Look what I found in the recycle bin

Would you still have that 40V Ryobi pack from the original post? i’m interested to reverse engineer the BMS board in that pack and wondered if you could post the part numbers of the 2 big IC chips seen in the pictures. i would guess that the square one is a microcontroller (TI?) and the rectangular one is a cell monitoring chip (LT?).

If we could hack the BMS then it might be possible to figure out why the packs are shutting down and how to repair them and then re-use the entire pack.

thanks, kenny

I maybe able to help soon. I still have one I havnt taken apart yet. My 4th one. In 3 months I’ve found 4 they seem to fail a lot. But the cells are still almost at original capacity. I’ve been putting it off being is highly disappointing they are 1300mah cells. When other brands have much better cells in them. A lot of people say there’s have Samsung 13q. All of mine so far have lg 25 amp 1300 cells not samsung. I’ve just been using them mostly for vaping since they are high drain. Or night lights. Each pack had a few cells that were shorted out. In 60 cells 18 were completely dead. The other 42 perfectly fine. Just low capacity. Figure I’ll hang on to them for hurricane season. In case power is out for a few days or a week

On a positive note I found a brand new pack a display I believe in the bin still had new plastic smell and the battery light worked on it. Had 5 Samsung 20q inside. At 2200 capacity roughly. So those are my batteries for the Q8 I’ll put solder blobs on 4 of them

ok i can answer my own question now.

There are two versions of BMS boards made by TTi in the ryobi OP4026 40V packs.

model # board # date
13086012 280146 jan 6, 2011
13086045 280296 dec 17, 2013

i had guessed just opposite for the two chips on the board: the square quad pack U3 is the battery monitoring chip by O2 Micro, OZ8940ATN; and the rectangular 28-pin SSOP designated U2 is a PIC16F1786-1/SS microcontroller.

i had found a 40V and a 18V pack in the recycle bin at HD. The 40V is completely dead, the cells have been totally drained. The other pack indicates 9V when reading from the outside terminals, but all the cells read 4.0V when opened up.

Depending upon the model, there are either one or two big FETs (IRF1404Z) on a heatsink on the bms board that switch the low side of the pack closed/open that functions like an ON/OFF switch. Something must be causing this to stick ON and draining the packs—there are a huge number of dead packs for sale on ebay, plus lots of posts from folks with problem packs. These cells should last 10 years—something is killing them early…

These packs, like nearly every other power tool brand, are built under patent 7554290, invented by Todd Johnson et al, and assigned to Milwaukee Electric Tool Corp. The BMS has no shutoff or low-power mode, and it gets it’s power from the pack—so it is constantly draining the pack. Too bad we have to pay these guys royalties for a POS system, there are better solutions out there e.g. Texas Instruments

^

Thanks for the info kennybobby. Not sure what it means, but it seems like good info for those that know about such things. I just pulled my 5th or 6th one from a recycle bin today. So far, 2 of them had completely dead cells and the others had cells that acted as if new (Low resistance, full capacity, stay cool when charging and discharging a 1 amp, normal warming under high current loads, etc.). So it seems the bms has some other issue that prematurely ends its usefulness. I heard (don't know if it is true) the internal bms disables the pack and intentionally fully discharges the cells when it deems the pack unsafe.

Great cells for around the house lights that don't need long run times.

i think you are right—the controller can disable the pack by opening the FET, which is device 480 is this simplified patent schematic image (440 is the microcontroller).

^

Interesting. Are you thinking those resistors may be used to do a controlled discharge of the cells when certain parameters are met?

If that is the case, it is best one break down a found pack as soon as possible to hopefully liberate them before getting below 2 volts/cell (IIRC what the 13Q can safely discharge down to). I will try to open up my pack tonight and measure cell voltage and voltage drop across those resistors.

The 40V ryobi are very difficult to desolder without shorting and arcing. They put a huge amount of solder on each cell connection and it requires a very high wattage solder iron and lots of solder wick to disassemble if you want to preserve the circuit board. If you don’t care about the board then it should be easier. i wanted my board for reverse engineering purposes.

Here is another patent schematic showing the cell draining/balancing resistor circuits [460’s], which could be used for draining all the cells in the event that a safety feature is triggered (out of range for temperature or voltage, defective temperature sensor, blown fuse, etc). i hope to trace the actual board circuits and identify all these components, probably in another thread so as to not hijack too much here…

^

I can send you my best board if your wanting one still. Just PM me the address you want it sent to and I will have it off to you. As you stated, they are difficult to tear down. So I don't think I have one without some damage.

I opened the pack and the cells were down to about.48v. I didn't have time to follow traces and try to find the resistors you diagrammed above. There are about 12 510ohm resistors and they are the biggest ones on the board. 10 of them are probably the ones in question. I tests voltage across some of them and got a reading of about .01 (IIRC). So it appears the pack is actively discharging the cells. When the "test" button is pressed, the 4 LED's that normally show level of charge all flash off and on.

Yes those 510 Ohm resistors are designated RF1 - RF10 on the board and connected to each 2-in-parallel Cell as shown in the schematic above where they are connected to the - end of each pair. If those were removed it would isolate that pair from the drain circuit. i don’t know how long it would take to drain a pack, best not to wait to salvage the cells. (EDIT note: The 18V ryobi packs have 5 cells and use 51 Ohms for the RF resistors)

i think RF11 and RF12 are in circuits that provide power for the digital section so those could be removed as well to just turn off the controller and stop the bleeding. i ended up taking them all off the boards.

i have 3 packs that indicated bad, one was actually overcharged at ~42.8 V, the others were around 3 to 4V, with cells at .2 to .4. i put them on a power supply and slowly stepped up in 1V increments while monitoring the current and temperature.

The 4V pack immediately took current at 50-90 mA and then it tapered back to about 25mA, then i incremented 1V and repeated this until the voltage got up to ~23 V for the pack. At that point the current draw was increasing with each 1V increment, , e.g. 200 to 300 mA. Again i let it hold at that voltage until the current dropped to ~25mA, then increment. Got the pack up to 32V and stopped, will see how it is in the morning.

The 3V pack didn’t seem to draw any current like the other one did—i stepped it up from 3 to 23 in 1 V increments with little to no current flow, then at 23V it started to draw/charge at 25mA, and after a few more increments it soon started behaving like the pack above until reaching 32 Volts, will check it tomorrow.

On the 42+V pack i had removed the fuse between the top and bottom modules (2P5S bricks that make up half-packs). Over just 2 days the bottom module had been drained off to 18 V, whereas the top half was still reading high at 22.8. The digital controls seem to be powered from the upper half, and likely sensed the “blown” fuse and initiated the drain-off for the bottom half. i connected a resistor and bled the top down to 20, and charged the bottom up to 19, will check it in the morning to see how it holds.

So long story short, nothing thermal was noted, but that doesn’t mean they are safe and good to go. Metal dentrites grow inside a cell during any charging that is done after an over-discharge event. These are sharp shards of metal that will puncture the plastic separator sheet in the cell and cause an internal short circuit, which leads to thermal runaway—much heat and eventually fire. So don’t try doing this unattended, recharging after a discharge below 2.5V is not a recommended practice and they can go off AT ANY TIME and burn down your garage, house or trailer. If it happens while you are sleeping, then you might just wake up dead…

My first recycle bin pull as a registered member. Nothing super special but a 20V worx Li-ion pack. Had a piece of blue painters tape with “bad” written on it. 11/2015 mfg date. Every cell measured 4.05v. So maybe the board in it died but every cell in it appears to be good.

http://i.imgur.com/SWot1Uf.jpg

You may be right on a “fatal discharge” circuit being built in to these packs, I don’t know.

I have always assumed that the reason there are so many like new packs in the recycle bin is because the store or customers make the mistake of fully discharging a pack and leave it for an extended time in that state.
With all the monitoring circuits in the BMS board, there HAS to be some parasitic drain, and if there is, it wouldn’t take much time for the pack in a fully discharged state to drain further to a point of no return. In other words a permanently damaged pack.
Take a look at this discharge curve I pulled from the thread

I had to estimate the capacity of an 18V drill pack, here is how I did it.

From that thread, the area under the curve is approximately the same as the area bound by the red lines and represents the Amp-Hour capacity of the pack. The horizontal red dashed line is the cutoff voltage.
Now notice the blue arrow, it points to an area under the curve to the right of the vertical red line that is bounded by the discharge curve.
It is a very tiny area!
The graph only goes down to 2.3V, but as you can see, if you were to continue the discharge curve any further, you wouldn’t increase that area by very much at all. There is very little capacity past the shut off voltage.
What this means is that if there is any parasitic drain in a pack, leaving a fully discharged pack in that state can kill it!

That is why I believe I find so may “like new” packs in the recycle bin that are dead. Most come, I believe, from tools on display in the stores.

I just spent the last 2 weeks in Ohio. Of course while there I checked out recycle bins whenever I could.
At this point I am very fussy and only pull packs that are physically in like new condition.
Here is a picture of my haul. and represents probably 10 different bins over that period.

I have not had a chance to test these yet.

1 - 56V 4.0Ah Echo
3 - 40V 2.4Ah Ryobi
3 - 18V 1.5Ah Ryobi
5 - 18V 1.3Ah Ryobi
1 - 20V 1.5Ah WORX
1 - 20V 1.5Ah Black & Decker
1 - 18V 4.0Ah Makita

I’ve started to get picky as well. One of those 40v ryobi is the 1300mah one. The one on the right op4026 the good ones are the 4040 like on the left. A lot of the ryobi 1.3-1.5 I’ll leave there. Or take to go dig in another bin. I usually walk up with stuff so I don’t draw much attention. The only place I can dig freely is lpwes. Since I worked there for a couple years and still know some people. Best buy only ran me off once. I prefer the 2.0+ tool packs I already have like 70 1300mah 25amp lg cells from ryobi 40volt. I don’t really have much use for such low mah cells besides vaping. And hurricane preparedness.

The battery monitoring chip in the Ryobi lithium packs (18 and 40V) will disable the Pack by opening the large FET (s) if the voltage drops below the LV threshold and not allow further discharging, but it also prevent recharging so the Pack is “bricked”.

Theoretically, if you can open the cover and manually charge up the cells directly from below the LV cutoff, it should be possible to un-brick it and use it once again in normal operation. i did this on 3 packs to test it out and they seem to be holding.

Those older packs with the 1300 mah cells may not be worth the effort since they are selling the new packs online with 2200 mah cells, 20 cells for $145 is ~$7/cell delivered to your door with brand new cells in a pack. That seems really cheap and you don’t have to worry about your garage catching on fire while you sleep because some salvaged cells went thermal. just sayin’

You are certainly right about that, I will not disagree.
In any case I still believe that it is the self discharge after a pack is fully depleted that is responsible for so many “like new” packs ending up in the bins. That 40V Ryobi seems to be disproportionately prevalent in the bins perhaps because they are used in “seasonal” yard tools. Just the kind of tool pack that will sit around for months slowly discharging itself during the off season.

I will say this, once you mentioned that bounce back effect it got me thinking back to where I compared the total discharge capacity of a cheap Carbon-Zinc AA cell versus an Alkaline.
At low current draws, 200 mA on the OPUS, the Carbon-Zinc kept bouncing back overnight and as I added each discharge session the Carbon-Zinc cell approached the total discharge capacity and probably would have exceed that of the Alkaline. The Alkaline would bounce back also, but not a much as the C-Zn
After a week of overnight rests and discharge sessions I lost interest in the experiment and didn’t continue on.
What I did learn from it though was that ordinary Carbon-Zinc cells are probably a better choice in low drain appliances such as computer mice and TV remotes.

I started the bounce back test with a drill pack, and you are right. They bounce back quite a bit overnight after the initial low cutoff at high draw. Knowing that is a relief to me as I now realize that a discharged pack is not sitting on the ragged edge of the cliff, ready to fall off.

I had been so busy, I didn’t even notice one of those 40V Ryobi’s was a 4Ah. :person_facepalming:
After all the speculation there is no mystery as to why those three packs were in the bin.
Actually 2, one of the 2.4Ah packs charged up and works perfectly and a full capacity. I have the tools and the charger :wink:
You are right, 1300mAh cells are not that useful, but functioning packs are, to me.
As for the other 2, after taking them apart I found that the 4Ah pack had all of it’s cells sitting at 3.3V
BUT

No hope to repair the BMS board, but the cells are in good shape.
The 2.4Ah pack has a similar problem. Both look as though they were standing upright and got wet. All of these cells are sitting at 2.8V Both of these 2 packs came from the same bin on the same day.

As an experiment I will clean this up and perhaps replace the FET. Even if I get it working, I will never trust it.

You are right! Even though that pic was shot in the garage those packs did not stay there. I put them back into my van which is parked away from the house. Until I get a chance to unload it they will stay there, then they will be moved into the shed.

2 years ago I performed an experiment and did just that with some drill packs. All held their voltage for 1 1/2 years even though they were out there for 2 summers and a winter. They perform surprisingly well considering.
BUT I DO NOT TRUST THEM and they stay out in the shed.

Those screws on the heatsink are all rusty and nasty, but i’ve repaired circuit boards that looked much worse. Alky-hawl and your wife’s toothbrush oughta clean er right up…

Craftsman = Ryobi

With all the packs I have pulled, I have never seen a Sears Craftsman Li-Ion pack.
Today I found one. As soon as I held it in my hand I suspected it was built at the same factory as the Ryobi.

The labels on the bottom look like they came of the same press.

Same cells, FET’s and heat sink.

Similar case and parts.


This last shot is a 100% sized picture of the BMS boards. The basic boards are identical and for the most part have the same identical componets. They differ only in some features that are specific to each brand. Pads are used on one or the other depending.



Just thought it would interesting if I displayed this.

Of the 4 ryobi packs I’ve found so far all 1.3ah cells the BMS board screws have been rusted. Looking like water damage of some sort. Testing my cells now finally getting around to tearing it down. I misplaced my t8 security bit for the bottom two screws so had to get another. Besides for high amp vaping. There not bad for testing a light you just built. They will provide low resistance and high amps for a good 5 mins. But for as edc use not gonna happen. For night lights work fine for several nights. I’m keeping them mostly for hurricane back up. I’ve given a couple away. To get people away from ultrafire batteries.

If you can use the full packs. Then the smaller mah would be useful. The one I got seemed to be working. So far all 20 cells same 3.63 volts maybe it wouldn’t charge right after water damage but 2 lights lit up on the battery charge when I pulled. I didn’t get to check today. Home depot was bogarting there bin today. Found one laptop pack at lpwes. A good one actually in frustration I damaged 5 of the 6 cells. Of course the garbage packs open right up a good one close to full mah is epoxied together.first time I’ve actually damaged the cells before besides a wrapper.

Just all the pack pulls I’ve kept over the last several months I can only imagine the 10s of millions of good cells that go to recycling yearly unclaimed. I swear I’d love to be the guy who goes and picks up all the bins in the area. After being ground zero for katrina. I’d like to be stocked up for immediate family to have a handful of lights and batteries for a couple weeks. Its usually a week or two before power comes back on. Also good to save my good cells and use these around the house.

Maybe one day I’ll find one of those 56v packs. Or some milwalkee 6.0 packs. These 1.3 ryobi 18 and 40volt are getting old. Still undecided if I’d grab one or just leave it next time. Just hate to see good cells be recycled for no reason.

Yes, that is very interesting, thanks for sharing. Would you be able to determine if the processor chip U2 has a hitachi part number underneath the white marks.