Charge phone off hall sensor power?

[4sken]

Would the average jasontroller be able to charge a phone such as a Nexus 4 off the hall sensor wires?
Controller in question:
http://www.ebay.ca/itm/Electric-Bicycle-Brushless-DC-Motor-Controller-24V-36V-48V-eBike-350W-1000W-1200-/271931627889?var=&hash=item3f50635971:m:meqqzwHK01ox0VTim5Uclow

 

[fechter]

Not very fast. The hall power will be limited to around 100mA and if you load it with a phone, something might overheat.
Most phone chargers can source 1A or more. It would be better to use a separate dc-dc converter. Depending on your pack voltage, those can be pretty cheap.

 

[slowhands]

Probably not a great idea, there is probably not enough current. You could easily screw up the operation of the motor if you overload the sensor supply.

There are very cheap converters on ebay that will hack your battery voltage of up to 60v down to 5V.

http://www.ebay.com/sch/i.html?_odk...XLM2596HV+60V.TRS0&_nkw=LM2596HV+60V&_sacat=0

Russell Graves has published an implementation using this part for lighting, but it would work for 5v USB just as well:

http://syonyk.blogspot.com/2015/11/building-dc-dc-converter-to-run-cheap.html

 

[amberwolf]

FWIW, there's a very good chance you could just wire your main battery terminals up to your actual phone's wall charger AC prongs, and have it "just work like normal". Then you plug it's other end into your phone, and charge up like normal.

It might not provide as much total power as it would if plugged into the wall, or might run warmer doing it, or both, but I've used a few such chargers to run stuff on my bike.

 

[4sken]

Amberwolf, I'm pretty sure the AC transformer in the charger will just be a dead short to 42V of DC power :?

 

[slowhands]

New chargers don't have a 60hz transformer, so no short. They rectify the AC, then convert the DC to some lower voltage using 100khz magnetics in a tiny converter. Typically rectified AC is 168v peak, but a DC-DC converter may work OK on lower voltage, like 48v DC. Some will have undervoltage lockout and not work, but some probably will just go ahead and work. It's not designed for it, but may just work with lower power capability. Clever, I would not have thought of that.

 

[amberwolf]

Amberwolf, I'm pretty sure the AC transformer in the charger will just be a dead short to 42V of DC power :?

Unless you have one of the old Nokia phones that ran off a NiMH battery (and would be pre-USB on phones), I really doubt you've got that old a style of charger.

It's probably an SMPS, many of which will run off lower-voltage DC (though not all will *start* on lower voltage, many will run from it once started). They've worked for me, from 40-something VDC on up, depending on the charger.

There's a number of threads on doing this around the forum, and posts on my old http://electricle.blogspot.com and some of my threads here have posts about it (best example in the CFL headlight/taillight post, probably).

 

[miuan]

I have a similar question. I want to power a hall sensor from another hall sensor in series, would that be possible?
More specifically, there is a thermal switch in my motor that shuts off hall supply red wire upon overheating. But the controller is sensorless so it will not stop the commutation. I want to rectify the 3 hall sensor outputs into one 4-5V line and use it to power the throttle hall sensor, thus effectively turn off throttle upon overheating.

 

[amberwolf]

Well, power doesn't actually come from the halls--it comes from teh controller, and the halls *ground* that rather than produce it.

So when the hall power is cut, then they will no longer ground any of it at all, so your throttle will get continous power when you least want it.

Instead, I think you might want to be powering the throttle off the same 5V line as the halls, so the thermal cutoff cuts that too.

Hopefully your controller will respond to loss of throttle power by stopping the motor, rather than some other behavior (you'll wanna test that before doing whatever you're gonna do).

 

[dogman dan]

Voltage converter. But in an emergency, you could tap into one cell group of your bike battery.

If you do a converter, make it a 12v cigarette lighter plug. Then lots of stuff could run on it.

 

[slowhands]

I have a similar question. I want to power a hall sensor from another hall sensor in series, would that be possible?
More specifically, there is a thermal switch in my motor that shuts off hall supply red wire upon overheating. But the controller is sensorless so it will not stop the commutation. I want to rectify the 3 hall sensor outputs into one 4-5V line and use it to power the throttle hall sensor, thus effectively turn off throttle upon overheating.

Hook the thermal switch to your ignition switch input on the controller. That should turn off the controller on overheating.

 

[miuan]

This is how my switch is connected. I can NOT use it as an external switch because there is no additional wiring to use in the motor axle. It works by disconnecting power to the halls, which is just fine with a sensored controller, but I am trying to find a way to cut off power with sensorless in the event of overheated windings. My idea is that rectifying the 3 hall output wires will always give 4-5V when halls are powered, and will drop to zero when the switch triggers. Using this line to power throttle would, in practice, achieve exactly what the switch does with sensored motor, i.e. turn off the power to the windings (unless one uses cruise function)

 

[fechter]

It would probably work better to disconnect the halls and use the wires and switch to tie directly to the throttle line.

 

[amberwolf]

My idea is that rectifying the 3 hall output wires will always give 4-5V when halls are powered, and will drop to zero when the switch triggers.

As I said, that won't work, because the halls aren't providing hte power--the controller is, via pullup resistors to 5V, at each hall signal line. All the halls do is ground the signal when active. If they're not powered, the hall lines are all at 5V.

 

[themadhatter106]

I charge my phone on my bike all of the time when using it as a GPS with a handle bar mount.

For only $6 you can get a 12V DCDC converter that will put out way more power than the 5V regulator inside your controller will. Once you have 12V just use a car cell phone charger.

24V-72V to 12V DCDC: http://www.ebay.com/itm/231052282907