Repairing Roomba Original
Published May 21, 2006
Background: Battery Replacement
I bought an original Roomba vacuum when they were first released. It worked well for me for about a year, but after that had radically reduced battery life. I’m used to the idea that any product advanced enough to use NiMH batteries is advanced enough to have a proper charger, so I generally left Roomba plugged into the wall when I wasn’t using him. After a while, I noticed that the charger got really hot, and made the connection that it probably wasn’t a smart enough charger and I’d been cooking my batteries.
iRobot wants $60 for a replacement battery pack, so I opened my original pack to see whether I could rebuild it myself. It’s just 12 sub-C cells in series, so it didn’t look that hard to do — but buying just the cells looked like it would cost me about $40, and I’d still have to solder all of the tabs together. When I found replacement Roomba battery kits from eBay seller “all-batteries” (batteryspace.com) for $30 plus $8 shipping, I figured I wasn’t going to have a better opportunity, and placed my order. Further, the original battery was 2600mAh and the replacement was 3000mAh; so after the upgrade, Roomba was going to be not just functional again, but actually better than new (my observation, not a seller’s claim).
Batteryspace shipping the batteries fairly promptly, I printed the installation instructions from their auction page, and I set about rebuilding my battery pack. I ran into a few minor complications, like the new cells being ever so slightly thicker than the old (so I left off the heatshrink cover inside the plastic case), but for the most part the replacement went smoothly. It had been months since I had disassembled my old battery pack and I didn’t remember which wire went where, so I followed Batteryspace’s instructions with excruciating care, connecting the red wire to the terminal nearest the battery body and the black wire to the terminal furthest from the body. (If you’ve rebuilt a Roomba battery recently, just hold your tongue for a moment. It gets even worse.)
I reassembled the battery, measured the voltage, and dutifully prepared to charge it before first use. I snapped it into my brand new Roomba Scheduler (yeah, test a rebuilt battery on the most expensive device in the entire product line) because it has the fast, smart charger . . . Well, here’s the email I sent to Batteryspace that tells the rest of the story:
Last Friday, I received the NiMH battery pack I bought from you, printed out your installation instructions, and followed them carefully. I put the red (+) connection close to the battery and the black (-) connection at the far end as you indicate.
I put the battery into my brand new Roomba Scheduler, because it has the best charger. Its LED flickered and went out. I then put the battery into my original Roomba, and got a smell of ozone as its charger LED went out also. I put the new battery from my Roomba Scheduler back into each of my two Roombas, and neither of them can power up now.
I put a meter onto my Scheduler battery and found that your installation instructions are incorrect — the black wire needs to go by the battery and the red wire out at the end. The error in your instructions appears to have destroyed about $600 worth of my equipment.
I’m not sure how to handle the damage, but for starters, please correct your instructions so no one else ruins their Roomba.
Given my state of mind at the time, I thought I exercised an admirable degree of restraint in sending a polite email that could open a dialogue about how to proceed. I was thus outraged to receive this response:
Thank you for your email. I am sorry you experienced some trouble with our product. Please follow the link below to complete our RMA form:
Huh, an offer to refund the purchase price on my NiMH cells that have nothing wrong with them. That wasn’t exactly what I expected. (Actually, to be perfectly frank, it probably was.)
At that point, I really didn’t know how to proceed. I didn’t want to open an eBay dispute until I had some idea how much Batteryspace’s incorrect instructions were going to cost me. Based on the different lights I got on different devices, I suspected that the original Roomba, the Roomba Scheduler, and the Scheduler charger were all broken. Of course I couldn’t get warranty service on any of them; and I was reluctant even to entertain the idea of factory service, lest I end up footing a huge bill at my own expense. I figured I’d have a look at them myself before proceeding, and I’m disappointed to say that I took so long to do so that I can no longer even leave negative feedback for “all-batteries.”
This weekend, things had finally settled down from a long string of busy-ness — Technology: Art and Sound by Design final project, community orchestra, and fiddling with stepper motors and MOSFET bridges. I cleared space on the workbench, dug into the original Roomba, and (I’m pleased to say) got it working again 100%. Better than 100%, in fact, as it now has noticeably longer battery life than it did when new.
The following pages are a visual journal of the diagnostic and repair process — including another problem I identified and fixed along the way.