Intermittent Power Loss - Woosh Big Bear

Electrically assisted bikes, trikes, etc. that are legal in the UK
Dorset46
Posts: 8
Joined: 19 Jan 2022, 12:13pm

Intermittent Power Loss - Woosh Big Bear

Post by Dorset46 »

Hello all, and thanks for accepting me - first post.
My 5-year-old Woosh Big Bear (front wheel motor) has developed an irritating intermittent fault over the past three months. Essentially, it fails to pick up power straight away after slowing down.
Typically it happens after coasting down a hill. When I start pedalling again, instead of picking up power after a single revolution, it seems to run on little or no power for typically 10 seconds or so. But this varies considerably - sometimes there’s no power loss, occasionally it’s so prolonged that I’ve had to switch the bike off and on again. It doesn’t seem to be a complete cutout - so I don’t think it’s as simple as a loose power lead, for example.
I’ve been in discussion with Woosh, who have been very helpful but are unable to put their finger on a likely solution. I’ve checked the battery mounting and cleaned and WD40’d the connections. I’ve also checked the crank-mounted sensor - it looks ok (close to the disk and running true).
If anyone has any ideas I’d be really grateful. I’ve had helpful chats with a local repair shop (listed on the Woosh main site) but he can’t figure out the issue either.
stodd
Posts: 705
Joined: 6 Jun 2018, 10:24am

Re: Intermittent Power Loss - Woosh Big Bear

Post by stodd »

I can't see why it would cause those issues, but worth checking the battery in the LCD.

Could be the cable from the crank sensor.

Was that regular WD40 or their contact cleaner? Regular WD40 is good at getting rid of damp, but not that good as a switch cleaner.

Also try posting at https://www.pedelecs.co.uk/forum/forums ... ussion.42/; a bigger community than here and some real experts.
Dorset46
Posts: 8
Joined: 19 Jan 2022, 12:13pm

Re: Intermittent Power Loss - Woosh Big Bear

Post by Dorset46 »

Thanks - I’ll give all these a go.
hemo
Posts: 1438
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: Intermittent Power Loss - Woosh Big Bear

Post by hemo »

I would check the brake levers/ cutoff/s are not sticking or are slow to fully seat back.
Also have a look at the BB sensor & magnet disc, ensure the magnet face is clean and the gap between sensor face and disc is 1mm. Check the magnet disc is firm on the axle and can't rotate around the axle manually.
Dorset46
Posts: 8
Joined: 19 Jan 2022, 12:13pm

Re: Intermittent Power Loss - Woosh Big Bear

Post by Dorset46 »

Will do. The sensor gap is more like 3-4mm, so I’ll clean and adjust that. Thank you.
hemo
Posts: 1438
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: Intermittent Power Loss - Woosh Big Bear

Post by hemo »

In that case then 3 - 4mm is way too much for the Hall to pick up the magnet.
Dorset46
Posts: 8
Joined: 19 Jan 2022, 12:13pm

Re: Intermittent Power Loss - Woosh Big Bear

Post by Dorset46 »

Right. That’s very useful - thanks. I’ll adjust it tomorrow and test it out.
Dorset46
Posts: 8
Joined: 19 Jan 2022, 12:13pm

Re: Intermittent Power Loss - Woosh Big Bear

Post by Dorset46 »

Thanks for all the advice to date. I moved the sensor to about 1mm from the disk, and cleaned/WD40’d and dried the whole area with the bike upside down. No luck so far.
With it upside down it’s easier to gauge what’s happening. When working normally, a gentle turn of the pedals kicks the motor into full power pretty much straight away. It still does this on occasion. At other times, with the pedals gently turning, the power cycles on and off, and power seems much more dependant on pedal speed. (I know this is normal for many bikes, but the Woosh has always taken off immediately. I could, for instance, turn the pedals slowly using no leg power at all, and the bike would happily cruise at 15mph). In any event, the motor power does not seem adequate for much of the time. Nothing mechanical is binding.
Hopefully this might generate further ideas. Again, many thanks for all the advice.
Jdsk
Posts: 24478
Joined: 5 Mar 2019, 5:42pm

Re: Intermittent Power Loss - Woosh Big Bear

Post by Jdsk »

Do these sensors have any diagnostics built-in, such as indicator LEDs?

Thanks

Jonathan
Dorset46
Posts: 8
Joined: 19 Jan 2022, 12:13pm

Re: Intermittent Power Loss - Woosh Big Bear

Post by Dorset46 »

Nothing visible, Jonathan. It’s a pretty basic machine!
hemo
Posts: 1438
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: Intermittent Power Loss - Woosh Big Bear

Post by hemo »

I thought the Woosh Big Bear sensor had a Red led on the sensor head, if so it should blink as the magnet passes.

One can try testing the PAS voltage via the wiring, if it uses the JST SM3 wire connectors that allow for meter probes to placed up the ack of them.
With a meter set at 20vdc and the bike power on probe between the Gnd wire and 5v to check 5v is present on the Hall sensor, if so then try probing between Gnd and the other (signal wire) whilst having someone turning the cranks. One should see the voltage change from 5v to 0v or a very low value as it passes each magnet.
Jdsk
Posts: 24478
Joined: 5 Mar 2019, 5:42pm

Re: Intermittent Power Loss - Woosh Big Bear

Post by Jdsk »

Thanks

Jonathan
Dorset46
Posts: 8
Joined: 19 Jan 2022, 12:13pm

Re: Intermittent Power Loss - Woosh Big Bear

Post by Dorset46 »

Hi Hemo. Is that the sensor by the rear wheels spokes - not the one on the crank? I think there is a red led there - though I’ve never seen it light up…. But I’ll give that a try - thanks for the info.
hemo
Posts: 1438
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: Intermittent Power Loss - Woosh Big Bear

Post by hemo »

No, the wheel one is the speed sensor, though it may be possible the rear sensor if not picking up properly may affect how PAS works. I have never actually worked on a Big Bear but do have a Big Bear conversion kit, my hub motor has an internal speed sensor so never an issue.
Does the KM J lcd display work ok and show speed.
hemo
Posts: 1438
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: Intermittent Power Loss - Woosh Big Bear

Post by hemo »

I would carry out the electrical test I mentioned on the sensor as any anomaly will show up in the reading and would mean a faulty PAS Hall sensor.
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