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18650 at what amp do you discharge test at ?
#1
Just what's to know at what A are we doing our discharge testing, should it be 1A or 0.5A ?
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#2
At the current i plan to run it at. In My case Always 1a. I think 0.5 is to low and you dont weed out enough low quality cells.

I rather bin 1 to many than letting Them pass.... Bytbil also have a system i havent swapped cells in last almost 5 years now Smile
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#3
I've done all mine at 0.5a because my OPUS gets too hot at 1.0a and shuts off  Smile

However, my battery bank is sized to be <= 0.5a/cell max load and in practice, it averages 0.2a - 0.3a max pull per day.   So 0.5a testing is adequate for me.
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#4
With a little bit of basic searching, here are a few threads you could consider reading:

https://secondlifestorage.com/showthread...hlight=amp
https://secondlifestorage.com/showthread...hlight=amp
https://secondlifestorage.com/showthread...hlight=amp
https://secondlifestorage.com/showthread...hlight=amp
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#5
Always 1000mA, never 500mA.
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#6
I test at 1 amp, but when I use repackr to build my packs they test higher AH then what the opus gave me.

Example on a 3s16p I built, the AH rating of the pack after running through repackr was going to be 27ah. When I tested the pack from fully charged to discharged (bms shutsoff) I got 31ah out of it. When I charged it back up, the charger stated it took 31ah to fully charge. The pack I discharged running normal low amp devices 3 to 6 amps.

That's just something I noticed. I don't know if testing cells at lower amps would give different results. Myself I don't like waiting all day to test cells, thats the main reason I go with 1 amp.
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#7
Jonny thats because you didnt test att same current per cell
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#8
The only common charger/testers that do a 1A charge and discharge are the OPUS and the SKYRC. Besides home built and some testers such as the ZH-YU ZB206+ Battery Tester, 2B2L3 or equivalent ,ichargers, hobby chargers, or equivalent. Also the up and coming megacellcharger.

Testing cells at 1A charge and discharge is one way of determining a cells health. But not the only way.
IR is another and if the IR of a cell is outside of the perimeters i.e. higher than it should be the cell can be put aside and not even to be bothered with testing. Sanyo reds come to mind. If the IR of a Sanyo red is above the recommended IR you will have a heater plain and simple.
So yes 1A testing is a very good way to make sure you have a good cell. But if you test a high IR cell at that amperage you will have a very hot cell. A "Heater".

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#9
If you test each cell at 1A, then you but them together of 10p and test the whole pack at 5A, you are then only tested per cell of 500mA. This will equate to a higher capacity of the pack.

To get an equivalent testing, you need to test the pack at the cell tested amp * the cell count. So, if each cell was 1A, and you have 10P, then the pack needs to be tested at 10A. This will get to the closest of the two results. They may be slightly off as slightly lower IR cells will help slightly higher IR.
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#10
You also need to check the voltage and current of discharge end. Some testers like the SKYRC units are adjustable the others have defined setting. That can give different values too.

There are many factors like temperature resistance and so on wich can change the values.
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