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Old 12-01-2008, 03:56 PM   #1
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voltage drop in storage?

(2) SRM-27 interstate batteries, delivered in my new 2008 a/s.. removed for winterization... charged both with portable 3-stage... equalized.. then let sit in tempered workroom (~68 deg)
day 1: 13.20v
day 30: 12.82v

according to your typical SOC chart, that's going from 100% to 60%, -.38v... just sitting...

is this acceptable performance?

(btw- they're back on a storage trickle)
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Old 12-01-2008, 04:19 PM   #2
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Yes, the 13.2 volts you measure the voltage directly off charge, and it should come down to 12.6 volts and hold that for a long time. All batteries will self discharge because of internal resistance. You should charge them every month or so, or put a "maintenance" charger on them.
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Old 12-01-2008, 05:21 PM   #3
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Here's a state of charge chart for you:

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Old 12-02-2008, 01:26 PM   #4
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Your battery will self discharge at a rate of 2% per month to per week or so depending upon battery type, temperature, age, and so forth. This is why you should have some sort of device on them to assure a top charge and sulfation inhibition if storing them for more than a few weeks. Letting batteries sit, especially if at less that full charge will cause them to age faster than they would if properly maintained.

If after 30 days, your voltage is at 12.8v a proper interpretation is that the self discharge rate for that battery in those conditions is still fairly low. (i.e. battery is in good shape!)

Take note that battery state of charge measurement from voltage (as well as from hydrometry) needs to have a surface charge removed and a battery at rest. That's why it's probably best to not get too enthused about measuring battery parameters unless it is in use and with proper interpretation.

For storage, use a device that will maintain a top charge and inhibit sulfation.

In use, don't worry until the voltage after a half hour of no significant charging or discharging gets below 12.4v. When it gets down to 12.0v in these conditions, put a battery charge on your priority list. Keep in mind that batteries aren't really precise devices. Cycle to cycle variations, temperature, age, use profiles, and other things can make as much as a 20% difference. So, don't micro manage or get too worried about trying to measure things.
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Old 12-02-2008, 01:53 PM   #5
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Quote:
Originally Posted by finalcutjoe View Post
(2) SRM-27 interstate batteries, delivered in my new 2008 a/s.. removed for winterization... charged both with portable 3-stage... equalized.. then let sit in tempered workroom (~68 deg)
day 1: 13.20v
day 30: 12.82v

according to your typical SOC chart, that's going from 100% to 60%, -.38v... just sitting...

is this acceptable performance?

(btw- they're back on a storage trickle)

Was your 13.2 v. measurement taken pretty much right after charging? If so, I think you would have found it would drop down to 12.? within an hour or two.

With our last trailer, I used to keep the conventional single lead acid depp cycle batt. in our garage when we were not using it in the trailer.

I had it wired to a charger that would automatically turn on for 8 hours once every week. You can also get automatic chargers that can be left switched on all the time and will not overcharge the battery.

When we bought the airstream with its two batteries, they were just about shot. I bought two new AGM (absorbed glass mat) batteries as replacements.

I bought these because it is claimed they have a much slower self discharge rate. The info with them said you could leave them off charge for up to a year.

I am planning to just leave them in the trailer which we store at a spot some miles away from our home. When we bring the AS home to prepare for a trip, I will put a charger on them for a few hours if needed.

I went this route because I needed new batts anyway, and I found that the storage compartments on the Airstream were not the most convenient for battery removal.
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Old 12-02-2008, 05:22 PM   #6
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Bad pun warning!

I posted here earlier today and it's gone. Could there be a short in the circuit? A dead battery? Watt happened? Was there resistance to my questions? I'm not getting wired or amped about it, though I am shocked. Time to calm, ohmmmmmmm.

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Old 12-02-2008, 08:17 PM   #7
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Hey, that's General Jack Ripper!

I just happened to stumble across finalcutjoe's topic of batteries here. I've no important comment on his battery situation but I must say I recognize his photo on his comment of General Jack Ripper from the movie "Dr. Strangelove."

Maybe finalcutjoe wants Mandrake to protect the "precious bodily fluids" of those batteries!
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Old 12-03-2008, 12:41 PM   #8
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Take two and I'll try to avoid the puns.

I have a dealer installed solar panel with a monitor. The brand is SolarPRO CC20. The '08 Safari came with 2 batteries and I think they're series 24, the cheapest made. I keep the trailer plugged into shore power all the time when it's sitting at home, figuring the 3 stage charger will keep the batteries topped up without overcharging them. I believe the solar charger has its own controller preventing overcharge.

After one year and about 8,500 miles it seems the batteries aren't holding a charge very well when we boondock. They have enough water in them as I check and top off periodically. My old battery tester has died, so I have to get a new one to check the cells. The SolarPRO monitor tells me battery voltage and I checked the voltage at the batteries with a multimeter and they both read 13.8.

So, I noticed Brian's new Airstream has bad batteries. Perhaps dealers don't charge them until their dead after letting people in the trailers to try stuff, shortening life.

Are batteries with short lives common?

I would like to replace the batteries if they are bad with better ones. The battery box is pretty small and difficult to enlarge. A cursory look seems to indicate about 3/4" extra space on two sides, but I'm not sure a better battery, which may be bigger, would be very easy to cram in.

I don't know if different models have different size boxes. What success have people had putting in better (bigger?) batteries? Ideally, 6 v. golf cart batteries are my desire. Has anyone replaced the factory batteries with 6 v.?
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Old 12-04-2008, 07:47 AM   #9
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Quote:
Originally Posted by CrawfordGene View Post
Take two and I'll try to avoid the puns.


So, I noticed Brian's new Airstream has bad batteries. Perhaps dealers don't charge them until their dead after letting people in the trailers to try stuff, shortening life.

Are batteries with short lives common?

Well, it was a "New to us" trailer, an 05 that we just bought, so really I was pretty much expecting the batteries would be shot. I think that three years or so would be a typical life, especially if the batteries were not well looked after either by the previous owner or the dealer while the trailer was in his possession.


Actually, I just went out to my trailer yesterday and found that my new AGM batteries had dropped down to about 10.5 volts in a month!!!

I don't know why that should be, they are supposed to hold their charge for up to a year. I have brought them back to the house to charge. I will then take them off charge in my garage and keep a close watch off them. Perhaps they are defective & if so, back they go!

I did check to make sure that the battery isolation switch in my trailer was switched off, so parasitic loads shouldn't be the cause - unless maybe the
isolation switch is defective.

Next time I put the batts. back in the trailer, I will check to be sure there is zero current draw when the battery isolation switch is off.


Brian
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Old 12-04-2008, 08:15 AM   #10
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If you are going to let them sit in the trailer all winter, why don't you disconnect one of the battery cables......this will eliminate those phantom loads. I just metered my AGMs which have been sitting for 6 weeks with the ground disconnected, voltage is 12.55 Also, have a second set in the garage that have not been charged for 3 months, they read 12.5v.
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Old 12-04-2008, 08:19 AM   #11
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Originally Posted by wasafari View Post
If you are going to let them sit in the trailer all winter, why don't you disconnect one of the battery cables......this will eliminate those phantom loads. I just metered my AGMs which have been sitting for 6 weeks with the ground disconnected, voltage is 12.55 Also, have a second set in the garage that have not been charged for 3 months, they read 12.5v.
I guess caused I'm lazy!!!

No, actually, I figured that if I turned the battery isolation switch to off, that would be the same as disconnecting the batteries - am I wrong in this? I'm not sure, the AS is the first trailer I have had with an isolation switch.

Also, if I were to disconnect, would I not need to disconnect both batteries? Presume that thay are just wired in parallel.

Any comment appreciated as I learn the quirks of AS trailers!
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Old 12-04-2008, 08:48 AM   #12
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I had some AGM's in my A/S for last couple of years. This year when I was boondocking (first trip out) I had to run the generator to keep a charge in one of them. They were both replaced with a series 27 and have held up well. I always take my batteries out of the trailer during the winter. They don't fare well in 10 below zero weather. They are kept in my garage and I just purchased a battery tender to make sure they keep a good charge. The battery tender also works well in keeping the battery charged on my Yamaha generator. We are going to get a solar system installed this next spring so I am not sure what type of battery we will go to because we will increase from 2 to 4 batteries.
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Old 12-04-2008, 11:11 AM   #13
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isolation switch

Quote:
Originally Posted by Wingeezer View Post
I guess caused I'm lazy!!!

No, actually, I figured that if I turned the battery isolation switch to off, that would be the same as disconnecting the batteries - am I wrong in this? I'm not sure, the AS is the first trailer I have had with an isolation switch.

Also, if I were to disconnect, would I not need to disconnect both batteries? Presume that thay are just wired in parallel.

Any comment appreciated as I learn the quirks of AS trailers!
One comment on the "isolation" switch or the "store-use" switch. You said you thought that the switch eliminated all battery usage. I don't think that's true. I've noticed on my 2006 Safari that the electric jack works with the switch in the "store" position, an effect I didn't expect.
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Old 12-04-2008, 03:21 PM   #14
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Jack..

Cant say about the rest, but the jack is wired totally directly to the battery bank with its own inline fuse. I have noticed that my stereo (factory a/v) package power light stays on even with the switch off, so I remove the face of the stereo.

Probably some other stuff staying on as well...
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