Battery operated stir plate, anyone done this?

Recently I completed a build of a DIY stir plate with the following parts.

Parts list:

• Radio Shack 7x5x3 Project Enclosure: $6.00
• 80mm case fan; example: $9.00
• Stir Plate circuit: $10.00
• Rare Earth Magnets, can be had from old PC hard drive: $FREE.99
  • [ame="http://www.google.com/search?hl=en&q=remove%20rare%20earth%20magnets"]Removal[/ame], the first link should be a YouTube video.
• Hardware: Nuts and bolts, image: $2.00
• Nylon Spacers, Qty:4, 1/2 inch long, image: $2.00
• Felt Pad: image: $2.00

Optional Requirements:

• soldering iron
• JB weld
• patience :cross:

So after acquiring all the parts needed to complete stir plate, and messing around with several stir bars in the flask I got things working pretty well. I am thoroughly happy with the stir plate circuit, and even if it cost me a little more than buying all the parts individually, I do not mind spending an extra buck or two knowing I have all the parts needed to complete the project. The instructions that accompany the stir bar circuit package leave a little to be desired especially if someone is unfamiliar with soldering, i.e. soldering a capacitor backwards.

I have used the stir plate several times, and everything works well, but I desire/want to make my DIY stir plate battery operated. The reason I would like to have this feature is to be able to put my stir plate in my fridge while I build a starter. The little reading I have done on building a starter requires the wort and yeast to be at a desired temperature to build certain types of yeast. If the ambient temperature is too high then the yeast count is high, but the yeast strength is weak, and stronger yeast cells can be built in a cooler environment such as a fridge. This holds especially true for building lager yeast starters.

Now I am no EE (Electrical Engineer) but here is a list of features I would like.

Feature List:

• rechargeable battery/batteries
• simultaneous charge/use

The PC case fan I am currently using requires 12V DC and 0.45A. This leads me to believe a couple of batteries could run this stir plate in the fridge for several hours. From the little reading I have done on the subject Li-ion batteries provide better support for charging and using simultaneously as opposed to NiMH batteries.

In closing, if anyone has or knows any information about this subject I would greatly appreciate any advice, i.e. in the form of a solution would be preferred. :cross:

*Note: I probably should have phrased the thread title as "Battery powered" instead of "Battery operated" :-/

Well you would need 8 aa,aaa,c, or D batteries to power that fan. The bigger the battery the longer it will last.

Sounds complicated.. (I didn't read all of it, honestly)

An easy way to make a stir plate:

Old record player (look at a thrift store), attach strong magnet to turn table (center somehow). Rig up a "plate" to sit over the turn table (plexiglass shelf) as close to the magnet as possible. Viola. stirplate (runs at 33 or 45 rpm!).

I'm not sure where one buys stir-bars. I work in an organic lab, so I have hundreds of them.. never tried to buy any as a "layman".

Do you have a local hobby shop nearby? Particularly one that deals in RC cars or planes? If so, go in and ask about some rechargeable battery packs. You could use a Ni-mh pack that is specifically built for RC cars. They're 9.6 volts, but when charged, are actually a bit higher. They're also cheap and easily charged. If you want something in the way of a Li-ion, they should have those as well, although they are a bit more costly.
If you don't have a hobby shop close by, check out hobbyking.com. They're overseas, but are very cheap and ship pretty fast. Just remember that any rechargeable pack is gonna need a charger of some sort as well.

I guess I don't see the need. It's not a portable device while in use, why not plug it in? "This leads me to believe a couple of batteries could run this stir plate in the fridge for several hours."
You don't want to run it in the fridge and several hours actually is a couple days.

IMO, you can make excellent starters at room temperature for both ales and lagers. Somewhere in the vicinity of 65-75F or so works well. No real need to refrigerate the starter and if too cold it could and probably would, inhibit yeast growth. Seems to me that you are seeking a solution to one of them non-problems. However, if you still want to do it that way, I would simply power it with a wall wort and run the wiring under the door gasket or figure out some other way to run the wiring. Battery power would be the very last option I would pursue.

Couldn't you just put the cord through the door hinge and run it that way? Just make sure it's long enough.