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Does radio shack sell a varible load volt meter ?

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Does radio shack sell a varible load volt meter ?

Old 09-11-2008, 11:29 AM
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dignlivn
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Default Does radio shack sell a varible load volt meter ?




Tower is out of thiers and Horizon wants twice as much.

So, does R/S sell one ? I do have a VW on board but
don't trust it.

Thanks,

Bob
Old 09-11-2008, 11:35 AM
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draftman1
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Default RE: Does radio shack sell a varible load volt meter ?

I dont think they do. that load meter is mainly an r/c product. it really cant be used for any other type of batterys. but I could be wrong
Old 09-11-2008, 01:30 PM
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Default RE: Does radio shack sell a varible load volt meter ?

any voltmeter that applies a load the the circuit under test will do...some of you engineer gurus know what a good load should be?
Old 09-11-2008, 01:53 PM
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Default RE: Does radio shack sell a varible load volt meter ?

RS sells some battery checkers, but I didn't see any suitable for our use. Any load from 0.25-1.0C I'd think would be fine. The idea is to draw enough current from the cells so they don't float. Ideally I suppose you'd want to measure with a load similar to what the battery will experience in use. A simple power resistor would suffice. Use V/I=R to find what size of resistor, and then P=vi to find the needed power rating. For a 4.8v 2000mah battery with a 0.25C load, that would be a 500ma load, so we need a resitor at 4.8/.5 = 9.6 ohms, call it 10 ohms. For power rating, that is 4.8*.5 = 2.5 watts. Double for safety margin, so load with a 10ohm 5 watt resistor in this case.
Old 09-11-2008, 02:15 PM
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dignlivn
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Default RE: Does radio shack sell a varible load volt meter ?



Thanks Guys,


John, you way over my knowledge level. I thank you
though.


Bob
Old 09-11-2008, 02:39 PM
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Rodney
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Default RE: Does radio shack sell a varible load volt meter ?

It is very easy to make any voltmeter a loaded voltmeter. All you have to do is attach a resistor between the two probes, the size of the resistor determines the load. For a 4.8 to 6 volt (4 or 5 cell NiCad or NiMh) us a 10 ohm 5 to 10 watt resistor, for the 8 cell transmitter use a 22 ohm 5 watt. This will load them to about 500 milliamperes. Do be sure to use the higher wattage resistors, not the readily available 1/4 to 1/2 watt units. Make the load removable and you have a useful voltmeter for other uses. Even the very inexpensive ones will suffice for our use.
Old 09-11-2008, 02:49 PM
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Default RE: Does radio shack sell a varible load volt meter ?

wow thats great info. I need a battery checker also. thats what Im gona do. thanks
Old 09-11-2008, 02:50 PM
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Default RE: Does radio shack sell a varible load volt meter ?



Thanks Rodney,

You wouldn't happen to know the
nomenclature for the higher end resistors ?


Bob
Old 09-11-2008, 04:50 PM
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Default RE: Does radio shack sell a varible load volt meter ?

One better, here is a resistor you could use. This is a 11ohm resistor rated for 5watts. It would work for testing 4.8v- 6v packs with an ~500ma load. RadioShack will probably have a similar resistor.

http://www.jameco.com/webapp/wcs/sto...ductId=660383&
Old 09-11-2008, 08:56 PM
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Default RE: Does radio shack sell a varible load volt meter ?






Thanks John,


Bob

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