1.2 volt system instead of 12v

[taylorp035]

I have thinking about this idea for at least a year, and I was wondering what you guys had to say.

The idea would be to build a verticle axis windmill using my 33rpm/v treadmill motor, which is good for 16 amps continuous, maybe higher.  The diameter would be about 3-4 feet.  The idea would be to use 10 1.2v 10Ah Nimh cells in parallel, to make a 1.2v, 100Ah pack.  Then I would make a second battery holder so I could transfer the cells to make a 12v 10Ah pack.  This way, the windmill would only take 40-45 rpm to hit cut in speed and there would have to be no gearing.  Plus, on ebay you can buy these cells for $3.58 a piece shipped, so it would only cost $36 for the pack.  I was thinking you could buy a Pb battery, which is about 10Wh/$ compared to the 3.4Wh/$ for the nimh, but you couldn't discharge the Pb as far, and it would be very heavy + possible spills.

If I charged the nimh cells in parallel, they would be balanced, and I doubt I could over charge the cells with my treadmill windmill @ 100Ah.  Plus, the idea is scalable in sizes of 10 cells.  A 10 cell pack would give me 120Wh, which I could then charge my laptop from.

I haven't designed the windmill yet, but I calculated a tsr of 1 and 8mph windspeed + 3ft diameter ~70-80 rpm, which would be awesome.  I just wonder if the motor would burn out at 200-300 rpm because I currently have no data for this.

Always getting into a mess

Taylor

[taylorp035]

http://cgi.ebay.com/Rechargeable-D-Battery-10000-mAh-Ni-MH-1-2v-4-pcs-toys_W0QQitemZ300405721101QQcm
dZViewItemQQptZLH_DefaultDomain_0?hash=item45f193880d

http://cgi.ebay.com/Rechargeable-D-Battery-10000-mAh-Ni-MH-1-2v-2-pcs-toys_W0QQitemZ300410314050QQcm
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[Bruce S]

Taylor;

 Couple things if I may.

A battery holder for 1.2Vdc 100Ahr, then switching to 12Vdc 10Ahr can get hairy and not sure it's the best way to go.

These are real nice batteries and similar to NiCds; one miss step and you'll receive the entire 100Ahr in one split second which could be fatal.

You wrote about the treadmill motor being good for 16A continuous.. at what voltage?

It may be possible, if the motor will not get up to say 13V to wire the battery packs up for something closer, say 6Vdc.

NiMh type batteries will take a charge pretty easy and can deliver it much the same as any other style. If you're having problems with say an inverter screaming because of low voltages. The way around that would be to wire 12 of them so you have 14.4. This will help with the initial dip.

This is what I have had to do for our e-scooter due to the initial loading.

Can you post the info of the treadmill motor? or is it in a previous post?

More than 1 way to get around a problem :-).

Cheers;

Bruce S

[taylorp035]

I have done this similar set up before with 2500 mah nimh AA cells, where I charged them in groups of 3 cells, then I put them in series with between 10 and 13 cells.  I have a youtube video where i powered my laptop doing this:

http://www.youtube.com/watch?v=Isswvcz7Mcg

You make a good point about maybe going with 12 cells.  I just want to charge all of the cells at once b/c I don't want them to get out of balance.

As for the ratings on the treadmill, the voltage was about 150v, or about 33 rpm/volt.  I was charging at 12v into a Pb battery, but I found cut in was at a higher speed than I wanted and b/c my wind resource is really bad at 10ft high and surrounded by trees.  Here is my youtube channel, which there are lots of videos of my windmill and my previous versions.

http://www.youtube.com/user/MrPizzaman09#p/u/14/Ck3TUw8x0yw

As for the possibility of shorting them out, I have been using LiFePO4 A123 cells in my battle bots for 3 years now, and they will discharge at 100C no problem, so I know what shorting batteries out will do.  If I only remove one cell at a time from the packs, I don't see any issues.


I hope to do some real testing with a lathe at some point, but the last time I tried hooking it up, it didn't fit.  I tried my drill press, but any rpm over 300 or so would cause the whole thing to shake violently.  I think I will have to make a 3/8" to 5/8" shaft conveter so I can use my 3 different speed hand drills.

[Bruce S]

Can't access youtube here at work, so I'll have a look at them this weekend.

Since you can get the voltage up to 12V is it possible to rig it up to charge them in banks of 6V instead?
I've found setting them up in a series/parallel that the individual cells have a more balanced charge rather than a long string of cells.

Just a thought to keep the mill in a usable range that you can still use now.

Cheers;
Bruce S 

[taylorp035]

Thanks for you input bruce