Bike hub to charges battery bank

Thread Starter

stephen potter

Joined Jan 7, 2019
3
Hiya all
Looking at .E bike hub is rated at 200w 36volt
Now my bank is 12volt could the voltage be dropped to around 14.4 / 14.8volt but would like to keep the wattage ! Is this possible ?
This would be powered via a Chinese scooter engine ,or does anyone know what the amps are on a Chinese scooter stators
 

drc_567

Joined Dec 29, 2008
1,156
... DC to DC voltage conversion is possible, but may be subject to heat loss, resulting in unacceptable efficiency. A possible alternative, requiring some modification, would be to access the AC generated voltage of the bike hub, before it is rectified to DC power. The bike hub AC voltage could then efficiently by converted by a transformer, (possibly 3 required ) to an acceptable voltage. ... At the lower AC voltage, rectification and voltage regulation could be accomplished at a greater efficiency.
 
Last edited:

wayneh

Joined Sep 9, 2010
17,153
Hiya all
Looking at .E bike hub is rated at 200w 36volt
Is that when operated as a motor, or when running as a generator? Most motors won't make anything close - as a generator - to what they can handle as a motor. And consider that rpm is everything. If you can't spin this thing at high rpm, it's not going to get anywhere near 200W.
Now my bank is 12volt could the voltage be dropped to around 14.4 / 14.8volt but would like to keep the wattage ! Is this possible ?
It is possible, but the question is if you really are seeing that voltage and what current the battery draws when applied. The generator may not be capable of supplying enough current to threaten the battery, even if you don't drop the voltage. You'd want a way to stop charging when the battery is full. You don't want to trickle at high voltage. But for bulk charging you may not have a problem. You need data and specifications.
 

oz93666

Joined Sep 7, 2010
737
These hub motors are brushless DC motors ... very powerful magnets moving close to coils ....

The rated power and voltage occurs when maximum speed is reached ... if the wheel is spinning at half the speed you will get half the voltage

I'm not clear what you are doing "powering with a scooter engine" explain more please.
 

Thread Starter

stephen potter

Joined Jan 7, 2019
3
Hiya
Basically I'm choosing off the CVT on a scooter so will have a 1-2hp 50cc engine that is quite , god on fuel and electronic start, this will be eather belt or chain driven to the 'hub motor ' to charge a battery bank , the engine has .A stator but am unable to find the specs or I would use another of them ( they charge full at8000rpm but can't find wattage /ampage)
 

Thread Starter

stephen potter

Joined Jan 7, 2019
3
50cc Chinese scooter engine I'll be dropping off the CVT and it's rear gearbox
Contacting to go chain drive or via belt drive to The Hub motor is this way I can adjust a gear ratio I basically live on a boat of crew and then you wait to charge our batteries I already have a wind turbine solar panels and a 240 volt generator via a charger but very loud
There's also the option over 350w 24 volt permanent magnet alternator /motor also a 48 volt 1000w brushed motor available to me I'll have to purchase all of these anyway so I've got no way of just testing a current battery charger has a peak of 30 amps , but use slot of fuel , have just been informed Harley have a 48a altinator
 
Good day!
Any idea on how to increase the converted mechanical power to electrical power? Any specific electronic components? Or any idea on how to create your own version of inverter?
 

drc_567

Joined Dec 29, 2008
1,156
... An standard alternator will produce 3 phase AC voltage internally. This occurs before it is converted to the DC form. If the DC operating voltage is 24 volts, then the internal AC voltage, before it is converted to DC, would be about 17 volts RMS (RMS = DC equivalent). Therefore you need to bring the internal AC voltage down to about 10 volts AC (RMS) using a triad of 17/10 volt transformers, one for each phase. 10 volts AC is what you need. When rectified, and smoothed out with a filter capacitor, the 10 volt AC phase output voltages will be about 14 volts DC... enough to charge 12 volt DC batteries. Therefore, the next step is to plug each 10 volt AC phase voltage, coming out of the transformers, into a 3 phase diode rectifier bridge, which will produce the 14v DC charging current that you are trying to obtain. The output of the 3 phase rectifier bridge should be reasonably efficient.
... Modifying the alternator may require knowing which internal connections to connect with. ... An alternator/starter repair shop will be able to assist with this modification.
The selection of transformers will depend on the amount of power that the system can handle, and also a correct input/output AC voltage ratio. For a 350 watts system, each transformer would need to be rated (sized) for 150-200 volt-amps (VI = units of transformer power) ... always allow extra VI in order to avoid over-heating. A 3 phase diode bridge is available from various suppliers.
... Finding a transformer with a voltage ratio of 17/10 may be a problem. ... Some transformer shopping may be required, depending on the alternator AC output voltage that is actually used.
 
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drc_567

Joined Dec 29, 2008
1,156
If the 350 watt 24 volt DC permanent magnet alternator is in working order ... good bearings and so forth, it should require no extra wiring to power the rotor ... just a matter of keeping it spinning. An alternator diagram indicates that the diode rectifiers can be cut loose from each of the three stator phase voltage connections, at which point a jumper should be passed out of the case to one of the three transformers. Assuming that each stator voltage is approximately 17 volts AC, the one remaining design obstacle is to obtain a transformer to reduce the 17 volts to a more reasonable 10 volts ... If that can be accomplished with off the shelf parts.
 

drc_567

Joined Dec 29, 2008
1,156
... have to put a hold on the previous alternator idea ... seems to be difficult to find any off-the-shelf transformer that will have the right specifications.
 
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