No such thing as Self-Balancing 18650V (Makita)

[parabellum]

This means that cells JUST SITTING THERE will also eventually self balance given enough time

I suppose that why I find my loose cells in the box, previously charged with single 18650 cell charger, adjusted to 4.2V, in between 4.16-4.18V after few weeks.

[flathill]

You just burned off some "surface charge"

Very few batteries will self balance as well as a few types of sony cells
Lots of batteries have chemical balancing via redox shuttling (lower charge efficiency at top end acts as overcharge protection), but the sonys have something else going on that makes the self balancing effect much greater
Must be related to self discharge vs state of charge

[parabellum]

I also overcharged 1 accidentally to 4.25V in series connection and just trow with others but then could not find this cell after few weeks, all where similar voltage (except few died self discharging cells) So they are definitively self balancing in my terms.

[John in CR]

Dumping the surface charge doesn't make any battery balance. They all do that. Luke explained it, and knows what he's talking about, end of story.

Too bad Makita improved their packs, because now the ones the Makita charger rejects aren't nearly as good as they were a couple of years ago, and they take much more work to recycle. Yet the price remains the same for packs people get for free even though overall battery prices have declined significantly. I certainly wouldn't buy any more and I love the convenience of Konions.

John

[pwbset]

Too bad Makita improved their packs, because now the ones the Makita charger rejects aren't nearly as good as they were a couple of years ago, and they take much more work to recycle.

Rats... and here I just bought 26 packs from Doc's latest offer. Maybe they are pre-2011. *sigh*

[ambroseliao]

The ones Doc sells are definitely pre 2011. No worries.

[999zip999]

Started out 2p15s sub packs up to 21ah.. Turned over to a 10p3s sub packs for a rack to 18s. 73.7v. After a week 73.7v cells 4.088-4.072v. I ran it to cutoff 62v. at 30a on my 9c 2810 got 8.71ah, 15.68mi. 37.5wh. Then checked it at 65.62v. by time I got it apart one cell ( 10p ) 3.634v then 3.646 - 3.656v all the rest. Charged to 73.7v on a turned up Ping 48v5a charger maybe 3a. all cells 4.079v - 4.089v. 10p18s. With four 4mm bullets sets in the series line to be taken out after every thing checks out. Love them for now. Till the 25 - a123's show up.

[999zip999]

Con's It took alot of makita 3.0 packs to get there, lot's of zero 0's. Water damage used and even dented inside the case ?, and the Canadian mail strike ect. Plus $$. The ah is little low so far.

[flathill]

Dumping the surface charge doesn't make any battery balance. They all do that. Luke explained it, and knows what he's talking about, end of story.
John

I never said burning the surface charge had anything to do with balancing! I'm saying Nasa confirmed the model that the self balacing is related to self discharge vs state of charge for hard carbon cobalt (not spinel) sony batteries, so more could be at play than luke's explaination related to redox shuttling or a loss in charge efficiency nearing full charge

It is interesting to me that other sony batteries also self balance, and I know you dont care
whatever end of story

[999zip999]

This bleeding or self discharge only happens over 4.1v. ? So my charging to 4.085v dosn't allow for this type of self balancing ?

[JRP3]

I think IBM was marketing a redox additive for cells that would activate at 3.9V and hold a cell at that voltage while others were still charging. Seems like a good idea, don't know if it's being used in some cells or not.

[flathill]

Not sure about IBM but 3M offers redox shuttle additives

Here is a paper that lists sony as having a 2 types of redox shuttle additives for LiMn2O4 (konion type cells)
http://escholarship.org/uc/item/39w108nw#page-3

note enerdel was working on Anode (-) Hard Carbon / Cathode (+) Lithium Manganese Oxide
Maybe we'll be able to buy them now that the Russians bought them in bankruptcy after they made a poor investment in Think

I think konion must also have hard carbon anodes as sony was the first to delvelop the hard carbon anode way back...

If so the konion may have all three self balancing mechanisms which makes them so wonderful:
1) redox shuttle chemical balancing
2) hard carbon results in synergistic self discharge vs state of charge behavior (model confirmed by nasa, cells diverge to a state of dynamic equilibrium, equilibrium spread depends on cell SD uniformity)
2) Luke's theory that spinel anodes have a sort of inherent self balance effect due to a decrease in charge energy efficiency (I haven't read this anywhere else on paper or internet but maybe it is related to the voltage plateau vs coulombic efficiencies)

[JRP3]

Right, 3M not IBM

[liveforphysics]

I never said burning the surface charge had anything to do with balancing! I'm saying Nasa confirmed the model that the self balacing is related to self discharge vs state of charge for hard carbon cobalt (not spinel) sony batteries, so more could be at play than luke's explaination related to redox shuttling or a loss in charge efficiency nearing full charge

Some mechanism causes them to bleed faster as they increase in SOC, hence decreasing efficiency (more of that energy goes into heat rather than stored charge) as they increase in SOC, and when the sit, the cells with highest SOC decrease in charge the most rapidly.

I don't fully understand the mechanism behind it, but I've observed it carefully in a number of tests and examples, and it sure is nice to have!

[999zip999]

O.k. LFP When was the last time you been in the dumpser looking konion cells ? So do I need to go above 4.1v to get this self balance burn off ??

[liveforphysics]

O.k. LFP When was the last time you been in the dumpser looking konion cells ? So do I need to go above 4.1v to get this self balance burn off ??

Yes. The higher you charge the string, the faster the high cells will bleed down. I think around 4v the entire effect is gone (which is great, because otherwise sitting on the shelf they would all be junk in a few months).

[999zip999]

So after ride 73.4v GO to 68.8v 6.565ah, 44.6wh., After 40 min. in kitchen to check.
Cells 3.812-3.822v.
Charghing now.
Older Ping 48v5a. charger
Turned up to 73.3v at 3a. or Help ?
When final charge tonite let you know.

[pwbset]

You really should be charging to a minimum of 74.7v if you're uber-concerned about cycle life and preserving the cells or 75.6v if you want to charge them spec at 4.2v/cell. Unless you're running the VT cells and then 73.8v is the spec charge for 18s.

[pwbset]

Just saw your post above so can assume you're running V cells if you harvested from the 3ah Makitas. In 10p you should very reasonably be able to pull 11-12ah+ to a 54v LVC of 3v/cell. Every decent used V cell I've ever played with averaged 1.25-1.35ah per cell discharging at 2-3C down to 2.7-3v.

You need to up your charging voltage a bit I think.

[999zip999]

73.6v. 18s one cell ( 10p ) at 4.074v. all the rest 4.081-4.086v. Yes I will turn it up when I take it apart for balance wires. But don't want to push the old ping 48v5a charger. Every thing works. And if I keep the hvc lower isn't that better on the pack ?

[parabellum]

And if I keep the hvc lower isn't that better on the pack ?

Sure, but being somewhere in the middle is best. Approaching HVC 4.2V is not good, approaching extreme low LVC is even worse.