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Basic: Trying to hookup 20v Decker lithium battery - to a 20V four wire Hoover vacuum. Same parent company.

kellys_eye

Jun 25, 2010
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The yellow and white wires coming from the PCB at points marked 'tx' and 'rx' point to some form of communication between the battery and the main device such that unless you emulate or simulate that signal the device isn't going to acknowledge its presence therefore never power up.

Maybe you can take the device out of the original battery and leave it connected?
 

HarveyCat

Nov 5, 2022
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Thanks! Unfortunately, I do not have any battery for the Hoover Vacuum. There are some people on the web that seem to use a 10k Ohm resistor to bypass this.
 

kellys_eye

Jun 25, 2010
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You could do worse than try it yourself. I'm not familiar with the batteries you refer to so can't really comment but it could be that the tx/rx designation is a deliberate ruse to make potential hackers think twice when, in actuality, the wiring might only NEED a resistor to 'prove' the correct battery is fitted - i.e. for different models using different batteries the manufacturers could fit different resistors and detect a 'wrong' battery accordingly. It's a 'cheat' by any other name but manufacturers will do anything to make you buy a different battery rather than allow you to swap them between models.

Putting a resistor across (between) the tx/rx wires won't do any harm at all.
 

HarveyCat

Nov 5, 2022
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They suggested putting it between only one of those and the negative wire.

 

kellys_eye

Jun 25, 2010
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Whatever..... sometimes you have to experiment to get the result you want!
 

HarveyCat

Nov 5, 2022
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Whatever..... sometimes you have to experiment to get the result you want!
Thanks - I will try - I ordered an assortment of resistors. Any idea if I can use 1/4W or shoukd I use something heavier 1/2W or 1W?
 
Last edited:

HarveyCat

Nov 5, 2022
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again, I am stuck - the two middle terminals read as if they are also negative terminals - but I am still mot able to get the vac to go. Here is the inside of these batteries.

i did get an assortment of resistors and tried a 10k Ohm on each of the center terminal wires run to the marked end negative terminal.

any thoughts?

38C4221F-28B9-414B-AB4E-2E89CB1B8C78.jpeg65813DC3-9C79-411F-AE36-43BFE99AF8E8.jpegE1BF94F8-5542-4A1E-842A-6C59FA260ACA.jpeg
 

HarveyCat

Nov 5, 2022
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Here is a dumb question - do I need that little circuit board? Vacuum motor runs fine if I put power right to it - can I keep just the switch and skip the board? Haha

E2BC1CD5-5E0C-4735-8D40-44531C584F9B.jpegB3B5A2E6-0100-45C6-95F6-AB9492E0E8F8.jpeg3E1F480D-3BE5-402C-B48B-5AC0B852113D.jpeg
 

kellys_eye

Jun 25, 2010
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Can you show the reverse side of the connector board (from the battery)?

The fact the the reverse of the main board contains 'oodles' of electronics makes a difference and you should have shown that initially too. Don't 'hide' anything else we get led down the wrong path.
 

HarveyCat

Nov 5, 2022
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Very sorry - not trying to hide anything - thanks for the help - I was at work without the vacuum. BTW - no charging is done by vacuum - just drain. I use a decker battery charger to charge batteries.
 

kellys_eye

Jun 25, 2010
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If all you want to do is power the motor from the different battery then simply connect the motor TO the battery via a switch. Simple 'on/off' is all you get (no power level changes) and it'll work - always assuming the motor is rated for the battery voltage of course!

If you need power control then install a variable speed controller module - many available on eBay for low voltage motors.
 

73's de Edd

Aug 21, 2015
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Sir HarveyCat . . . . . . .

What I am seeing on your last picture . . . . . is being the money shot.

On the bottom corner left is heavy RED cable that should be the 5 X 18650 battery packs + output
and the heavy BLACK cable which should be its - output.
The RED wire goes up to a power switch ? and comes out as a YELLOW wire and travels down to the board and connects to one of its pads and right between that pad and the lower pad that has the RED HOT motor wire connected to it is a white surface mount fuse F1.
Therefore you should thereby have a direct connection between the Battery + and the Motor + if the switch is turned on.
Confirm all of this with an ohmmeter and NO power connected.

Now, aspect two . . . . . .

To see if there is being a direct connection between the other battery wire, the heavy BLACK one earlier mentioned, and the path that it takes to a pad on the PCB and the other heavy black wire that connects into the motor.
If that circuit path is found open circuit, then, check the power device in a TO-220 black case, right beside them ( Pass on its ID #) to see if it has those 2 wires attached to 2 of its 3 terminals.
If so, you then have that situation of it probably being a POWER FET of a very low RDS on and in need of a weak gate turn on voltage to connect the two black wires via its Drain-Source conduction path.

On battery operated Power tools, that is being VERY VERY VERY common in their design and is used in the respect of disrupting a negative return line with one or two power FETS in order to stop operation in HEAVY overload conditions or the detection that you have finally depleted the battery charge condition, on down to its 2.5 V lower threshold of its cells.


Thaaaaaaaaaassit..

73's de Edd . . . . .

My favorite part of a marathon is watching the reaction of runners who reach out and grab one of my plastic cups of vodka.
 

HarveyCat

Nov 5, 2022
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Now, aspect two . . . . . .

To see if there is being a direct connection between the other battery wire, the heavy BLACK one earlier mentioned, and the path that it takes to a pad on the PCB and the other heavy black wire that connects into the motor.
If that circuit path is found open circuit, then, check the power device in a TO-220 black case, right beside them ( Pass on its ID #) to see if it has those 2 wires attached to 2 of its 3 terminals.
If so, you then have that situation of it probably being a POWER FET of a very low RDS on and in need of a weak gate turn on voltage to connect the two black wires via its Drain-Source conduction path.

On battery operated Power tools, that is being VERY VERY VERY common in their design and is used in the respect of disrupting a negative return line with one or two power FETS in order to stop operation in HEAVY overload conditions or the detection that you have finally depleted the battery charge condition, on down to its 2.5 V lower threshold of its

Wow - very impressive - thanks for the education. So is there some way I can bypass the PCB in that area and carry my black negative heavy wire right through - since my battery doesn't have the two extra terminals to supply what this PCB design is looking for?
 

HarveyCat

Nov 5, 2022
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If all you want to do is power the motor from the different battery then simply connect the motor TO the battery via a switch. Simple 'on/off' is all you get (no power level changes) and it'll work - always assuming the motor is rated for the battery voltage of course!

If you need power control then install a variable speed controller module - many available on eBay for low voltage motors.
Thanks again! If I go this route - am I loosing anything vital? Don't vacuums like these just run at full tilt constantly? Also if I do this should I add a fuse? And if so what type should I get?
 

kellys_eye

Jun 25, 2010
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Fuse? Yes, the controller board would normally have the current limiting circuitry but a fuse in the battery lead is a wise idea. Not sure of its rating as I'm not familiar with the motors consumption. Try a 5A fuse to begin with. If you have a test meter you can measure the UNDER LOAD current and fit a fuse that's around 50% higher than the measured value.

Most vacuums have two or even three 'speed' (suction) levels but the one I have is always used at 'full blast' anyway!
 

HarveyCat

Nov 5, 2022
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Thanks - I went for it - I ordered a fuse yo add later. Runs well - battery can get up to 185F after running a while. I will compare to my other 20v Porter Cable that uses the same batteries now.

5AAEE4E4-9DF3-437E-9B97-C63E63B7DE92.jpegA79A4B5B-138A-4D1A-BB3D-4400215C6B93.jpeg89733D3D-98AC-47C2-BFBE-778705F084FA.jpeg766C3361-146D-4C51-9F93-CD5DDBAD9A2F.jpegD019FAD7-A2C6-4B5F-99C7-C0BDC4339F35.jpeg62085BC7-2162-4E7D-BF61-262F0040B731.jpeg
 

73's de Edd

Aug 21, 2015
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Looking at the third photo down and the black vacuum orifice and then comparing it to the slotted cuts surrounding the battery . . . . surely you're loosing ~ 50 % of your suck capability with that air leak fallacy.
 
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