Converter

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vgilbertson

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Feb 19, 2012
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34
I have a Magnetek model 930, series 900, 30 amp converter charger. When pluged into 120 Volt AC it is charging 12.6 volts, the battery never shows full charge just good. Brand new marine battery.
Last night I ran thr generator for an hour before shutting down. Heater ran all night until about 4 am and then went to fan only - low fan speed from low battery. Fired up the generator and the furnance would fire and then shut down. Started the engine of the camper and the furnace ran just fine and the battery meter showed fully charged.
Appeares to me the converter is not putting out enough volts to charge the battery.
Any help is appreciated.

Vern
 

rsalhus

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Jul 20, 2006
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1,335
Your 30 amp charger/converter is designed to charge your batteries at 14.1 volts with no load on the charger/converter.  When you're running other 12 volt appliances like your furnace and such, you don't have as much power to charge your batteries as you do when there are no loads on the charger/converter. 

The next time you have the generator on, turn off as many 12 volt appliances as you can and check to see if your batteries are charged at a higher rate.  Another thing, charging your batteries for one hour may not be enough to bring them up to full charge after a full night of running the furnace.
 

John From Detroit

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Apr 12, 2005
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Davison Michigan
Rsalhus got it almost right

He said "Charging for one hour MAY not be enough"

The correct phrase is "charging for one hour WILL not be enough"

A full charge takes a minimum of 2 hours assuming the battery is at 90 percent to start with, longer if it's run down any.  That is the MINIMUM time,
 

Gary RV_Wizard

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At our Silver Springs FL home
Plugged into 120v and with battery(s) in good condition, the converter should be showing at least 13.1v and more like 13.3-13.6v. If it can't get the battery(s) past 12.6, that usually means a bad battery (weak cell) or a corroded connection somewhere. While it is possible for the converter/charger to fail in such a way that it still works but with low voltage, that is not the usual failure mode.

You can voltage test the 930 with the battery disconnected, but that may not prove much either, since you can have voltage but very little charging current (amps). It's worth checking, though. With no battery connected, voltage should be in 13.6 or more.
 

rsalhus

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Jul 20, 2006
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A full charge takes a minimum of 2 hours assuming the battery is at 90 percent to start with, longer if it's run down any.  That is the MINIMUM time,

The amount of time to bring a bank of two 85 AH batteries from 90% SOC to 100% SOC would theoretically be less than one hour.  But to bring the same batteries from 50% SOC to 100% SOC would take over four hours with a 30 amp charger.  (These are pretty optimistic estimates that don't take into consideration the type or condition of the batteries, the temperature, or the fact that a 30 amp charger doesn't charge at a 30 amp rate for the entire charge time.)

The actual formula used to calculate the above battery charging times is as follows:

    Charging Time (Hours) = Battery Size (AH) X (100 - Battery SOC in %) X .01
                                            ----------------------------------------------------------------
                                                      0.7 X Maximum Charger Rate (Amps) 
 

vgilbertson

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Feb 19, 2012
Posts
34
With the battery disconected the Converter reads 28 volts, with the battery attached it dropes to 12.6. Battery is brand new and biggest AMP hour I could get to fit the space.
With the camper engine running the battery shows 14.4 amps which I assume is the alternator on the engine bypassing the converter.

Thanks
 

Just Lou

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Dec 25, 2005
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8,105
Sure sounds like that converter needs to be replaced.  Output should be at least 13.6 to 13.8 into any good battery.
 

vgilbertson

Active member
Joined
Feb 19, 2012
Posts
34
ordered a Inteli-Power 9160 Converter Battery Charger 60 Amps and a charging wizard.

thanks for your help
 
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