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post #1 of (permalink) Old 01-04-2005, 09:36 AM Thread Starter
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Winter battery voltage and multimeter stuff

Hey,

I am trying to figure out if my cheap multimeter is inaccurate. Shouldn't a battery voltage be 13-14 volts? I got a 12.48 and a 12.38 from 2 different batterys. It is winter but that seems low.

Also I checked a brand new 9v and came up with 9.2, I cant remember but I thought those should be 9.6v.

Thanks

Mike
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post #2 of (permalink) Old 01-04-2005, 09:54 AM
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Re: Winter battery voltage and multimeter stuff

It's close enough for a cheap DVM. The Charge voltage ( engine running ) across a battery should be between 12.4 and 14.7 volts. It's dependent on the <ul type="square">[*]alternator,[*]engine RPM,[*]electrical load[*]pulley size and[*]voltage regulator quality[/list]
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post #3 of (permalink) Old 01-04-2005, 10:00 AM
 
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Re: Winter battery voltage and multimeter stuff

12.65v is fully charged battery volatage with the engine off. 12.45 is 75% charge. your meter is fine, most likey your batteries are not chatrged to their full potential during these cold months.
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post #4 of (permalink) Old 01-04-2005, 11:43 AM
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Re: Winter battery voltage and multimeter stuff

Usually the folks at a Radio Shack or an electronics store will test yours.
They'll show you a better one, then hook them both to a battery at the same time - in the hopes of selling you theirs. You can see the difference if any, then compensate for it.
They usually are pretty helpful.
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post #5 of (permalink) Old 01-04-2005, 07:04 PM
 
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Re: Winter battery voltage and multimeter stuff

The other thing to keep in mind is that a low battery in the meter will give funny readings. It doesn't have to be much below peak voltage either, if its an older meter throw in a fresh battery and recheck.

Sorta out of line here, but checking secondary voltages on a xfmr, with a low battery, you can be upwards of 40-50 volts off what you expect... Then you start scratching your head, trying to figure out what you wired wrong blah blah blah... when it turns out to be a low batt in the meter.


Food for thought.
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post #6 of (permalink) Old 01-04-2005, 08:00 PM
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Re: Winter battery voltage and multimeter stuff

[ QUOTE ]
The other thing to keep in mind is that a low battery in the meter will give funny readings. It doesn't have to be much below peak voltage either, if its an older meter throw in a fresh battery and recheck.

[/ QUOTE ]

Very possible if it is a cheap <u>digital </u> volt meter.

The typical cheap analog movement (taught band or what ever) only uses the battery when checking resistance.

Just a thought.

Dale
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post #7 of (permalink) Old 01-04-2005, 10:05 PM
 
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Re: Winter battery voltage and multimeter stuff

very true... I don't hardly see the analog cheapies anymore.
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post #8 of (permalink) Old 01-04-2005, 11:08 PM Thread Starter
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Re: Winter battery voltage and multimeter stuff

Thanks for the help guys.

I was confusing the 12.65v on the battery by itself with the 12.4-14.7 running. Thats why I thought the numbers were low.

I did check the voltage with other multimeters including a fluke and they all varied a little bit. Seems the cheap ones have an uncertainty of about 2.5%.

Also if I were to purchase a multimeter, what would you suggest? I found a fluke 16 for $85 shipped and it has a temp probe.

Mike
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post #9 of (permalink) Old 01-04-2005, 11:53 PM
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Re: Winter battery voltage and multimeter stuff

Fluke is a good brand.

Myself I have a bunch of cheapie Harbor Freight multimeters.
I have one in each vehicle (12 vehicles,) a couple in my tool box, even one in the house (makes 15 or 16?)
Not very accurate, but I'm not doing scientific work that requires much accuracy.
Plus, when you run over it, loan it out to never return, or somehow ruin it, no real loss.

And, I have an older Simpson Analog meter if I need a real good one.

Most of the time you just need to know "is it hot?" or "does it have continuity?"
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post #10 of (permalink) Old 01-05-2005, 12:14 AM
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Re: Winter battery voltage and multimeter stuff

I'd say go with a cheapie digital meter. I got one at Ace Hardware for around $20 and it does everything I need it to. They'll be accurate enough for what you'll be using it for on the Jeep and you can spend that $$$ elsewhere.
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