Ryobi 18V battery "repair" - Page 1
Forum section: electronics / repair

author: Wimberleytech
author_rank: Super Contributor
timestamp: August 02, 2019, 06:28:03 pm
content: I have a Ryobi 18V Li Ion blower. The other day, the wife said it was dead. Sure enough. I put the battery on the charger and it registered an "error." I did not know if it was the battery or the charger. I checked the voltage output of the charger and it was fine (I guess). Then I disassembled the battery. As one would expect, it was a series of 18650s.I did not see any obvious failure on the board or batteries.Next I googled and found a youtube video of a guy that individually juiced up each 18650 one a time...just for 10-15 seconds. This brings the voltage of the battery up a little. Once you bring all of the batteries up to some (unknown) threshold, the charger is happy to fill it up.There is some undervoltage lockout in the charger or the battery that prevents it from being charged if below some threshold. I see lots of complaints about these batteries. Sadly, there are probably lots and lots of the packs in landfills that are, in reality, functional.I charged the battery fully and it is working.I wish I had a schematic of the battery board and charger, but that is probably unrealistic. I think there is an error in the design...if I had a schematic, perhaps I could fix it. Might be coded into a micro which would be a challenge, if not impossible, to address.Any similar experience in EEVBlog world??

author: coromonadalix
author_rank: Super Contributor
timestamp: August 02, 2019, 07:01:49 pm
content: show us photos of the opened battery pack ...take voltage of each cell and report backIf you have a bms (battery management system) it may tell the charger something is wrong with the cells, normally they are at 2.7 v each, but sometimes, one of them die, and the others are overcharged and the voltage of each cell rise and create an error in the bmsI saw many problems with dewalt flex 20/60v battery, the cells are not even, some of them get near zero volts, and the bms tell the charger to quit charging .. it does not do a good job, i had cells at 4 volts, and others at 2.7v, and a few at zero volts, even tried to boost / kick them, no avail. They have 15 cells grouped in series of 5.And the flex batteries are very advanced in technology, tons of smt fuses, and small smt ic's, they are dunked in somekind of clear sillicone, impossible to service.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 02, 2019, 07:12:45 pm
content: Oh I dont recall the brand (dont want to make a mistake)I saw that at a tool shopThe battery bms communicate how many times you charged it, the temperature of the pack etc ... you can see that on pc with the software and once you got over x quantity of charges "even if you are supposed to be in the warranty period" they tell you its over get a new battery...

author: Wimberleytech
author_rank: Super Contributor
timestamp: August 02, 2019, 07:13:35 pm
content: I have put mine back together, but here is a video dealing with the same battery system.

author: The Soulman
author_rank: Super Contributor
timestamp: August 02, 2019, 09:55:44 pm
content: I'd be interested to know what that minimum charging voltage threshold is.If a lithium based battery's voltage has been to low it is most likely already damaged and it is notvery safe to "fast" charge it, also the reason why the charger would have minimum voltage requirement.On the other hand why would the battery's voltage be to low in the first place, the bms should prevent discharging below a certain level.I rather stick with my metabo.

author: Wimberleytech
author_rank: Super Contributor
timestamp: August 02, 2019, 11:39:59 pm
content: Quote from: The Soulman on August 02, 2019, 09:55:44 pmA google search reveals that this is a VERY common problem with these batteries. Something is amiss. The next time it happens, I will record the numbers and try to sneak up on the threshold.

author: soldar
author_rank: Super Contributor
timestamp: August 03, 2019, 12:45:33 am
content: I had a phone that did this. If the battery was below a certain level it would not recharge. If you "jumpstarted" it manually then the phone would charge it. I believe it was Ericsson T39.