This guide will take you through how to open the Karcher WV2 Window Vac and repair it by replacing the internal rechargeable battery when the battery has failed and is not charging. A failed battery is one of the common causes of the Window Vac not charging and running. The tutorial is based on the yellow WV 2 model but is applicable to other Window Vac and Window Cleaner models from Kärcher 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.
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!
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). Support us by buying from Ionic Industries here
- Replacement Window Vac battery with solder tags. Support us by buying from Ionic Industries here
To start with, empty the water reservoir then unclip the blade and head assembly of the Window Vac from the main body.
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.
Unhook the back of the black plastic base cover and pull it down slightly so it partially covers the recharging socket.
Using the screwdriver unhook the 2 recessed clips in the bottom of the base cover. These are arrowed below for clarity.
Unclip the side-clips and remove the base cover.
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.
Carefully remove the side of the Window Vac, making sure you don’t pull any internal cables.
Lift out the power switch, unhooking its cable from the first clip.
Lift the suction assembly out of the remaining side of the yellow casing.
Unhook the power switch cable from the rest of its clips
Unclip the suction pipe from the motor housing. Clips are arrowed below.
There are 3 clips holding the motor housing together, arrowed below.
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.
Note the flexible seal (white) and grease around it in the piece of motor housing removed.
Carefully remove the motor and PCB assembly from the housing.
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.
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:
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.
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.
Do the same at the negative end of the battery.
Remove the battery from the PCB and put it somewhere safe where it can’t short out against anything.
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.
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. Please support us in writing these repair guides by buying your replacement battery from us at Ionic Industries here. Positive ends:
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.
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:
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.
The completed PCB:
You can now peel off the insulation tape from the motor.
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.
Loosely fit the PCB and motor to the piece of motor housing as shown.
Check that the power switch cable runs through its groove in the seal.
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.
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.
Clip the other piece of the motor housing into place, making sure the power switch cable is still in place.
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.
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.
Clip the suction pipe back onto the motor housing making sure that the clips are engaged.
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.
Fit the other half of the main body and drop the 6 screws into their holes.
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.
You now have a fully repaired Karcher Window Vac!
Plug your Window Vac into its charger for a full charge. An upgraded, higher capacity battery might take longer to recharge than the original battery but it will run for longer between charge-ups. You can also start using it before it is fully charged as this will not harm the battery.
Please tape over the terminals on your old battery to prevent short-circuits and recycle it at your local civic amenity or supermarket battery collection point.
You can leave any hints, tips and questions about how to fix your Window Vac in the comments section below.
Frequently Asked Questions
To replace the battery in your Window Vac follow our comprehensive photographic guide. We show you how to open up the Window Vac casing, remove the old battery and fit the replacement battery.
Nearly all Window Vac models are fitted with a 65mm x 18mm cylindrical Li-ion battery. These are available from us here. The WV5 model has an external, clip-on battery pack.
The model number for your Window Vac is normally marked on the body of the Window Vac behind the water tank and starts with the letters ‘WV’. Unclip the water tank to reveal the model number.