Testing for compatible 18650 cells

Joined
Feb 27, 2022
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I have two different used 18650 cells. Both are 2500mah. How can I test them to know
if they are compatible in the same pack? I think they need to have same max discharge rate.
I can't find any specs online. Thanks
 
you need an IR tester, something like the yr1030. If the IR is similar they will have the same discharge characteristics. If one cell IR is .20 and the other is IR .50, then they wouldnt work on a high drain device. High discharge cells are in the IR .20 range, laptop cells are in the IR .60 range. You want your cells to be as close in IR as possible, especially in high drain packs.
If you will be building battery packs the IR tester will save you alot of time by quickly telling you which cells are good and which are bad. Even if the cell checks good on the charge/discharge test, the IR can still be high which will give you problems if you use those cells. I didnt want to spend the 60 dollars for the IR tester but it was the best investment I've made, save me alot of time in sorting through cells. You can test the cells quickly before you even place them in the charger so you don't waste time.

yr1030 internal resistance tester.jpg
 
Probably need the context of your usage. How many cells, and how big a battery. If you're building for high current, I would just say to avoid mixing cells period.If they have different discharge curves, you might get strange results.

I have a YR1030 too. It's useful. For ebiking, 40 milliohms is about the upper limit for me, and I need 4P-5P to keep the voltage sag manageable. I bought mine from China so it was about $42 shipped, wiyh a three week wait.

I just got one of these electronic loads from China for about $37 too. I had planned to use it to test the capacity of my ebike batteries, but it can only take about 180 watts, which limits current to 3-4 amps. HOwever, on a 4.2V cell, I can test at 4-6A if I want. which is more real world than the 1/2 A I get from my Littokala 500 tester.

tester.jpg
 
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