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Old 01-14-2013, 12:58 PM   #11
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You originally said that you purchased the second battery after you bought the unit which already had a battery. That may have caused your problem(s). It is always best when connecting batteries that they be of the same age. When batteries of different ages are connected the age difference will cause charging issues. It's difficult to explain but because of the age difference one B+ will charge faster than the other and then the charger may reduce its output which slows down the charge of the older B+. Over time the older B+ is always in a low state of charge, Etc. etc., etc.,. I think you get the idea. When you separated the batteries it took longer to charge the older B+ which does illustrate what was happening. When B+'s are charged the sulphate is removed and two things are made, water and sulfuric acid. That's why you never add acid again to a b+ only water. Slow charging always works best. If you keep the different aged B+'s together each will have a different charge acceptance rate and the charger can't tell which is which. The different state of charge of each B+ also acts as an impedance or resistance to the other B+ which interferes with one B+ accepting a charge.
I hope this makes some sense. Bottom line is it's always best, like sneakers to replace both at the same time. JMTCW
TeJay
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Old 01-14-2013, 12:59 PM   #12
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Could be, though I'm not sure why both batteries would not show the same signs.Are you suggesting that I might have rapidly discharged the battery set too often? I suspose that is possible, but again, why is only one battery of the set showing signs?
This is how to wire a 2 battery set. Wire length is critical to balance the current flowing into and out of each battery.

If the resistance across one battery (including wire resistance) is higher than the other one, the one with the higher resistance will "loaf" and the other one with lower resistance will be overworked and over charged.

This happens also when batteries have different internal resistances as well (normally caused by different manufacturers, type, age, charge cycles, and charge depth differences, and size). When "pairing" deep discharge batteries special effort must be made to change them out in sets when they are replaced.

If water level in any battery falls below the plates, the battery is being over charged and the plates exposed to air will be permanently damaged.

If you need to charge a battery that has significantly low water you must find out why. Also when adding water you should fill only to the "fill ring" on the inside of the cell filler cap to allow room for expansion as the electrolyte warms when charging to prevent the electrolyte from blocking the cap vent and "boiling" out the top of the battery (actually hydrogen and electrolyte spurting out).
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Old 01-14-2013, 01:55 PM   #13
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This is how to wire a 2 battery set. Wire length is critical to balance the current flowing into and out of each battery.
That is exactly how I had them wired up. And I made sure the "parallel" wires were the same length and a larger size, lower gauge, than my main lines.
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If you need to charge a battery that has significantly low water you must find out why. Also when adding water you should fill only to the "fill ring" on the inside of the cell filler cap to allow room for expansion as the electrolyte warms when charging to prevent the electrolyte from blocking the cap vent and "boiling" out the top of the battery (actually hydrogen and electrolyte spurting out).
The two times I filled the set, nothing was dry (I used a flashlight to look). And I make sure to only fill to the bottom of the fill sleves.

Is it me, or do the terms "water" and "electrolyte" get used interchangeably when talking about flooded batteries?

FWIW, I suspect TeJay is onto the issue. I was aware of the need to purchase identical batteries when pairing them up and made the assumption that the were close enough (type, WH, age). Guess not.
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Old 01-14-2013, 07:05 PM   #14
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LOL
yea, it is far easier to just say "water" when referring to electrolyte.

Sounds like you might have waited too long to add the second battery.
If paired properly they "should" give up the ghost at the same time.
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Old 01-14-2013, 08:10 PM   #15
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Sounds like you might have waited too long to add the second battery.
I added it within a few weeks of buying the camper . Both battery's manufacturing dates are in Aug 2011, but they are not the same manufacture and I don't have a good idea of the original battery's full specs (they are not on the label as discussed in an old thread).

For the time being I'll charge them separately until I need them at which point I'll make sure they have the same voltage before I wire them up. Or, I guess, I could scrap one of them?
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Old 01-14-2013, 08:35 PM   #16
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If they are not from the same manufacturer the internal construction could be very different. This is enough to throw your system out of whack.

If you had to add more than a few ML to a cell, most likely you have reduced the capacity by some unknown amount.

If you are wired correctly, you could just suck it up and run the batteries you have until you are unhappy with the run time. Then, when you are not happy, scrap them both and buy an identical replacement set from the same manufacturer and know you have a "pair."
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Old 01-14-2013, 09:59 PM   #17
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The term electrolyte refers to a mixture of water H2O and sulfuric acid or H2SO4. They are mixed at a ration of 36% acid to 64% water, if my memory serves me right. When a battery becomes discharged the only atoms that are lost are H & O which means water. They are lost in the form of gases. That's why a spark around the top of a charging battery can/will cause a violent explosion. I've seen it done. That's also why you only ever add water. The S or sulfur comes out of the solution as a sulfate and bonds to the plates. Recharging removes the sulfate atom and recombines with hydrogen to make H2So4 or acid. Herks info is also correct and adds good info to the discussion. The internal resistance of each B+ can be way different in ways of plate construction, connections, etc.

You can struggle along with what you have knowing that they will charge at different rates and probably won't provide a current supply as well as two matched B+'s would but you know it so you won't expect more. When time runs out and it will and when the $$$$ is available you'll do well to get a SET of Trojan B+'s and be done with it.
Best of luck and learn, learn, learn. That's what keep life interesting for many of us technomechanical geeks.
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Old 01-15-2013, 07:26 AM   #18
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If you are wired correctly, you could just suck it up and run the batteries you have until you are unhappy with the run time. Then, when you are not happy, scrap them both and buy an identical replacement set from the same manufacturer and know you have a "pair."
I think that is what I'll do, we don't have any dry camping planned for this year (except maybe a weekend trip). I'm sure the existing setup will serve me well enough 'till the 2014 season.
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Old 01-15-2013, 07:44 AM   #19
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Originally Posted by TeJay View Post
The term electrolyte refers to a mixture of water H2O and sulfuric acid or H2SO4. They are mixed at a ration of 36% acid to 64% water, if my memory serves me right. When a battery becomes discharged the only atoms that are lost are H & O which means water. They are lost in the form of gases. That's why a spark around the top of a charging battery can/will cause a violent explosion. I've seen it done. That's also why you only ever add water. The S or sulfur comes out of the solution as a sulfate and bonds to the plates. Recharging removes the sulfate atom and recombines with hydrogen to make H2So4 or acid. Herks info is also correct and adds good info to the discussion. The internal resistance of each B+ can be way different in ways of plate construction, connections, etc.

You can struggle along with what you have knowing that they will charge at different rates and probably won't provide a current supply as well as two matched B+'s would but you know it so you won't expect more. When time runs out and it will and when the $$$$ is available you'll do well to get a SET of Trojan B+'s and be done with it.
Best of luck and learn, learn, learn. That's what keep life interesting for many of us technomechanical geeks.
TeJay
TeJay - GREAT post!
Thank You
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Old 01-15-2013, 11:23 AM   #20
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Thanks Herk. Don't live in PA anymore but was born in Sewickly in 44 and still have a few relatives around Pittsburgh.

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