Thanks for the advice. I think i need a bigger one than you pointed out...if i'm getting 8-9 volts i have a max of 32-36 watts. (says 0-4 amps) Off had I don't recall how many amps I will get. Its an old treadmill motor but I really would hope to be getting near 100 watts.
I'm sure they make them bigger.
When it says that it has "Output voltage :5-42V continuously adjustable" Does that mean i can set it to say 14 volts and it will always step up to that no matter what the input or does that mean i can contantly fiddle with it manually (not really an option)?
The price is certainly not outrageous.
On using 12v chargers I just wonder it they are set to reduce from anything to 5 volts or reduce it by 60% or whatever to end at 5 volts (so if starting at 6 it would end at 2.5 or something)
Thanks again.
To answer you questions, yes, you should be able to set it once to 14 volts and have it maintain that as your input varies. There's a little micro processor on there that monitors the output voltage and varies the intake as needed to maintain your set output. You might need to adjust it slightly from time to time but in general the output voltage will be held as you set. As for power, looking closer at them it looks like the primary limitation is the amperage, many handle up to 3A which won't represent much power for you but the link below is to a model that at least claims to work up to 10 amps, so if your turbine was supplying 7 V you could output as much as 70 W. To get 100W through this your turbine output would have to get up to 10 V.
This looks like the closest fit:
http://www.ebay.com/itm/LED-Voltmeter-DC-DC-Step-up-Boost-Power-Supply-Module-3-0-35V-to-3-5-35V-100W-/290801352577?pt=LH_DefaultDomain_0&hash=item43b51c7f81When you say your getting 8-9 V is that open circuit or across a load, and if across a load, what kind of load? If you're seeing 8-9 V open circuit voltage then I'd expect it to drop lower when you're actually drawing current. Before you buy a converter like this, or a bunch of 6V stuff to run off this turbine, I'd recommend having a pretty good idea of the power it can put out and the voltage you'll get under load. To do this you'll want to connect a load (a big resistor such as an incandescent light bulb for example) and measure both the current and voltage the generator is outputting. If you don't have an easy way of measuring current then you can calculate it based on the resistance of your load (Voltage = Current * Resistance) but it's best to measure both directly because resistance tends to change as the resistor heats up. You're going to have to play with the load you put across it to get something that roughly simulates your intended use conditions. If you want 100W from this turbine at 6V then your looking at 16.7 A and a resistance of 0.35 ohms... which is going to be difficult to manage, but start with a smaller load (higher ohm) and see what you find out. The best load I can think of would be a car headlamp, which is probably something like 40-60W at ~14V. I know you want more than that, but it seems like a good place to start. I wouldn't rule out a mechanical gearing or (better) chain and sprocket however, as it sounds to me like you might not be turning this motor fast enough to really get it humming.
On your question about chargers. I am about 95% sure that all or almost all 12V-5V "USB" adapters use a linear regulator which outputs 5V from any input voltage higher than ~6V (within reason). The one or two I've taken apart were done this way and I don't think there's a great alternative way to do it.
Out of curiosity, how big is your turbine?
Cheers,
