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Old 08-19-2008, 08:55 PM   #15
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Originally Posted by mustang View Post
This is not in camping application but I think it might hold some truth for camping. I Drag Race a Mustang (No chargeing system) I was using deep cycle batteries but I couldnt make it 3 rounds with minimmal draw. I talked around and I needed more "reserve capacity" Now I can race all day without a charge maybe 9 rounds depending how far I go before elimination. I learned no matter what I replace batteries in I look for reserve capacity. This has made all the differance in the wolrd for me. Optima didnt have what I needed but the big advantage to optima was mouting them in anyposition or a roll over. I didnt care about either. I went with a good NAPA brand. I am not that sold on Interstate anymore. Mine didnt last all that long. New Castle Battery or NAPA is where I had my luck. New Vastle has been in there since 1999. When I hunt I back it up with a NAPA out of my Mustang hooked in parralel
The lower amp rated batteries will generally have more reserve capacity, and last longer. One significant reason is there is more liquid to keep the battery at a more even temperature, and since there is less lead, there is more space between the plates. If there is more space between the plates, there is less chance of two plates touching under a load, and it will take longer for the "stuff" to build up in the bottom of the battery to touch two plates and short them. Sometimes less really is more.
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Old 08-19-2008, 09:40 PM   #16
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Overlander63...sorry, I've got to call you on your reserve capacity comments above...not true.

Reserve capacity goes hand in hand with amp hr rating...the higher the AH rating, the GREATER the reserve capacity.

The reserve capacity 'number' for most of the batteries we're concerned with here is the number of minutes a battery can accommodate a 25 amp load till the individual cells drop to 1.75 volts - 10.5 volts in a 12 volt battery, 5.25 volts in a 6 volt battery. It's really just a 'number' that allows a buyer to compare batteries...and helpful to give you an indication on how long you can run your stuff...

You get longer reserve capacity minutes in a battery with a HIGHER amp hr rating.

Take a look a the following chart made by US Battery...scroll down to page 3 for the RV type 12 volt batteries:

http://www.usbattery.com/usb_images/usb_bro_1aa.pdf.pdf

Always buy the heaviest battery in the size you are looking for...a heavier battery means more plates and a greater AH rating, and a longer running time for your stuff, after all, isn't that what we all are looking for...

It's true that in a flooded cell battery the fluid can migrate to some degree to allow for more electrons to be released and improve the capacity to a small degree...remember how you cranked and cranked an old beater trying to get it to start and then the battery gave out...then if you let it sit for 10 minutes or so, you could get another 'crank' or two out of it...well as the battery 'rested', the fluid could 'soak' deeper into the plates to allow for some limited additional electron flow.
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Old 08-19-2008, 10:30 PM   #17
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Specific Gravity Reading

I have been going round and round with Interstate's tech support and Parallax trying to determine why the 2 batteries in my 1 year old Safari won't go past 1.250 specific gravity (75-80% charged) even after being plugged into shore power for 4-5 days or using an $80 smart trickle charger for 24-36 hours.

I have used 3 different testers to verify the specific gravity readings as being accurate. Sam's Club load tested the batteries and they both passed as 'good' on 2 different machines.

Finally today Interstate's tech support told me today their deep cycle batteries require 14.8-14.9 volts to fully charge. Obviously my trailer won't charge that high and neither will my trickle charger.

So, given that I check the electrolyte weekly and top off with only distilled water and have cleaned the cables regularly, does anyone have an idea why the specific gravity on my batteries remains so low. Ideally I'd like to hit 100% (1.27) before dry camping.

Last winter when I had the batteries in the warm garage and trickle charging every 2-3 weeks, the specific gravity on both batteries was around 1.27-1.28.

Would anyone mind checking their specific gravity at full charge and let me know what reading they get? Thanks!

Any thoughts or suggestions would be greatly appreciated.
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Old 08-19-2008, 11:09 PM   #18
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When using a manual charger, I run batteries up to 1.275 and then turn it off...they will then 'float' back down to about 1.265 or so...Full charge!

I don't agree with Interstate about that high charge voltage...most automotive charging systems run around 14.2 to 14.5 or so, and are able to charge 12 volt deep cycle batteries just fine. You need a minimum of 13.7 volts to charge 12 volt batteries.

I suspect your smart trickle charger isn't working properly, or perhaps too low rated, amp wise to get both batteries up to snuff in a reasonable amount of time.

The lower amp trickle chargers are really just 'maintainers', and not really designed to full charge up batteries...don't know about yours.

The parallex should do the job, however.

The only other thing that comes to mind, is that you have old batteries in your rig...even though you bought it a year ago, perhaps the batteries had set around, in a discharged condition for months before you got it...

A load test is kind of a go-no-go test...it will detect if you have a shorted or weak cell. If the battery still has some life in it, it will still hold a load during the test.

I would recommend you put your batteries on a high amp charger, perhaps a 40 amp charger, and run them till they get warm, to perhaps break down some of the sulfate on the plates...equalize charge, some call it. Then see if your SG as come up to 1.275 or so.
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Old 08-20-2008, 04:00 AM   #19
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We love our Optima Blue Tops. Great service life and warranty if you ever need it. They cost a little more but like our Airstreams, they're worth every penny.
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Old 08-21-2008, 12:27 AM   #20
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At the risk of being somewhat negative, I don't think Optima Deep Cycle's are the best choice for an RV battery system's use.

Optima's have their places, but they just don't have a very good Amp Hour rating for RV usage if you boondock for any amount of time.

If you mostly use your RV in places where AC is available, you'll be OK.

Optima's have only a 55 AH rating, due to their construction of having the plates wound in a tubular shape...take a look at the bottom, and you'll see all the space between the cylinder shaped cells that have no battery plates.

If you want a completely sealed battery, look for an AGM type that has about a 75 AH rating in the same size as the Optima.

Flooded cell deep cycle's in the same size typically have 85-90 AH ratings and are about half the price of Optimas.

The higher the AH rating of your batteries, the longer you can run your stuff between charging cycles...
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Old 08-21-2008, 04:16 AM   #21
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Thanks for your observation Mexray as your points are well taken.
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Old 08-21-2008, 07:27 AM   #22
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Didn't read all the responses, so sorry if this is a repeat.

I have an '04 that I took delivery on in December of '03. I still have the orig batteries. They don't last very long, but there were several reasons. First, I allowed them to totally die 2x. A clear no no. Though I did keep the water levels to normal, my old converter that came with my Airstream would literally cook the batteries. I have very recently replaced my factory installed converter charger with one of the WFCO kits that best converter sells. It is a 3 stage charger that does not cook the batteries. Took maybe an hour to swap out, if that.

My strongest suggestion to you, regardless of what batteries you buy (because suggesting batteries around here is like a Ford/Chevy type discussion) replace your converter/charger if you haven't already done so. It cost something like $240 and I am ready for whatever battery I buy. Not replacing the converter can limit the life of any battery you install IMHO. If you have good mechanical skills there are other non-kit type 3 stage converter/chargers that may be even better than the WFCO kit, again best converter sells these too, and he's a forum member.
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Old 08-21-2008, 08:18 AM   #23
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Originally Posted by Mexray View Post
Overlander63...sorry, I've got to call you on your reserve capacity comments above...not true.

Reserve capacity goes hand in hand with amp hr rating...the higher the AH rating, the GREATER the reserve capacity.
That's what I would think, but the capacity stickers on two identical sized batteries we stock conflict with this. Two group 24 batteries, one with higher cranking amps, the other with more reserve capacity. I'll see if I can smuggle a camera in to take a photo of the labels (cameras are frowned upon there). Maybe we can 'cypher out why--typo, maybe?
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Old 08-21-2008, 03:56 PM   #24
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alternators on vehicles run at a high rateing because the components (ignitions and fuel pumps and brains ) require them to. I am not a big fan of interstate they were once a great battery. You will tell the dgreat batteries from the fair ones by picking them up. Get a heavy one and it will last. I tell you NAPA make s one heck of a good battery. or New Castle does to. Get a high reserve capacity. My Napa is Higher than the optima. Remeber there is a starting battery and a deep cycle. also AC Delco Voyager
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Old 09-05-2008, 07:02 AM   #25
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I just got a BatteryMinder and reconditioned my batteries with it. Before reconditioning they'd each charge to 12.2 volts. After reconditioning 13.1 volts.

That gizmo it worth getting!

Anyone know if putting it on float, while the batteries are in the Airstream (with the AS switch in "Storage" mode works OK. Even in Storage there is a small load on the batteries from the LP detector and I wonder if that has any effect on it.
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Old 09-05-2008, 09:31 AM   #26
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One of the important steps for good batt life, is to keep them clean, really clean, on the top surface, in perticular, the ones with external (over the top) cell connectors. The film of electrolite that accumulates on the top serves as a conductive path to discharge. A good three-step charger will bulk charge at around 14.2, to 14.7, depending on depth of discharge, then switch to a lower setting of around 13.8 or so, then switch to a float of around 13.2 to 13.3, 13.26 is considered optimal. Each .1 (one tenth) of a volt over optimal float voltage doubles the currant, this leads to overcharging, and corrosion of the positive plates. Chronic undercharging leads to sulfation, and loss of capacity, sometimes this can be corrected by a process called equalization, in which a higher than normal charge voltage is applied for a controlled amount of time, ie; carefull checking of internal temp, terminal voltage, and specific gravity. This process is normally not needed with most batt use in RVs. Equalization process is most often used on large multiple batt banks in marine service, that are subjected to heavy load cycles, also helps to "even-out" variations between batts in large banks.
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Old 09-05-2008, 02:07 PM   #27
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I have two Deep Cycle group 27 batteries that I got at AUTO ZONE. They are all I want to get them in the battery boxes about 50 lbs each. I religiously check water at the first of every month and check the tops for corrosion. I still have the original UNI VOLT. NOT PROBLEMS YET.
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Old 09-05-2008, 06:46 PM   #28
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Regarding the post by SilverCottage, concerning specific gravity; Different batt makers specify different alloys, where the ratio of lead to antimony varies. What this means, is that for the same voltage, the specific gravity will be a little different between brands. The introduction of calcium also has an effect on specific gravity. A fully charged batt, that has not been charged, nor a load applied, for 12 to 24 hrs., should be close to 12.8 volts. The actual specific gravity could vary a little bit up or down.
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