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Author Topic: Repair lithium ion Vacuum  (Read 1852 times)

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Offline connectTekTopic starter

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Repair lithium ion Vacuum
« on: May 07, 2020, 01:42:10 pm »
Trying to repair my parents Hoover Stick vacuum.
It has 6 x 18650 li ion cells, yet the charger only outputs 21.6v, wtf!.
The unit never charges fully from day one.
I have charge on test bench to 25.2 v, (4.2v x 6).
Why would they supply a charger
That would only charge each cell to 3.6v ( 21.6 ).
Can some one help me with this problem.
Cheers.
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Online Miti

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Re: Repair lithium ion Vacuum
« Reply #1 on: May 08, 2020, 08:12:22 am »
Are you sure it is Li-Ion? Li-Fe only changes to 3.65V max. Pictures of the battery pack?
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Offline Kilrah

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Re: Repair lithium ion Vacuum
« Reply #2 on: May 08, 2020, 10:40:13 am »
Yup, sounds like LiFe. 3.6 for Li-ion would be almost empty.
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Offline connectTekTopic starter

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Re: Repair lithium ion Vacuum
« Reply #3 on: May 08, 2020, 12:04:01 pm »
Definitely Li ion.
Hoover 5221.
I have bench charged each cell to 4.2v.
At 3.6v they are flat,
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Offline connectTekTopic starter

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Re: Repair lithium ion Vacuum
« Reply #4 on: May 08, 2020, 12:16:12 pm »
A Pic
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Offline xavier60

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Re: Repair lithium ion Vacuum
« Reply #5 on: May 08, 2020, 12:27:43 pm »
That's really odd. I just had a look at my Dyson DC59.  It's charger is specified as 26.1V for 6 cells. It measures 26.12V unloaded.
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Online Miti

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Re: Repair lithium ion Vacuum
« Reply #6 on: May 08, 2020, 12:32:44 pm »
Yeap, that’s weird. I wouldn’t expect to change to 4.2V for safety and extending the life time, but 3.6?
How did you measure the charger voltage? Measure the battery when the charger shows full.
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Offline xavier60

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Re: Repair lithium ion Vacuum
« Reply #7 on: May 08, 2020, 12:40:47 pm »
I see on ebay they describe the Hover battery as "22.2V-21.6V".
I don't know about the 22.2V but 21.6V is the nominal voltage for 6x Li-ion cells witch is 3.6V per cell.
Maybe the charger just happens to be set to 21.6V and the charge circuitry in the battery pack is supposed to boost it to a higher voltage.

https://www.ebay.com.au/itm/Battery-Pack-For-Hoover-22-2V-21-6V-Ultra-Light-5221-Vacuum-Cleaner-5221BP-AU-/264409929485
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HP 54645A dso, Fluke 87V dmm,  Agilent U8002A psu,  FY6600 function gen,  Brymen BM857S, HAKKO FM-204, New! HAKKO FX-971.
 

Offline xavier60

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Re: Repair lithium ion Vacuum
« Reply #8 on: May 08, 2020, 01:38:20 pm »
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Offline connectTekTopic starter

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Re: Repair lithium ion Vacuum
« Reply #9 on: May 08, 2020, 01:54:06 pm »
Charger says 21.6v, I measured 21.9v.
As I said before, at 3.6v per cell the battery is almost flat.
I have input 25.2v from bench power supply and it charges
fine.
Weird.
Looks like a major design failure as I have read that many people
have replaced batteries, mmmmm I wonder why?
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Offline xavier60

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Re: Repair lithium ion Vacuum
« Reply #10 on: May 08, 2020, 02:05:08 pm »
Maybe the charger's manufacturer made a mistake, setting the voltage to the marked nominal voltage instead of to the proper charge voltage.
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HP 54645A dso, Fluke 87V dmm,  Agilent U8002A psu,  FY6600 function gen,  Brymen BM857S, HAKKO FM-204, New! HAKKO FX-971.
 

Online Miti

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Re: Repair lithium ion Vacuum
« Reply #11 on: May 09, 2020, 03:11:02 am »
Yes, nominal is one, fully charged is something else.
Can the charger be adjusted?
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Offline connectTekTopic starter

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Re: Repair lithium ion Vacuum
« Reply #12 on: May 09, 2020, 05:10:23 pm »
No, it's just a plug pack 21.6v
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