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Old 07-13-2015, 11:52 PM   #1
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Need help with reading voltage

Okay, so I hooked up my volt meter to one of my batteries. It appears to be showing about 14 volts. I will post a picture. Based on this, is my WFCO converter doing the right thing? Here are the details.

- TT is parked next to my house and plugged into shore power.
- TT has two 12V interstate group 24 batteries in parallel
- Nothing in the TT is on. The fridge is off. Water heater off. Lp detector is probably on and draining a tiny bit. Water pump off. No lights on.

So does a voltage reading of about 14 mean the WFCO is overcharging the battery?
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Old 07-14-2015, 04:48 AM   #2
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Yes it is charging properly, mine is at 13.5 volts

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Old 07-14-2015, 06:18 AM   #3
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Originally Posted by fonzie View Post
Yes it is charging properly, mine is at 13.5 volts
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Old 07-14-2015, 06:22 AM   #4
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That particular meter needs zeroing, but assuming your meter is "good" a reading of 14 volts is normal for charging a low battery.

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Old 07-14-2015, 06:23 AM   #5
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Assuming the analog meter is accurate voltage should be around 13.5
How long was unit plugged in when you checked voltage?
Converter could have been in bulk charge mode 14.4 volts.
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Old 07-14-2015, 11:38 AM   #6
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14 is on the upper end of acceptable for long term. 13.2-13.5 better. Suggest you get a digital voltmeter at Harbor Freight. Low cost and work well. Watch battery water level. If battery uses water voltage is probably too high.
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Old 07-14-2015, 03:55 PM   #7
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Yes. That is a $9 Analog meter. It is probably rated =/- 1 to 2 % of full scale accuracy. So the actual voltage could be 13.25 to 14.75 (on the 50V scale) It would be better have a cheap digital meter or an analog with a 20V scale. With battery work, a digital is much better, since the difference between 12.7 and say 11.7 is the difference between a fully charged battery and one that is almost dead. Decent warm charging voltage is 13.2 and cold as high as ~14.5. So you are always interested in small fractions. Best thing to do is to get a cheap digital and then measure a good fully charged battery with a very light load on it. It should be right around 12.7. If your meter reads close to that (12.6-12.8), the meter is good. If it reads slightly different at least you have a base line for future measurements.
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Old 07-14-2015, 08:36 PM   #8
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X2 for Jim

Get a cheap digital meter... 14.0>>>14.5V in bulk charge mode for low battery
13.1>>>13.4 for last 20% of battery filling or so.

Charge battery overnight...disconnect negative wire for 24 hours and take a reading at the battery posts...should be 12.6 or 12.7. You MUST wait for the charging surface charge to dissapate. OR get yourself a $20 load tester from Harbor freight or Amazon to wipe it out so you can get a REAL reading.
Also suggest a more expensive cheap digital meter with a clamp AC/DC meter so you can see the amps you are using and trace loads and problems...about $50 bucks vs. 10 for a basic digital meter.

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Old 07-15-2015, 12:01 AM   #9
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Thanks everyone for your help! Today I went and bought a $20 digital meter.

With the trailer unplugged from house, and nothing on in trailer except the vampires (LP detector, radio clock), the voltage read 12.85 and slowly falling. I had just gotten done plugging and unplugging trailer, running lights, testing a generator, etc. Seems about right.

Tomorrow night I'll check it again after being plugged in for 24 hours, with nothing on. I'm thinking it should read around 13.2 for float mode.

All in all I think things are working right, but I'll keep testing your ideas!

P.S. All these readings are with the batteries still connected to the converter. I haven't gotten to the point of disconnecting batteries yet.
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Old 07-15-2015, 07:39 AM   #10
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Your picture of the meter looks more like 13.5 to me. But, I would use a digital meter instead.

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