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Old Dec 10, 2012, 10:35 PM
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Turnigy 3000mah 4s ohm readings

Hey guys, I recently found a really informative youtube video that explains how to measure the resistance in your batteries and I recently did all of mine. (6 of them)

As far as resistance goes, the lowest in ohms is .035ohm and the highest is .044 ohm. The average for all of the 6 is about .037ohm. I was wondering, since I haven't used these batteries all that much, is this good for being in the early stages of its life? My voltage sag right now at 40a with two in parallel is around 3/4 volt which seems very high for the amperage.


This test was done under a 20a load at room temperature.
Battery: Turnigy 3000mah 4s 20-30c

----------Rest voltage--------voltage under load-----resistance (ohm)
Batt1-----16.57---------------------15.81--------------------.038
Batt2-----16.59---------------------15.87------------------- .036
Batt3-----16.58---------------------15.89--------------------.0345
Batt4-----14.96---------------------14.09--------------------.0435
Batt5-----15.79---------------------15.08--------------------.0355
Batt6-----15.65---------------------14.65--------------------.05


Another thing. When flying fpv, I have two of these in parallel so its 6000mah. I usually fly until my voltage gets below 14.8 and then land. When I land, my mah reading is only at around 3000mah and the voltage bounces back up to 15.2 or so. Should I continue to fly when my battery gets below 14.8v? What is the minimum battery voltage UNDER LOAD? not resting voltage just while a load is applied?

Thanks for the input!
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Last edited by noxnflame; Dec 10, 2012 at 10:51 PM.
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Old Dec 12, 2012, 12:50 PM
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Can anyone help me out?
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Old Dec 12, 2012, 01:14 PM
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At 14.8 is where I would stop flying on my 4s batteries. If you drain the battery much more than that you run the risk of puffing your battery. If you know when your battery hits the 14.8 level that would be the flying cut off and would set my timer for how ever long that is. Not pushing your battery packs to much will give them longer lives.
I have these same batteries and try not to let them get below the 14.8 mark.
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Old Dec 12, 2012, 01:20 PM
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I have done something similar with my EagleTree data recorder. In that case I make a quick change in the motor load (like pull the plane into a vertical climb) and see how much the voltage from the pack drops vs how much current changes. From that I calculate a rough resistance of the pack.

I think it is a valid measurement, just need to be sure that when the load was removed, the pack voltage pops back up to roughly where it was before the load. In other words the load is a short jolt and doesn't materially discharge the pack.

If I divide your resistances by the number of cells, I get an average cell resistance of 8-9 millohms. Note that the more discharged the pack is, the more it tends to have a slightly higher resistance.

I am not sure what this value implies for a 3000msHr pack. It seems a little high perhaps, but as long as you packs are just warm to the touch when you land, you are in good shape, IMHO.

As to what voltage under load you should land at, well that is a lot tougher. If you are that worried about getting the last safe maHr out of the pack, it just depends too much on the load you are putting on the pack. I would just use common sense. If you are putting 3000maHr back into two 3000maHr packs in parallel, you can certainly fly some more. Personally I just time my flights. Usually the packs aren't changing their characteristics that fast, and my flying also is similar flight to flight---at any given month-like time period.

I'd say you should just keep track of the pack resistances---if they start to climb, then it is telling you the packs are deteriorating.
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