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Best rate to test capacity of 18650 LiIon on Opus bt-c3100
#1
Just got this charger (ali). What is the best current rate when checking capacity on recovered 18650 batteries? Default is 500mA and it seems that takes 8+ hrs per battery (!?).
Is it better/faster to increase that current rate to 700mA or 1000mA? Will this speed up capacity testing time?

Cheers
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#2
If you want to process your cells faster - definitely use 700ma or 1000ma. However there are a couple of things to be aware of:

- Different discharge currents will give different results. So any cells you have tested so far will have to be re-tested

- You may have to do a fan mod on the Opus - as it can overheat at 1000ma - and it will pause, which does cause issues with accuracy.

I tend to charge batteries with another charger, and only use the Opus to capacity check. As soon as I have a result, I remove the cell and charge it with another charger. Also, it is worth checking cells for self discharge before capacity testing. By doing this, you save the time of testing cells that are to be discarded anyway.
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#3
Testing speed is directly proportional to the test current.
If it took you 8h+ @ 500mA test, it will take you 4h+ at 1000mA.
I usually test @ 1000mA, just to filter really good cells from the rest, but for some of the older ones it's necessary to test at 500mA or lower because they don't officially support higher discharge rates.
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#4
(02-11-2019, 01:03 PM)Overmind Wrote: Testing speed is directly proportional to the test current.
If it took you 8h+ @ 500mA test, it will take you 4h+ at 1000mA.
I usually test @ 1000mA, just to filter really good cells from the rest, but for some of the older ones it's necessary to test at 500mA or lower because they don't officially support higher discharge rates.

Exactly!!
The only problem is if you do discharge at 1A and don't have a proper cooling system on the OPUS it will overheat and stall lengthening the test.
Also as Overmind says if you plan on using the cells at 1A+ discharge rate you should for sure test them at that rate and avoid cells that cannot handle that. They might be good at 500mA or so.
The spec sheets for most "Laptop" cells usually have a 0.5C standard charge rate and a 0.2C standard discharge recommendation so I would follow that as close as possible when charging/discharging these cell.

Wolf
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#5
I also have a single opus only for the discharge test and I discharge at 700mA . I got a separate 8 slot charger to bulk charge and when I have excess cell waiting to discharge, I use 4 ZLB2L3 chips and those discharge at 500mA. At 700 on the opus I can check for hot cell, and got out about 20 from around 600 tested so far. With this method I get through around 12 - 16 cells a day.
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#6
You test at the rate you going to run the cells. I your max current per cell is 1A then you test at 1A...

You dont test at 500mA if you running at 1A. Ie always test at same or larger.
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