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Old 07-16-2010, 03:54 PM   #1
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Join Date: Apr 2010
Posts: 23
Battery charger ?

I have a 3 stage battery charger that I used for charging the two 12 volt batteries on our tt.We were out camping for a week and by the 3rd day the batteries needed charging,so I hooked up the bc through my generator and the first battery took about 4hrs to get 75% charge and the second one was charged for 5 hrs and also stayed at 75% before I removed the charger.My question is should it take this long to charge?The charger has 2,10,20,30 & 40 amp settings but I only used the 2 amp(trickle charge) as I was told this is the easiest on the battery.The batteries are both new and I use a hydrometer to test each cell.Any input would be greatly appreciated.

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Old 07-16-2010, 04:17 PM   #2
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Join Date: Sep 2009
Location: Maple Ridge, BC, Canada
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Not sure what type of "3-stage" charger that you use, but both my stand-alone 3-stage charger and the one built in to the trailer converter are automatic. In other words, once connected to the battery, the charger determines the initial rate of charge based upon the state of the battery, and charges to 100% (or near to it) depending on battery condition. It will then go to a "float" charge where it can be left indefinitely connected. With my stand alone charger, if the charger has been pulsing and charging for 24 hours continously without reaching 100% state of charge, the charger discontinues charging and indicates a battery that is non-rechargeable. Incidentally, my stand-alone 3-stage charge is designed to be connected to one battery only at a time .If yours is the same, perhaps you were attempting to charge both your batteries at once and your charger couldn't handle both ???

Just my thoughts on your problem.


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Old 07-16-2010, 06:09 PM   #3
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Location: Enumclaw, WA
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Trickle charging batteries is ONLY to be done after they are at full charge and in storage to keep them topped off. A good charger will put near full amperage at the battery bank until the bank reaches 90% charge then will taper off the amperage while increasing the voltage from 13.2 to 13.6 volts. A 3 stage charger will add an "equalization" charge of 14.4 volts and very little amperage (usually only about 1 amp) to "overcharge" the batteries and desulfate the plates. Battery banks are supposed to be charged at the rate of C/10 where c is the amp hour total of your bank. In our case we have a 720 amp hour bank, thus the bank should be charged at no more than 72 amps and tapering off the closer to 100% charge they get. If you have two 12 volt batteries typical of those provided for most RVs then you probably have between 75 and 110 amp hours in the bank and therefore you should be charging at between 7 and 10 amps, give or take.

You can charge several batteries as a bank. The charger doesn't care if you are connected to one or 6 batteries and it is preferable to do so to keep your batteries charged as a bank.
"I can fix it, and if I can't fix it, I can fix it so no one can fix it!"
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2009 Georgetown 378TS | 1998 Jeep Wrangler | 1998 Skeeter ZX202C
Nights camped in 2009: 53 | Nights camped in 2010: 55
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