Test/Review of Keeppower 16650 2000mAh (Black)

HKJ

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Hello. I have the Opus BT-C3400 and I can tell you that you can charge the Keeppower 16650 BUT it will only charge it to 4.2v.

What if you switch the internal switch to 4.35 volt?

The Opus charger is awesome and I chose that over the others (Maha, LaCrosse, etc) because it can charge Ni-MH, Li-Ion, LifePO4 AND when it's done charging... It does a trickle maintenance charge( around 24-34ma) on Ni-MH batteries to keep it full unlike others that cut off and the battery can self discharge sitting in the charger.

The trickle charge is bad for LSD cells like eneloop.

The Keeppower does have protection circuit however and it seems to only want to charge to around 4.30v before it kicks in and cuts off the charger. So it misses the mark by .05v.

The protection kicks in before the CV phase, this means you need to charge with a low charge current to get the most energy into the cell.
 

RI Chevy

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You may want to double check your max voltage. This base cell is not a 4.35v cell. It is a 4.3v max cell.
 

reppans

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The newer Keeppower 2500mah 16650 is based on the Panasonic/Sanyo UR16650ZTA cell, which specs 4.35v on the base cell. However, there is a specific note for the protected version on the Illumn site stating:

Please Note: The internal cell is capable of being charged to 4.35V, but the protection circuit is set to 4.20V, we did not notice a huge capacity difference with this.

Mine has seen 4.27v in CV mode from a CH1 without tripping.
 

Phlogiston

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I'm not surprised to see these cells charging to 4.27V or even 4.3V, 4.2V protection circuit or not.

Bear in mind that the acceptable tolerance on charging to 4.2V is ±0.05V, and the protection circuit will have a tolerance of its own. It wouldn't surprise me if the protection circuit tolerance was also ±0.05V.

Given that this is the case, the protection circuit will be targeted on a trip voltage somewhere in the range of 4.25V to 4.3V. This ensures that it will still allow charging to 4.2V in the worst case of low tolerance, and perhaps a bit more for chargers that go a little high but stay within the acceptable range.

It has to be this way; if the protection circuit were targeted on 4.2V, you'd have cases where users were unlucky enough to get a cell with a protection circuit whose trip voltage was as low as 4.15V. Cue unhappy users and returned products.

Of course, this means that the protection circuit could allow charging to a voltage as high as 4.35V in the worst-case combination of manufacturer decisions and high tolerance.

That's the reason why one should never rely solely on a protection circuit to terminate charging, as some of the worst charger designs and ill-advised improvisations do.

The protection circuit is not there to regulate a normal charge; that's the charger's job.

The protection circuit's job is to help safeguard the cell's user in the event of a potentially catastrophic problem, such as an outright charger failure (e.g. a short-circuit dumping the full 5V or 12V power supply voltage across the cell) or a user error (e.g. accidentally installing a cell with reversed polarity in a set of three or more cells in series).

From that perspective, it doesn't matter if the protection circuit permits a slight overcharge, despite the fact that this will shorten the cell's service life, and compromise its safety in use if the overcharge is repeated too often. It's just like the way a household fuse rated at 13A might not blow until 13.5A, but that's not an issue as long as it's guaranteed to blow in the event of a short-circuit (which will try to draw a great deal more than 13.5A).

Personally, I rather like the idea of a 4.35V cell with a 4.2V protection circuit. I'd happily charge it to 4.2V every time, trading a bit of capacity for the noticeably longer service life and slightly increased safety of not charging it right up to its rated limit.
 

reppans

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Personally, I rather like the idea of a 4.35V cell with a 4.2V protection circuit. I'd happily charge it to 4.2V every time, trading a bit of capacity for the noticeably longer service life and slightly increased safety of not charging it right up to its rated limit.

Yes agree on extra PC tolerances and I also like the idea of the higher voltage cushion, particularly with certain chargers like the Klarus CH1 which has a high CV.

HKJ's first post shows 4.3v max in the graph.

The cell in discussion over the few posts/day or so is the upgrade/later 2500mah version, not the earlier 2000mah version HKJ has tested. Maybe not the perfect thread for it, but also not too far off topic.
 

HistoryChannel

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What if you switch the internal switch to 4.35 volt?

The trickle charge is bad for LSD cells like eneloop.

The protection kicks in before the CV phase, this means you need to charge with a low charge current to get the most energy into the cell.

Thank you! I thought about changing the BT-C3400 to 4.35v but I charge a lot of 18650's and use the Xtar for 16650s.

I did not know that maintenance trickle charge is bad for LSD batteries!!! I'll stop doing that from now on.

I will try and charge using .25a to see if I can squeeze in every last ounce of energy into there.... Makes sense now. It usually trips around 4.29-4.3. I have never gotten it above 4.3v. I think it trips earlier if I'm charging at a higher rate.

Thanks everyone for this awesome discussion!
 

blanex1

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Feb 2, 2016
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i just ordered a pair of these keep power 16650 battery's to run in some of my surefire's 6p's! i'll be charging on a nightcore D2,from what i have read! they should work nicely in some other flashlights i have also,by the way there coming from germany,as it was the only place to find in stock!:(
 

recDNA

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My charger will stop at 4.2 volts no matter what and that is ok with me. That said what is the max safe charging amps? I charge at .5 amps but it would be easier to charge at 1 amp if it is within spec.
 
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