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First repair project
#1
Hi Everyone,
I hope this is the correct section for this post...

I'm new to the scene and looking for some guidance on my first "repair project".
We have a li-ion pack for our hoover linx vacuum that will not charge in its base. Before we recycle it, i came across info to potentially revive it.

As it sits, when i use the DMM on it, i get 0.63v - its a 18v 36 Wh unit.
From my research it may be too weak for the charger to detect and start charging, so some suggested jump starting with a high voltage unit to get it up to 4v-ish.
So, i pulled out an old 24v NiCd battery and hooked it up in parallel for ~30 min, came back and it really didn't change the stats when metered.

Any thoughts or next steps to try?

thanks!
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#2
How did you do that? By shorting the packs together? That can basically destroy both packs instead...

You need a regulated voltage source and if you have built in BMS or protection in the battery you need to bypass it and charge each cell yet alone instead. Il post a video tonight about how to do that.
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#3
You'll need to open the hoover linx pack & measure the voltage of each cell.
Also please let us know if it has a circuit board (a BMS) inside.
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#4
Reviving a battery "externally" will hardly work if it has issues. If it's showing 0.63V and won't charge then there is obviously something wrong and it won't be solved by connecting another battery in parallel. That probably did nothing anyway because of the BMS that is usually integrated in these devices/batteries.

You have to take it apart and find out what the problem is so that you can actually solve the problem rather then mitigating the symptoms.
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#5
sounds good guys, i'm learning!
ok just opened, yup theres a board, with 5 samsung 18650 cells
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#6
Measure the voltage across each individual cell to find out if there are issues with the cells. If they are healthy it could be a BMS issue.
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#7
(08-10-2018, 09:29 AM)DarkRaven Wrote: Measure the voltage across each individual cell to find out if there are issues with the cells. If they are healthy it could be a BMS issue.

each cell is 0.4 v
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#8
Sounds to me like the battery sat for a long time without any use and the bms slowly discharged the battery. Once the battery gets below a certain voltage, 2 things happen. 1) the bms won't allow you to charge 2) the bms "can't" allow you to charge because it can't open the FETs.

I would say put a hobby charger on them with the balance leads and let it charge up. If you don't have one of those and have a TP4056 or other single cell charger, connect and charge each parallel group with the charger individually (or with separate chargers; don't use an opus and wire in with alligator clips all 4s, you might blow the opus up) as they need to be electrically isolated. I would go with the single charging of each cell.
You only need to charge them up to about 2.5V each for the bms to kick on. You may find there is nothing wrong with the pack at all.

If after charging them up and the pack voltage is at least about 8+V and the bms still doesn't activate, it might have an internal kill switch that once it's flipped, can't be flipped back. If that's the case, you'd need to get a new bms board as these are not easy to tap into and reprogram.
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#9
(08-11-2018, 12:12 AM)Korishan Wrote: Sounds to me like the battery sat for a long time without any use and the bms slowly discharged the battery. Once the battery gets below a certain voltage, 2 things happen. 1) the bms won't allow you to charge 2) the bms "can't" allow you to charge because it can't open the FETs.

I would say put a hobby charger on them with the balance leads and let it charge up. If you don't have one of those and have a TP4056 or other single cell charger, connect and charge each parallel group with the charger individually (or with separate chargers; don't use an opus and wire in with alligator clips all 4s, you might blow the opus up) as they need to be electrically isolated. I would go with the single charging of each cell.
You only need to charge them up to about 2.5V each for the bms to kick on. You may find there is nothing wrong with the pack at all.

If after charging them up and the pack voltage is at least about 8+V and the bms still doesn't activate, it might have an internal kill switch that once it's flipped, can't be flipped back. If that's the case, you'd need to get a new bms board as these are not easy to tap into and reprogram.

Thank you for the response, i appreciate it. The voltage being too low is what i read as well elsewhere, hence trying to bring it up via hooking it to a high power source in parallel. However, as mentioned, it did nothing; and even could have caused damage as per another member.

Since i'm literally a newbie to a lot of this and wanting to be safe, i'll have to research what you said to ensure i understand Smile

Would i have to remove each cell from the block to charge? 
There's foam on each side terminal side, so i'll have to remove it and see if the cells are easily removable.

I don't have any charges yet, other then the typical DC vehicle charges and AA/AAA Mi-MH chargers.
From what I've read so far, i'm thinking of getting a IMAX B6 charger, which is what i believe you refer to as a hobby charger.
I found one on amazon Canada for ~50 CAD shipped, with decent reviews.
Not sure if i can post links, but its desc is "lemonbest New Universal iMAX B6-AC B6AC Lipo NiMH 3S RC Battery Balance Charger"

Again thanks, and any info/direction on a good beginner kit would be appreciated.
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#10
No, you do not have to dis assemble the pack to charge each parallel set. You will however have to find a way to attach the charge to them. If required I can post some photos of an example. However, please post a photo of the inside of your pack, so I can illustrate for you.

The IMAX B6 you are looking at is most likely a clone. There are many good clones out there, and also many bad ones. It depends on how serious you are. You will never regret buying a decent charger. However an iCharger and power supply will cost quite a penny. I can recommend many budget options.

I own many cheap chargers, they are good, but you must understand that they all do have shortcomings. I recently bought a Charsoon Antimatter off Aliexpress. It is most excellent. Not quite an iCharger, but definitely close.

Owning a decent multi chemistry (aka RC charger) is incredibly handy, they can charge virtually anything. In the case of reviving dead LiIon batteries, they are perfect. I use the NiMh charge, at about 50ma per cell to 'awaken the dead'. However, you do want to keep a careful eye. Make sure noting gets hot, and always prepare for the worst.
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