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iRobot Roomba battery not charging
Stefan Meyer and 3 other contributors
Last updated on Sep 2, 2026
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Community-Contributed Guide
An awesome member of our community made this guide. It was not created by iFixit staff.
Introduction
Go to step 1 ↓Is your Roomba no longer charging?
If the battery isn't the problem, the transistor shown is likely to blame. While replacement charging stations don't cost much, the transistor only costs a few cents.
Replacement: BDP948 ... available everywhere
Video Overview
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On this device, the replacement battery is quite new.
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The charging dock is flashing green.
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Check if the Roomba charges with a bench power supply:
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You need 19.4 V DC at about 1.25 A. Pay attention to the correct connection of the + and - socket.
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When connecting, the voltage drops to 13.6 V - the voltage of the battery - and the maximum charging current of about 600 mA flows. This is proof that the power supply is charging, but the charging dock is no longer doing so.
Ask FixBot
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Disassemble the charging dock until you can access the circuit boards. One of these is the switching power supply, and one controls the charging process.
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Switching power supply
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Charging board
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One of the transistors on the charging board is significantly discolored; this is likely the cause. You can desolder it and test it with a transistor tester, for example.
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The original PNP transistor STN790A is not very easy to find; a BDP948 is a suitable replacement transistor. It is rated for 45 V, up to 3 A, and has the same housing (SOT223), so it should fit.
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The transistor must be soldered well and sit flat so that it can dissipate its heat.
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Without the Roomba connected, there is 2.87 V at the contacts. When the Roomba is connected, the transistor switches and the voltage rises to 13.4 V - the replacement battery is being charged again.
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Follow these steps in reverse order to reassemble your device.
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