely off line from power to do the replacement. Hopefully it won't be too much longer before she starts to feel better. Were on the road so I don't have the luxury of moving her to the house.

[Canadian_Rainbi]

If the chassis batteries don't charge from the solar/shore power install a Xantrex Echo Charger or a Trik L Start

Either of these will charge the Chassis Batteries from the House Batteries when the House Batteries are at or above(approx) 13 volts (ie from the solar or shore power) And only when the Chassis Battery needs a charge. Neither will over charged. I have seen our House Batteries charging at 14.8 volts from the solar while the chassis batteries resting happily at 13.1

They are not quite equal. One may be better than the other depending on location and charging requirements:

The Xantrex will charge at up to 15 Amps while the Trik L Start is only 5A output. On the other hand, the Trik L start is sealed and good for damp/dusty locations and the Xantrex is vented. We had one (Xantrex)fail, probably due to being located directly above a battery with a leaky and corroding terminal.

We have used the Xantrex Echo Charger for several years and have not had a chassis battery problem since. It even allowed us coax an extra year from a questionable chassis battery.

[Greyghost]

2oldman wrote:
If there isn't enough room to take a pic, how will you wire them?

I've got about 4 inches above the batteries to work. I'll have more of a problem labeling the cables in the rear of the compartment sonce I can't really see them until I pull the first battery. I've created a drawing the shows the connections but getting the labels on the back ones will be a b---h. The batteries are in a tray but there is no way in heck that I can move it with 6 batteries in it.

[Greyghost]

Thanks Sailor_lou, I had not thought about the order of disconnect/reconnect.

[2oldman]

Greyghost wrote:
wont be able to take the pic's as there just isn't any room above the batteries..

If there isn't enough room to take a pic, how will you wire them?

[Greyghost]

wwest wrote:
You may be mistaken. Most MH's have an isolator system that connects the chassis charging system to the house batteries when the engine is running. Works well until/unless the house batteries happen to get deeply discharged, common occurance

House batteries are at 13.6VDC chassis batteries are at 10.04VDC

[sailor_lou]

Remove the NEGATIVE cables first when the batteries are coming out and attach them last as the batteries are going in. This way if you slip with the wrench and hit the surrounding steel structure you will not weld the wrench in place and burn yourself.

You may already be aware of this, but it's worth repeating.

Lou
05 Travel Supreme Envoy

[wwest]

Greyghost wrote:

wwest wrote:
Low electrolyte/water will have that effect.

Recharging a deeply discharged set of house batteries via the chassis/engine system will OFTEN result in "boiling" the electrolyte away

Thanks west,
I have had to start the engine by using the AUX start, but other than that, I've never used the chassis batteries to charge the house batteries. In those cases the house was boosting the chassis until the engine started. The house batteries are Trojan AGMs, the chassis are PrimaPower SLAs. I'm replacing the chassis batteries with Exide 31-AGM7s.

You may be mistaken. Most MH's have an isolator system that connects the chassis charging system to the house batteries when the engine is running. Works well until/unless the house batteries happen to get deeply discharged, common occurance.

I'm NOT a big fan of AGM batteries, 'way over-hyped, once they outgas they are DEAD. And even less of a fan of paralleling batteries. Weak cell in one battery drains the charge from the other battery. Even worse, SHORTED cell (common failure mode) can turn into an explosive matter quickly, RAPID outgassing from the charge, POWER, flowing in from the good battery.

[Greyghost]

wwest wrote:
Low electrolyte/water will have that effect.

Recharging a deeply discharged set of house batteries via the chassis/engine system will OFTEN result in "boiling" the electrolyte away

Thanks west,
I have had to start the engine by using the AUX start, but other than that, I've never used the chassis batteries to charge the house batteries. In those cases the house was boosting the chassis until the engine started. The house batteries are Trojan AGMs, the chassis are PrimaPower SLAs. I'm replacing the chassis batteries with Exide 31-AGM7s.

[wwest]

Greyghost wrote:
I need some guidance from those of you that have replaced your chassis batteries in a DP with solar. Both of my chassis batteries are no longer holding a charge. They will charge up but shortly after I stop charging they discharge down to about 10VDC.

When I change the batteries, what all do I need to disconnect before changing. I plan on taking the MH off of shore power and throwing the battery switch. I'm also considering removing the battery bank completely from the MH circuit by disconnecting at the fuses to the converter, inverter and charge controller.

Am I being too cautious or should I do anything else before I start the replacement of the batteries?

Low electrolyte/water will have that effect.

Recharging a deeply discharged set of house batteries via the chassis/engine system will OFTEN result in "boiling" the electrolyte away.

[Greyghost]

Thank you gentlemen, I wont be able to take the pic's as there just isn't any room above the batteries. I've labeled the cables and will probably tie wrap the ones together that need to be on the same post. It sounds like I wasn't being too paranoid. Thanks again.

[mtrumpet]

Just changed out both the chassis AND house batteries on mine just a couple of weeks ago.

I disconnected the shore power, shut off the battery disconnect switch to the house batteries and shut off the power disconnect switch (to the chassis batteries) located in the engine compartment. That was it.

Just be very very sure that you somehow note how all of those cables are hooked up BEFORE disconnecting them! Take a few pics with your camera phone, make a hand drawn diagram or label the cable ends if necessary - whatever it takes to remember exactly where those cable ends get reconnected.

[2oldman]

Yes. TAKE A PICTURE OF THE CONNECTIONS.

We see this all the time "I replaced batteries but I don't remember which wires went where."