Look what I found in the recycle bin

I’m… not really sure that you’re correct about the laptop safety features thing. When I think of laptops that hurt people I think of modern machines which did incorporate BMS’s. Sony has been in the news once or twice in recent years, and it wasn’t due to a lack of BMS.

That said, low-drain cells cannot be treated in the way I describe. The only lithium chemistry cells I’ve heard can be treated this way in the past were the A123 stuff, and they are both extremely high drain and extremely hardy. (approximately: 50C pulse discharge, 30C continuous discharge, 4C charge) I can only guess that Sony’s IMR chemistry is starting to catch up enough where they can be treated in a similar way. If not, the designers of that powertool pack are grossly negligent of course…

Well, those 2 German packs had all 5 cells in each pack sitting at exactly 4.01V. They are 2 year old packs and probably cycled many times. We now know that they are not balanced charged. How else can they all be the same unless they self balance?
I just learned something today.

Remember the issue in serial batteries is not whether cells are balanced - it is whether it is safe for the cells to pass current between cells when there is an active circuit.

For example, in a 2 cell light with lithium primaries in series, if one of the cells drains faster than the other cell, then the lower voltage primary cell may start taking on too much voltage from the better cell during use - when it may not be safe to do so. Same thing with a rechargeable cell that is not in good condition within a group of cells in a series battery, especially when a charge is being applied.

I think you are trying to focus on one purpose for balancing. Really you’ve got it backwards I think. In a situation like this, balancing is all about keeping that less-healthy cell “close enough” so that the pack still operates and nothing dangerous happens. If I’ve got one cell that underperforms by 15%, over the course of several cycles we may see the cells get more and more imbalanced, unless there is some mechanism to prevent that. With a BMS we ensure that all the cells are treated appropriately and that both charges and discharges terminate properly on a per-cell level.

The cool thing about cells which can burn off excess charge is that we can overcharge the whole pack in order to get it in balance and forgo the BMS in some situations. What about discharge you say? Won’t an underperforming cell get exceptionally unhappy if we reverse charge it during discharge? Well, it would… except that this is a high drain application. We won’t run into that scenario. As soon as one cell becomes discharged ahead of the rest we’ll feel it in the tool as a lack of power and stop using the battery. Then we throw the thing in the charger and it self-balances again as the waste energy is dissipated as heat. That’s my understanding of the situation.

EDIT: So that’s the primary purpose of a BMS: to allow a pack to continue to operate with less than ideally matched cells. It’s pretty common for cells to not be perfectly matched, look at any pack-pulls thread around here for info on that. The BMS keeps the balance from slowly becoming horrible/dangerous with those low-drain cells. A pleasant side effect of having the BMS may be that it can brick the pack if one cell becomes totally terrible… but that’s not really why the BMS is present in my opinion.

I keep thinking of the recycle bin on my computer when this thread is updated and shows up in the recent posts

Wow, nice, but I think I would not be brave enough to dumpster dive the recycle bin at my HD.

Very interesting discussion.
It really is a shame that there is usually no datasheet available for 18650 cells. It would be so nice to be able to find some good data, maximum ratings and a quick description of each cell… That would eliminate the need for us to speculate like that.
Anyway, if someone is interesting and wants me to test something specific on these cells I’ll be happy to do it! (But I opened the pack and separated the cells as 2 were shorted)

It’s hard to turn down free but aren’t 1300mah and 1600mah batteries a bit small? That’s before throwing in the unknown condition of these very old things. Would they only be suitable for running things in low mode?

Hi battery.

I don't know anything about these particular cells, but most high current cells have lower capacity. They tend to be hardier and can handle more charge/discharge cycles though. Some users may have special applications that the compromise is necessary trade off.


This whole self-balancing thing is way over my head. I didn't know it existed and am still skeptical in the case of these particular cells.

Hmm, have you considered the NiMH example I gave earler? Or maybe I didn’t. In that case: Think about NiMH series packs. They don’t get balanced, ever. That’s actually the whole story. Those cells store lots of energy, just like Li- chemistries, but they didn’t need to be balanced. Why not?

NiMH cells (as well as NiCd and Pb batteries) transform the excess energy into heat once full. That’s why they can balance on their own.
Lithium cells on the other hand, act almost like a capacitor. The voltage increases as long as you charge it. Of course, it’ll destroy itself at some point. The termination voltage (4.2V for most batteries today) is just a trade-off between capacity and security/longevity.
That’s why lithium cells (and capacitors) need to be balanced charged, to avoid any deviation that would cause one cell to be charged/discharged higher than the others.
No with the sony US18650V/VT, I noticed a very strange phenomenon, the battery “self discharges” down to about 4.1V. That also causes a battery of cells to balance by itself.
Example: 2S pack: Cell1: 3.95V Cell2: 4.05V
When charged to 8.4V: Cell1: 4.15V Cell2: 4.25V
After some time, both cells will self discharge to 4.1V. So they are balanced again.
I’m pretty confident with my observations, but it would be great if someone else could test this characteristic.

I guess you already know all that, but I just wanted to give all the facts so that we are all talking about the same thing. :slight_smile:

These are new cells and are IMR’s which are a different chemistry that ICR, which are the ones most commonly found in laptops.
IMR’s generally are of lower capacity (mAh) than ICR’s but are more suitable to rough treatment and can deliver higher current levels.
As in most things, there are trade offs. For very high powered flashlights, one may prefer to use IMR’s. There have recently been improvements in the capacity of IMR’s and 2000 and even 2500 mAh versions showing up.

I know that but 1300mah 18650s must be pretty old. The Sony VTC3’s are 1600 and those have been around for a while.

I would have figured for high power higher capacity would be more useful because the voltage drops pretty quickly within the first few minutes of high power discharge even on IMR.

They could be old, or they could be even higher drain. Frequently it’s a trade off between size, capacity, and drain rate. Since we’re stuck with a specific size we are left balancing capacity and drain rate. To get even more drain rate than the “usual” numbers, more capacity can be sacrificed. That’s what I would assume is going on here, but you could be right - it could just be a cash grab go get rid of some NOS cells, or maybe process advances have made the 1300’s really inexpensive to manufacture.

@ lagman - that all sounds fine, but what happens when one cell is somewhat more out of balance than in your example? I agree 100% that Ni- stuff burns off excess charge as heat. I do not remember for certain whether A123’s LiFe cells burn off excess charge that way, or simply take a high charge voltage and then settle in the way you describe with the Sony cells.

I think the 13Q’s are just a cheaper low end cell. I see them a lot in Ryobi packs, as Ryobi is a discount line of tools sold by HD. The upgraded drill packs have some of the Samsung 15M’s (1500 mAh) cells.
A couple of months ago, HD had a special buy on 18V, 4Ah drill packs that had 20R’s in them. They were a good deal, a set of 2 - 10 cell packs were $99. That works out to $5 per cell. Almost made sense to buy the packs to harvest the cells.
I bought a pack and sold one and gave the other to a friend. Everybody’s happy.

I’ve only ever been questioned once and I explained that the likely destination for the vast majority of the cells inside the packs I was taking was in a hazardous waste dump but that I would take them home for private use, disassemble them myself (not some chineese kid for $.02 a day) and the cells would be used on my personal equipment and the plastic trash recycled. They were more than happy with that answer and I’ve never so much as been approached again.

Here is a pic of the older Makita Li-Ion pack, the one I believe you have. There is no BMS and no leads to each cell. This is a 10 cell, 3Ah pac that was not used very much when apparently a pair of cells failed.

The 8 cells that were still good are in excellent condition and each test at over 1500 mAh each.
This next pack is also a Makita, but one of the newer improved packs. It also is a 3 Ah pack. Notice this pack has a BMS circuit and leads going to each individual cell. These newer packs can be identified by the star.

Now the 2 different packs side by side. The newer pack is on the right.

Tool batteries seem to work just fine in my lights at the beginning of the use cycle. In other words, 1250, 1400, 1500, etc samsungs/sonys are the exact same brightness with most of my one-emitter lights that are not high demand or direct drive —— compared to testing the same light with a 2400-2* cell. Even tested a bunch with my light meter. The tool batts don’t just last as long at full brightness, which is just fine for me for around-the-house lights. And they seem to charge faster.

I find so many of the Ryobi, makita and other tool packs that I sure wish they used 2800 samsungs or 2900 panasonics!! I did see some new packs that said they contained 2400 and 2600 mah batts. They are just too new to make it to the recycle bins yet, so I don’t know what’s in there. When I do find one, BLF will be the first to know what they contain!!!

Tool pack cells are IMR type and generally have lower capacity, but can deliver more amps. For very high powered lights with multiple emitters in parallel, they may be preferred.

I somehow missed your post…
Thanks for the pictures! The first pack looks exactly like mine… no balance leads.