Do I have a battery problem?

I may have a battery problem but I just don’t know, here is what is going on. I have 2- 6 volt Deka 115ah batteries that appear to be taking a charge Ok up to a certain point. I put them on a charger that is putting out 14.6 volts (checked with a meter) after it reaches 13.6 volts the charger goes into storage mode. I unplug the charger and let the batteries rest for 6 to 8 hours and the voltage drops to 12.67 volts. I have the batteries out of the TM and in the garage with nothing hooked up. The batteries I assume were new when I purchased the TM in late April ’09. During some dry camping last summer and fall the battery volt would drop into the yellow by morning around 12 to 12.1 volts. The solar panel would bring them back up during the day but would go down real fast at night. I don’t know if I have defective batteries and need to replace them after only a year or should I buy a generator. This is the same problem I had in my 2720 with the same brand of battery. See my first battery drain question same problem with batteries out of the TM. HELP!!!!

[Wavery]

Originally Posted by kenngeri2720

I may have a battery problem but I just don’t know, here is what is going on. I have 2- 6 volt Deka 115ah batteries that appear to be taking a charge Ok up to a certain point. I put them on a charger that is putting out 14.6 volts (checked with a meter) after it reaches 13.6 volts the charger goes into storage mode. I unplug the charger and let the batteries rest for 6 to 8 hours and the voltage drops to 12.67 volts. I have the batteries out of the TM and in the garage with nothing hooked up. The batteries I assume were new when I purchased the TM in late April ’09. During some dry camping last summer and fall the battery volt would drop into the yellow by morning around 12 to 12.1 volts. The solar panel would bring them back up during the day but would go down real fast at night. I don’t know if I have defective batteries and need to replace them after only a year or should I buy a generator. This is the same problem I had in my 2720 with the same brand of battery. See my first battery drain question same problem with batteries out of the TM. HELP!!!!

12.67V is a full charge. You can expect that the batteries will lose a small amount of charge over time, even when disconnected. If the drop is, as in your example, you have a fairly large draw on them. You should track down that draw. Hopefully, you are not using your fridge on 12V. If you are, that's your problem. The 12V fridge will drain the batteries in a short time.

If you are suspicious of the batteries, take them to a shop and have a "Load test" performed. Sometimes, a battery can show 12.6V but will not take a load. If that's the case, the battery is toast. Also, be sure that your batteries have plenty of water in them, they should be check at least twice a year. If you use them a lot, they should be checked more often. If they need water, use "DISTILLED WATER" only.

The other thing to remember is, if you have 2 batteries wired together and one is bad, the bad one will draw the good one down. If that's the case with 2-6V batteries, you have a problem. It's not a good idea to pair an old battery with a new battery because a weaker battery will always draw down a stronger battery. It's best to buy batteries in matched pairs. This is the evil of using 2-6V as apposed to 2-12V. If you use 2-12V, you don't have to pair them because you can use one at a time (with a switch). When using 2-6V, they must be hard wired together to achieve 12V. If one battery goes bad, you have no back-up (unless you carry another 12V battery with you).

I also use the 2-6V system and I except the risk because I like having the higher capacity of the 2-6V system. As in everything else, there is always a trade-off.

Attached is a handy chart for lead acid type batteries.

[Bill]

Lead-acid batteries do something that is annoying, and can be surprising if you're not expecting it. As you know, a battery is a bunch of lead plates dunked in a pool of acid. Everything that happens in a battery happens at the surface of the plates, where the lead contacts the acid. When you discharge a battery, the acid that is in contact with the plates gets weaker, and when you charge a battery, the acid that is in contact with the plates gets stronger. But the acid that is farther from the plates stays at about the same strength for a while. So if you discharge a battery, and measure its voltage right away, it will measure lower than true, since you are really measuring the layer of weak acid. And when you charge a battery, and measure its voltage right away, it will measure higher than true, since you are really measuring the layer of strong acid.

In both cases, if you measure the voltage right away, you get a false reading. You need to let the battery rest for a while, so that the acid mixes and comes to uniform strength throughout. Then, when you measure the voltage, you get a true indication of the state of charge. This rest period should be at least an hour, and some sources recommend at least 6 hours, depending on how accurate you want it to be.

So you need to be aware that when someone quotes you a voltage that represents "fully charged" or "50% charged" or whatever, this is the voltage after the rest period. It is not the voltage immediately after charging or discharging.

This becomes annoying in the real world. Sometimes you charge the battery, measure the voltage, declare it charged, and then go away for a while. Come back an hour later, and the voltage is lower! What happened? Why did my battery discharge? Well, it didn't discharge - it's just that the acid mixed. You need to beware of readings taken before a rest period.

Years ago, RockyMtnRay explained this better, but I can't find his post.

Bill

Unless you determine that there is an internal short, then I would run 5 cycles of a desulfate charge followed by an equalize charge.

I was about to replace my pair of Interstate group 24 batteries because the pair would only last a single day instead of the usual 2 to 3 days.

Now they last 2 days, but I am not sure they would make it to 3 days. They are now 5 years old.

If your charger does not have desulfate and equalize modes, I bought mine at Amazon for about 90 bucks a couple of years ago.

[Wavery]

Originally Posted by Bill

Lead-acid batteries do something that is annoying, and can be surprising if you're not expecting it. As you know, a battery is a bunch of lead plates dunked in a pool of acid. Everything that happens in a battery happens at the surface of the plates, where the lead contacts the acid. When you discharge a battery, the acid that is in contact with the plates gets weaker, and when you charge a battery, the acid that is in contact with the plates gets stronger. But the acid that is farther from the plates stays at about the same strength for a while. So if you discharge a battery, and measure its voltage right away, it will measure lower than true, since you are really measuring the layer of weak acid. And when you charge a battery, and measure its voltage right away, it will measure higher than true, since you are really measuring the layer of strong acid.

In both cases, if you measure the voltage right away, you get a false reading. You need to let the battery rest for a while, so that the acid mixes and comes to uniform strength throughout. Then, when you measure the voltage, you get a true indication of the state of charge. This rest period should be at least an hour, and some sources recommend at least 6 hours, depending on how accurate you want it to be.

So you need to be aware that when someone quotes you a voltage that represents "fully charged" or "50% charged" or whatever, this is the voltage after the rest period. It is not the voltage immediately after charging or discharging.

This becomes annoying in the real world. Sometimes you charge the battery, measure the voltage, declare it charged, and then go away for a while. Come back an hour later, and the voltage is lower! What happened? Why did my battery discharge? Well, it didn't discharge - it's just that the acid mixed. You need to beware of readings taken before a rest period.

Years ago, RockyMtnRay explained this better, but I can't find his post.

Bill

Good explaination Bill but the poster stated, "I unplug the charger and let the batteries rest for 6 to 8 hours and the voltage drops to 12.67 volts (which is fully charged)."

I may be wrong but I don't think that the poster expected the batteries to stay at 13.6V.

Bill & All thanks for the good information I guess after reading other post I expected the batteries to charge to and maintain 14.4 volts as others have stated. You guys are a wealth of knowledge and the best site to go to for an education on trailers and there sub systems. Thanks again!!!!!

[Keith Wire]

Ken,

It has been referenced many times on this site, but I still think it needs repeating every once in a while.

Just about everything you ever wanted to know about batteries for RV's can be found in the two part document "The 12volt Side of Life".

Take a look see what you think.

Keith

I enjoyed the "12 volt side of life". It caused me to look up the WF-8955AN that is installed in my TM. I was glad to see that it had a three stage converter/charger. It was as Mark Nemeth had described for a good charger - Absorption/Bluk/Float.
http://www.wfcoelectronics.com/docum...0%20Series.pdf

[Bill]

Originally Posted by Keith Wire

It has been referenced many times on this site, but I still think it needs repeating every once in a while. Just about everything you ever wanted to know about batteries for RV's can be found in the two part document "The 12volt Side of Life".

Agreed. Lots of good information, not too deep technically, but an easy, understandable read.

Bill