Saturday, September 28, 2013

Teardown: Black & Decker PD1200 Dustbuster Flexi partial teardown - Battery and charging circuit analyzed

Some month ago I bought a Black & Decker PD1200 Dustbuster Flexi Vacuum cleaner
The Dustbuster Flexi PD120, in all it's glory :-)
Now, the PD1200 is a nice object, useful, functional, well-working... It only has a tiny defect, I've nicknamend it "DarinFast" (a mockup english translation for the italian "ScaricoFacile")
When it was new, the battery lasted 9 minutes... now I'm not brave enough to check them again... but I know batteries are getting worse.

I would like to use it to clean my car... but 9 minutes are not enough...
So today I decided to take a look inside the PD1200, to see if I can find a way to use an external power supply (like a car cigarette lighter).

So here are some shot of a partially dismantled PD1200.
I just opened the lower part, with the battery and the charging circuit.
To open the lower part, you need to remove the 8 screw that hold it to the motor block.
After removing these 8 screws, the lower part can be opened, but it will also detach from the main motor block (so keep a eye on the parts, and don't let them fall on your feet :-) ).

Click the image to see them bigger, these are Full Res photos.

Battery and cable,
The 2 battery pack are connected in series, via the yellow cable.

 Detail of one battery pack, the black wire go straight to the motor.
The battery pack can be lifted

 Under the other battery pack you can find the charging circuit.

 Some more circuit images

 Lateral photo of the battery pack/circuit/cabling.

Here you can see the connection between the battery block and the motor block.
Kudos to the Black & Decker engineering team for using a detachable connector.

The detached motor block

The detached battery block

Now get to the interesting parts.
Here you can see a schema of the connections/wires
The first block on the left is the charging circuit, I considered it a "black box" :-)
The wire on the left are the external power connector of the PD1200.

The battery have an interesting connection scheme: the positive wire is always connected to the motor, and to the charging circuit.
The negative wire from the battery get connected to the motor only when you switch on the PD1200
When the PD1200 is switched off, the negative battery wire is connected to the negative wire from the charging circuit.
In the drawing you can see the "connector" that connect the battery block to the motor block.
And the switch (I draw it under the motor) with the 2 possible connection (1 when it's switched on, 0 when it's switched off)
 After looking at the connection scheme I've answered one of my question:
Question: Can I modify something so that the charging connector can be used even as an external power supply?
Answer: No! because the charging connector is not in any way directly connected to the battery, nor to the motor.. and the charging wire between the charging circuit and the battery are much smaller than the wire that power the motor.

So, the only way to use an external power supply is to add another connector.
It should be a connector that interrupt the negative wire from the battery when in use: this way I will be able to leave the positive wire from the new connector always connected to the motor, and still be able to use the switch to turn the engine on and off.

Now here is some photo of a corner of the battery pack, where I think I could place a new connector.

Now I know what I nee to buy to mod my PD1200... :-)

Update: The PD1200 motor is power hungry :-)
Today did some test to check the power requirement of the PD1200 motor.
I detached the battery block from the motor block, and I put a tester between the motor ant the battery, to measure the current used by the motor.
I must say that I'm surprised: the PD1200 consume up to 10A @ 12V
This mean that the PD1200 have a 120W motor.
Now I understand why the PD1200 battery drain so fast, with a discharge current of 10A no battery can last much...

The battery pack inside the PD1200 probably have a capacity around 2000 mAh, this is compatible with the measured discharge time of about 9/10 minutes.

The PD1200 consume the maximum current (10A) when the motor is running at the maximum speed, and it's sucking only air, without obstruction.
If you close the suction tube, the motor run at a higher RPM (because the air pressure get lower, so with the same power it can move faster) and also use less current: with the aspiration hole totally obstructed it require 'only' 6.5A.

Now I know that if I want to use an external power supply, it must be able to give 10A, and must use big enough cable (the cable of the tester I user to check the used current got hot in just some seconds...)


  1. Hi,
    I have the same exact item PD1200, and have the same problem as you: batteries do not last long enough!
    And it's such a nice cute compact device, it's a shame.

    Have you made any progress in using this directly connected to 220V?
    I'm not a pro so any detailed explanation is appreciated.
    Thank you in advance.

    1. I didn't made any progress...
      the fact is that the store where should I buy the power connector is exactly on the other side of the city, where I hardly go.
      Also I still have not decided if it's best to use an external power adapter, which should be able to supply 120W (12V at 10A), or try to build a mini power pack using 3 or 4 18650 battery (3 battery = 11V, 4 battery = 14V) 11V is a bit low, 14V is a bit high... maybe I could try to use a 4 battery pack with 2 diode to lower the 14V to 12.6V...

  2. Thank you for your quick reply Massimiliamo.

    I might end up getting the PAD1200, the car version of this one and use it with a tiny 220V-12V plug. It is less powerful but quite sufficient.

    For this PD1200, a battery will still be a battery at the end I think... long waiting time to charge, limited-to-minutes runtime, and the worst, it's often not immediately availabe since there's never enough charge in battery (my maim reason for trying to use a power adapter)

    It appears a 220V 12V 10A converter is quite bulky. Plus this high current and heating is another issue to consider too.
    Do you think it can safely be done? Wonder what will happen if the motor runs at full power for 30mins. (PAD1200 appears to be designed that way but I wonder about this one).

    1. The 12V @ 10A is one of the issue... I was thinking about adding to the PD1200 a connector like the one you can see there but they seem to be rated for a max current of 5A.
      But I think that small connector that can withstand a 10A current should exist, because on ebay there is no shortage of 10A power supply... ant they all seem to use small connector.
      I really need to check at the local electronics store...

  3. I like your idea of converting it to Li-ion 18650 is there enough space to fit 4 in each side ?

    1. I'm not sure if there is enough space to fit 4 18650 in each side, maybe I'll try to take some measure the next time I'll dismantle it.
      Anyway, the 18650 battery must bee of good quality, to be able to sustain heavy discharge current. During my experiment the PD1200 absorber up to 10A @ 12V so if you fit 8 18650 battery in two parallel 4 battery pack, each pack need to be able to sustain a discharge current of at least 5 A (maybe even 6 or 7A... because 4 18650 battery should top out near 15V...)
      Will it work @15V will it run faster? or will it burn?

    2. Your idea of useing 2 diodes sounds good to me but im'e not a technition.
      You can get biger Li-ion batteries Like 26650 / LifePO4 38120S 10AH put it gets expensive where as 18650 can be pulled out of old laptops, power tools ect... an easy upgrade maybe just to replace those Ni-MH with some they use in remote controle cars up to 5000 / 7000mh and you might be able to use the same charger?

    3. I don't know the technology used in the PD1200; I suppose the batteries are NiMh, but I'm not sure.
      This hypothesis come from the reasoning about how the PD1200 battery charging circuit works.
      If the PD1200 is connected to it's power supply, the battery are always charging, and them are charged with a low current (it take 12/24 hours to charge the PD1200).
      Typically the NiMh battery can be charged indefinitely if charged with a sufficiently low current (see "Trickle charging" here
      Anyway I know very little about battery charging, so I don't know if the charging circuit of PD1200 can handle bigger NiMh battery (maybe it can, ad they will probably charge very slowly.... but it may also be that it can explode)
      I don't like to do experiment with rechargeable battery, they can be dangerous (especially the Lithium battery... but you never know)

  4. Yes. Confirmed. Three 18650/2000mA mounted externally works For 15-20 minutes but ve to take them out to recharge individually as the built in changing circuit doesn't support this. enough room to house the 18650 but it just not charge up so external mount and charge is the only option. You may try higher output battery like 3400mA. Motor runs too powerful with 18650! Improvement cost is around ten quid conclusively include battery holde. Three battery and the charger bolt and nuts

    1. Good to know! I'm happy that someone have been able to give a decent runtime to the PD1200.

      Personally, I got tired and I gave away my PD1200, and bought a Dyson DC62.
      The Dyson DC62 cost a ridiculous amount of money (about 330€) but I must say it's worth it. Now I have about 17 min. of runtime, a much powerful suction, and a really efficient and easy to clean filter :-)

  5. Hi,
    Does anyone know the Ohm value of the resistor that in picture 10 is hidden by the red cable? In my PD1200 it's burned...

    Thank you

    1. Hi, I looked at some other photos I took that day.
      The cyan resistor has 5 band: Brown, Black, Black, Silver, Brown. So it should be a 1 ohm resistor, with a 1% tolerance.
      Now the question is: why it's burned? something got shorted?

    2. Thanks indeed! I will try it out as soon as possible and I'll let you know!
      Rather than shorted, overloaded by a non genuine power supply unit, capable of 5A...
      But for some minutes I've heard the motor turning like a jet fan! LOL

    3. If you plan to use an external power supply to directly run the motor, I think you need an external power connector, and connect the cable in a way to by-pass the charging circuit.
      From my measurement the motor of the PD1200 consume about 10A at 12V, but the wiring on it's standard power connector/circuitry is thought just for battery charging with way lower current (I think the battery charge at about 0.2A). This connector/circuitry can't handle the 10 A you need to run the motor.
      I must also say that it's pretty hard to find a power connector rated to handle 10A (I was looking for it time ago, but I didn't find it)

  6. Hello,
    My power supply stop working and I was thinking about using a 12v 1A power supply instead, but after reading the above post...
    Will a 12v 1A power supply be safe to use?

    1. I don't have any-more the PD1200, so I can't check.
      Maybe a 12v 1A power supply could work for battery charging.
      Power supply sometime are "regulated", sometime are not. I don't know if the original one was regulated.
      IF the original one was regulated, you need a new regulated power supply (a "not regulated" would probably burn/break something)
      But the fact is that you ideally need a power supply identical to the original one.

      Maybe you can take the original, broken, power supply to some electronics shop, they should be able to give you a proper compatible power supply.

  7. The Nicad battery leak all over, thinking of connecting directly to the car battery with some clamps to clean the car. no problem with 12v @ 10A

  8. Update - Finally had converted the dust buster to use the 12v ciggy lighter. Put in a 10A fuse for safety measure as well. Connect red and black cable, left the yellow alone. Word of advise, try not to run the vac for too long as it might heat up the stock wiring in the car.

  9. You can buy 'C'sized batteries with tags and make up your own battery pack with a MUCH more powerful set of batteries - here is a UK shop...

    1. Maybe, but:
      *) the battery charger probably won't be able to properly charge a different battery pack
      *) It's not easy to find batteries that can withstand a discharge rate of 10A

  10. I need a new charger for my PC1200-XE. I happened to have another charger lying about (Output 12V, 4A), but it doesnt seem to charge the dustbuster. The batteries have a little charge left in them, and when I connect the charger, the blue light come on, but fades within a couple of minutes, and it doesnt seem to charge at all. I can't seem to locate a replacement charger, so I was hoping to get some advice on the appropriate amperage needed, which I cannot find any information from the B&D website. Any suggestions welcome.

    1. If the original charger is broken, and the new charger have the same specification (volts, ampere, connection scheme) it should just work.
      If it doesn't works, probably there is some difference somewhere?
      Is the wiring of the connector right?
      If the original charger really broken? maybe the problem lie elsewhere...

  11. I know nobody's posted here for a while, but I've had my PD1200 in the cupboard for 2 years, never used because 8mins use for a full charge is useless.

    I'm going to get a 12v 10a mains supply, tap into the existing charging jack, remove the battery pack & charging unit completely, rewire the switch so that its fully mains powered only.

    I don't see any problem with this, other than making sure that the wires used are the 'thicker gage' wires from the motor. for added protection a RCD plug can be fitted to the mains plug, to protect from shorts.

    obviously the clever engineers at B&D never intended the motor for extended use, so I suspect the life of the motor will probably reduce significantly. BUT.... beats gathering dust in the cupboard.

    tools required;
    solder iron, wire (thicker the better), ball of steel switching it on for the first time once done....

    any thoughts?