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Introduction

Use this guide to replace the battery in a Dyson DC35 cordless vacuum when it won't run, won't charge, or the green charge light doesn't come on. The battery stores power for the motor and may also be called the battery pack or rechargeable battery. Similar Dyson cordless models, including the DC31, DC34, DC44, and DC45, use a similar battery removal process, but always match the replacement battery to the battery already installed.

What you need

Step 1 Check the symptoms and prepare safely

Pull the trigger and check whether the vacuum runs.
A dead battery commonly causes no response from the trigger and no green charge light.
Disconnect the charger and remove the vacuum from the charging area before working on it.
Don't open, puncture, crush, heat, or cut into the battery pack.
If the battery is swollen, hot, leaking, or damaged, stop and keep it away from flammable materials.

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Step 2 Open the vacuum body

Press the top lever to release the front assembly.
Separate the vacuum into two pieces.
Pull the air filter out of the front of the vacuum.
Let a washed filter dry completely before reinstalling it, as moisture can damage the motor.

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Step 3 Remove the battery screws

Use a Phillips screwdriver to remove the front battery screw from the opening near the filter.
Use a Phillips screwdriver to remove the rear battery screw from the back of the handle.
Keep the screws separate, as the longer screw goes in the rear hole during reassembly.

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Step 4 Remove and identify the battery

Slide the battery out through the bottom of the handle.
Identify the old battery style before ordering or installing a replacement.
Choose a Type B battery if the old battery has a tab on top.
Choose a Type A battery if the old battery has no tab on top.
DC31, DC34, DC35, DC44, and DC45 models may look similar, so match the replacement to the removed battery.

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Step 5 Install the replacement battery

Insert the matching replacement battery up through the bottom of the handle.
Push the battery in until it sits flush in the handle and the screw holes align.
If the battery doesn't seat correctly, remove it and recheck whether the vacuum needs a type A or Type B battery.

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Step 6 Reinstall the battery screws

Insert the longer screw into the rear hole and tighten it with a Phillips screwdriver.
Place the front screw into the front hole near the filter opening.
Use needle nose pliers to start the front screw if it is hard to hold in position.
Tighten the front screw with a Phillips screwdriver until it is seated.
Don't over-tighten the screws, as the plastic housing can strip or crack.

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Step 7 Reassemble and test the vacuum

Reinsert the air filter with its small tab facing up.
Seat the lower end of the front assembly into the main body.
Press the top of the assembly together until it clicks into place.
Pull the trigger to confirm the vacuum runs.
Place the vacuum on the charger and check that the green charge light comes on.

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Step 8 Handle the old battery and troubleshoot

Recycle the old battery as lithium-ion e-waste according to local rules.
Don't cut the wires or open the battery case, as the cells and circuit board are soldered inside.
If the vacuum still won't run or the green charge light still won't come on, remove and reseat the replacement battery.
Confirm that the replacement battery matches the old type A or Type B battery.
If the problem remains, stop using the vacuum until the battery and charging system can be checked.

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Conclusion

After installing a new battery, charge it to 100%, and keep charging it for at least two more hours. Use the vacuum until it shuts off because of a low battery, then charge it uninterrupted to 100%.

Charge the new battery fully before regular use, and keep the filter clean and dry for best vacuum performance. Take your e-waste to an R2 or e-Stewards certified recycler. Repair didn't go as planned? Ask our Answers community for help.

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