Another voltage regulator thread full of questions.

On the heat generated, our charging system generates about 16 amps. A lot of those inexpensive rectifiers are rated at 30 amps.
When a 30 amp rec gets 30 amps of current through it creates the most heat. Running 16 amps through a 30 amp rectifier it only creates about 1/2 the heat.
The 30 amp 3 Phase rectifiers I have come in an alloy case. I think this case design is enough of a heat sink for the 16 amps we put through it.
I do use an alloy mounting plate. No so much as a heat sink but a way to mount it.
Looking for pic. Been in rearranging things and can't find it. I'll get back with one.
Leo
 
Even better, the system is 3-phase so each rectifier circuit only ever sees about 70% of that current because it is shared between the phases.
 
I found it! This one is 35 amp. I ordered a few from China a few years back. Got a few so if one failed I'd have a spare. Have not needed a spare yet.
It has one center mount hole. When I bolt this to a plate I do use heat sink grease. The plate is big enough I can make mount holes as needed.
Leo
 

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The following is just to give some ideas on making heatsinks. Here is my mockup:
Heatsink.jpg
The observant out there will notice the rectifier is not 3-phase, but it does have the same footprint as that from WindyNation. Also, two of those fins are cardboard with silver paint on one side. The cooling fin at the base should be thick so that when the assembly is bolted together is does not distort thus compressing the other fins giving good thermal contact with the rectifier. If possible put some thermal contact grease between each fin. My base fin is 2mm thick, but 4mm would be better, and is the width of the rectifier. It should/can be wider if you wish and have the space available. The design all depends on how much space you have. Take 5twins, very neat, very effective and very compact. Personally I would copy his if you have an old computer heatsink lying about.
Fin.jpg
The face that contacts towards the rectifier should be filed flat very carefully to maximise the contact area. Often when cutting thinner Aluminium the edges will distort to make the surface uneven. The length of my fin is 6cm which is too short, should be at least 8cm. The edges have been bent up to improve air circulation. The other cardboard fins should be made of Aluminium and also be longer. I would make then 8cm in length with 1mm Aluminium or whatever you have available. To minimise the dimensions of the heatsink the fins could be bent out at 90 degrees.

So in summary what would I do: I would make a copy of my mockup with the following changes:
  • replace the cardboard with 1mm Aluminium
  • make the fins 1cm wider on each side
  • add an additional 1cm to the ends of each fin bent at 90 degrees
That should do, but if I had an old computer heatsink lying about I would copy 5Twins because it's the bees knees!
 
Well I mounted my new rectifier, same vicinity as Randy did for his.
I didnt make any greater heat sink than the large piece of polished aluminium it is mounted to, I may in the future move it back to under the battery but before I do that, I wanted to make sure everything was hummin along.
Used a little heat paste at the point of contact.
Still charging at low RPM but I guess that beats the alternative.
 

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Norton7d, well done. That is plenty of heatsink. When you have the bike running pull up on the side of the road and check how warm the rectifier/heatsink is. My guess it will be mildly warm. What you do not want is for it to be too hot to touch. Let us know the voltage output at say 1200 rpm, 2000 rpm and 4000 rpm. What is nice is a stable Voltage at beyond 2000 - 2500 rpm somewhere in the range 14.2 - 14.8 Volts. The optimum voltage for charging is considered to be 14.2V, but different regulators are manufactured for different voltages covering the range above. Certainly 13.8V is too low and 14.8 is at the upper limit.

On my previous XS650 a Delco regulator gave me 14.2V and a Fiat gave me 14.5V. The stock electronic regulator gave 14.3V. If you find the voltage at 2000rpm - 3000rpm says below 14V, then check your headlight. If it is an H4 55/60W then change to a 35/35W and you will find the battery charges better around town.

Good Luck.
 
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