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Ryobi 40V BMS troubleshooting and repair

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i plan to put an index here in the first post of the schematics and any firmware that i can extract. When it gets enough critical mass i may start a github or hackaday project for collaboration and sharing.

Ryobi makes a bunch of power tools that use these packs, but the packs seem to fail quite prematurely and often. Many have been disassembled to find perfectly good cells but the BMS has shut off the pack. The bms chip seems to have a permanent failure mode "feature".

The LG and Samsung cells (10s2p 18650) that are used have no-explosion and no-fire specifications for both over charge and discharge, so it is a big waste of cells--just check out all the folks trying to sell their junk pack on ebay because it won't charge or work anymore.

Index:
1. T1 and T2 terminals, what is the function? Ryobi 40V BMS troubleshooting and repair

2. Driving the FETs, Ryobi 40V BMS troubleshooting and repair

[Edit 3/27/22]
3. How to do a Reset on the board--see post #91 for the old packs, and post #135 for the newer ones.

[edit 6/2022]
4. Identify the small transistor part numbers and how the charger communicates to the battery in post #67. #67



p.s. There is also an 18V thread with similar issues as the 40V, just for reference: Ryobi 18v lithium battery. Internals and charging

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Hello Kenny,

For the female connector, i ordered twice adapter on aliexpress, for 2$ each.
i'm waiting them, to verify or modify to adapt to the battery

I picked up a couple bases for these that hold the battery beautifully and have 2 wires coming from them for charge/discharge. I also got a friend to 3D print a holder that holds the battery nice but requires the connector and wires(damn limits of 3D printing). I was also planning a wood project to hold the batteries the same as the plastic version. As soon as I get the pins that I ordered I will upload a video to my youtube channel showing all 3 and parts/price breakdown. Hopefully I can do this by May 2021...ish.

Here are some of my projects.


City
 

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I've bought a few of these. I want to package 4 of them together as a pack for my black and decker 36V self propelled lawm mower. So my primary interest is in paralleling the packs and alternative charging methods.

The BMS can be completely bypassed, thus creating the option of both parallelization and alternative charging. The BMS has access points to every terminal for each of the cells in the pack that can be tapped. They are labeled on the board as CL[1-10][+-]. So CL1- is pack ground, while CL10+ is the pack positive terminal. The two half packs are joined with the tab between CL5+ and CL6-. Note that the MOSFETs switch ground to the power tab -, while CL10+ and power tab + are connected directly together.

So it's simple enough to simply solder a wire to CL1- (which is pack ground) and CL10+ and have direct access to the pack without the BMS. A balance harness can be soldered to CL1- and to each CLx+ lead for x from 1 to 10 to have cell level balance access completely bypassing the dormant onboard BMS.

With deals on Ebay for 6 packs for $90 USD which translates to $0.75 USD a cell, it may be worth the gamble to purchase a lot, test the individual cells, and for the ones that pass, strap them together for a already packages, medium capacity, high power pack.

ga2500ev
I have seen lot of video and read lot of suggestion regarding a way of doing something when ryobi battery is a problem, so for me the best way of making a difference is to replace all battery / only tha bad one and make another 2 packs of 10 cells and use tge same board, because of what I read it seams that it is always a battery problem voltage is not the same at everyone. Is it somenthing that you have tried?
thank to let me know
 

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Ryobi 40v rev Q

ok, i got all 13 of my voltages.
G-1 = 4.0
1-2 = 4.0
2-3 = 4.0
3-4 = 4.0
4-5 = 4.0
5-6 = 3.8
6-7 = 4.1
7-8 = 3.6
8-9 = 4.1
9-10= 4.1
G-5 =19.8
5-B =19.9
G-B=39.9

That charger is from when i used to vape. made for 4.2v charging, easy. when I hold the leads on say 5-6 I watch it charge really fast in about 8 seconds(at only 0.5A) then when i let off and reapply voltage starts back at 3.8 and climbs back top 4.2v. Whats going on here?
 

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Hello Kenny,

This morning i monitored the dialog during 1h30.
I discharged a fully charged battery with my electronic load at 5ah for 10 min.
And i plugged in the charger.
For the first 50 min the data was the same
After 50 min until the end of charge, the data move constantly every 20-60 sec.
The refresh rate is not constant.

By observing the scope curve, we can say that the dialog is asynchronous.
I think in this dialog, there are a acknowledge pulse. We can observe two different kinds of groung level.
The small pulse may represent a logic 0 , and the large pulse a logic 1.
Or the opposite.
Anyway, i can count 32 bits.
Only the fisrts 16 bits move.

Kenny, i don't understand why the charger will make this dialog.


1011111000100010 1001100000000100 start
1011111000100010 1001100000000100
.
.
0011111010100000 1001100000000100
0011110110100000 1001100000000100 end
My battery was like this at the end.
0011110110100000 1001100000000110 end
 

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Lots of people keep asking on my video about resetting the older packs with the PIC contacts. If anyone wants to comment on that:

My video DOES show the super simple reset of the newer packs with the RST contacts, so I'd also like to post if there is a way to do it with older boards.

The most common cause in newer batteries is the thermocouple trips on overheats and stupidly (IMHO) doesn't reset after a cooldown. My use case was thick weed cutting with a sold cutting head in Texas heat.

So far, confirmed working resets on OP40501 and OP40401.
 

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i would like to find or make some sort of female connector to mate with the Ryobi battery in order to use it as a power supply for other projects. Seems like that would be a good 3-d printer item if i can find the mating electrical contacts.
There is a YouTube channel called “Serendipity Sue” where the guy who runs it has done just that via 3d printing.

The above video shows that female connector in use.
 

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Hi there
maybe someone can help me with a problem on the Ryobi batt.
I just change the 18650 elements on the Ryoby 18V battery (10 pieces of 18650)
and now the battery is not started anymore.
Anyone have idea how can I reset is please ?
Thanks a lot
Denis
 

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Did you compare the internal battery resistance?

I have several functional batteries but which lack capacity.
The battery works well on the mower but after 10/15 min , it stops and restarts every minute.
This symptom is confirmed on the 2.6 ah dated 2011/2012.
When you replace the cells, the problem goes away.
I tested each cells of the defective battery, i didn't noted any failure, just a loose of 20% of the capacity ( 1100 mA vs 1300 mA )

At the begining , the problem was only on the 2.6 Ah.
Now, I have a 2016 5Ah with this problem.
PCB desoldered, 18 V battery pack separated to be tested on my power supply and electronic load.
I manualy charge the 18V pack at 21 V 2Ah ( 4.2V by cell ).
And i discharge at 5Ah with a cut-off at 14V ( 2.8V by cell ).
Periodicaly, i checked the individual cell voltage. The cells had a good balancing.


Both batteries pack have the same capacity and i don't see any problem
I don't know why when you replace the cells, the problem disappears.
 

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Discussion Starter · #153 · (Edited)
i didn't know there was any activity on this thread--i thought i was subscribed to get PM notifications, but that didn't seem to work. :LOL:

i made some edits in posts #1, 2 to identify how to reset and the serial comm of T1, try to clean it up a bit so you don't have to read everything to get to what is needed.
 

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Seeking some guidance

Have an older pack OP4026. Was working now isn't.

What I know: Pushing the button with the 4 led's and no LED's turn on (light)
The OZ chip (at U3) appears to be "on". It is warm/hot to the touch, reads at 100F, but this can vary. Sometimes it registers cooler like in the 80s and feels cool other times it gets hot. Best way to describe is it feels like it is on/off or pulsing.

Is it normal for this chip to be drawing power/warm?

I also read about the mosfet, but mine appears to have only 1, so I wasn't sure how to test/reset and if that was even a good idea.

I tried the reset method mention on post 91, but no luck.

Is there another way to reset? Should I try to charge the cells between CL1- - CL1+ above 3.7?


Measuring between:
CL1- and Bat+ = 41.80v
Bat+ - Bat- = 20.98V
Bat+ - T2 = 41.74V
CL1- - CL1+ = 3.383V
all others in the series eg CL2-CL3 and the respective counterparts read 4.2 to 4.328 V
 

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Discussion Starter · #156 ·
It's not normal. It is trying to bleed down those too high cells and will burn itself up unless you take action. It doesn't need reset, it needs to see lower cell voltages.

Your cells are way too high for some reason. Put an external load like a resistor or light bulb or cooking stove eye (burner element) between CL10+ and CL1+ (no need to include cell 1 because it is already low). Try to get a load of a couple of Amps or so, and monitor the voltage to get the cells down to about 3.8 to 4.0V. Then adjust cell 1 up to match the rest, then try the reset.

i usually just add some wires with a spot of solder to the blobs of solder already on the board to use for cell voltage adjustment. Good luck hope it works.

Any ideas how the cells got to be overcharged?

[edit]
But first measure the voltage of each cell to make sure there is not a shorted pair somewhere in the pack. Don't try the bleed off unless all the cells are about the same voltage or higher than 4.15V.
 

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Thanks for the response kennybobby. When you say lightbulb, is that like an automotive 9006 bulb?
Or just a regular incandescent bulb?
Something else? I don't have a stove element so might need some other ideas.

I've got some resistors in the following values: 100, 220, 330, 1K, 2K, 5K, 10K, 100k,1M

No idea how the cells got so high in value. I had it on the charger and took it off to use and then the fun began.

Here are all the values I see:

CL1- CL1+ = 3.324
CL2+ CL3+= 4.223
CL4+CL5+ = 4.299
CL6- CL6+ = 4.301
CL7+ CL8+ =4.303
CL9+ CL10+ = 4.307
 

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Discussion Starter · #158 · (Edited)
i was thinking of some sort of high power resistance that could take about 2 Amps, such a 100W light bulb or outdoor spotlight bulb, or element from an electric range or oven. i get them at the thrift store for a buck and they can be strung together to make variable electric loads. How about a battery tester for a car starter battery--have anything like that.

An old electric heating blanket? A heater strip to keep water lines from freezing?

An electrical resistance load of about 20 Ohms rated at about 80 Watts or higher. Do you have any old TVs or scrap electrical equipment, or circuit boards, electric drill motor (corded variety), etc.

Your cells are way too high, don't know how that happened but it is not good. something may be broken with your charger.

i suspect that your resistor assortment are small 1/4W resistors with metal leads; they would not be suitable, need a power resistor for something like this.
 

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I tried the 100W bulb and it burned out after about 20-30 seconds (might just be a bad bulb). I will go to the thrift store tomorrow to get an electric stove element. Don't know if the pack will last that long (overnight).

Do I leave the element connected for a little while or is it a quick touch then remove situation?
 

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Discussion Starter · #160 ·
Measure the resistance with your DMM. You might want to get 2 just so you can adjust the load if it draws too much with only 1.

You will want to connect it for a length of time to get the cells down. You could do some touch testing just to get an idea of how much current it is drawing.

The current will be the voltage divided by the resistance, so if the 9 cells have a total voltage of about 41 and the range eye is about 8 Ohms, then it will be drawing 41/8 = about 5 Amps. At that rate it would drain your cells to the lower limit in about 30 minutes; so i would recommend to let it run 3 minutes, then stop and measure the voltage; then 2 minutes and stop and measure; then 1 minute and stop and measure. If not there yet continue with 1 minute intervals. It is better to go slow and measure often than to get in a hurry.

With 2 range eyes, the R would be double, 16 Ohms; so current would be 41/16 = about 2.5 Amps, a lower drain rate.

If cell 1 is at 3.8, then the target for the 9 would be about 34 Volts, so you are looking to bleed it down from 41 to 34 at whatever rate you can get with 1 or 2 stove eyes.

Once you get the high 9 more in line with cell 1, then i suspect that the battery will operate as normal again, but if not then try the reset. Measure all the cell voltages to see how closely they are balanced; if they are widely varying then some manual balancing may be needed.
 
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