Battery voltage low

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Canoebear

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When plugged in to shore power with my battery switch on so they (2) are in the circuit the voltage across my batteries is low, 11.5 volts.  If I read the voltage from my converter with the batteries disconnected, it is 13.6 volts.  I've had the batteries checked with a load gauge and was told they are OK.  Does a converter ever put out a voltage like the 13.6 I have and not provide the current required to charge the batteries when they are connected to the converter?  Or should I have my batteries rechecked by someone else?

Thanks.
 

Bobtop46

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Mar 11, 2011
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837
Location
Bronson FL
13.6 from the converter to the battery is normal.  Have you checked the water in them and how old are they?  Have there been any deep or total discharges?  Look for loose corroded connections and a bad ground.

Your suspicions are correct in this situation something is suspect with the batteries. 
 

Gary RV_Wizard

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Feb 2, 2005
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West Palm Beach, FL
Converter output voltage of 13.6 is normal (float charge for a lead acid battery).  The amount of current that flows depends on the battery state and the management algorithm in the charger.  So yes, it is possible that the charger reads 13.6v but delivers very little current (amps). Just how much and when that happens depends on the brand and model of converter/charger. Multi-stage chargers show a lot more variation than older/cheaper single stage models.

How are you reading the 11.4v vs 13.6v "from the converter"?  Do you physically disconnect the battery cables to read the 13.6?

There are some battery conditions that could cause oddball voltage readings, and bad connections between the charger cable and battery is another possibility.
 

lynnmor

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May 14, 2013
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1,586
Check the voltage at the converter, then on each side of circuit breaker or fuse to the battery, then on each side of the switches.  Breakers and switches go bad.  Check connections and grounds.
 

John From Detroit

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Apr 12, 2005
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26,277
Location
Davison Michigan
Normal circuit battert to converter et-al is something like this.

Chassis ground--Battery---Fuse or breaker--Switch--Everything else including house fuse panel and converter.

Now the suspect list (In the same order)
The connection between negative lead and chassis

Battery conections.. all of them

Fuse or breaker (# one in suspect order)
The switch (#2 in suspect order since you said "Connected"

All other connections.

Finally the converter fuses. but that would depend on where you measured.

One final suspect.  shorted cell in battery
 

Henry J Fate

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Jun 14, 2018
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1,979
It appears that the 11.4 voltage reading at the batteries is the battery voltage. Best guess is that the charge voltage from the converter is not finding its way to the batteries which could be caused by several conditions. Definitely check the battery voltages by removing the positive cables from them and any interconnection between them. Check each battery's voltage. While your there see if you can find a date on the batteries if you are not sure of the age. Voltage readings on each battery should be about the same. Assuming you are in a unit that you drive and one you drive fairly frequently, you may be using the charge in the batteries from the engine alternator and have not been charging on axillary power. (plugged in, generator)

Assume that the problem is not solved until you find the 13.6 volts at the batteries. It may turn out to be slightly less than that with the load of the batteries applied to the converter but never below 13 volts.

Good Luck
 

grashley

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May 7, 2015
Posts
6,591
Location
Western Kentucky
I agree with Henry.  If you measure 13.6V at the converter, it is working.  If you measure 11.5V at the batteries, the converter is not getting power to the batteries.  My first guess is the battery switch.  Flip the switch and recheck battery voltage.  If still low, check voltage on both sides of the switch.
 

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