Manta's basic cell experiments

[Bob]

Manta:
 I have a Electric bar-b-q element out there  probly 5KW and a few other things like Electric dryer heating element coils ( nicrome wire I am sure)
How would I go about makeing a 30 amp current limiter for my cells out of say the dryier coil ?
... every inch of the coil will have a certain amount of resistance, that I understand.
...but I want 30 amps at 12vdc... for my current limiter
... I'm not making the connection here <GRIN> take me back to school one more time please ! HAHAHHA
...
Bob.......

[candyman55]

Bob,
I'm not sure what the dryer coil looks like, but the grill element probably won't work. I tried an electric oven element (probably the same as a grill emement) if you hook both ends on the meter you get 12volt through. But the way the electric elements are made, the solid wire only extends a little ways into the element itself and then there is a smaller coiled wire slipped onto the ends and as you said this wire is very brittle and you cannot get it out without breaking it.

There is a small resistor inside of delco alternators that may work, and tractor supply also has one in the tractor electrical stuff that may work. I got em both but haven't tried to limit my amps that much (yet)

[Manta]

Bob,

If you treat the element as a simple resistor you would get, for 110 volt 5 Kw

Current =         5000/110 = 45.45 amp

Resistance =     110/45.45 =   2.24 Ohm

So the useful characteristics of your element are :-


Volt  (E)          =  110
Amps (I)          =  45.45
Watts (w)        =  5000
Resistance (R)  =   2.24

Now,  if you put the same element across 13.5 volt you get;-

Volt =   13.5
Res  =   2.24
Amps =  13.5 / 2.4 = 5.625
watts =  13.5 * 5.625 = 75.94

You need to know how long the element is to be able to work out the Ohm per Inch . It will be small,  fractional even.

Let's say it was 10" long.  This works out at 2.24/10 = 0.224 ohm per inch.

So we want a resistor that drops 13.5 volt at,  say,  20 amp.

For this we need

volts  = 13.5
Amps =  20
Res   =  13.5/20 = 0.076 Ohm

Power  = 13.5 * 20 = 270 watt

Length = Ohm per inch * resistance required  = 0.224 * 0.076   =  0.078"  ( 78 thou)

This is unusably small.  But it is based on a fictional 10" coiled element. If the wire was straightened out it many give you a short but usable length.

But you get the idea.

Do a short basic prog and run a few 'what if' type entries for different values till you come up with a working size.  Even a spreadsheet.  I love spreadsheets,  but I prefer my own programs.

Enjoy.

Manta

[Bob]

WOOO HOOO !
THANK YOU !
that is what I wanted ! now I can do it !
thank you very very much !
...
Bob........

[Manta]

The following may be of interest.
I found a piece of perforated stainless steel that came from the outside of a truck air filter element.
It's only a bit,  but if I remember right the original was about12" high and 10" diameter.

Could be a useful source of ss. Check your truck service stations;  they probably throw them away when they change them.

Manta

[Bob]

OH yah ! Dumpster diveing at the truck stop may be a good way to get 12" to 18" preferated SS that way ! ... might be a pain to get the steel off the filter but it can be done !
 good thinking !
Thanks !
Bob.........

[crb]

Found this on hho forums,
I'm running brute force systems with an inline 1 ohm 225W resistor as my "current limiter" circuit. This clamps my current at @ 14 amps and divides the voltage so I get @ 3 vdc (14A) at the cell.

Thought this might be a little food for thought!
 

[Bob]

Howdy CRB !
thanks for the info !
sounds like if I wanted a higher amperage "Current limiter" all I would have to do is use 2 of those resistors in parallel and I'ed have a 28amp current limiter..... er I think anyway!
...
or would I have to use 1/2 ohm resisters in parallel ? 225w ?
...
...
I really like the idea of using a Current limiter on the system because of the ability to run Higher
electrolyte concentrations it would give me ....
any comments on that ?
...
Bob.......

[crb]

Bob,  Just a guess on my part,  Maybe!!

crb

[Manta]

crb,

Yes,  there are both good and bad sides to using a resistor to limit the current. The good side is that you can do it easily,  the bad side is the voltage drop. With a resistive limiter you are never going to get all the voltage. I don't know how this effect things practically;  leave that for you big amp men to test.

You could try putting the resistor after the cell.  I.e  between the cell and ground.

Manta

[Bob]

Manta:
I thought that is the way you'd have to hook up the current limiter into the system... AFTER
the cell....  there are other ways Perhaps ?
...
 I'm working up the currage to try and make a resistance coil, from a old Electric dryer heating element
or perhaps a electric water heater element.
but before I do that I need to get my cell back togather and back on the truck <GRIN>
...
its getting too darn cold to be outside very long up here and my tinkering is very limited now !
HAHAHAHA ... Panzy! I guess!
HAHAHAH
Bob......
 
 

[Bob]

Manta:
  Ok I let it slide for a while but Now I really need to understand it... <GRIN>
your saying that if I put a resistor after the hydroxy cell to ground... as a current limiter.
that the voltage will drop on the cell ?
 I am guessing that is because they are in series and the voltage in series is divided among the elements of the series chain...right ? 
...
or is how much voltage the elements see Dependant upon their absorption of the power/amperage
I seam to remember that it was a messy formula and you had to take the inductance of the element into consideration... like 1/r1+1/r2+1/r3 or something like that.

My problem is if I have a 2 Ohm resister, able to handle say 2000watts ( glowing white hot!)
after my Hydroxy cell... what will be the voltage to my cell ...
the resistor will stop any more amprage from going through the cell than can go through the resistor
I got that through my head now... but what about the voltage ?  now much will it drop ?
will it simply be devided by 2 ? because there is 2 elements in the chain ?
or is it more complicated than that ?
...
My cell needs at least 3vdc per plate and sense their hooked in parallel to the power source what ever is on the line will go to each plate... so reduceing it from 12vdc to 3vdc isn't a bad thing at all
...so if that main line was reduced to 6vdc because of 2 elements in the line  that wouldn't be a bad thing ....
... do you see my confusion ?... I'm not sure I understand this current limiter idea completely.
...
I understand that with a current limiter in line that is going to slow down the electrons through the cell to the max the current limiter can pass... so no more than the current limiters rating can pass
 ...
but dropping voltage ? whats that all about ? hehehehe
Bob.......

[candyman55]

Bob,
I don't think that the resistor no matter where you put it will decrease your voltage, only your amperage.
If you put he resistor after the cells would that not make the cells act as a large heatsink and increase your cell temp? If you want to decrease the voltage you have to either run more cells in series or use a 6 volt system.

[Manta]

A cautionary tale.

As some of you may know I bought a multi channel data logger.  A Pico ADC-11. It looked like a very good instrument for gathering details of the experiments.. BUT

If anyone is contemplating getting one of these do first check with Pico that it will work with your computer.
I am having to send mine back as it wont take reading for more than three minutes without crashing the computer.  Pico acknowledge the problem and say they don't have an answer to it. It only occurs on certain computers. The ADC-11 I have is a usb version.  Maybe the parallel port version is better. At least they have offered to refund my money,  about $200.
They do other loggers,  maybe a different one will work.

You have been warned.

Manta

[Cowboy]

Bob,

  It doesn't matter where you put the resistor, it will create a voltage drop.  The total of that voltage drop depends entirely on the resistance of your cell.  Being a 1 ohm resistor I doubt it will use more than one or two volts off of the circuit.  That being said, you may need to drop a cell on your series design to continue production.  it will still be a 12V drop from + to -.