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36v BMS Wiring Query
#1
Hi All

I am making some progress with my 36v Drill conversion project; I managed to pick up two nearly new batteries from a ryobi lawn mower, they are 18v on pack but 20.8v on voltmeter.

This was a wonderful find, they are extremely well made so all I have had to do is remove the ryobi BMS pcb but leave it's wiring intact, I then connected the two batteries in series connecting the postive of one to the negative of the other.

The cells are connected in parallel pairs, then in series the 5 pairs make up the 18v/20v

My query is about how I wire my BMS, it is pretty straight forward for the 10 red wires because they go to the existing wiring with one wire going to the joined terminals, so that is all good.

The problem is how do I connect the three soldering points B- P- and C- as I do not have a separate charger.

The Drill battery is removed from the drill and plugged into the charger to charge, so it uses the exact same connections for output to drill and input from charger, just not at the same time.  This still from the video below shows how it is usually wired



My drill has a negative and positive output, there is a 3rd which seems to be an earth but it does not go anywhere in the charged (there is no third terminal) and in the drill it does not really go anywhere.

So the two questions I have are

How do I wire in those 3 BMS soldering points ?

Does it matter that the voltage of these 10 cells are around 40v ?

I have included this video not because it is great technically but because it has the same BMS I got from eBay.



Thanks in advance
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#2
Moved thread to proper location. Please make sure to post threads in the proper location. This is a question thread, not a build thread.
Also fixed your youtube link as it wasn't using the proper tags. Please Preview posts "before" posting
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#3
Sorry if this was in wrong thread, thanks for sorting tags.

Does anyone have any suggestions on how to wire this?
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#4
Is this just a quiet forum or have I worded something wrongly?

I just need to know how you wire something that uses the same wires for battery output as charger input.
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#5
If it uses the same wires, then they are connected in parallel. I don't understand where you are getting confused at, sorry

I believe daromer has a video with that bms, but not sure. Check out his channel "DIY Tech & Repairs" and search for "bms"
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
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