GTECH E-Scent MTB - Motor Issues

[leecashman]

Hello community,
I've just signed up to the forum, so thanks for having me!
(This is the THIRD time I've posted this in the last few hours but it keeps disappearing!?)

Anyway, I'm a pretty unfit 44 year and was looking to cycle to work - a 14 mile round trip.
I love my mountain bikes, so after lots of looking around I settled on the GTECH E-scent MTB - Cycle Republic had one reduced from £1,899 to £1,000 on the Cycle2Work scheme, so was perfect for what I needed.

Only got the bike last week, and have a bit of an ongoing issue I'd like some advice with.
The bike has a bottom-bracket based PAS sensor, and the standard Bafang 250w hub motor rear wheel. The idea with this setup as you'll all know is that the motor will kick in if I pedal a bit harder, so gently pushing me up those hills and saving my ancient legs!

The issue I have is that the motor kicks in very randomly. I get the initial 'push' off the line, but then the power delivery is very sporadic - whether I'm on ECO or MAX mode. I realise these things are restricted to 15.5mph but it's not that - I can be plodding along up a slight incline at 8/9mph - and when I push on the pedals, the motor actually 'drags' we back! Making it harder to pedal. It feels like engine braking in a car. In order to get the motor to assist, I have to kind of 'coast' the pedals round - i.e., keep rotating the crank but without putting any pressure on the pedals. Then it works fine.

I've tried disconnecting the PAS and the motor (so therefore just using it as a non-elec MTB) and the 'dragging' sensation is still there. The harder I pedal, that harder it fights back. If I then freewheel along, it doesn't drag.

My thoughts are that there must be something wrong with the motor? Something shorting out or binding that's causing the motor not to engage and disengage fully.
Any one has this or have any ideas what I can look at to resolve? I've done the usual (clean and WD40 all the connections, etc) but to no avail.

Obviously with it only being a week old I am currently in conversation with Gtech about getting them to send me a new rear wheel! But if it's something simple I can sort all the better.


Thanks in advance for any advice.

Lee

 

[wheeliepete]

and when I push on the pedals, the motor actually 'drags' we back

Check the tightness of the nuts on the rear hub, sounds like the wheel maybe twisting in the frame and making the rear brake drag.

 

[leecashman]

Check the tightness of the nuts on the rear hub, sounds like the wheel maybe twisting in the frame and making the rear brake drag.

Thanks wheeliepete - will do. I've ordered a paid of semi-slicks which turned up today so will fit those over the weekend and make sure everything is properly tightened. Might even be worth removing the rear brake caliper to test your idea? Thanks

 

[Atlav4]

hi i own a gtech escent and yes i have observed this happening but only on a long incline and yes at about 8-9 mph this seems to happen when in eco mode which is assist to 8mph so does this inbetween assist and leg power and can feel like a brake being applied have had many rides now and very happy with bike overall but buying second hand when this happened thought whoops Now on approaching the offending inclines i move to max mode and dry pedal to the summit returning the mode back to eco as i like to pedal above assist as much as possible (improved range) hope this helps or we both have knackered pedelecs

 

[leecashman]

Hmmm... so it's MEANT to be like that? I mean, I literally never use it on ECO mode as it does nothing. And as my commute is only 7 miles it isn't a problem regarding battery. When you say 'dry pedal' to the summit, are you meaning the same as what I'm doing to get the motor to engage? i.e. - you're moving the pedals round in order to get the PAS working, but not putting any pressure on them?

 

[lutin]

Hi there - fellow gtech escent owner here.
So my commute is only about 6 miles round trip. I use the assist for 99% of it. I literally only spin the pedals at the minimum amount required to engage the motor. I very rarely try to move the bike under my own steam, but when I do - oh boy is it tough. I think I might have posted about it on this forum even, and the conclusion was that the resistance was just the 'surprise' difference between full assist and no assist whatsoever. That and a combination of a slightly heavier bike. I wasn't ever fully satisfied with that, and I still can't believe how hard it is to pedal with the motor off.

Not much help, sorry.

 

[leecashman]

Worth pointing out then when I'm pedalling above the assisted range (so over 15.5mpg in MAX or over 8mph ECO) is when this problem is bad. It makes it almost impossible to pedal above the assisted range due to the drag. Surely that can't be right?

 

[leecashman]

Hi there - fellow gtech escent owner here.
So my commute is only about 6 miles round trip. I use the assist for 99% of it. I literally only spin the pedals at the minimum amount required to engage the motor. I very rarely try to move the bike under my own steam, but when I do - oh boy is it tough. I think I might have posted about it on this forum even, and the conclusion was that the resistance was just the 'surprise' difference between full assist and no assist whatsoever. That and a combination of a slightly heavier bike. I wasn't ever fully satisfied with that, and I still can't believe how hard it is to pedal with the motor off.

Not much help, sorry.

Lutin, that's really helpful. It's exactly what I'm experiencing. If it's the case that the bike is meant to be like this, and that 'resistance' is just how it is, then I'm taking the thing back. As much as I like it, it's just unusable like that. I have an old Giant Team Issue which is also 19kg - and it feels NOTHING like the Gtech. It's easy to pedal. For the Gtech to be that hard to move outside the range of the assistance is rubbish.

 

[Atlav4]

i use my bike 2 times a week for exercise and enjoyment for approx. 1 hour most of the time this is around 9-10-11 miles on road off road pavements etc was out today 10 miles 58% battery left 47mins at average speed of 12.7 mph all in eco apart from one climb where the problem you mention occurred previously gradient isn't that steep but speed drops to about 8 or 9 mph this time i went to max mode and kept the pas working by easy peddling and the problem did not arise this time ? majority of time im above pas level in eco and the bike feels like any other mtb no better no worse hope this helps im no experienced pedelec or a gtech rep just relaying my findings

 

[Nealh]

Lutin, that's really helpful. It's exactly what I'm experiencing. If it's the case that the bike is meant to be like this, and that 'resistance' is just how it is, then I'm taking the thing back. As much as I like it, it's just unusable like that. I have an old Giant Team Issue which is also 19kg - and it feels NOTHING like the Gtech. It's easy to pedal. For the Gtech to be that hard to move outside the range of the assistance is rubbish.

From the sounds of it the bike (GTECH) might be utilising a speed controller and what you feel is normal, ie: once the assist max speed level is reached the power /watts backs right off and the drag you feel is actually the heavy hub being cycled with no power.

A speed controller gives max current at all PAS levels with each PAS level having a max speed set, once you reach the max speed of each level the current drops right off and you are left trying to pedal the hub bike unassisted until the speed drops enough for current to flow again. Once you have sussed the max speed of each level to go faster you need to either up the assist level or ride in a higher assist levl all the time.
A controller with speed setting is a crappy/poor set up and uses more battery wh.

Most decent hub bikes use current control for controllers which is more user friendly and smother in operation. With current control each assist level gives max speed with each level giving more power/watts.
Luishi for example gives something like 40,50 60,70 & 100% current in each of it's five PAS levels.
The KT gives something like 13, 20,33, 50 & 100% current in each of it's five PAS levels
Both of the above offer a better ride experience and you only need to use the power you need.

 

[Nealh]

To see /tell if your controller is a speed controller try each PAS level and see if each level has a different set max speed.

 

[Atlav4]

On the escent Bafang torque sensor bb links to controller in battery housing the power cable controller to Bafang rear motor The mode is set by the switch on the battery on/off min/max speed of min approximately 8mph and max approximately 15 mph

 

[Nealh]

Ah a TS BB, on hubs they aren't very desirable. Might be a programming issue then or a sensitive TS when pressure is applied, tbh they are a PITA.

 

[Atlav4]

Yes it’s a strange feeling through the pedals like the motor seizing up momentarily then releasing It’s only happened twice for me like I say on a slope 8 or 9 mph in eco probably in too high a gear pushing hard on the pedals The escent assist stops when you stop peddling (no brake cutoff) this is instantaneous and may contribute to the anomaly

 

[Nealh]

Yes a low gear is crucial as motor stalling may be evident in to high a gear, hence the motor hesitating. For inclines motor rpm used is important, ideally needs to be a low wound high torque hub.

 

[Atlav4]

Next question should put this on technically page but the bb torque sensor has a thin wire running to the controller housed in the battery bracket the thicker power cable runs from controller to the hub motor signals are sent to the controller from the battery on/off min/max Now then Gtech battery range let the eBike down badly So if a bottle battery with the same hailong 4 port connection was fitted still work on the last mode the Gtech battery was set ie min or max Then a larger capacity battery could be fitted with some alterations to the cradle???

 

[leecashman]

On the escent Bafang torque sensor bb links to controller in battery housing the power cable controller to Bafang rear motor The mode is set by the switch on the battery on/off min/max speed of min approximately 8mph and max approximately 15 mph

Yeah that's what I'm reading. The ECO Max is about 8 and the MAX Max is 15.5. it would be fine if you could pedal beyond that speed but the drag makes it incredibly difficult.

 

[leecashman]

As the bike (and this setup) has been around a few years now I was hoping someone would've figured out some mods for the Gtech. Alas not. Unlike most people who want to modify their pedelec, I'm not looking for more speed or even more battery life - i'd just like it to bloody work better!!

 

[Atlav4]

Hi try a ride in max mode and keep your speed below the cutoff speed with easy pedal rotation cruise as much as possible then as you begin to pedal again the pas should kick in try a few mile circuit flat as possible this may help to have the motor running for a period of time might help???

 

[leecashman]

Cheers mate. I never come out of MAX now anyway due to these issues. But I will give your suggestion a go and see how I get on. I've put the slicks on the bike this morning so at least it will be a smoother stuttery ride!