New Guy

[lathamjames]

Hi ive been considring building a bath unit for my jeep grand for a couple days now and i was hoping i could gain a little insight first. Just a heads up im not a electrician or a mechanic thats why im asking. Ive done alot of thinking and my best idea so far is to build a case with several sealed sections in it each containing a positive and negitive. 3mm spaceing right? I have the notion of bending the plates around one another to create a multi surface or multi plate effect. I thought it would be best to share plates between sections it you know what i mean,- /+\ /-\ /+\ /-\ /+\-. Would it be best to share the neg or pos between two cells? I found cheap solar cells here http://www.goldmine-elec-products.com/prodinfo.asp?number=G17277 are they fiesable so you woudnt have to worry about the power drain from the alternator? Realisticly what can i expect from this? Will i gain HP or Torque? If i did maybe 6 cells and connected them in series that should give me around 2 volts per cell being about right, right?

[Owen_]

welcome,
First off, have very low expectations, and plan on doing a lot of work, and spending a lot of money (the work to money ratio is somewhat up to you).

The most important thing to think of when designing a cell is voltage. H2O will split at 1.23V but you will need a little more to compensate for resistence in other part of the cell (electrodes, wires ext) most people aim for 1.8-2V.
If your using the alternator which puts out around 14V you'll need to have multiple cells in series so that the voltage across each cell is with in reason (ex; 7 identical cells connected running at 14V will have a voltage drop of 2V across each) Most people use neutral plates, that are not connected to + or -, in between there pos and neg plates |+| |N| |N| |-| each gap works as a cell so that the voltage in this case is divided by 3.

With those PV cells you linked to, you could use four of them the get a 2V charge, and that would be a very different type of cell, as you don't need neutral plates.
From my past investigations PV cells don't put out enough juice to be bothered with. but let's look at those ones
lets do a little math; .5V x 3.5A=1.75watts per PV cell
x4 cells= 7 watts
A very efficient cell can make 7 milliliters per min per wat (MMW)
so that would give you 49 ml per min
Most people recommend around 1 lpm (litter per min) per Litter of displacement in you engine. Some say less so lets do the math for .5
So lets say you have a 4.0 (just a guess, and an easy number)
you need 2lpm and you get 49 ml per 4 PV cells (let's round that to 50ml)
2000ml/50ml= 40 sets of 4
So you would need at lest 160 of those cell to give you 2lpm at noon on a clear day.

I think it might be a better plan to charge a supplemental battery with cells, so you're saving up electricity when your parked and can use it at night

Look at "dry cells", keep thinking, and please don't buy some crappy kit

[lathamjames]

Awesome Have to say dry cells scare me a bit. They look like their waiting to kill. So i did some more reading and got this idea. If you take a microwave transformer a rewind the secondary to say 2.5 watts it should give you say 350 amps. Could you use this idea on a 12v battery? Is there a simpler way for me to get a lot of amps at a low voltage? And could you explain one thing? See if i understand it right. The cell decides how many amps to pull not the battery decideing how many to send. I know thats a strange way of putting it.

[BeaverRat]

Yes, here is a simple way of putting it: The Power Supply has a voltage that it runs on, and everything connected to it runs off of that voltage. The Power Supply can provide the cell with power, but the electrolyte solution as well as plate setup determine how many amps the cell pulls. A cheap way to get lots of amps at 12 volts is to mod a PC ATX PSU.

[Owen_]

Amps = Volts / Resistance in ohms

All these things can be ajusted, but sometimes it's more truble than it's worth.

the resistance of your cell has to do with design and the water solution in it.

Changing voltage of a DC current requires some expensive stuff. I don't think it's worth wile, and you'll have a lot of losses from the transformer.
AC is a diffrent story, with the right (and cheap) transformer you can get any voltage you want, and switch it to DC easily (just not back)

[chuggins143]

Out of curiosity, how many amps could one get out of a PC ATX PSU? I realize that they vary with what they're rated at... some are 300W and some are 600W and so forth. What I guess I'm getting at is that some of the power being generated is at several different voltages, what's a realistic expectation percentage wise? I.E. - will a 300W supply put out 30%? ...say a constant 100W @ 12VDC or some such before eating itself? I've messed with a couple at work just trying to find a descent supply for working with electronics, but never tried to push it to it's limits.
:D
Chad