Battery Charging Voltage

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Capn D

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Jun 4, 2004
46
Hunter 380 Clear Lake, TX
Ok, all you electro-techo-experts: I've got a 2000 H380. Freedom Inverter/Charger, Solar Panel for the charging battery. Everything has been hunky-dory (on power) since we received the boat. I noticed in the past month, however, that the house batteries show a topped-off voltage around 13.5 volts. The starter battery sits around 15 volts. All of the batteries were replaced in the past 9 months. Is the starter battery possibly a bad battery, or should I look at the solar panel or charger? While on sail (with inverter on) and afterwards, all the batteries seem to hold a charge well. I'm just concerned with the high voltage on the one battery. -David
 
D

Don

specific gravity?

the voltage sounds suspect - I'd check the questionable battery cells with a hydrometer to make sure. It sounds like a bad cell. Don
 

Capn D

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Jun 4, 2004
46
Hunter 380 Clear Lake, TX
High Voltage

Will a bad cell run the voltage up, or down? I may be answering my own question, but will a bad cell cause the charger to overcompensate? dd
 
D

Don

yup

a bad cell appears to the charger as under-charged making the charger try harder, i.e., increasedvoltage and current
 
May 6, 2004
916
Hunter 37C Seattle
David, if you reading voltage on a remote

or hardwired meter, and or don't have flooded cells to use the hydrometer on, just start with a digital voltmeter (multimeter) and stick the probes on the start battary terminals to check whether your hardwired meter is accurate.
 
W

Warren Milberg

Many charging...

...systems charge at 14v+ and so that is normal. If you test a battery with a DVM that is connected to a charging device, or recently removed from one, you will get a reading higher than the "normal" 12.6 - 12.8 vdc. My advice as a starting place to see what's cooking (literally) with your batteries is to disconnect them from everything for at least 24 hrs and then test them with the DVM. That will give you a true reading.
 

Capn D

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Jun 4, 2004
46
Hunter 380 Clear Lake, TX
I'll bet you're right....

Thanks. They are flooded cells. I'll take a DVM to them first. I suspect you're right that it's a bad cell. The setup is 1 starter battery with the typical factory configuration of the solar panel and the charger/inverter. Then, I've got 3 house batteries. They were all replaced at the same time about 6 months ago. The 3 house batteries are showing a charging voltage around 14.2 to 14.5. When I switch over to the starter battery, it's a good bit over 15v. Next weekend, I'll test it online, then pull it for a day and test it disconnected. -David
 
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