Is there an affordable battery capacity tester ?

With all this fuss about fake chinese cells in Keeppower batteries, perhaps we can use something to measure the capacity without having to rip open a cell ?

I mean if a cell gives me 90% (or maybe 95?) or greater compared to what is advertised, then it is probably a genuine cell right ?

EDIT: Actually, I already have one of these Turnigy Accucel 6 chargers

Maybe I can use this to measure my 18650s ?

EDIT2 : I found the alligator clips which connect to this hobby charger.

Now how would I connect them to the flat ends of the 18650 ?

Was thinking tape but maybe I can grab some neodymium magnets from amazon ?

EDIT3: The reuslt is in. 2114mAh !!! (@1A discharge down to 2.70v)
Not bad at all for a 4 year old trustfire rated at 2500
Interestingly the protection never kicked on at 2.75 and it went down to 2.7 as I set my Accucel 6 to.
I’ll test the green panasonic 3400 protected from wallbuys as well as the keeppower 3400s when I get them (any day now)

EDIT4: The first Keeppower 18650 3400mah I just tested only gave me 3090 mAh… Discharged it down to 2.8V @ 1A using my Accucel 6

Worth noting that it has never been used and only charged once fully using a nitecore i4 and allowed to cool before discharging.

Yup, you can get some magnets and stick them to the leads.

If you’re too curious to wait for them, sticking the leads with tape will work too.

Use the Ni-MH mode to discharge a fresh cell to 2.70-2.80V at your desired current, up to 1A I think.

Make sure the Accucel-6’s fan is running properly because the charger will get fairly warm.

It has a Li-ion discharge function though. Why use the nimh mode ? Does it matter ? Btw trying to find my adapter for this Accucel. Haven’t used it in a bit lol

the very cheapest battery capacity tester (not charger) would be ZKETech's EBD for 10$, comes with USB software and such:

http://mjlorton.com/forum/index.php?topic=468.0

Oh sorry, didn’t explain that. It’s because manufacturers rate their battery capacity by discharging to 2.75V, and the charger cuts off at 3.00V, so it may not display its entire capacity, although it won’t be too much of a difference.

Thought I had read that it is bad to discharge a Lithium cell below 3 volts.

Say if I discharge to 3 just to play it safe, roughly what percentage of the capacity would that represent ?

Or OK to go all the way down to 2.75 or 2.8 ?

Yes, it is true that the life of the cell will increase when it is discharged to 3.00V as opposed to 2.75V, but not noticeably.

If you discharge the cell to 3.00V, you should get over 95% of its entire capacity:

Got it thanks. Measuring 95% of it should be good for me. Down to 3v @ 1 amps it is.

I’m gonna measure this trustfire blue 2500mah right now.

As soon as I get the 3400mah greens and black keeppowers, I’ll measure those too and report back.

This is interesting. Right away the voltage sagged from 4.2v to 3.6v @ a discharge of 1A on the trustfire blue 2500mah

7 min into the discharge, it is at 3.51v….Not looking good lol

Yeah, that indicates a lot of voltage sag due to high internal resistance.

You better toss the poor old (and/or abused) XXXFire cell. :slight_smile:

Nah ! I was testing this single cell (protected btw) in my SRK 4x XML2

It ran for an hour on low mode (with like 5 min of high in there) and the protection didn’t kick in ! Only got slightly warm.

I think it should still have at least 1AH of capacity. Which isn’t so bad for an old protected xxxfire

Btw 15min mark and it’s at 3.42V still with 250mah taken out.

Hmm… did you say it started from 4.20V?

Yup.

As for the resistance. It may be the gheto tape being used which might be making a bad contact on the terminals ? I need some magnets. Not sure where to get em fast. Im in canada btw.

So you put it in your SRK, ran it for an hour on med (5 min on high), put it in the Accucel-6, and it read 4.20V?

Oh never mind, that test was independent of the discharge. :smiley:

Let us know what its final capacity is. :santa:

Will do but oohhh look at this!

Talk about false advertisement lol

Thats a good idea. Rubberband instead of tape.

A rubber band works too, too bad I don’t have any of those thick ones.

It is bad to discharge Li-Ion cell below 3 volts open-circuit voltage, not under-load voltage. Cell discharged to 2.7V at 1A will pop up back to 3.2-3.5V as soon as you disconnect load from it.

Ok thats makes sense. Thx!

1100mah so far and its at 3.26v. Changed it to stop at 2.7v (either that or 2.8… Can’t set 2.75. Protection circuit should kick in at 2.75 anyway.

I’m impressed considering it is a trustfire that is around 4 years old and advertised as 2500mah

The reuslt is in. 2114mAh !!! (@1A discharge down to 2.70v)
Not bad at all for a 4 year old trustfire rated at 2500
Interestingly the protection never kicked on at 2.75 and it went down to 2.7 as I set my Accucel 6 to.

I’ll test the green panasonic 3400 protected from wallbuys as well as the keeppower 3400s when I get them (any day now)

Panasonic 3400 full capacity is tested down to 2.5v under load.