Prevailing wisdom on battery chargers that can test cell impedance, etc

ChromeDog

Newly Enlightened
Joined
Sep 11, 2009
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3
I've been looking for chargers that work with 18650's through AAA's, and noticed that some of the new chargers have the ability to test internal battery impedance, etc. Are any of these worthwhile and reliable, and in the around-$30 range?

I just bought a Nitecore D4 ($65 for D4 + four OLight 18650's...couldn't pass that up). But I would like to run other tests on batteries, which the D4 does not do (as far as I know). It would be great if someone made a simple tester, since the D4 will probably be fine for charging.

I know that the MiBoxer C4 can run tests on one battery. Enthusiasts seem to like the SkyRC MC3000, but that's expensive, with some reported structural problems. Anything else come to mind?
 

peter yetman

Flashlight Enthusiast
Joined
Mar 23, 2014
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5,100
Location
North Norfolk UK
I assume you've looked at HKJs site?
http://lygte-info.dk/
He has a comparaison chart here somewhere in there that I always find helpful.
For the record I use a pair of Xtar Dragons for testing and charging, but they are well above what you want to spend.
P
 

grayjay70

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Joined
Dec 12, 2018
Messages
31
I recently got a MiBoxer C4 charger as my first charger with any measurment/testing capability and have spent the last month using it to test and sort my collection of various batteries. I think that some of the older reviews of the earliest MiBoxer C4 might have had even lessor capability, but on the new unit I recently purchased while only the 4th slot is capable of measuring the cells discharge capacity (in mAH), all 4 of the C4's charging slots measure and briefly displays the cells impedance at the beginning of each charge cycle (maybe for 10 seconds ?) before it enters the charging cycle so you need to watch carefully if you want to catch and record the impedance value. Once the charge cycle has begun, the mA charging rate is displayed instead of impedance, the maximum automatic charge rate that is selected by the charger is based on the cells impedance so the max auto charge rate can also be roughly interpreted as a general indication of the cells condition when comparing similar batteries (higher selected charge rate = healthier battery). It is common to see the charger slowly ramp-up the auto charge rate during the course of a recharge cycle.

In the course or running capacity test on my collection of 50+ batteries, having only the 4th slot available for discharge capacity is somewhat of a hindrance but I learned that the bottleneck of slot 4's three-part charge/discharge/charge test cycle can be greatly sped-up if you first recharge the cell to full on one of the other three charge only slots, then move it to slot 4. As compared to starting in slot 4 with an discharged battey, it will take the charger much less time to realize that the cell is already full and then switch into the discharge test cycle. Once the discharge capacity test has reached the lower terminal voltage to end the discharge test, the display saves and shows the discharge capacity measurement and switches back into a recharge cycle. In order to maximize throughput of the slot 4 test capability, you can just record the measurement of the capacity right after the discharge test completes, move the cell back into another of the 3 slots for re-charging and re-load slot 4 with the next (preferably fully charged) cell to get its discharge capacity tested. Using this method, I can get almost 3x as many discharge test done from slot 4 in a given time as compared to having a battery run through all three cycles in slot 4. I also learned that worn cells with high impedance will recharge/discharge at the very slow 100mA charge/discharge rate and so can take a long time (up to 20 hours) to complete the discharge capacity test if allowed to run at the auto-selected discharge rate. If I am testing a high impedance cell that defaults to 100mA discharge rate, I will usually manually select the discharge current at a somewhat higher 200mA rate to cut the time of the discharge test in half. The discharge capacity test results might be slightly different from the faster rate but they are still very close and are probably a better indication of the actual capacity if using the worn cell in a moderate discharge rate application. If a battery cannot test well and handle a 200 mA discharge rate, it is likely going in the trash anyway! Best thing I got from thus testing and sorting my battery collection was learning which worn cells not to intermix and use for more demanding applications such as lighting and photography, reserve the cells that are in best condition for the high drain task and use the worn cells for TV remotes, bug-zapper and kids toys.

Also, while possibly not as accurate as the discharge capacity test with a strict voltage termination cutoff, all 4 of the C4's slots do provide a measurement of the mAH that are recharged back into the cell when it is topped-off. I find this particularly useful when I use the C4 to recharge the 4 individual cells from my headlamp. I keep a matched set of 4 cells for use in this headlamp and they presumably all discharge to approximately the same level when the headlamp is in use. The recharge top-off capacity measurement that the C4 provides is thus a useful indication of the comparative capacity between the 4 cells that were all discharged together in use. If one of the 4 cells had its capacity degraded and it was only capable of accepting a lower re-charge mAH capacity before terminating the recharge cycle, that (and an elevation of the cells impedance measurement) would show up on in the course of routine recharging on all 4 of the C4s slots and I could cull and replace that worn cell from the set.

The C4 charger does have some limitations and quirks but overall I have been very pleased with its overall value for my battery sorting needs, much better than the old dumb charger I was previously using that provided no feedback. Ive also used it to sort the individual 18650 cells from disassembled laptop packs, very helpful for sorting and identifying individual damaged cells so that the remaining cells can be re-purposed.

The one thing I do find that it lacks that I could use is a way of testing assembled packs of cells in series, the C4 only handles the voltage of individual cells disassembled from the pack.
 
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