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Gadgetman

reading a "multifunction voltmeter"

11 posts in this topic

I have gotten tired of using the different types of battery meter devices that are out there and bought the above mentioned meter. My question is what should afully charged 12 volt batter read? somebody told me 12.8 is a fully charged battery and it is ok until it gets below 12. At what point do you decide to recharge? And what reading correlates to a half charged battery? Is this the best type of battery guage or what should I use?

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12.8 is a little on the high side, but it depends upon temperature also.

12 volts is way too low. 12.2 volts is 50% discharged.

11.9 is completely discharged.

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A volt meter can give you an idea on state of charge, but will do nothing to tell how the condition or capacity is.

I've seen many batteries showing a good voltage level of 12.5 volts or more, only to have them pancake once loaded.

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Quote:

I've seen many batteries showing a good voltage level of 12.5 volts or more, only to have them pancake once loaded


That was one of my batteries on opener last year. Showed full volts, didn't have enough juice to run my electric motor.

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A battery near death can still display full voltage on a voltmeter, especially a good one that doesn't load the system when applied.

Voltage is only the potential difference between the two test points but not the potential current capacity.

Bob

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Thanks for your opinions, I guess my real question is how can I determine the state of charge (or discharge)of my batteries. I bought the Minkota batttery gauge and it is very inaccurate. It showed a brand new and freshly charged battery as only 60% "full". Needless to say I brought the battery back to the auto supply store I bought it from. They put it on their super duper battery tester and assured me that the battery was fully charged and in great shape, and that my little battery gauge was junk. I dont know what to believe

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Why not just buy a good automatic charger that will charge and maintain the batteries?

We use one of those fancy battery testers at the shop and I don't have a whole lot of confidence in them myself. I have had plenty of good batteries come up as bad and plenty of bad batteries showing good but wont crank an engine over. Your never going to really know with a 100% confidence that the battery is good, fully charged, or won't go bad half way into a day.

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A hydrometer is your best way to measure how well your battery is.

Full 100% charged = 1.280

75% charged = 1.240

50% charged = 1.200

25% charged = 1.160

Dead 0% charged = 1.120

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I have several good automatic chargers and also an on board "dual pro" charger. I guess I'll have to trust them and hope I am not left in the lurch. I am not real excited about the hydrometer option as I am sure i would drip acid all over everything, tho that is probably the only real way to try and accomplish what I am trying to accomplish

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Cold cranking amps is the key. If your battery does not have the amps, it will die shortly. A 12 volt/600 cc amp rated battery, that tests out at 200 amps is a "get replaced battery" for sure. I do think with a multi tester, you can get a amp reading. I do know a multi-tester will not give you a correct under load test. A person would have to spend over $500.00 for one of those testers. Goood luck!

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