Voltage/Battery concerns

[PeterDove]

I have bought one of Eds minigens and am very happy with it. I want to start charging Lead-Acid deep cycle batteries with it, but the voltage coming from these units is very high >40V. What do I need to do to? Do I need some complex electronics to dynamically convert voltages?

Thanks

Peter

[AbyssUnderground]

You can use a DC>DC converter but lead acid batteries will drag down the voltage until they are charged, then it can be dangerous for them. You can connect them directly but you must keep an eye on it the whole time it is connected.

If you connect them in series then you don't have to worry if you get the right number in the string. It all depends on how you want to use the system.

[PeterDove]

Hi,

Thanks for your reply! Much appreciated.

What does drag down the voltage mean? Does that mean it will charge properly using the current? Or will it convert some of the voltage to current too?

I guess my point it that I could connect it directly but if it will only charge via current then its a huge waste with the high voltages.. Probably more efficient to convert the exessive voltages into a larger current?

Peter

[asheets]

What this means is that, when you hook up your gen to your batteries, the batteries will hold the circuit voltage down to 13.6VDC until they get completely charged (at which point the circuit voltage will increase back to nearly the max the generator can produce, cooking your batteries).

My suggestion would be a simple voltage regulator.  You can build one out of a few discrete parts found at radio shack, or you can get a standard one out of a car alternator.

[fungus]

asheets-you can certainly NOT use a car voltage regulator. They are designed for a completely different purpose. See the FAQ here that explains it. The battery will absorb excess voltage -until it is full-. Then the power from a wind gen must be diverted to another load to both keep the battery voltage down and to load the wind turbine. Shunt controllers do this. There is several homebrew circuit diagrams such as http://www.homepower.com/files/shuntregulator18.pdf (that U am using right now) and plenty more out there.

[kurt]

asheets, a voltage regulator out of a car alternator works by varying  the field current of the alternator it will not work with a permanent magnet alternator.

[Flux]

The high voltage is of no concern to your battery but you are right that you are not going to get best output. From Ed's description they are high voltage devices and for best results you would be advised to rewind as he suggests. Ideally with the minimum turns to give you the cut in speed that you need. That way you could trade volts for current.

You could also use a dc/dc converter or a transformer and rectifier, either of these methods will give additional losses that may cost you more than you gain from the tiny machine.

I would suggest that you measure how many volts you get at your cut in speed then reduce the turns and increase wire size to give you 12v cut in at that speed. Just change turns in ratio of original o/c volts to 12v. That way you will get the best possible output. if you use it as it comes then I think you are looking at about 25mA which is hardly enough to supply the battery self discharge.

Flux

[asheets]

You're right -- I have no idea what the hell I was thinking when I typed that in...

Actually, I do know what I was thinking...  I was thinking about the voltage regulator on the back of dashboard instrument clusters that provides constant voltage to things like the gas guage.  I'm thinking something like this -- http://www.national.com/pf/LM/LM317.html -- except more robust to handle lots of amps.

[asheets]

Of course, I forgot to mention that a shunt controller is truly the best.  IMHO, though, it does require the most parts and knowledge to get going right -- but it is the most efficient way to do things.

[asheets]

SOmebody else contributed a link to a shunt controller that is only slightly more complicated than a simple voltage regulator - -http://www.homepower.com/files/shuntregulator18.pdf