Are My Batteries Toast

[Mike&Chris]

Recently I unplugged our Anthem from shore power to move it temporarily. Afterward my son-in-law reconnected it but unfortunately he turned the wrong breaker back on. I didn’t notice until late the following day and by then the batteries were down to 11.8. I realize this probably shortened their lifetime but I’m more to learn what my future expectations should be. If anyone has expertise in this area I hope to hear what you think.

[oneknight]

11.8 is dead, but certainly not toast. If they will charge back up they will be fine.

[FlatsixV2]

Should not be an issue!

[brobox]

I have had power outages a couple of times while in storage where the batteries got lower than that...never any permanent damage. Short term should not be a problem.

[757driver]

11.8 volts is not even 80% discharged with the AGM batteries. Fully charge them back up and you will be fine.

[Mwoodofd]

The battery experts have answered the battery livelihood. I am curious to know how long it was unplugged before you noticed it down to 11.8?

[LWBAZ]

Mike, I agree with what everyone else has posted. Deep-cycle batteries are designed to tolerate hundreds of discharge cycles. It’s true they’ll deliver a larger number of cycles if they’re lightly discharged versus fewer cycles if they’re deeply discharged, but the total number of Amp Hours you can pull out of them during their lifetime will be virtually the same either way.

Included below is a chart from Lifeline that shows Expected Life Cycles versus Depth of Discharge (DOD). You probably have Discover batteries, but I doubt there would be a lot of difference if Discover publishes a similar chart.

Let’s assume you’re an avid dry camper, rarely staying in RV parks with shore power. Let’s ignore any solar panels you may have and assume you’ll always run your generator to recharge your house batteries. And let’s say you have an 800 Amp Hour battery bank (which is what I believe you actually do have).

Looking at the chart, if you never let your house batteries run down to less than 10% DOD, you’d get 5,000 cycles out of them. With an 800 Amp Hour battery bank, 10% of the available capacity is 80 Amp Hours. 80 Amp Hours x 5,000 cycles = 400,000 Amp Hours.

Instead, let’s say you always let the batteries run down to 50% DOD before recharging. In that scenario the chart indicates you’d get 1,000 cycles. With an 800 Amp Hour battery bank, 50% of the available capacity is 400 Amp Hours. 400 Amp Hours x 1,000 cycles = (guess what) 400,000 Amp Hours.

The difference between the two scenarios is that in the first case you’d be starting your generator quite a few times per day for relatively short periods of time, whereas in the second scenario you’d need to run your generator once or twice per day for longer periods of times. No free lunch either way, but just about all of us would agree that the second scenario is preferable to the first.

In the real world, nobody dry camps all the time and most Entegra owners do so rather rarely. As Don indicated, at 11.8 volts your batteries were still somewhere above 80% DOD. The effect of doing that one time (or even a dozen times) is truly insignificant to the life and/or health of your batteries. There is even a school of thought that suggests an occasional deep discharge is actually good for deep-cycle batteries that are only lightly discharged most of the time.

Another thing to keep in mind is that the house battery voltage you see displayed inside the coach is often/usually a tenth of a volt or so lower than the actual voltage measured at the battery bank itself. I won’t bore you with why that’s the case, but I’ve found it to be pretty consistent across various brands of motorhomes and batteries. So your 11.8 number was probably more like 11.9.

Bottom line, look for something else to worry about.

[twinboat]

Originally Posted by Mwoodofd

The battery experts have answered the battery livelihood. I am curious to know how long it was unplugged before you noticed it down to 11.8?

The OP stated he noticed it the following day.

[brobox]

Larry, good refresher on battery life. I am one of those from the "old school" since I rarely boondock anymore I do try to put a "hot charge" on the batteries once a year. Since I won't Equalize my AGM batteries. I do let them run down to let them get a hot charge and exercised once a year. Target rate for the discharge is 11.9v. I don't know if it does any good, but it makes me feel better and I can time how long it take for my batteries to get to that point each year. If I am to that point in 1/2 an hour, my batteries have a problem and probably won't make that years trip. The one year I did not do that, my batteries died on the way to Entegra for my PDI. After that experience I will check the new coach every year now.

[Mike&Chris]

Thank you guys, that’s good to know!

[757driver]

Originally Posted by Mike&Chris

Thank you guys, that’s good to know!

Mike,

As an FYI when reading the DC voltage for the house batteries on your Vegatouch panel while the coach is in use with an average DC load, 12.0v is roughly a 50% DOD (depth of discharge) so at 11.8v you were not that far below that. Also, If you don’t have it selected AGM2 will give you a much better charge profile that is closer to what Discover Battery recommends as compared to the AGM1 setting.

[LWBAZ]

Originally Posted by 757driver

Mike,

As an FYI when reading the DC voltage for the house batteries on your Vegatouch panel while the coach is in use with an average DC load, 12.0v is roughly a 50% DOD (depth of discharge) so at 11.8v you were not that far below that. Also, If you don’t have it selected AGM2 will give you a much better charge profile that is closer to what Discover Battery recommends as compared to the AGM1 setting.

As always, Don is correct. The AGM2 profile will get you as close as any of the pre-programmed charging profiles. If you want to get obsessive about it, you can find additional details in this thread:

http://www.irv2.com/forums/f278/reco...ks-411944.html