Hand powered generator

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joecool85

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I'm looking at building a simple hand power/pedal powered charger for my 5AH SLA, I heard (and have read some) that I could use a DC motor as a generator. I found a 24v DC motor rated at 135w that I think would do the job, am I correct?

here is a link for the motor: **broken link removed**
 

That motor is geared - looks like a high torque low rpm type. You may have a great deal of difficulty turning it regardless of whether it will work properly. A PM DC motor would work backward.

Try surpluscenter.com

A quick check brought up this 200mA generator for $5.95

https://surpluscenter.com/item.asp?UID=2006121209071439&item=10-939&catname=electric
 
You may want to see if you can determine:

A. The amount of power over time that you'll want to deliver to the battery.
B. The amount of power that you or someone else might be able to generate.

You might compare the two to see if it makes sense. It was a surprize to me to see that a well conditioned athelete could only deliver some fraction of what I thought was possible. The folks who've made the various bicycle trainers might know the answer. Keep in mind that the generator will not be 100% efficient.

If the whole thing does make sense consider other sources such as automotive alternators or even a generator - I think you can still get them from junkyards. I don't know that these are better - just alternatives. The word "surplus" made me think of the old WWII hand crank generators. Surf for info on those - as a way of determining what you might expect of a person's capability.
 
What voltage?

What current?

A miniture permanent magnet synchronous mains AC motor will give you 240V excellant for shocking people.

Seriously, I take it you need 24V, any 24V PM motor will do but it will need to be spun a bit faster than it runs when connected to 24V to make up for the losses.
 
Ideally I need about 14v @ 1amp

I had read that using a motor like this you normally get a little better than half of the voltage the motor would use (IE, a 24v motor would produce 12-15volts or so)
 
I'm not too sure about that, but I'd check out the efficiency of the motor. Look at the datasheet and the input voltage vs current and output torque and speed, workout ratio between the input and output power. I think it's a reasonable assumption the the losses will be mostly in the voltage. A 24V motor with an efficiency of 75% will produce 18V.
 
Take a look at the overall plan. Charging a 5AH battery @ 1 amp will take 5 hrs of hand-turning. Or are you planning to maybe use a few hundred mAH at once and only have to replace that?

The output voltage of a permanent magnet motor is roughly proportional to rpm. So a 24v motor turning at half its normal speed may make 12v.

You likely will require a lot of gearing. The hand works effectively only at fairly low rpm, too low to turn a motor successfully. Getting the right speed is key.

Having an ergonomic mount and handle is important if you're turning it for a long time.

Bicycle power- using leg kicks- is FAR more powerful yet easy to do for a long period. Making an ideal setup is not hard, you just need a bicycle or exercise bike and you've got usable shaft power right there.
 
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I forgot to let you guys know that shortly after I posted this, I came across a excercise bike I'm going to use, so the generator will be running off that. And also, you got it right on the charging. The max charging is 1.5amps on that battery anyway, and I plan on using maybe 250ma a day, so that would take like 20 minutes to charge back (most SLAs charge at 80% efficiency).
 
For the sake of general sanity please use amp hours when refering to a batteries capacity, as 250ma's a day means nothing. That could be 250ma's for 1 second once a day, 2.5 amps for a tenth of a second once a day. or 10ma's constantly (roughly) 250mah's a day is what you meant to say =)

All aside, 20 minutes a day on an exercise bike generating that much power will get you some legs =)
 
I seem to recall that a bicycle powered generator can provide roughly about 100W?, but it takes some serious pedaling to do that!.

As suggested, it will seriously improve your leg development!
 
I'm not so sure. I mt bike for upwards of 2-3 hours at a time, and when I grab my road bike it is normally for a 5-10 mile trip. I think my legs can take generating 250mah a day lol.
 
If you want to save time, use a heavy weight and a pulley system to drive the motor. It's more effcient to put a large amount of energy into lifting an object all at once and then slowly release it to generate the electricity.
 
Sceadwian said:
If you want to save time, use a heavy weight and a pulley system to drive the motor. It's more effcient to put a large amount of energy into lifting an object all at once and then slowly release it to generate the electricity.
Click to expand...

That seems like something that might be more efficient for generating larger amounts of power. I want to keep this thing pretty simple. Looks like I'm going to go with the motor I found on eBay along with the excercise bike I grabbed. Hopefully it'll do the trick. At minimum it will be a learning experience, and at best it will be creative way to charge my SLA batteries.
 
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