winter stom misadventure... does 646 se have a temp cut off?

[yeshelp]

HI
where i live today there was a lot of snow accumulation and then it started raining on top of that making the streets full of heavy wet snow and sluch .

i have a 646 se and was riding at normal speed. then i entered in a grocery stored and after 4 minutes inside the speed of the chair drastically dropped but nothing stoped working , just very very slow movement. nothing special was showing on the joystick but i touched the motor and they were very hot. The joystick battery level was showing still in the green so i dont think it is a battery lack of energy even thouhg my batteries are AGM not Gel.

I'm trying to figure out what happened cause i got in troubles with the staff closing the store and yelling at me to get out ! ouf lots of pressure and emotions i tell you.

I have 2 hypothesis
first hypothesis is that all this snow makes it hard for the motor to push and might be similar to be going uphill in winter condition for a long time. Maybe there is a temperature cut off in the motor to prevent the motor to burn. does anybody knows if such a protection feature is in this chair?

my second hypothesis is about water, the cars passing me by were splashing me a lot so maybe there is a protection feature is water goes into something, is that possible?

I guess for now i'll carry my charger in case it was a lack of energy in the batteries but i sure would like to know what you guys think could have happened and how to prevent it.

[Burgerman]

have 2 hypothesis
first hypothesis is that all this snow makes it hard for the motor to push and might be similar to be going uphill in winter condition for a long time. Maybe there is a temperature cut off in the motor to prevent the motor to burn. does anybody knows if such a protection feature is in this chair?

Yes. Thats exactly what happens. Its called thermal rollback. It has nothing to do with motors its the power module reducing power to protect its electronics. If like me your chair is programmed to actually respond propery and agressively you can make it do that just by sweeping the drive etc.

my second hypothesis is about water, the cars passing me by were splashing me a lot so maybe there is a protection feature is water goes into something, is that possible?

Water in power module or joystick and you stop!
Water in motors no problem. They will work underwater.

[SweetBearCub]

Yep, you got hit by thermal rollback, where the chair's brain/controller hit a certain (programmable) temperature cutoff, and to protect itself, it reduces power to a lower level to try to allow the system to cool, since driving in adverse conditions (rain, snow, similar) takes more sustained energy from the controller, which generates more heat.

Personally, I lowered the thermal rollback cutoff temperature on my chair, because I wanted to be more conservative. It was set at 60C if memory serves, and I reduced it to 55C. Resist the temptation to RAISE the cutoff, unless you have the means to replace a fried controller!

Depending on the joystick or possibly a display that you have, my owners manual for an S-6 series chair says that you should see specific warning icons for thermal rollback, unless you have a setup with no screens like some simpler joysticks.

The manual specifies to leave the system powered on while it cools. I would guess that it's running a timer, and that timer doesn't run while powered off, but this is just an educated guess.

See page 28, with the icons for motor temperature and control system temperature.

https://www.phc-online.com/v/vspfiles/d ... manual.pdf

[steves1977uk]

I have mine set to 70C on a 100A Pilot+ system, never had any issues for the past 9 years in it's daily use. I have a 70L wheelbarrow (it has 4 wheels) that gets filled with horse s&%t when I help Melissa poo-pick the fields and my chair pulls that easily over quite thick grass. Unsure how my Dietz chair would cope as that's quite a bit heavier and there's no option to adjust the thermal rollback temp on R-net.

Steve

[Burgerman]

I raised all mine on pilot plus systems to 70C too. They still roll back if you torture the chair. Mine have been doing that 70C rollback at least weekly since '95... Yet to have one fail.

On modern day chairs using r-net its not adjustable even on OEM software. So you are stuck with its 55C setting. But lower impedance mosfets mean its less of an issue. You can still make it do it easy enough though.

[SweetBearCub]

I raised all mine on pilot plus systems to 70C too. They still roll back if you torture the chair. Mine have been doing that 70C rollback at least weekly since '95... Yet to have one fail.

On modern day chairs using r-net its not adjustable even on OEM software. So you are stuck with its 55C setting. But lower impedance mosfets mean its less of an issue. You can still make it do it easy enough though.

It's interesting that the Pilot+ systems and VR2 systems can edit controller thermal rollback temperatures, but that's not an option on the supposedly more advanced R-Net system. Go figure.

[Burgerman]

Theres no supposedly about it. Its a lot more advanced! But they decided that allowing the temp rollback settings to be changed in the field was a problem for them! (warranty most likely). But it doesent get as hot regardless.

[yeshelp]

Thanks a lot for you answers,

Very usefull.

For the future, when i am in thick snow or wet snow , does riding at lower speed can reduce the chance that the temp cut off happens? I imagine that yes but speed , volts, , amps , heat can something mislead.
have a good day

[Burgerman]

Yes.

[slomobile]

Slower generates less heat unless it disproportionately increases the time required to get over an obstacle.

In slush with occasional large ice chunks, like the chunks that fall off car wheelwells in snow, keeping your kinetic energy (speed) up can bash through these in no time. But trudging along slowly till you get stopped by one, then ramping up throttle to get by, presents a locked rotor condition briefly which generates lots more heat than steady minimal load top speed over the same distance.

In general though, going faster consumes watts faster, heating faster, draining battery faster, thus traveling fewer miles.

I have had 1 brake lock up in the slush once. The other motor just dragged the stuck wheel along in a slightly curved straight line. Did not spin as I thought would happen.

Another interesting winter discovery, floods from broken pipes in really cold weather dry up faster than in summer. The outside air is so dry that interior heat evaporates water quickly and moves it outside through any crack not covered by vapor barrier.

[ex-Gooserider]

Another possible failure mode that I see as possible, unless you have definite indicators to say it happened (since you said they didn't indicate a problem) is if you have seating functions w/ 'safety switches' that might have been tripped and put the chair in 'turtle mode' - either because moisture got into the switch or you got ice / road crap buildup around it that made it do a false trip....

ex-Gooserider

[yeshelp]

Hi Everyone

Thanks a lof for your contributions it really helped me understand the dynamics.

i wish you all a good new year and holidays!

[yeshelp]

Hi everyone

life being life i had another winter problem with the same 646 se wheelchair:

I was going up a medium hill in 4 th speed. i was giving medium joystick power keeping the speed low (maybe i reached a peck inadvertly) but all of a sudden the joystick light stopped and so did the chair...

I waited 30 minutes and tried to disconnect the joystick and reconnect without success.
Any idea what the problem is and how to solve?

thanks

[Burgerman]

You must have a bad connection somewhere. You really are going to need to find it.

[yeshelp]

is it possible that a sudden stop like that could also be caused by a to many amps ? the motors were not so hot when it happened in the hill .

[Burgerman]

Only if batteries are bad or a bad connection. Max amps is limited by the power module. If THAT overheats because it doesent like the heat then it doesent suddenly stop, it reduces power so the chair is slower or weak.

[yeshelp]

i kind of gave it a final look before sending it to reparation and i found a little white button (like 4 or 4 millimeter)(i think it is called a mamelle in french not sure but it does look like a tip of breast, well men have them too) on the side of the computer infront of the batteries kind of between the front the wheels but more in the center.

i pushed it and then the joystick started working again . I m happy about that. i do wonder how to unterprete the situation. reminder i was going up hill and everything stoped suddenly including the light of the joystick.

Anyone knows what this button does and what situations do make it enter in action(being activated)

[Burgerman]

Sounds like a breaker tripped. I hate them. They oxydise and cause a bad connection. And then they get hot at a lower current. Which causes them to oxidise more. Rinse and repeat. I throw them away, and fit a 150A midi fuse instead. So as I said, its a bad connection... Inside the breaker. Which evenually heats it up and causes it to trip.

[yeshelp]

HI Burgerman

If i understand right the more the time passes the more often i risk to see it trip?

SInce pushing a button is not so time consuming i guess i can just keep on using this setup until it becomes anoying or too frequent?

When you say 150A midi fuse instead. you mean that at time of change you insert a fuse more amp resistance capable?

there must be a reason why they choose a fuse less than 150A. Isn't there a consern if the protection feature is not there anymore?

thanks

[Burgerman]

They fit breakers as they do the same job as a fuse. (mostly they fit fuses today). But are resetable. But breakers are unreliable, subject to wear, oxidation etc. So in time they ar higher resistance nd heat up and trigger too soon. They are a simple bi-metalic strip that has the power running through it. They open a set of contacts if they heat up too much.

The job of a fuse or breaker is to disconnect power if theres a short circuit or something to protect the battery loom. Thats all it does. So as long as you choose a fuse that the chair will never blow, but that will not melt the wires you are good to go!

Your description is lacking though. We dont know for sure that the thing you pressed was a breaker. And if it was it may be only used to disconnect whatever 3rd party "thing" controls the servo steering system. Only you can know.

[yeshelp]

ok ill think about it
thanks

[yeshelp]

ok ill think about it
thanksThe job of a fuse or breaker is to disconnect power if theres a short circuit or something to protect the battery loom. Thats all it does. So as long as you choose a fuse that the chair will never blow, but that will not melt the wires you are good to go!

so a 150 amp fuse would be good for the chair i have right?
is there a link to buy online this piece?

thanks

[shirley_hkg]

https://www.ebay.com/itm/322287656777?m ... media=MORE

[Burgerman]

Too big physicaly, seach midi fuse, 150A.

[Burgerman]

https://www.ebay.co.uk/itm/132373294247 ... BM0tq868Rh

Anything from 100 to 150 will be fine for most users.

[ex-Gooserider]

Hi everyone

life being life i had another winter problem with the same 646 se wheelchair:

I was going up a medium hill in 4 th speed. i was giving medium joystick power keeping the speed low (maybe i reached a peck inadvertly) but all of a sudden the joystick light stopped and so did the chair...

I waited 30 minutes and tried to disconnect the joystick and reconnect without success.
Any idea what the problem is and how to solve?

thanks

Unless it was something aftermarket, the push button was definitely a breaker - that is what was used on the (6x6 chairs at least in the US) and was almost certainly the problem... If it was water getting into something the joystick might (probably would) show error codes or messages, but would stay on and do something... However a bad connection in the power to the controller such as a breaker trip will kill everything...

I'd agree w/ BM about the benefit of switching to a fuse that is big enough that it will NEVER blow under a normal load, but (barely) keep the wiring harness from melting if you have a short circuit... (Remember that the function of any expensive electronics is to protect cheap fuses by blowing first.... )
ex-Gooserider