$7 ebay 18650/nimh capacity tester + mini review. Are these any good?

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tek-0
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$7 ebay 18650/nimh capacity tester + mini review. Are these any good?

I recently bought one of these capacity testers from ebay. It’s a little device that connect to battery and a resistor, and as it dumps current from battery into the resistor, it counts a mAh reading. So it’s a capacity tester. I’ve had it for few months and i’ve discharged a number of batteries with it. It seems to work but how accurate it is, I have no idea. At least it seems to get rather close to official specs of different batteries.

Using it is simple: it needs usb power and a resistor. You connect a battery with “any means necessary” – there are just wire holes. Resistor dictates how fast a battery is discharged. When a battery is connected, it first shows the battery voltage. Then, pressing up and down buttons it is possible to choose termination voltage. If only “ok” button is pressed, it chooses this automatically, using 3.0v for li-ion and 1.0v for nimh. A couple of “minus” presses and you get to 2.7 or 2.5 volts and you can measure true capacity of all li-ion batteries. You could also press “plus” and set the termination over 3.0 volts. When it starts doing it’s “thing”, it rotates mAh, current and voltage readings in the screen, and when it reaches the set termination voltage, it only flickers mAh reading in the screen, indefinitely.

The supplied 7.5 ohm resistor causes a current of about 0.5A for 4.2volt batteries, and 0.2A for nimh. The formula for current is: voltage divided by resistor ohms. I bought a few other resistors from my local electronics store, so I could measure my little 10180 li-ions, which didn’t like the 0.5A discharge current. I also connected an mp3 player as well as a flashlight as a load, and it seemed to work ok. One just has to be aware of the max 3 amp rating..

So here are some of my measurements that I did with this device:

4 × 2000mAh eneloop AA (2009): 1470, 1505, 1505, 1512mAh (1A discharge to 0.9v)
2 × 2000mAh eneloop AA (2013): 1763, 1798 mAh (1A discharge to 0.9v)
4 × 900mAh eneloop AAA (2014): 823, 832, 837, 864mAh (0.3A discharge to 0.9v)
2 × 10180 li-ion (2014): 68, 72mAh (70mA discharge to 2.7v)
Panasonic 3400mAh 18650 (2014): 3401mAh (0.5A discharge to 2.5v)
Panasonic 2900mAh 18650 (2014): 2909mAh (0.5A discharge to 2.5v)
Keeppower 2600Mah 18650 (2013): 2665mAh (0.5A discharge to 2.7v)
Keeppower 700mAh 16340 (2013): 634mAh (0.5A discharge to 2.7v)

If somebody knows more about this device and how accurate it is, feel free to chime in.

!imagebam.com! !imagebam.com!

Edited by: tek-0 on 11/16/2015 - 12:43
mattlward
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When I clicked for a full size view of the image on this page… it popped a window that gave me all kinds of warnings!

EDC rotation:
FW1A, LH351D 4000k (second favorite)
FW3A, LH351D 3500k
FW3A, SST20 FD2 4000k
FW3A, Nichia 4000k sw40 r9080 (favorite light!)
FW3A, Cree XP-L Hi 5A3
Emisar D4V2, SST20 4000k
S2+, XM-L2 T6 4C

tek-0
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Yeah.. sorry about that. You should have an adblocker in your browser.

Bright_Mike
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I’ve been wanting a capacity tester. Looks interesting.

Werner
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But when it is discharging with a simple resistor you never get a constant current discharge….current decreases with the battery voltage going down.

tek-0
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So how does that affect the final mAh count? Do analyzing chargers use the constant current discharge?

mattlward
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There are several that are electronic loads that do maintain constant current. Back when I was racing 1:10 scale electrics we used various homemade CC discharge units and a few that were not CC. If you took the time, back then, to build a CC discharge tester they worked very well.

I am considering one of the following 2, the first allows for charting and controlling the process via PC. I will likely go with it or the next model up to allow for more current draw.

EDB Mini V03
Tester

EDC rotation:
FW1A, LH351D 4000k (second favorite)
FW3A, LH351D 3500k
FW3A, SST20 FD2 4000k
FW3A, Nichia 4000k sw40 r9080 (favorite light!)
FW3A, Cree XP-L Hi 5A3
Emisar D4V2, SST20 4000k
S2+, XM-L2 T6 4C

Werner
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Check out HKJs Reviews(I usually browse his test through this site: http://budgetlightforum.com/node/30711#node-30711 after selecting the battery from the drop down menu you can click on the blue link to see a full review) , you will see that with rising current capacity and voltage go a bit down. there is no problem with that as long as you just want to use it to check your batteries and give them a full discharge from time to time, but you can’t really good compare it to other measurements from others. But it’s questionable if these selfmade tests are comparable anyways as they always differ from the used equipment…
What was the biggest discharge current you have used?

The hobbychargers use constant current discharge. I have the 50W version which only can discharge 10W or 1A. It’s okay to test if a small battery is still working or if the voltage is breaking in fast under load. It also can charge all types of batteries and the price was around 25$. It’s not suitable for high currentrates/capacity(imagine a 40Ah battery with 1A)

——
I would like to see a nice capacity tester which can discharge up to maybe 10A and is reasonable accurate with four wire measurements and a cradle like this https://www.fasttech.com/products/1883214

mattlward
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We did cell matching and pack testing at 13 to 15 amps CC. Now days with lights, I would like to test at 3A and 5A. Mainly to verify condition of older batteries. I would like to be able to grade aging cells and relegate them to lower draw applications when the time is right. So, maybe test my most used cells 2 times a year… I do catalog my cells, right now it is only done by charge terminate voltage always on the same charger and by 1 month self discharge voltages. Not very scientific.

My days in RC were right at the leading edge of going from analog speed controls and crap chargers to good CC NiMH chargers and I beta tested for the original Tekin solid state speed controls. In the day, I was good at racing them and garnered enough attention to become a sponsored driver… it was fun.

Matt

I agree, will have to own one of those cell holders this winter. Have been looking at them for awhile. Simon also sells them.

EDC rotation:
FW1A, LH351D 4000k (second favorite)
FW3A, LH351D 3500k
FW3A, SST20 FD2 4000k
FW3A, Nichia 4000k sw40 r9080 (favorite light!)
FW3A, Cree XP-L Hi 5A3
Emisar D4V2, SST20 4000k
S2+, XM-L2 T6 4C

svicar1
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Does somebody tested the module??
are the results reliable?

I dont understand why the current must be constant?
the module is monitoring current and voltage…why current must be constant??

tek-0
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If I’ve understood right, milliamp-hours (mAh) only measures current over time, while milliwatt-hours (mWh) is a measure of current times voltage over time, so it’s a better metric to measure overall energy stored in a battery. Right?

svicar1
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does somebody tested the module?
Are the results reliable?

thankyou

djozz
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svicar1 wrote:
Does somebody tested the module?? are the results reliable? I dont understand why the current must be constant? the module is monitoring current and voltage...why current must be constant??

The capacity of a battery varies with the discharge current, so you want to give a capacity-number-at-a-certain-current (in his battery tests, HKJ measures the capacity of a battery at a couple of different discharge currents, depending on the type of battery the differences can be quite small and sometimes considerable). This requires a constant current discharge or you will get an 'average' capacity over a range of currents, which btw can also be a useful number.

svicar1
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so you say that is better to use CC discharge module

what about this?
https://www.youtube.com/watch?v=U2Z60AjtaYk

WarHawk-AVG
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More accurate than NOT having anything to test capacity…but many decent lower priced analyzing chargers tell capacity

P.S. mAh (per SOL) are now referred to as pirate ninjas Smile