Can I swap battery from my old bike into new bike (both are 36v lithium)?

Chrisg149

Pedelecer
Sep 4, 2020
40
4
I’m planning to upgrade my faulty old electric bike with a new Woosh Santana CD. Annoyingly, I recently bought a new battery for my old bike and wonder if via an adaptor cable I can utilise it as a backup for the new bike?

Is this idea feasible? Thanks. Chris
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
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Though it can be done if you're good at DIY, it's probably not a good idea. Why don't you fix your faulty old bike. If it has a good battery, there can't be anything wrong with it that's going to cost a lot.
 

Chrisg149

Pedelecer
Sep 4, 2020
40
4
I did attempt to fix the old bike and bought an inexpensive new controller, but the same problem persists - a twitching hub motor when throttle on. I did initially hear a mechanical clunk within the hub motor when it stopped working; so fault would appear to point to there. My old electric bike weighs a third more than a modern, hence considering new one. Chris
 

Benjahmin

Esteemed Pedelecer
Nov 10, 2014
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Can you be a bit more specific, does the fault only occur on throttle or on pas as well?
Rough running on motors is often a wiring fault. have you checked the connector at the motor, is it fully home, is there any sign of heat or mechanical damage?
The other possibility is that it's a hall sensor. What motor is it? What controller does it have?
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
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I did attempt to fix the old bike and bought an inexpensive new controller, but the same problem persists - a twitching hub motor when throttle on. I did initially hear a mechanical clunk within the hub motor when it stopped working; so fault would appear to point to there. My old electric bike weighs a third more than a modern, hence considering new one. Chris
If the controller doesn't have learn wires to auto sync motor phase/halls then you have to do it manually via a simple chart, there are 36 possible phase/hall combo's and only up to six will work correctly. That is assuming the hub motor is /was in good working order. If you want to try the process let me know and I will post the chart for you to follow.
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
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I’m planning to upgrade my faulty old electric bike with a new Woosh Santana CD. Annoyingly, I recently bought a new battery for my old bike and wonder if via an adaptor cable I can utilise it as a backup for the new bike?

Is this idea feasible? Thanks. Chris
It can be done, though one needs to do it correctly and safely.
Consideration in to both battery voltages need to be considered if paralleling them up as one battery. A bad bodge job or widely uneven voltages can end up as a fireball, rare but extreme events should one occur.
 

Chrisg149

Pedelecer
Sep 4, 2020
40
4
Can you be a bit more specific....
My old bike has no pedal assist, just throttle twist grip feeding a Bafang 36v 250w rear hub motor via a KT controller. Applying throttle will faintly twitch the motor on each twist, but ceases after a few repetitive twists. The clunk of death happened when attempting a long steep hill on prolonged full throttle and heavy pedaling. On inspection the thick phase wires were melted. So with cleaned up wiring and a replacement controller still giving the same fault , it seems to point within the hub motor? Replacement motor with wheel seem to be in the region of £200 which I feel could go towards a new lighter bike. I’d hate to fork out that money and it wasn't a faulty motor! By the way, thanks forum for all your supportiveness. Chris
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
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Basildon
You probably blew the hall sensors when your motor wire shorted. Hall sensors only cost a few pence each and are not too difficult to install as long as you can solder. Alternatively, you can get a sensorless controller.
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
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Inside the hub there isn't much to g wrong, hall sensors may have failed, an external test with a meter will taka a couple of minutes to see if that is so.
The nylon gears on the clutch assembly may have failed.
 
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Chrisg149

Pedelecer
Sep 4, 2020
40
4
If there is a simple way to test hall sensors then I’ll have a go – point me to instructions/video. I have to declare that my soldering of small circuit boards isn’t great as I discovered when trying to replace controller mosfets. I had to give up and instead bought an inexpensive replacement controller. I’m still suspicious though of the definite physical clunk within the hub motor when it gave up – would a blown hall sensor cause that! Thanks again.
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
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If there is a simple way to test hall sensors then I’ll have a go – point me to instructions/video. I have to declare that my soldering of small circuit boards isn’t great as I discovered when trying to replace controller mosfets. I had to give up and instead bought an inexpensive replacement controller. I’m still suspicious though of the definite physical clunk within the hub motor when it gave up – would a blown hall sensor cause that! Thanks again.
Clunking in the motor is 9 times out of 10 an electrical fault. The motor gets knocked around by loads of pulses of electricity. the timing of the pulses is critical and the three wires make three lots of pulses. When any of the pulses get interrupted or the timing goes off, the remaining pulses work against each other, so it's like hitting the motor with a lump hammer in both directions at the same time.

Assuming that the controller works because you replaced it, switch everything on, then measure the voltage between the black and red thin wires that go to the motor hall sensors to confirm that you have 5v, then check between each of the other colours and the black while you rotate the wheel backwards. you should see the 5v going on and off.
 

Chrisg149

Pedelecer
Sep 4, 2020
40
4
Assuming that the controller works because you replaced it, switch everything on, then measure the voltage between the black and red thin wires that go to the motor hall sensors to confirm that you have 5v, then check between each of the other colours and the black while you rotate the wheel backwards. you should see the 5v going on and off.
Done your testing turning wheel backwards: Black & Red = 5v. Black & Yellow fluctuate between 0 & 5v. Also Black & Blue the same. But Black & Green remains 5v the whole time. It would appear this is the faulty Hall Sensor? I viewed a Pedelecs entry 1st March by "Eagle" that has instructions and video on replacement, it looked rather daunting to me with awkward fastenings, extractor tool and delicate soldering. Maybe beyond a beginner? I noticed my hub motor had lost most of its black paint coating (heat?) and didn't spin smoothly (bearings?). So next feasible step? Chris
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
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The hub isn't working so you have nothing to lose by opening up and trying a repair, it can't get any worse then not working. Also whilst at it one can replace bearings total cost about £10 if you have a soldering iron, once open it is far easier to replace all bearings 2 or 3 rather then just one.
A hall sensor £1 or £2 often ss41 bipolar is an ideal replacement though some have a marking/designation on them.
 

Chrisg149

Pedelecer
Sep 4, 2020
40
4
The hub isn't working so you have nothing to lose by opening up and trying a repair....
Agreed. The helpful video posted on Pedelecs 1/3/19
includes an extractor tool and heat gun, neither of which I own and would be reluctant to buy for perhaps a one time use. So can I attempt the job with just my rudimentary tools? Thanks. Chris
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
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Minimum needed is a soldering iron.
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
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When you turn the wheel backwards, you get cogging from the magnets - a notchy type of resistance. That's not the bearings. You have to rotate it forwards to feel the bearings. You can run that motor with a sensorless or dual mode controller that costs about £40 if the bearings are OK.
 

Chrisg149

Pedelecer
Sep 4, 2020
40
4
You can run that motor with a sensorless or dual mode controller...
Link below is for cheap Dual Mode Sensor/Sensorless that is very similar to existing one. Existing is 36v 250w "Rated current 7A", while link below is same except for "Limit Current 15A" - not sure if this matters? Being dual mode does anything need to be switched within controller or do I just ignore the hall sensor connection? Ebay has exact sensorless match "Rated current 7A" but is £50, as opposed link below of just £14 - worth the risk! Thanks.
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
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The gear cluster doesn't need removing if the hub has side plate screws and are accessible.

Is the controller compatible with your display, does it have the correct wiring for it ?
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
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It's a very basic controller that'll work with a throttle, but it only gives full power when you pedal. It has the conector for a three speed switch, but from past experience, that's probably 15 mph restricted, unrestricted and unrestricted plus 10%.

If you decide to buy it, leave the halls disconected. You have to do the self-learning procedure after connecting and switching on. You have to short or put a switch between the red and blue ignition wires to switch it on.
 

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