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-   -   voltage drop in storage? (http://www.airforums.com/forums/f449/voltage-drop-in-storage-46718.html)

boondockdad 12-01-2008 03:56 PM

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)

SteveH 12-01-2008 04:19 PM

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.

nickcrowhurst 12-01-2008 05:21 PM

Here's a state of charge chart for you:
 
http://www.ccis.com/home/mnemeth/12volt/voltchart1.gif

bryanl 12-02-2008 01:26 PM

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.

Wingeezer 12-02-2008 01:53 PM

Quote:

Originally Posted by finalcutjoe (Post 643811)
(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.

Gene 12-02-2008 05:22 PM

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.

Gene

mistermcfrug 12-02-2008 08:17 PM

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!

Gene 12-03-2008 12:41 PM

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.?

Wingeezer 12-04-2008 07:47 AM

Quote:

Originally Posted by CrawfordGene (Post 644430)
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

wasafari 12-04-2008 08:15 AM

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.

Wingeezer 12-04-2008 08:19 AM

Quote:

Originally Posted by wasafari (Post 644632)
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!

dogpound 12-04-2008 08:48 AM

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.
Bob
Member Four Corners Unit/CAC
WBCCI # 10105
AIR # 28748

mistermcfrug 12-04-2008 11:11 AM

isolation switch
 
Quote:

Originally Posted by Wingeezer (Post 644637)
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.

SafariSS 12-04-2008 03:21 PM

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...

Wingeezer 12-04-2008 06:26 PM

Quote:

Originally Posted by SafariSS (Post 644758)
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...

Interesting comments. If some things that consume power remain connected, I wonder what the purpose of the store / isolation switch is? I thought its purpose was to disconnect everything to prevent any drain on the batteries.

wasafari 12-04-2008 06:38 PM

good question Winger
 
That isolation switch will still allow the propane monitor to suck juice from your batteries, only way to really kill it is either remove the batteries or disconnect them....fwiw I just ran out and metered mine again, 12.7 and holding for 6 weeks now (AGM's with ground disconnected) and it's been butt ugly cold here to boot.

68 Overlander 12-04-2008 09:09 PM

Something caught my attention on the OP post. Equalize. Not sure why that was done and its possible it was needed. My point and recommendation is to avoid equalization until necessary. Its hard on batteries and for lack of a better way of putting it, it does revive batteries that have sulfated but causes some scar tissue so to speak so wait until the surgery is necessary. I know that sounds corny but equalization for the sake of it will shorten their life. Sometimes it is definitely necessary and a great way to revive your batteries. These were 2008 new batteries so that is what caught my attention.

boondockdad 12-05-2008 09:47 AM

Thanks all…
I'm in the middle of tracking down electrical system gremlins, and I wanted to first be sure my batteries were good/holding charge...
I had the trailer in storage for about four weeks, with the 'kill switch' engaged (that is, set for storage), and I found dead batteries...
So-
Lets say the batts were at 12.5v when I stored… how would I derive the SOC from a 2% drop in voltage, and a .08 amp parasitic draw?

My thinking could be way off here… but that draw over four weeks, would amount to about -50Ah drain on a bank of 200Ah… so theoretically, the batts should be at 75%.. with the 2% dead load- that would amount to about 25% off the SOC… is it logical to assume we’re at 50% SOC on the batteries (dead)?

boondockdad 12-05-2008 10:02 AM

Quote:

Originally Posted by SafariSS (Post 644758)
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...

the CD disc changer stays on as well... unless you open the door... and IIRC it would cycle every so often, and draw as much as an amp...

IMHO, the wiring in this a/s is for sh*t

boondockdad 12-05-2008 06:26 PM

Quote:

Originally Posted by mistermcfrug (Post 644241)
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!

hilarious movie... Peter Sellers at his finest (next to Pink Panther Strikes Again... and Shot in the Dark!)... Lionel Mandrake, President Muffey, Dr. Strangelove...

"Fluoridation is the most monstrously conceived and dangerous communist plot we have ever had to face."

-General Jack D. Ripper


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