Riddle me this, Batman...

Ok, I've got a couple of Redilast 17670 2000mAh cells, using the 'Japanese' Sanyo 2200mAh 4.30v 16650.

Tonight, I break out the SF 6P LED with EDC+ 3 mode P60 XM-L2 U2 and run the cell down just to loosen things up a bit and recharge the cell.

I get the VP2 out and figure I'll try charging it up to 4.30v, since that's what it's able to take and set the VP2 to 3.8v, figuring that I'd just watch it carefully and yank it off at about 4.30v, calling it a 'done deal.'

I watch the charger as it approaches 4.30v and at about 4.20v, I take it off just to measure things and I get a low reading on my RatShack DMM (22-805,) like 4.15v-4.16v.

Most of my readings match the voltage on the VP2, +/- .001v, so I'm a bit perplexed, but I trudge on.

I re-install the cell and let her rip for another 20 minutes, as it approaches 4.30v on the VP2.

She gets to 4.31v on the VP2 and I figure I'm done, but after pulling the cell off, it only reads 4.15v.

What's up with that?

This is a protected cell, but should the 'over-charge' protection have kicked in at only 4.15v on my DMM?

Confused and thanks, Chris

It is because you take it out before the CV phase is finished, then the voltage drop will be rather large.

Here I charge a cell where the over voltage protection trips and prevents a proper CV phase:


The dark red voltage drops about 0.12 volt when charge is stopped.

I think its the redilast ptc which is set at 4.2v doing its job not allowing any more charge- i cant get get much more[ maybe 4.17] on all my protected cells of different brands,just a thought.