Asking for advice/help with Ryobi battery BMC blown component - Page 1
Forum section: electronics / repair

author: PiSoft
author_rank: Newbie
timestamp: November 30, 2022, 09:58:01 pm
content: As per the title.The full story goes as the following. I bought a Ryobi ONE+ battery with charger second hand, condition unknown. It was cheap, was more for curiosity. As expected the battery did not move any tools but registered as fully charged soon after connecting to the charger. I tried to jump start it as seen on countless videos on youtube. I made a mistake and mixed up the polarity from another battery and I blew something inside. I heard a click like noise but did not really smell anything.I took the battery apart and found a component blown. Unfortunately I have no idea what is this component... In fact I am not very educated with PCBs and their components. However I would like to make this battery working (again for my own benefit rather than for saving money).I seek for help identifying the remains of the component and would like to try to replace it on the board. I have the equipment to do it but nothing more really. I used to replace capacitors in PC motherboards with success so I'd like to consider myself capable of changing the component itself.Please look at the pictures and if you have any idea what it can be let me know.Thanks for your help in advance!

author: fzabkar
author_rank: Super Contributor
timestamp: November 30, 2022, 11:28:28 pm
content: Can you see any more of the markings under the diode body? I'm guessing 1NxxxxD ??What are the dimensions of the diode body?

author: wasedadoc
author_rank: Super Contributor
timestamp: December 01, 2022, 04:12:17 pm
content: Lithium cells are dangerous in the hands of those who don't know what they are doing. I fear that is the case here.

author: PiSoft
author_rank: Newbie
timestamp: December 06, 2022, 10:25:57 am
content: Thanks for the answer and I apologize that it took me long to reply. I have managed to take out the half body of the diode and found the following numbers/letters. N400 on the top and DUE on the bottom. The diode body is 5mm long and about 2.6mm in diameter (if it is a useful info)Thank you for the help in advance!

author: PiSoft
author_rank: Newbie
timestamp: December 06, 2022, 10:29:47 am
content: I agree with Li cells being dangerous and yes, I am being very much a beginner. I'll make sure I do all precautions to my best! Everybody had started somewhere, it looks that is my starting point! ;-)

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 06, 2022, 01:32:40 pm
content: Most likely a zener to suppress inductive voltage spikes. Can you check if the positive side directly connects to the output positive? The voltage rating would probably be on the order of 24-30V for a 5S pack.

author: fzabkar
author_rank: Super Contributor
timestamp: December 06, 2022, 05:10:37 pm
content: It's probably a 1N4001 rectifier. Simple reverse polarity "protection".

author: PiSoft
author_rank: Newbie
timestamp: December 06, 2022, 08:45:59 pm
content: Well... Since I made the mistake of connecting another battery in reverse polarity and then heard a click, and found this thing blown... This sounds very plausible!