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Old 09-12-2019, 12:29 PM   #261 (permalink)
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The silly thing with motorcycles is they use generators and shunt excess power generation to a heat sink. I'd like to shut my generator off too. I wonder how much power it robs from the engine? Probably should have done that during track days.

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Old 09-12-2019, 08:43 PM   #262 (permalink)
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Quote:
Originally Posted by redpoint5 View Post
The silly thing with motorcycles is they use generators and shunt excess power generation to a heat sink. I'd like to shut my generator off too. I wonder how much power it robs from the engine? Probably should have done that during track days.
No, it uses PWM to short current through the stator to cancel out the rotor's magnetic field. That gives increasing copper losses as the rpms go up, but removes excess iron losses. The regulator itself is pretty efficient, and they could make it more efficient with bigger MOSFETs. If it used the regulator to burn off power that thing would go up in flames in seconds even if it had the biggest heatsink ever.

This control strategy is actually more efficient than an alternator up to a certain point, but the stator losses go up quadratically with speed due to the permanent magnet and start wrecking efficiency. I would guess that at the rev limit, a motorcycle generator is probably under 30% efficient vs. maybe 40% on a car alternator.

Since the stator is so undersized on a motorcycle, I think the highest efficiency option is to wire in a synchronous rectifier and DC-DC converter. I'm kinda curious how many motorcycles already have synchronous rectifiers, since you can use the same MOSFETs to do the PWM, so it would reduce the number of parts.

The actual best thing to do is to put in a bigger stator with lower winding resistance, but I'm guessing you'd need to do a lot of cutting to make that happen

Last edited by serialk11r; 09-12-2019 at 08:51 PM..
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Old 09-12-2019, 10:04 PM   #263 (permalink)
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Were you able to test the voltages?


I am talking to the chinese seller to work on my new order. And he sent me a picture saing new caps 650 usd, refurbished ones 135 usd. (Asking are these the ones)

So they are not new (despite the guy claimed they were in the beginning).

So, measured the caps and one of the end caps is a dead short. That's definitely not a great way to fail, a shorted cap will cause the other caps to go up in voltage and have a cascading failure. Eventually the whole thing becomes a short across the positive and negative terminals on the battery. I was lucky enough to actually be looking at the pack when it failed, and pulled it off when I saw the LEDs on the other balancing boards start to get brighter.

I wonder what caused the failure?
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Old 09-13-2019, 04:11 AM   #264 (permalink)
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Are the others at the same voltage?
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Old 09-13-2019, 06:18 AM   #265 (permalink)
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Are the others at the same voltage?
They're all still very close, yes.

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