Karcher Window Vac Battery Replacement Guide

This guide will take you through how to open the Karcher WV2 Window Vac and repair it by replacing the internal rechargeable battery. The tutorial is based on the yellow WV 2 model but is applicable to other Window Vac and Window Cleaner models from Kรคrcher including the WV 50, WV 55, WV 60, WV 70 and the Plus, Premium, White and Classic variants. The model number of your Karcher is marked on the body of the Window Vac, usually behind the water collection reservoir.

The basic method is:

  • Open and dismantle the Window Vac
  • De-solder the old rechargeable battery
  • Solder in the replacement battery
  • Reassemble the Window Vac

This is documented in detail below along with lots of pictures. Click on any picture to enlarge it.

karcher-window-vac-wv2-repair

Disclaimer

Any damage to yourself, your device or anything else is entirely your responsibility. This guide is for professional, educational purposes only and is offered without guarantee or liability.

Warning: Lithium-ion batteries are volatile and if shorted or overheated they will go into thermal runaway and ignite creating a severe burn hazard. Do not short-circuit, disassemble, crush or expose contents to water. Lithium reacts violently in water like Sodium and Potassium did in those science experiments at school!

Video

We have also created a short video from this guide to Karcher Window Vac WV2 Battery Replacement on our YouTube channel, which you can also watch below.

Tools / Parts / Equipment

  • Karcher WV2 Window Vac
  • Compatible charger
  • Soldering iron: Electronics grade (about 18-25 watt) with chisel tip
  • Solder: Lead-free silver solder is great for this
  • Solder sucker (also known as a desoldering pump) and/or desoldering braid
  • Small flat-bladed screwdriver: 2 to 3mm wide
  • Large flat-bladed screwdriver: 5 to 6mm wide
  • Electrical insulation tape
  • Craft knife
  • Torx T-8 screwdriver (star-shaped bit). Available online via Ionic Industries here
  • Replacement battery with solder tags. Available online via Ionic Industries here

How-To

To start with, empty the water reservoir then unclip the blade and head assembly of the Window Vac from the main body.

karcher-window-vac-wv-2-blade-removed-repair-50-60-70

Unclip the reservoir. You can see your Window Vac model number and other details on the body. This is a WV 2 model made in 2016.

karcher-window-vac-wv-2-reservoir-removed karcher-window-vac-wv2-serial-date-code

Unhook the back of the black plastic base cover and pull it down slightly so it partially covers the recharging socket.

karcher-window-vac-wv-2-remove-base-cover-1 karcher-window-vac-wv2-remove-base-plate-2

Using the screwdriver unhook the 2 recessed clips in the bottom of the base cover. These are arrowed below for clarity.

karcher-window-vac-wv-2-remove-base-plate-clips karcher-window-vac-wv-2-base-plate-cover-unclip-3

Unclip the side-clips and remove the base cover.

karcher-window-vac-wv-2-base-plate-cover-unclip-sides karcher-window-vac-wv-2-base-plate-cover-unclip-side karcher-window-vac-wv-2-base-plate-cover-removed-50

Using a Torx screwdriver of the correct size (T-8 size, available online via Ionic Industries here) remove the 6 screws from the side of the Window Vac.

karcher-window-vac-wv2-remove-6-torx-screws karcher-window-vac-wv2-casing-torx-screws

Carefully remove the side of the Window Vac, making sure you don’t pull any internal cables.

karcher-window-vac-wv-2-how-to-open-cleaner-50-60-70

Lift out the power switch, unhooking its cable from the first clip.

karcher-window-vac-wv2-power-switch-remove

Lift the suction assembly out of the remaining side of the yellow casing.

karcher-window-vac-wv2-suction-assembly-remove

Unhook the power switch cable from the rest of its clips

karcher-window-vac-wv2-unclip-power-cable

Unclip the suction pipe from the motor housing. Clips are arrowed below.

karcher-window-vac-wv2-suction-pipe-remove

There are 3 clips holding the motor housing together, arrowed below.

karcher-window-vac-wv2-motor-housing-clips

Release the clips and carefully remove the side of the motor housing, making sure you don’t pull any internal cables. Try to leave all the internal parts in the remaining piece of the housing.

karcher-window-vac-wv2-motor-housing-open

Note the flexible seal (white) and grease around it in the piece of motor housing removed.

karcher-window-vac-wv2-motor-housing-seal

Carefully remove the motor and PCB assembly from the housing.

karcher-window-vac-wv2-battery-motor-removed

Check that the impeller blades on the end of the motor can spin freely. If the motor is seized or stiff this could be the cause of the fault so apply a drop of light oil (not WD-40) to each end of the shaft, arrowed below.

karcher-window-vac-wv2-oil-stiff-motor karcher-window-vac-wv2-oil-seized-motor

Note the 2 ends of the battery. This is a 3.7V Lithium-ion cell with 6mm wide solder tags welded to each end. Positive end:

karcher-window-vac-wv-2-battery-positive-solder-tab-70

Negative end:

karcher-window-vac-wv2-battery-negative-tag

Time to get your soldering iron warmed up now! While you’re waiting cover the metal can of the motor with insulating tape to stop it touching and shorting out the PCB components during the following steps. Also fold a piece over the tip of a large flat-bladed screwdriver.

karcher-window-vac-wv2-motor-tapekarcher-window-vac-wv2-battery-pcb

Starting at the positive end of the battery, heat up the solder joint on the PCB while simultaneously prying the battery away from the PCB with the large screwdriver. Lift it clear by a few millimetres.

karcher-window-vac-wv2-battery-removal-pos-1 karcher-window-vac-wv-2-battery-removal-plus-2 karcher-window-vac-wv-2-battery-removal-pos-3

Do the same at the negative end of the battery.

karcher-window-vac-wv-2-battery-removal-neg-60

Remove the battery from the PCB and put it somewhere safe where it can’t short out against anything.

karcher-window-vac-wv-2-battery-removed-1

Using the soldering iron and a desoldering pump, desoldering braid or craft knife clean up the PCB slots so they are clear and ready to accept the replacement battery.

karcher-window-vac-wv2-battery-pcb-hole-plus karcher-window-vac-wv2-battery-pcb-hole-negative

Compare the original battery (on the left) with its replacement (on the right.) This replacement has 5mm wide tags which will fit more easily through the holes in the PCB and is available online via ionic Industries here. Positive ends:

karcher-window-vac-wv2-battery-replacement-positive

Negative ends:

karcher-window-vac-cleaner-wv-2-battery-replacement-negative-75

Straighten the solder tags on the new battery and test-fit it to the PCB. Observe correct polarity! The positive end of the battery has a groove around the outside.
Make sure you fit the battery to the correct side of the PCB. It goes on the same side as the other components. Use some folded pieces of paper or some thin card to keep the battery slightly clear of the PCB and other components.

karcher-window-vac-wv2-fit-new-battery-replacement-positive karcher-window-vac-wv-2-fit-new-battery-replacement-negative

Trim the solder tags to length with some sharp scissors and then solder the battery in place. Make sure you solder all the way round the slots. Positive terminal:

karcher-window-vac-wv2-solder-new-replacement-battery-positive-2 karcher-window-vac-wv-2-solder-new-replacement-battery-plus-50-1

Negative terminal:

karcher-window-vac-wv2-solder-new-replacement-battery-negative-2 karcher-window-vac-wv-2-solder-new-replacement-battery-negative-1

The PCB has tracks on both sides so also solder the outer surface of the solder tags to the PCB on the component side of the board.

karcher-window-vac-wv-2-solder-new-replacement-battery-positive-70 karcher-window-vac-wv-2-solder-new-replacement-battery-negative-3

The completed PCB:

karcher-window-vac-wv-2-solder-new-replacement-battery-75

You can now peel off the insulation tape from the motor.

karcher-window-vac-wv-2-repair-replacement-battery-50

The new battery will have some charge in it so if you like you can test the new battery by holding the motor by its metal can so the impeller is clear of obstruction and then pressing the power switch.

The first step in reassembly is to make sure the power switch cable is still clipped in place to the top of the charging socket.

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Loosely fit the PCB and motor to the piece of motor housing as shown.

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Check that the power switch cable runs through its groove in the seal.

karcher-window-vac-wv-2-motor-cable-slot-60

Check that the charging socket is positioned between the two clips, arrowed below, and press it home making sure the battery is in its cavity.

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Check that both ends of the motor are lined up in the grooves and that the mini-PCB on the back of the motor is level and around the clips, arrowed below.

karcher-window-vac-wv-2-motor-front-aligned-50 karcher-window-vac-wv-2-motor-rear-aligned-55

Clip the other piece of the motor housing into place, making sure the power switch cable is still in place.

karcher-window-vac-wv-2-motor-housing-closed-75

Make sure all 3 clips are fastened. There might be a gap between the two halves of the motor housing near the charging socket and power switch cable. This is normal and will be closed up when the Window Vac is fully assembled.

karcher-window-vac-wv-2-motor-housing-clips-60 karcher-window-vac-wv-2-motor-housing-gap-70

Keeping your hands clear of the impeller blades, hold the motor housing and press the power switch to turn on the unit and check it runs without rubbing. If it rubs check the alignment of the motor inside the housing. If it does not run check your soldering and the battery polarity.

karcher-window-vac-wv2-premium-motor-running

Clip the suction pipe back onto the motor housing making sure that the clips are engaged.

karcher-window-vac-wv2-unclip-power-cable

Place the assembly back in the main body and carefully push the power switch back into place, then starting at the switch end re-fit the cable into its clips.

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Fit the other half of the main body and drop the 6 screws into their holes.

karcher-window-vac-wv2-remove-6-torx-screws

With the Torx screwdriver first turn the screws anti-clockwise until they click. This will avoid cross-threading them. Then tighten the screws clockwise until they’re snug.

Starting at the furthest edge from the charging socket, clip the black base cover back onto the Window Vac and then re-fit the water reservoir and blade assembly.

karcher-window-vac-wv-2-blade-removed-repair-50-60-70karcher-window-vac-wv2-repair

You now have a fully repaired Karcher Window Vac! Please leave any tips, comments and questions about how to fix your Window Vac below.

38 thoughts on “Karcher Window Vac Battery Replacement Guide

  1. This must be one of the best ‘how to’ guides on YouTube! VERY clear instructions and pictures. Unfortunately, the fault on my Karcher appears to be in the PCB itself…

    1. Thanks Peter! Try checking the PCB for water damage. If a track is damaged you might be able to bypass it by soldering a wire in place.

  2. This guide to replacing the rechargeable battery on the Karcher WV2 is really well done. Thank you, ionic. But what a daunting, intricate job it is just to replace a battery. The device is really useful but if one has to go through this kerfuffle every time the battery fails, does it not suggest a very poor design?

    1. It suggests that it’s not designed to be repaired, but for the Karcher to be thrown away and a whole new one bought!

  3. Wow, Amazing tutorial! Very detailed and very good pictures. Thank you Ionic! I’ve managed to open the motor housing and I’ve found traces of a huge flood: very much rust on the metal parts, contacts and motor body. But the wheel (and motor) is spinning freely. My window vac is not charging anymore, no led indicator. I suspect that the water burn some electronics on the PCB, but the battery is looking good (besides the rust on the tags). I have 2 variants: (a) either replace the PCB, or (b) either try to bypass the PCB by soldering/tightening 2 wires on the battery, trying to charge it (I have the charging station from Kaercher for WV5 window vac). Can you help me telling for (a) where can I found a replacement for PCB (and the model/code)? The (b) variant is feasible? Will it work the assembly once the battery is charged? Thank you

    1. Hi Max, glad the tutorial was helpful!
      (a) Unfortunately I don’t know where to get a replacement WindowVac PCB, maybe from another Window Vac that has a dead battery?
      (b) Do not connect the charger directly to the lithium-ion cell. There is important battery management circuitry on the PCB that must be connected between the charger and the cell to stop it from over-charging.
      Sorry I can’t be more help ๐Ÿ™‚

      1. Thank you for info. Regarding b) I’ve mentioned that I already have the charging station from Kaercher for WV5 window vac and I think this device contain the necessary electronics for (balance?) charging the li-ion batteries. Actually, it has two ports where I can charge simultaneously both the battery inside the vac and another replaceable battery (provided by Kaercher). I can provide some pictures (of the charger and the battery if I may, but also you can find them on the net. My question is about the third connector of the charger: what is its role? A ground connector or is a connector for charging the cells inside the battery? Does the battery has multiple cells?

        1. Regarding the removable WV5 battery, it looks like the third connector pin is possibly for a temperature sensor. There might also be battery management circuitry inside the plastic casing of the WV5 battery. It looks like it is a single cell inside the casing as it’s rated at 3.7V.

  4. Excellent tutorial. Unfortunately for me I think it’s not my battery but the on/off switch. After several attempts the VW2 switched on but then wouldn’t switch off until the battery was discharged. Do you have a similar tutorial for switch replacement and where can I buy one?

    1. Unless Karcher can supply a replacement switch for your WindowVac you’d have to fit a generic waterproof switch instead ๐Ÿ™

      1. What’s a generic switch mate and what does it look like?

        1. I’m not sure if your WindowVac has a momentary or latching switch. You can get a waterproof equivalent from Maplin, RS Components or CPC. You will need to drill a hole for it somewhere suitable in the WindowVac casing and wire it up correctly. If your original switch lights up you probably don’t need that function in the new switch.

    2. I have a similar fault on my wv1 won’t switch off. Not the switch. Just bridge the two contacts with say a screwdriver to prove it’s ok. Sure you will find a replacement if required https://www.ebay.co.uk/itm/Momentary-Tactile-Switch-SPST-Push-Button-Miniature-Micro-PCB-Mounted/251356012322

  5. Can any 1 help please my karcher light is on when charger is in but when take it out it goes off is that just a new battery I need please help some 1

    1. What model of WindowVac do you have? And does the motor run at all after charging for a few hours?

  6. I put a 3.7v Ultrafire fully charged in it and the red light flashes, it briefly starts then turns off. Anyone know why?
    Maybe the battery I’m using isn’t lithium, would that matter?
    There are no markings on the Ultrafire for mAh as it rubbed off. If it is not 2100mAh like the original would that prevent it working?
    If I put a working Karcher battery into the unit it powers on fine.

    Any ideas why this isn’t working?
    Can I use a 3.7v cell out of a laptop battery?

    1. Ultrafire batteries are infamous for being unreliable. Use a good quality Samsung/Sanyo/Sony/LG cell with the solder tags pre-welded in place. Follow the link on our shop page for a suitable replacement.

  7. Just wanted to add that I used your superb tutorial to lead me to the non working internals for a repair.

    My very common symptom was a green light flashing when switched on but no suck. Suspecting a seized motor I nearly gave up as the fan spun nicely. Couldn’t figure it till I held part rusty motor in my hand and when I switched it on and felt a tiny kick, so I then knew fault was inside the motor.
    When i pulled the fan off I realised that the fan had spun freely sure enough – but the motor didn’t. Minor seize up. (Best part was someone else before me had got that far, but gave up).
    Freed the motor – couple of drops of machine oil and some super-glue for the blade and re-assemble.

    WHY dont you do a seized motor tutorial (and point out my near miss ๐Ÿ™‚ )

    A lot of peeps will like you for it, and you might recommend that they replace the battery (that you will be happy to supply) at the same time as that would be good practice. ๐Ÿ™‚

    1. same green light- but alas free motor.
      Green light only flashes when switched on – not when off with charger connected.
      Have checked charger voltage – OK. Bat voltage circa 3.09 – should be 3.3.
      Does this sound conclusive need new bat?

      1. The battery voltage when fully charged, measured at the battery terminals, should be just over 4 volts (4.2V maximum.)

  8. This link:
    This replacement has 5mm wide tags which will fit more easily through the holes in the PCB and is available online here.
    Takes you to this battery:
    Karcher Replacement Battery Window Vacuum VAC Cleaner VW60 VW70 VW75 PLUS Li-Ion
    I want a battery the same as what your article and video is about – a VW2

    Any ideas?

    1. It’s a suitable replacement. V W is just a typo of W V. The battery listed is suitable – you can always contact the seller to make sure, stating your Window Vac model.

  9. Hello, I am looking for an SOT-23 semiconductor for the windows vac. It is located near by the charging socket. Do you have some good hi-res pictures of this pcb area to check which part is needed?

    1. Sorry, we have no photos of those components. Is the transistor burnt out? It could be similar specification to the other transistors on the PCB.

  10. Thank you! I have to try this! Just one problem – how to get a battery shipped to Sweden. Anyone who knowยดs another shop to buy them from? Shipping to Sweden.

    1. Hi Lena, this eBay seller offers Karcher batteries with shipping to Sweden and various other countries. Hope that helps!

  11. Thank you for the clearest guide on the internet to this particular problem. I’m sure that you could have an alternative career as a technical writer. We have to rebel against our throw-away society.

  12. Excellent tutorial, battery replacement done in 30 min. As an engineer I must say that the design must be done by purpose and make anyone to just buy a new unit. shame on the designers ๐Ÿ™

  13. Totally agree with Paul on the poor design. I stripped my WV2 before finding this site. What voltage is the motor? as my PCB is knacked (led light flashes all the time but no motor due to water damage) although charging now after clean up( checking that voltage does’t rise above 4.2V). Will do a botch job if voltage is same as battery.
    When fitting both sides of the motor enclosure together would it be a good idea the smear Vaseline on the joints to try and stop the designed water leaks?

    1. The motor is probably rated at 4.5V or 5V. Good idea to use vaseline, silicone grease or even silicone sealant around the joints of the enclosure.

  14. Thanks to your posts I was able to repair my wv2, it was just a sticky motor. John in cyprus

  15. We have a 4 year old Karcher WV2. A week ago it stopped working and with your excellent guide I stripped the unit. It looked as good as new and there had been no water leakage into the motor/pcb area. Some very light oil on the motor bearings and a couple flicks of the impeller and it was working fine again.
    Luck didn’t last long! Today it is completely dead and with no lights. The charger has a healthy 5.9v output when measured on the pcb. The WV2 has the 3.65v battery. Voltage across the switch is 1.3v and there is only 1.3v across the battery with, and without, the charger connected.
    Clearly the battery will not charge sufficiently with only 1.3v input so I am reluctant to buy another battery. I would have expected a gradual decline with an old battery, getting slower & slower as the charge & voltage dropped, not OK yesterday & dead today.
    Do you have any ideas or things I could try, or measure, in order to fix the vac please?

    1. Hi Mark,
      A healthy Li-ion battery will not have a voltage below 2.4V, even under load. If the battery is measuring 1.3V when not in use then it is faulty ๐Ÿ™

  16. Dear Sirs,
    Thanks for your quick reply and I agree with you that 1.3v when resting would be no good.
    Regardless of whether the charger is ON or OFF, the battery voltage remains the same at 1.3v.
    I would have expected the voltage across the battery to rise when the charger is ON, so could this indicate a fault within the pcb circuitry? Would it not need a charging voltage of 2v or so to charge sufficiently to rest at 1.3v?
    Also, I’m only getting 1.3v across the switch with charger both on and off.
    Do you know of any simple test that I can do to confirm whether the pcb is charging correctly or not – other than by fitting a new battery please? Any help you can offer would be most welcome. Thanks again, Mark.

    1. If the Li-ion battery is reading less than 2.4V when disconnected then it is probably no good. Other than fitting another battery I don’t think there is a safe/reliable way to test the charging circuitry.

      1. Dear Sirs,
        Do any of your site’s contributors / writers have any knowledge regarding open circuit voltage, will the pcb/charging circuit be damaged without having a battery connected?
        My thoughts are if it is safe to do this, we would get the voltage available to charge ie 4 – 5v. This would then prove the pcb and point to the battery being at fault – possibly a short circuit within its pack that could then pull the voltage down to the 1.3v I mentioned. What do you think of this plan, it all depends on doing a safe open circuit test ???
        Anyone knowledgeable out there please?
        There must be scores of other people trying to prove a pcb vs battery fault.
        Thanks again, Mark.

        1. Spoke to an electronics friend of mine and he said it should be OK to desolder the battery for an open circuit voltage test as the charging current is low.
          I removed the battery and found the pcb voltage to be much too low ie 0.9v.
          The circuit board is therefore faulty so condemning the vacuum.
          Will keep the battery though as this should be OK for any future use.

          Hope this will be of help to others.
          Mark.

          1. Thanks for the tip Mark!

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