Re: Hilfe einen Verteiler für Igaro D1 in Deutschl

Posted by: acharnley

Re: Hilfe einen Verteiler für Igaro D1 in Deutschl - 09/04/16 12:34 PM

Originally Posted By: ConRAD
So far, as very well suggested above, sometimes “EFFICIENCY” is not a top priority. What is most important is indeed the effective power that a certain AC/DC converter can draw from the AC side (generator) of a system and deliver to the DC side (load) at a certain speed.
To make it clear once again: “if one device gets an input of 3.0 W at 20 km/h and has an efficiency of 80% and the other device gets a input of 3.5 W at 20 km/h and has an efficiency of 75%, than the second device is the better device, in spite of its lower efficiency”.
To make evaluations on how good an AC/DC is, I personally do not even need very sophisticated laboratory instruments since I make all relevant measurements directly on DC side.
To do that I use a real generator, a real AC/DC converter (the one under test) and an adjustable ohmic load made-up of calibrated ceramic resistors.
The wheel/generator speed is controlled and finely tuned via an asynchronous motor powered by a 3-phase inverter. At this point the test method is extremely simple: I adjust (sink) the load till to get the maximum transferred DC power to the load taking care of course that the voltage doesn’t go below a certain “low limit”.
For instance for usb 5V voltage I’d set this limit to 4.75V.
The results seem to be pretty reliable so far.
The basic estimate criteria would be that an AC/DC converter is as better as bigger is the amount of ACTIVE POWER that it will let to flow from the generator to the load.
The test system I use is THIS ONE, home made but pretty well performing.
Here below a couple of sample plots based on a Shimano DH-3D32-QR hub dynamo and an e-werk respectively set at 4.9V (1st plot) and 5.6V (2nd plot).
As you can see at 20 km/h it doesn’t seem to be able to transfer more that 2.75W:

You're now referring to current limit. Probably the eWerk (which uses a buck and boost) has a 500mA limit for one or both of it's chipsets. This is normal for high voltage PWM chipsets (and another reason why I don't use them in the D1).

I believe efficiency is more important because most tourers are not riding at a constant 20kph. The time a tourer really needs the most power is on a bad road in central Asia, with a wind, going up a hill, at 10kph.

Evidently a device should support a full 500mA output and ideally 0.75A as this is what many smartphones use as there 2nd level input (1st being 1.5-2A for a wall charger).

Igaro D1 is 3A / 15W limited. It's advertised as 2A because the chance of getting 15W out of a dynamo is very low and I don't want to give an impression that it's achievable in real world riding.

I'm aware of the techniques uses to smooth the input to assist in high current output; mosfets with capacitors, back to back electrolytic on the AC. I ended up with an expensive Japanese electrolytic outside the case (so it's replaceable should it be necessary after 10-20 years) and MLCC's to further reduce ESR.

PS) my request for the Igaro D1 to be tested and compared to your device has been ignored. frown