18650 Battery Capacity Meter: Optimal Discharge Current for Low and High-Current Batteries

Question

Hello

I have a 18650 battery capacity meter with adjustable discharge current, in the range of 0.3-5A. I would like to know what is the optimal discharge current for low-current batteries (e.g. from laptop batteries) and high-current ones (with short-circuit current> 30A). Differences in the results of some pieces at 0.5A and 1.5A are quite significant (up to 500mAh), hence my zagwozdka.

Greetings,
Mariusz

Xantix · Accepted Answer

Well, the most optimal would be a measurement with current consumption for a specific application. As you noticed, the same battery will have a different capacity in the flashlight and a different one in the mp4 player, etc. Therefore, for example, using a given battery for a 0.3 A pulling device is best to measure the capacity for just such a load, because in practice you are interested in the value you can realistically get in a given device, not a standardized test result. By the way, maybe there are some established recommendations for measuring the capacity of li-ion cells as it is the case in e.g. car batteries - but I have not heard of such recommendations. I would practically assume that for low-current applications the discharge current is within 0.3-0.5 C while for high-current something in the range of 2 C to 5 C.

Anonymous · Accepted Answer

Higher current, greater losses on internal resistance and less capacity, everything is correct. Panasonic declares capacity for its cells at 1C, 25 * C discharge current and 2.5V final voltage. You download the datasheet, look under what conditions the capacity was declared, play it back and you can only determine the state.

Adamcyn · Accepted Answer

A lot. Compare with the following charts:

Pawel_1985 · Accepted Answer

Oximon - if you want to check the manufacturer whether it supplies the cell in accordance with the declared capacity, then do this test with a discharge of 0.2 C.

Practically in every documentation that I reviewed concerning cells, at the capacity indicated, the discharge current was just 0.2 C.

By discharging cells with high currents, you can get capacities much different from what the manufacturer declares, and this will not mean that the manufacturer is lying, because he is not lying, but only examined the capacity under certain conditions (discharge current, low ambient temperature, etc.)

SPEAKERS_XP · Accepted Answer

0.2C discharge is commonly used to determine the capacity of Ni-MH batteries. For Li-ion, this is no longer an iron rule - you should rely on the cell manufacturer's specifications, there is always a specific discharge current for the declared capacity.

Most Li-ion batteries of good quality without much difficulty will reach a value close to the nominal capacity at a discharge current of 1A - this is a good value to screen out any scraping from disassembly.
500 mA is also not useless, but using such a load it is good to measure the resistance of such a cell.

Oximon · Answer

Great, thank you very much for your substantive answer!

Oximon · Answer

Thank you all for your help!

18650 Battery Capacity Meter: Optimal Discharge Current for Low and High-Current Batteries

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