How I test lithium cell capacity.

I couldn't agree more, watt-hours represents the actual energy a battery holds, mAh doesn't measure anything. Even multiplying the the mAh rating by the voltage isn't accurate, since the voltage changes as the cell charges/discharges. So, do you take the average voltage. That implies the cell has a purely linear charge/discharge curve.. The fact that mAh is so misunderstood is good for manufacturers however, as it allows them to portray their product with the largest numbers...

Gordo

Clive, I got a charger off eBay (c.£20) called a Litokala Lii-500. It has the normal 4 spring-loaded cell slots but sports a capacity-test mode whereby it will fully discharge then recharge Li-Ion or NiMH cells and show the capacity on the screen once finished. I have a dummy AA cell with wires terminating in alligator clips that I pop in to test non cylindrical cells, such as small LiPo etc. As well as capacity, it also reads cell resistance..

Gordo

Hmmmm. At what rate do you discharge your cells? Too many mA & you’ll get a false ‘flat’ but too few & you’ll be there forever. Interested in your opinion Clive.

I've ordered something like that from ebay but I found this on amazon <a href="https://amzn.to/2CI02Hr" rel="nofollow noopener" target="_blank">https://amzn.to/2CI02Hr</a>

It’s worth noting that the little boost converters very significantly in their efficiency, I’ve seen them range from less than 60% to as high as 91% efficient in the power banks I’ve tested and that’s as important as the capacity of the cells. Cable quality varies too, most cheap 30cm ones seem to lose 5-10% at 2A but I’ve seen some as high as 25% voltage drop which is pretty terrible.

Some of the 18650 cells have protection circuit built in. Is it a problem with charging this protected cell with a protected charger. Double Protection! Also, is there a way to tell if the cell has the protection circuit?

Wouldnt be more appropriate to state the watt/hr? Obviously a 1000mAh 3.6 cell boosted at say 7.2 volts would show 500mAh. This whole mAh is confusing and misleading when dealing with V boosted power banks and accus in general

That would be quite useful

Neil Tonks

Another excellent video! Is it possible at some point to make a video about making your own battery packs from cells an "ordinary" person might find themselves coming across? IE I have a few laptop batteries which have died and various mobile phones. How could these items be suitable repackaged and electrically protected to make a portable power bank? I hope that makes sense! :)

Thank you

Neil Tonks