Thanks. Bought it there for £28 delivered- looks very fresh. Is there a need to fit a small fan onto it to keep it cool or should it be ok?

Also because the old rectifier was running the battery down all the time would I need a new battery or should it still be ok to use with the new rectifier

pf85 wrote:Thanks. Bought it there for £28 delivered- looks very fresh. Is there a need to fit a small fan onto it to keep it cool or should it be ok?

Also because the old rectifier was running the battery down all the time would I need a new battery or should it still be ok to use with the new rectifier

Have you done proper tests on the charging system yet?

For future reference this should always be your first port of call..

With the bike running and everything connected up measure the voltage across the battery terminals at idle and at 5000rpm.

13.8-14.4v is a good range, anything out of this and it's likely to not charge.

Next step is to disconnect the Genny and set your meter to AC volts... mesure the voltage between sets of yellow wires at 5000rpm.. you should have 50v

Fully charge the battery and put the headlight on for 1 minute to remove float charge. Take the battery off the bike and measure the voltage, leave the battery for 24 - 48 hours checking the voltage every so often (couple of hours) a knackered battery quite often discharges itself very quickly... after 48 hours you shouldn't have much of a voltage drop. :)

I'm surprised SMPS regulators aren't more common on bikes.
It seems all bikes use shunt regulators. They basically just burn excess voltage to maintain 14.4V output. It wastes quite a bit of energy. They waste up to about 300W. Thats fuel and power wasted.

Lope wrote:I'm surprised SMPS regulators aren't more common on bikes.
It seems all bikes use shunt regulators. They basically just burn excess voltage to maintain 14.4V output. It wastes quite a bit of energy. They waste up to about 300W. Thats fuel and power wasted.

Switched modes can be more efficient however it's likely to be larger, more complex, more expensive and subject to vibration.. while simpler linear regulators are simpler to build :)

Wasteful but effective

This is something like the argument for class A and A/B amplifiers for audio equipment. Interesting subject tbh. :)

I think the cost should not be an issue. The extra cost for a SMPS Reg would be paid for with the fuel it saves in no time.
The vibration issue can be sorted out if they use solid caps and do a vacuum seal of the unit in epoxy...
I think the reason is just cost. They want the bike to be cheap to make and sell.
If more bikes had dying Regs there would probably be aftermarket SMPS Regs available, but its probably mostly the Honda regs that die?

Cheap computer power supplies sell for 10 quid wholesale. Not expensive at all. Ofcourse economy of scale determines the price, but theres a lot of bikes that could be running SMPS regs.

Why would a transistorised regulator save fuel ?

Old reg/recs die, newer models have better heat sinks and are placed in cooler places.

Its the difference between a linear power supply and a switchmode power supply.
Linear burns excess voltage. Switchmode power supplies pump little bursts of energy into storage devices thousands of times every second and then output them in a smooth (ish) fashion. The effect is that 70-94% efficiency is achievable with a SMPS depending on how well its designed etc, while the linear power supply on a bike is probably less than 30% efficient. It depends on the voltage the rectifier puts out.

SMPSes often don't need heatsinks at all because they convert energy efficiently, hardly any gets wasted as heat.

Lope wrote:Its the difference between a linear power supply and a switchmode power supply.
Linear burns excess voltage. Switchmode power supplies pump little bursts of energy into storage devices thousands of times every second and then output them in a smooth (ish) fashion. The effect is that 70-94% efficiency is achievable with a SMPS depending on how well its designed etc, while the linear power supply on a bike is probably less than 30% efficient. It depends on the voltage the rectifier puts out.

SMPSes often don't need heatsinks at all because they convert energy efficiently, hardly any gets wasted as heat.

I think you need to brush up on switching mode power supplies more.

Computer power supplies have big fans and big heatsinks inside them, they still generate and burn off excess heat.

The altenator is generating AC voltage that varies between 50 - few hundred volts, it's not like you have a stable 240v line supply thats already regulated that you can easily step-down with a transformer (as in the case of many switch mode power supplies) you still need to regulate this variable voltage to a stable voltage.

Which is what the Reg/Rec does. Adding further circuitary to make it switched mode would be pointless as it directly regulates it down from xAC -> 14.4v DC

Where did you get your figures from.. the generator itself only have a peak output of 350watts, so it's highly unlikey that it's burning off 300 watts of power.

I don't think you'd be saving lots of fuel, i've ran a total loss bike before (no generator) and it doesn't improve fuel consumption dramatically.

Pardon my simple brain, but how can any different sort of reg/rec possibly save you fuel??