Sunder said:Yeah. Be aware they are ACIR though. So more impedance than resistance.
Great for weeding out outliers, but don't rely on it for doing any maths or for advertising your packs if you sell them. The "real world performance" for eBikes will be lower than the meter suggests.
Matador said:I tried it with my VTC4 cells. I would get reading of 21-22-23 mOhms DC resistance with the genuine branded SKYRC Imax B6 mini (or SKYRC ImaxB6AC V2). The older SKYRC IMaxB6 did not have the DCIR meter function I think...
Id also did some resistance tests on these cells using different resistor values while simultaneously measuring amp and voltage drop.
Values were in similar ranges..... 20 -22 millioms DC.
What I noticed is that sometimes values can be a bit off like as much as 25 milliohm instead of 22 milliohms. But that can be solved by repeating the measure on the cell and eliminating measurement values at the extremes of the ranges.
Details of how I measured DCIR here
https://endless-sphere.com/forums/viewtopic.php?f=14&t=28285&start=175#p1299346
I compared with result I got with using different resistors and tracing graphs to get the slope (which gives the DCIR):https://endless-sphere.com/forums/viewtopic.php?f=14&t=87173&start=25#p1276187
These test I did last year when I was still in Canada. I'm now in NYC, stuck with no VTC4, but I bought 60 LG MF1 cells from alarmhookup. These are 2015 sept/october new old stock of LG cells. They measure around 65 mOhms in the Vruzend v1.0... 2150 mAh max 10A draw...
Matador
Sunder said:As long as you can get good contact, they are very consistent. There's two wires per probe, and both need good contact.
flippy said:It is pretty good considering the price.
But remember to measure at the right voltage/SoC of the battery. Resistance changes with charge.
Volt_Ampere said:IR changes a lot with ambient temperature of the cells! Only way to get accurate cell IR is with a 4 wire method. The B6 IR will not be accurate especially on multi cell batteries.
flippy said:there is no hard number for used cells. check the datasheet on the factory new IR and compare that to the current number.
as long as all cells are equal a higher number is not a problem. your heat production and voltage drop will rise the higher the IR is.
you have to decide what level of wear/IR is acceptable to you. usually there is a capacity loss when the IR gets notiably higher.
Sunder said:ir.png
You can also do the maths backwards, to make sure that under the loads you want to put it under doesn't cause sag big enough to trip LVC.