Worth charging high voltage chemistries over 4.2v?

I have some laptop pull 4.3v cells (LG LGABC1865) and I decided to try the "hidden" 4.35v setting on my Opus BT-C3100 V2.2 charger. The spec sheet says not to go above 4.30 +/- 0.03v but the danger of charging is heat (after there is no more Li to move to the resistance shoots up). I charged at 500mA and for the first few tenths of a volt above 4.2 it was still allowing high 400s of mA demonstrating Li was moving. By the time I hit 4.33v current was down to 150mA or less and the cells were cool to the touch. Eventually they terminate for low current at around 4.33 or 4.34v. I'm not at all worried about damaging them with the extra 0.05v (and besides they are free laptop pulls).

I have 8 cells 2800mAh cells that tested out at about 2.1k from 4.2v down to 2.8v. The first 4 tested out at 2.5k from 4.3 to 2.8v (a 14% improvement on the raw numbers before rounding). The 2nd 4 are testing as I type this.

So is it worth it? I think it is.

Mike

do not have an analyzing charger as I feel after following this forum for years none of them are really that accurate in their analyzing. I have some new LG 4.35v cells I charge on my Xtar VP2's. But hey if you can get lap top pulls to charge that well then by all means I would say worth it.

cells tolerate a little bit of overcharge. 4.20 / 4.30 / 4.35 are just nice round numbers for standardization, they're not intrinsically related to the low-level chemistry.

some people think that 4.20v is some kind of brick wall but actually: 4.21v trades little bit cycle life for capacity. 4.22, 4.23.... but it's NOT linear! and you can't keep going up without some bad things happening

CelticCross74 said:

do not have an analyzing charger as I feel after following this forum for years none of them are really that accurate in their analyzing. I have some new LG 4.35v cells I charge on my Xtar VP2's. But hey if you can get lap top pulls to charge that well then by all means I would say worth it.

Click to expand...

So there is another thread where I argue that these analyzing chargers are not very good at measuring IR but in the case of capacity current and time are two things that the charger can determine with a very high degree of accuracy, so current*times should be very accurate too. Plus I am doing my 4.2 vs 4.35v comparisons on the same charger.

These 9 cells are not even my laptop pull champions! I have 4 ancient LMC hybrid IMR Panasonic CGR18650A 2000mAh cells measuring 2100 (and they were the survivors of a pack with 2 DOA cells), 9 grey wrapper NCA Panasonic NCR18650 2900mAh cells testing out at 2800 and 9 NMC hybrid INR Sony SFUS18650GR G7 2400mAh cells testing to 2300. Keep in mind these are only going down to 2.8v while the ratings are down to 2.5.

I will pitch any cell under 2.5v (it does not even get a serial number for my sorting). Of those that survive, I have strict capacity (generally 2/3 rated), IR, 90 min relaxation voltage, and 72 hour leakage requirements. 36 of 53 LCO and LCA pulls did met those criteria as did 25 of 25 high drain cells (A mix of LMO, LMC hybrids, and NMC hybrids). I'm starting to form the opinion that high drain cells survive much better in a laptop environment.

My source of laptop batteries (6 floors worth of recycling cabinets at work) mostly gathered between 2013 and 2015 has completely dried up. Everything is flat pouch cells for ultralight laptops and batteries seem to fail less often now.

Mike

Arizona_Mike said:

....... I charged at 500mA and for the first few tenths of a volt above 4.2 it was still allowing high 400s of mA demonstrating Li was moving. By the time I hit 4.33v current was down to 150mA or less and the cells were cool to the touch. Eventually they terminate for low current at around 4.33 or 4.34v. I'm not at all worried about damaging them with the extra 0.05v (and besides they are free laptop pulls)..................So is it worth it? I think it is.
Mike

Click to expand...

I think you are fine. I'm not sure I understand the concern as everything looks normal to me. A charger with a preset termination voltage whether that is 4.20v or 4.35v always will have the current taper as the voltage on the battery approaches the chargers regulated preset termination voltage. Ideally a CC/CV chart would show the voltage linearly rise until it hits the CV (constant voltage) point and then hold that level. But in reality their is resistance in the charger cradle, etc and so the curve looks kind of rounded as it approaches CV. I see this more pronounced on some chargers with the spring loaded contacts.......but nothing wrong with this. I would agree with you that the extra 0.05v won't matter since the charger looks to be terminating on the short side of 4.35v.

The final results are in from all 8 cells and the increase in capacity charging to 4.35v instead of 4.2v is 14%

Mike