U2 and/or U4 MOSFET Failure Question Roomba Sage (4110)

The very latest news and updates for the iRobot Roomba robotic vacuum, the Scooba Robotic Washer and the Dirt Dog workshop sweeper. All discussion and troubleshooting questions go here.

U2 and/or U4 MOSFET Failure Question Roomba Sage (4110)

Postby keithj » November 2nd, 2018, 11:24 pm

I recently purchased a new battery (and external fast charger) for my iRobot Roomba Sage (4110) that had been "mothballed" and I wanted to make sure that the charging circuit in the Roomba was still good. To that end, I fully charged the battery in the external charger then let my Roomba clean until it returned to the docking station (well over an hour run time). At that point I checked the voltage of the battery - 14.9V, then I let the battery charge for 1/2 hour in the Roomba on the docking station and then I checked the voltage again 16.7V. 1/2 hour later 16.9V, then 45 minutes after that the light was green and the voltage was 17.0V. I was thinking all was well as I ran a similar test again and got roughly the same results though my max voltage was not quite as high the second time -- either way, the battery was charging so I figured my charging circuit must be good...

Fast forward a couple days after I had I left the Roomba on the charger (presumably fully charged since the light was green) and it wouldn't run so I checked the battery voltage again and it was down to 11V. So, my question is this -- if one or both of the MOSFETs were bad, would that allow the Roomba to charge up (assuming the voltage wasn't too low), but not allow the battery to maintain its charge?
keithj
 
Posts: 4
Joined: November 2nd, 2018, 11:02 pm

Re: U2 and/or U4 MOSFET Failure Question Roomba Sage (4110)

Postby TechGuy » November 3rd, 2018, 1:42 am

It will not charge your battery if 1 or both U2/U4 are failed.

Now, you spent the money on a new battery and an external charger. You can continue to charge your battery externally for next year or more.
Charging battery directly: 400 Series, 500 Series,.H-Bridge Repair How to Desolder
TechGuy
Robot Addict
 
Posts: 1559
Joined: February 17th, 2009, 11:52 pm

Re: U2 and/or U4 MOSFET Failure Question Roomba Sage (4110)

Postby keithj » November 3rd, 2018, 3:29 pm

Understood, :thanks:!
keithj
 
Posts: 4
Joined: November 2nd, 2018, 11:02 pm

Re: U2 and/or U4 MOSFET Failure Question Roomba Sage (4110)

Postby mfortuna » November 3rd, 2018, 4:16 pm

U2/U4 normally fail when the battery voltage is too low. The steps you took should have prevented a MOSFET failure. You could look for an SCI to serial cable and monitor the charge circuit via a USB to serial adapter. Or you could to what tech guy said and use the external charger.
Mike
Reds x 3, Dirt Dog, Disco (now a parts bot), Create, Scooba 350, and Security Dawg
Evolution Mint
Neato XV-11
Shark Ion 750
User avatar
mfortuna
Robot Master
 
Posts: 5832
Joined: February 5th, 2006, 10:35 am
Location: NH

Re: U2 and/or U4 MOSFET Failure Question Roomba Sage (4110)

Postby keithj » November 14th, 2018, 5:45 pm

Thanks @mfortuna! I had considered purchasing the SCI to serial cable to monitor the charging circuit (and for fun if I ever get some time), however, I wasn't 100% sure my Roomba would work with that because I've found some mixed information. Wikipedia (I know, not the best source, though I've seen it else where as well) states "Models with an interface (400 series since October 2007 plus 500 and 700 series) come with a Mini-DIN connector supporting a serial interface", but also states "Roombas pre-October 2005 upgraded with the OSMO hacker device allow monitoring many sensors and modifying the unit's behavior."

Based on my serial number (expanded below), it looks like my roomba was built on October 18, 2005 so I don't think I'd need to upgrade with the OSMO device, however, I'm still not too sure about the first part (Oct. 2007), but I'm hoping that's just a typo. Can anyone here say with confidence that my roomba does indeed support the SCI to serial cable? If so, this: https://www.amazon.com/EZSync-Serial-Ro ... B06XDPMY4Z should work (notice that also states Oct. 2007), right?

Here's my detailed SN as well as it's decoding:

JEN0411005101803sssss

MM Manufacturer ID: Jetta
U Status: new
LLLLL Model number: 04110
YY Year: 05
mm Month: 10
dd Day: 18
RR Model revision: 03 indicates OSMO Software Code 1707 and E128 chip
sssss Order that robot was made
keithj
 
Posts: 4
Joined: November 2nd, 2018, 11:02 pm

Re: U2 and/or U4 MOSFET Failure Question Roomba Sage (4110)

Postby vic7767 » November 14th, 2018, 6:01 pm

Your Roomba has the 7 pin mini din connector and you will be able to monitor the charging data via the SCI channel.
Roomba and Neato Mods, come visit: http://www.vic7767.com/
User avatar
vic7767
Robot Master
 
Posts: 14773
Joined: January 14th, 2006, 8:31 pm
Location: Haughton Louisiana - USA

Re: U2 and/or U4 MOSFET Failure Question Roomba Sage (4110)

Postby keithj » November 14th, 2018, 10:05 pm

Excellent -- thanks @vic7767!
keithj
 
Posts: 4
Joined: November 2nd, 2018, 11:02 pm


Return to iRobot Roomba and Scooba Chat

Who is online

Users browsing this forum: BrettS, felixxx, KeldBroe, ps0001, vic7767 and 193 guests