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Old 01-07-2012, 06:47 PM   #1
mrbicknell
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Default lipo usage time

Hey guy's, I am trying to work out a good usage time for my lipos. I know how to work it out if I know what amps the motor is pulling, but I have a few models with old brushed motors which i don not know the amps. How can I work out a flight time?

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Old 01-07-2012, 07:08 PM   #2
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You really must invest in a meter to actually measure the current draw.
If you consider the cost of replacing a LiPo damaged by over discharging (or for that matter the ESC and motor by over loading) it is a sound investment.
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Old 01-07-2012, 07:16 PM   #3
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yeah, I am new to all this and my dad only ever flew nitro stuff. I shall look for a meter. Silly question, how do I use one, like a volt meter I guess, but how do I use it to measure the amps being drawn?

Thanks
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Old 01-07-2012, 07:44 PM   #4
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The watt meters go in line between your battery and ESC. They measure voltage applied from the battery and current draw, display volts amps and calculated watts.
You can also get different type of meter that is a clamp around one of the wires between the battery and ESC that will measure current. Little different set up to do the same thing, but not as dedicated

http://www.sears.com/craftsman-digit...p-03482369000P
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Old 01-07-2012, 08:02 PM   #5
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ok cheers, I will try and find one
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Old 01-13-2012, 08:58 AM   #6
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Ebay .... Hobby King .... Local Hobby Shop ?

It's a common item and called by the generic term : Wattmeter

I use mine every day to check LiPo's charge and usage ... balance etc.

With new set-up out of interest - I run up to check amps and watts ...

For about $30 ... it's a good tool.

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Old 01-13-2012, 02:18 PM   #7
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Originally Posted by mrbicknell View Post
. . . how do I use one, like a volt meter I guess, but how do I use it to measure the amps being drawn?

Thanks
Here's an illustration using an inexpensive DVM that are widely available:


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ID:	156335 In this example, voltage can also be measured with a twist of the dial. The unmodified meters can usually measure up to 20 amps.

~Tim
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Old 01-13-2012, 07:48 PM   #8
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yeah, I'm sure I have one of those, I will check it out, Thanks
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Old 01-13-2012, 10:25 PM   #9
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Originally Posted by mrbicknell View Post
yeah, I am new to all this and my dad only ever flew nitro stuff. I shall look for a meter. Silly question, how do I use one, like a volt meter I guess, but how do I use it to measure the amps being drawn?

Thanks
One of those generic "wattmeters" will serve your purpose well. As for the common digital multimeters, their maximum current range is generally on the order of 10 Amps, far to low for most electric motors used in our models. (My kilowatt sized motors typically pull some 60 amperes.)

Take a look, this explains some of this stuff.
http://www.wattflyer.com/forums/showthread.php?t=52821

If you want to spend the $$$$, (About $60) the Sears Craftsman #82369 meter can measure the current pulled by just about any electric motor you have access to. Including the starter and alternator in your car/truck. Its current ranges are 0-40 and 0-400 Amps, AC and DC. It doesn't require special connectors, just clamp it's jaws around one battery cable. Note that most clamp on ammeters are AC only, not suitable for our stuff.

This meter can also measure current pulled by your AC appliances and so on, but it needs to clamp its jaws around ONE wire of the power cord. Clamping around the usual two wire extension cord will result in zero current measured.

But, this Sears meter can't measure things like ampere hours and such, only the usual volts, amps, resistance, temperature and so on.

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Old 01-14-2012, 11:28 AM   #10
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See chapter/post 71 in this e-book
http://www.wattflyer.com/forums/showthread.php?t=31368

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Old 01-14-2012, 01:51 PM   #11
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cool thanks
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Old 01-18-2012, 06:20 AM   #12
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nice info
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