[Solved] Selection of BMS for a screwdriver - Selection of BMS for a screwdriver converte

Screwdriver is bosch gsr 9.6 ve.
Bought on allegro.
Picture

Today I started it because I wanted to clean it. It seems that virtually unused, clean inside, the factory grease did not have enough color - probably because the fur was on the key and used those that had these self-tightening.
The parameters can be seen in the picture. There is no specification for this particular version on the network. Data for a very similar model say they were in three versions 9.6, 12, 14.4vV on NiCd.
I want to convert to li-ion and try to determine what BMS to use.
The idea is not to burn the engine or destroy the transmission on the one hand, while taking full advantage of it.
The engine has a body length of 57mm, diameter 38mm. Makita 6280D has the same engine size
Data from here: https://www.elektroda.pl/rtvforum/topic3303667.html
Gearing on normal wheels, thickness 5-6 mm module 1-1.5 depending on the degree.
Axle on which the 1/2 '' fur is screwed

I plugged in today for a laptop li-ion and barely started - too low current, or my fancy connection in series on magnets has too high resistance.
The atx power supply is ok. Easy on it with gusts up to 5A. As I tried to stop by hand to 16A occurred.
I have not tried because the power supply will not pull out again, and the meter is up to 20A. It's just dt9208 on Chinese cables.
In addition, the voltage probably went down because the codegen fan slowed down

I am considering two variants of bms 15 and 30A working current. Over current protoection respectively 20-30A and 60A.
The question is whether based on the parameters described, the dimensions of the engine, transmission, etc. It is possible to estimate which BMS is better.
How much current could be with NiCd? Is 60A OCP not too much?

I guess you have misread the model - photos from the Internet of this model look different.

Here, the 2S2P package would come if it came in the original battery housing or 2S1P.

As for the BMS 20A it will be okay, 60A would be suitable for the xS3P package, as long as there are no 18650 li-ion cells which would bear a higher continuous current than 20A if you are going to pack 18650 there.

In addition to the "good" screwdriver, safety should be taken into account, it is better not to exceed 20A per cell, and with decent batteries like 25R, VTC5 or VTC6.

I read the model well. The seller sold several such screwdrivers. Below one of them where you can see the model number.

Attached are specifications of a similar version, in Russian. I have the batteries in this spec. The masses and dimensions of the elements match.
Part of the list that I found for myself and for this specification looks almost identical - differences in housing.

The battery housing comes with 4 18650. So, rather a 4s1p package.
In this configuration I was thinking about 25r or vtc4.
Samsung has given discharge specifications for max 25A, as well as for hi pulse, but the service life is given for 250.
Vtc4 has a spec lifetime of 30A in the range of 500 cycles, no rating for hi pulse. It's just that 25r after 250 cycles has more capacity than vtc4 after 500 cycles, but it's for 30A cycle.

I guess I'll have to build a shunt and check how much power goes from the car battery at high load.
On these 16A which I got from ATX it was not crazy and it felt that the screwdriver would want more.

In this video, a man measures the current for an 18V screwdriver
www.youtube.com/watch?v=lPxHA-cc8I0
It turns out that gusts to 25A

The 4S1P package has no reason, the voltage on this package will be from 12V to 16.8V depending on the degree of charge, and the factory battery has a nominal 9.6V as it is written on the housing, i.e. with 8 cells charged up to 1.5V will be max 12V

Rather, the 2S2P package, the screwdriver may not reach its maximum capacity but at least there is certainty that it will not burn or the gearbox will not spill. It would be most convenient to use the 3S package, but with the use of the original housing, only modeling lipo will come into play so as not to waste space.

VTC5 and VTC6 have great efficiency and endure a lot, I use these batteries despite the fact that the loss of capacity over time is noticeable.

It is worth considering LG HG2 if they cope with this task, they work great in the field of smaller currents like 10-12A per cell, in return they have a capacity of 3Ah.

Very reliable and professional cell measurements are carried out by the owner of the lygte.info website, I strongly encourage you to review his tests, I think they will help with the selection of appropriate cells.

As for the supply voltage, the shreds of documentation show that the differences between the versions for different voltages boil down to the battery and the mounted holder. (in 9.6 there is 10mm in 12 and 14.4 13mm)
This time I decided to test on a Russian car charger. I added a filtering capacitor and a resistor to discharge it.
The rectifier measures current up to 8A, it lasts 10 before the fuse burns, but now the fuse is bridged with a thin wire. Voltage between 13.4 and 18V.
The screwdriver works well at these voltages. I tested up to 17V.
No load, it consumes 2A in each gear. There is a 6-8A peak during the start. When I try to stop with my hand it is up to 8A, but I can't stop with my hand.
I am intrigued why atx showed current up to 16A - maybe a problem with the meter.
After these tests I am again starting to consider whether bms 15A would be better. Then actually hg2 would match. Except that they have the lowest discharge voltage of 2V, and bms with this cut-off voltage I have not seen. So I won't use this capacity anyway, but the service life will be much longer.

Where do you buy links?

One more thing.
The switch works strangely. On the rating label, revolutions 0-400 and 0-900.
He is very sensitive at first, then it makes almost no difference how hard I press. Although when I am around the max and pulsates with the button, I can also see the pulsing of the current, although it may be caused by the fact that then the motor starts to work like a generator.
I think it should be smoother.
I've never had a screwdriver, somehow it wasn't needed.
Is there supposed to be smooth regulation in the whole range of switch operation? How is the speed control implemented? In network it is a triac, and in battery pwm?

Speed control should be carried out by PWM, everything will become clear as you post photos of the interior of the screwdriver, in the event of a failure on the electrode there are probably a few threads with diagrams of proprietary speed controllers for screwdrivers as this is one of the most common faults.

I'm not sure if I can advertise sellers here, but cheap and good you can buy new links after unpacking on the Allegro website in the BatLit store. If necessary, they can be welded into the necessary package for an additional charge. They pack parcels safely and you can really buy new cells for pennies.

When it comes to completely new cells, the bto website professionally deals with distribution of cells, at tme you can also buy 25R or HG2 at good prices, but they have a small selection of cells.

Thank you for help and useful information.
I have still done a test on lead batteries. One is some paddock with 9.45V, the other one is connected to the rectifier during the test.
The regulator works ok on this one, then it is smooth. So it's probably a matter of modifying the control. Probably there is a divider that indicates filling based on Vref and practically gives full.
The engine stop current is 18-20A on it. 12-18A when charging. The screwdriver seems to be weak.
On this efficient battery, the holding current is over 20A. Working current under 18 + A load. It's much stronger, but it's not crazy.
If I wash myself, I will stop at the 2nd gear. On YT, I saw that people couldn't stop by hand. Strange, after ~ 20A is ~ 300W power.
I would suspect a reducer, based on separate gears, but after all, the rated speed is similar to those with a planetary reducer.
So I have no idea why I can stop and youtubers can't. Well, unless I'm so strong.

At such currents it is only 30A bms. 15A would almost always cut off.
Thanks for the help and info where to buy checked links.

Since the forum mechanisms want me to write how I solved the problem before closing the topic. I categorically declare that I wrote it in the previous post a few days ago