Does the Bosch Active line reduce power when it's hot

[MikeS]

The same thing has happened to me twice now. After a long climb over maybe 600 feet using Tour and Sport mode, I enter the last stage of about 100 feet of very steep climb and I just can't make it even though I am definitely in bottom gear and have switched to turbo mode. Stop the bike, roll back downhill to the start of the steep bit. Wait a couple of minutes and then climb the 100ft relatively easily. Now it could be that my thighs have recovered but somehow I think it's the Bosch system recovering and providing me with more juice after the 2 minute break.
Is this likely?
Mike

 

[Danidl]

That has not been my experience, but it is plausible. ..if the battery is outputting a lot of power it will get hot, the motor will get hot also, so it would be no big deal for designers to include thermal management.. the Comms links are there and they do cost enough that the extra sensors would be negligible.

 

[EddiePJ]

Out of interest Mike, what level of charge was left remaining in the battery when this occurs?

With the Performance Line and CX Line, I have completed climbs covering distances of over ten continuous miles, with an elevation gain approaching 8,000ft and have never experienced any issue with the motor getting hot. I have experienced the battery getting hot though, but this has never affected the available level of assist.

In respect of power drop, there is very noticeable drop in the level of available assist as the battery becomes depleted. I'm not saying that this is what is happening in your case, but it is another possibility.

.

 

[MikeS]

Battery at nearly 90%. Maybe it’s just my physical condition but my legs didn’t feel particularly tired at the start of the steep bit and if they were I doubt 2 minutes would have restored them
It would be good to get more feedback from active line plus owners, as obviously the very time you may need maximum assist is at the end of a long climb
Mike

 

[MikeS]

I thought I might as well ask Bosch directly - but any email message I try to post via the email web form comes back with a send error message.
Mike

 

[soundwave]

bosch will not reply in most cases as you need to go through the dealer if there are any problems.

same with magura or sram they dont deal with customers only dealers,

given the heat we have had anything over 40c then the batt and motor wont be v happy with above them temps for long and shut down to prevent damage like a pc cpu.

try it with cooler temps and see if it still shuts down first as those motors are new so not much info either way atm.

 

[MikeS]

bosch will not reply in most cases as you need to go through the dealer if there are any problems.

same with magura or sram they dont deal with customers only dealers,

given the heat we have had anything over 40c then the batt and motor wont be v happy with above them temps for long and shut down to prevent damage like a pc cpu.

try it with cooler temps and see if it still shuts down first as those motors are new so not much info either way atm.

Nah Soundwave - I'm in the north east of England - our heat wave peaked at about 24 deg
Been doing a bit of research and some thinking. Bosch have really put some time into developing a whole range of motors batteries displays and algorithms. I think the clue may be in their page that describes the sort of riding that each motor is suitable for. The Active Line Plus is really for commuting and a bit of out of town work. - it doesn't even have that EMTB mode where it swaps between turbo and sport automatically. Nor does it have the feature where you get instant power as soon as you press the pedals (which is very useful for setting off on steep hills). I suspect that my very steep climb following a mile and a half of steep climb is probably going beyond the designed application for the active line motor, and Bosch have built in something that protects it - even though they are not saying so.
Mike

 

[GLJoe]

The Active Line Plus is really for commuting and a bit of out of town work... I suspect that my very steep climb following a mile and a half of steep climb is probably going beyond the designed application for the active line motor, and Bosch have built in something that protects it

That is possible, however a counter argument is that because the Active line probably doesn't provide as much maximum power, its less likely to overheat in the first place, so it would be the CX type motors that would be the ones we'd hear about cutting out under heavy and extended load.
??

 

[MikeS]

That is possible, however a counter argument is that because the Active line probably doesn't provide as much maximum power, its less likely to overheat in the first place, so it would be the CX type motors that would be the ones we'd hear about cutting out under heavy and extended load.
??

Yeah - good point. But remember mine wasn't cutting out just producing less assistance than if I rested it for 2 minutes then gave it another go. If I had to guess, I would say that first attempt after a longish slog felt like trying to do the last steep bit in Tour mode, whereas after a brief rest the system really did deliver the Sport mode for the last 100 ft.
Mike

 

[chris_n]

New legs required

 

[MikeS]

New legs required

Halfords sell them but only offer a 2 year warranty
Mike

 

[GLJoe]

Yeah - good point. But remember mine wasn't cutting out just producing less assistance than if I rested it for 2 minutes then gave it another go. If I had to guess, I would say that first attempt after a longish slog felt like trying to do the last steep bit in Tour mode, whereas after a brief rest the system really did deliver the Sport mode for the last 100 ft.
Mike

Ok, my bad, let me re-write my post:

That is possible, however a counter argument is that because the Active line probably doesn't provide as much maximum power, its less likely to overheat in the first place, so it would be the CX type motors that would be the ones we'd hear about reducing power under heavy and extended load.



It would be interesting to find out the real cause, but tricky to find out how. Can you get someone else to ride with you. When you reproduce the problem, quickly switch bikes and see if the 'problem' sticks with your bike, or somehow transfers itself onto whatever you happen to be riding.
FWIW, when I managed to get my wife into ebike riding, there were a number of occasions early on when we thought there was a fault with the bikes. It was as if they stopped giving the power delivery they should (yet when I then gave them a go, all seemed fine). Turns out it was simply because they are mostly torque sensor activated, my wife's fitness at the start (or lack of it) meant that after extended effort like climbing a long hill, her legs simply couldn't provide the force to adequately activate the assist, even though this wasn't as obvious to her at the time as one might imagine!
I'm not saying that's what it is for certain, but dont' discount it.
Maybe get someone else to ride your bike up the slope to where the problem occurs and you are waiting - you jump on and continue the climb and see if you can then finish the climb on full power?