Roomba battery, Temperature shutdown mods?

[soviet911]

Hello Everyone.
Most people know that roomba's battry 5xx series have a built in temperature sensor and that the roomba will keep the battery below 60°C. Most people agree that this is quiet a high upper limit and thus wears down the battery fast.
Has anyone considered increasing the reading of the thermal resistor by adding resistor in sires to the one in the battery so instead of the thermo resistor reporting 20°C it would report let say 40°C so when the battery reaches 40°C roomba thinks its 60°C and would shut down or stop charging. This would probably extend life of the battery in the roomba, has anyone done any type of write up on this as searching for me proved futile on this subject?

If not does anyone know what type of thermoresistor they use, and how its wired? I'm interested in trying this over the summer as a side project and if some knows this info it would save me some time.

I think this can work ether by increasing the base resistance reading of the thermo resistor, or by passing original thermo resistor with a different one. The problem would be, how hot does the battery get during run time, since if you make the alarm go off at 30°C and the battery hits that high it will stop vacuuming until you resume it. Then the question can you program roomba to wait for the battery to cool down and then make it continue its cleaning mission?

Thanks alot for any advice or information.

EDIT 1: Found this website ( http://mysite.verizon.net/gsplews/Rapid ... ation.html )that suggest that the thermo resistor used is the model below, and my idea will not work as they use an inverse relation of T to R ( so with increasing temperature resistance is reduced)
http://www.meas-spec.com/downloads/Seri ... 10K3A1.pdf

Maybe the right approach is to install a small fan to cool the battery instead when it reaches a certain temp..need to think about this.

[Gordon]

Read this post (it has 5XX Roomba thermistor data, whereas mysite data preceded the 500-series' existence): viewtopic.php?p=75740#p75740
Not long after the 500s hit the floors, vic7767 posted a runaway 535 charging event that took battery temperature up around 60C, however, I tend to think that iRobot got a fix on that early high temperature situation. At least I have not read anything about too hot batteries in many months.

People do claim Roomba batteries get hot while on a Cleaning Mission, but I have seen no data to substantiate that. A hot battery is easy to check in a 4XXX Roomba (mine were never hot at mission end, but I never ran hour long missions), but more difficult in a 5XX Roomba.
I am certain that the MCU only looks at thermistor data while in Charging Mode. Not during a mission.

[soviet911]

Thanks, that helps alot. I will look into getting a ressitance loger or tempreture logger to get the data of the roomba during charging and running and see how hot it gets before spending much time on this.