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Reepicheep
| | Posted on Tuesday, October 05, 2010 - 08:28 am: | 
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Jdugger, we know it's a shunt because of how it is wired.
Shunt regulators go in parallel, inline regulators go in series.
(Disclaimer, this is based on the M2 I took apart, I havent had an XB apart, and I don't own an 1125). |
Chameleon
| | Posted on Tuesday, October 05, 2010 - 11:05 am: |
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quote:I'm not sure why manufacturers haven't switched from shunt regulators... I wonder if there are reasons we haven't thought of (rapidly varying mechanical load on stator leading to long term durability problems, etc).
You mean like the long-term durability problems we already have?
I think we all know the reason why they haven't switched to better designs - because they're cheap, short-sighted, and are trying to maximize profitability while only managing to shoot themselves in the foot. |
Reepicheep
| | Posted on Tuesday, October 05, 2010 - 11:27 am: |
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Speaking as somebody who works in complex environments every day...
quote:There's no problem so bad that a little fixing can't make it worse! 
My XB9SX used a shunt regulator and worked perfectly from the day I bought it, through 30,000 miles, until I sold it. The problem is with the 1125 implementation of the system, not a core flaw of the system itself.
That's not to say a thing shouldn't be fixed or improved... just that well working, well sorted, and well understood solutions are very valuable.
Something is wrong on the 1125 though, that's for sure! |
Avc8130
| | Posted on Tuesday, October 05, 2010 - 11:33 am: |
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What about a Compufire regulator? Supposedly they make MUCH less stator heat than even the MOSFET based RR.
http://www.posplayr.100megsfree3.com/FH012AA_Charg ing/SSR_vs_FH012AA.pdf
ac |
Jdugger
| | Posted on Tuesday, October 05, 2010 - 12:10 pm: |
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> Jdugger, we know it's a shunt because of how it is wired.
Great, I believe you.
So, tell me why my regulator runs cool to the touch with ALL of the street lighting equipment off the bike, and with a racing battery that doesn't have the charging load of a lead-acid one on a bike that's constantly revved to the moon generating a LOT of current out of that stator that isn't used and needs to be shunted.
I'm just saying, *something* here isn't adding up, ohm's law and all.
I can leave the KEY ON on the bike for HOURS and the volts will drop from 14.2 with the motor running to 13.4 on the battery, and not get below 13.0v for more than 3 or 4 hours. So, I know the electrical load of the bike's systems is very, very low. That would mean I should be shunting almost everything the stator generates and the regulator should be nice and hot. It's not. |
Dannybuell
| | Posted on Tuesday, October 05, 2010 - 12:54 pm: |
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Avc8130 - nice link. IDK anything, it looks like the compufire generates less heat because it generates less amps? |
Reepicheep
| | Posted on Tuesday, October 05, 2010 - 01:39 pm: |
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Most of the heat is in the stator.
Heat is Volts times Amps (expressed in watts). For a common sense feeling of what a watt means, think about a 15 watt soldering iron, or a 100 watt light bulb, and what they feel like in heat.
Lets consider the two states the regulator can be in.
1) Regulator is an open switch (current going into battery and bike).
In this case, the volts is probably 13.9 or something, but the amps going through the regulator are zero. So Watts are 13.9 times 0, or zero watts, no heat being dissapated.
2) Regulator sensed voltage climbed above 13.9, and threw the hammer, and is shorting the output of the stator to ground (diode bridge keeps the battery voltage from going back into stator).
So the current is now really high. Say 20 amps. But the voltage across the regulator is only the forward drop across an SCR, or 1.2 volts. So that's about 20 watts.
In either case, the regulator isn't dumping *that* much power. It will do high volts with low amps, or high amps with low volts, but never both. That's how it keeps from exploding.
A MOSFET could do even better, it could go basically down to almost zero forward volts. That's how I got a device about the size of my thumbnail to manage 70 watts of heated gear for my thermostat thing with no heatsink. |
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