EDIT: I got two new batteries in the mail today and checked their resistance. One read 58 mohms on cell #1 and 5 & 9 mohms on the other two cells. The second new battery read 4/5/8 mohms. I then noticed that the wires from the balance board going into the charger was not fully pressed in on the left side. I pushed it back in and now the new battery that had read 58 on cell one reads 6 on cell one. I rechecked the two batteries i wrote about below and they read 5 & 6 on cell #1. I'm embarresed that I didn't catch this before I posted the stuff belowHowever, is there a general rule that says resistance above __ means the battery is worn out?
End of edit. HB~>I have two Turnigy 3S 1300, 30-40C LIPOs that sat around at storage voltage (3.85 v per cell) for a couple of years. I didn't take an initial internal resistance reading when they were new. But after using them for about three flights each today and yesterday, the charger didn't bring the 3 cells back to the same voltage in storage mode. Cell #1 had considerably higher voltage than cells #2 and #3 when the charger (a Hitec X2 AC purchased about 2017) said the batteries had reached storage voltage and shut off.
So, I checked the internal resistance and Battery A had 58 mili ohms in cell #1, 8 mili ohms in cell #2 and 11 mili ohms in cell #3, and a combined resistance of 77 mili ohms. [or is it micro ohms?]
Battery B had 58 mili ohms in cell #1, 4 mili ohms in cell #2, and 4 mili ohms in cell #3, and a combined resistance of 66 mili ohms.
The model is a modified Sig Akromaster (18 ounces with battery), a Brodak FM-0c timer, a GForce 2212 1250 KV with a max amp rating of 17 amps and an APC 7 x 5E . I've got a Watts Up meter and have taken readings on the ground that yield 13 amps at the speed setting I'm using. Upon recharging the batteries I have never drawn more than 997 mah (about 4 minutes 30 seconds of run time.)
Ok, so what does the internal resistance indicate?
1) That these batteries should be retired and discarded?
2) They are still usable, but are not performing optimally?
3) Do these readings indicate that the #1 cell in each battery is bad/going bad or that the #2 and #3 cells are bad/going bad?
4) The instructions that came with the charger do not say if the resistance readings will vary with the voltage in the battery. So, are the resistance readings meaningful only if they are taken each time with the battery and cells at the same voltage?
I've never checked the internal resistance on any LIPO battery pack I've ever purchased. If I had been checking, I guess I would know some of the answers to my questions. I guess I'll have to start a log on all the battery packs I buy from now on and record their initial internal resistance readings.
Thanks,
Joe Ed Peerson