Dry Cell Question

[keiththevp]

If I am running a 20% solution of NaOH at 14 volts and with a pwm I would like to draw about 30 amps, does anyone have any idea how many neutrals, and plates I should be using, also gap size?

I have never tested with this concentration before but I would like to start to avoid the freezing issues.

[Painless]

You need to use a number of neutrals that would bring your per-gap voltage as near to 2v as possible without dropping below that. 6 neutrals will give you 2v per gap, but in automotive applications there is potential for the voltage to drop below 14. I would recommend 5 neutrals.

Good luck!

Russ.

[daddymikey1975]

another point to consider is the magical 6" plate profile..

most have had luck with plates up to 6" square with great results.

Some have theorized that with plates over 6" sq. that there could be the potential for less voltage across the entire plate.

For example.. if your connection was at the top of a 10" plate, the internal resistance of Stainless Steel being what it is, there would be less of the source voltage at the extreme opposite end of the plate, thereby reducing efficience and having part of the plate not producing what it could produce. (again, this is the accepted theory..we don't have any conclusive tests that I'm aware of yet to prove or disprove this theory)

I hope this helps
mike

[alpha-dog]

another point to consider is the magical 6" plate profile..

most have had luck with plates up to 6" square with great results.

Some have theorized that with plates over 6" sq. that there could be the potential for less voltage across the entire plate.

For example.. if your connection was at the top of a 10" plate, the internal resistance of Stainless Steel being what it is, there would be less of the source voltage at the extreme opposite end of the plate, thereby reducing efficience and having part of the plate not producing what it could produce. (again, this is the accepted theory..we don't have any conclusive tests that I'm aware of yet to prove or disprove this theory)

I hope this helps
mike


Just take your meter and read accross a S/S plate. I don't believe you'll read very much resistance. It's just BS to think that S/S will have a problem like that.

[SmartScarecrow]

Just take your meter and read accross a S/S plate. I don't believe you'll read very much resistance. It's just BS to think that S/S will have a problem like that.



well, maybe not ... I built a device of 20 gauge 316L a couple years ago that used plates 12" by 12" ... after running the device for a few days of testing, I pulled it apart to have a look inside ... the patina that forms on positive plate faces show definite lack of formation the farther I got from point of electrical connection ... so I decided to make connections at to opposing corners and the formation of the patina settled down and got regular ...

now I could be all wet, but the way I interpreted this was that the resistance of the SS was keeping the electrical charge from being active across the whole plate surface ... basically, I had dead areas on the plate surface ... I would love to see someone repeat my experiment, see it for themselves and maybe offer some other logical explanation ...

[alpha-dog]

well, maybe not ... I built a device of 20 gauge 316L a couple years ago that used plates 12" by 12" ... after running the device for a few days of testing, I pulled it apart to have a look inside ... the patina that forms on positive plate faces show definite lack of formation the farther I got from point of electrical connection ... so I decided to make connections at to opposing corners and the formation of the patina settled down and got regular ...

now I could be all wet, but the way I interpreted this was that the resistance of the SS was keeping the electrical charge from being active across the whole plate surface ... basically, I had dead areas on the plate surface ... I would love to see someone repeat my experiment, see it for themselves and maybe offer some other logical explanation ...

What about the amount of gas it produced. Could it be a linear comparision or a noticable loss of production

[SmartScarecrow]

What about the amount of gas it produced. Could it be a linear comparision or a noticable loss of production

gas production was same with same input watts ... as far as I can tell, the lack of patina was not in any way related to production ... I did not run enough tests to know for sure, but I suspect that if I had stepped up the watts a little at a time, I might have found that with connections at both corners, the device might have been able to handle more watts than with only the single connection ... wish I had been more attentive to detail but let that one slide past me ... was an obvious test I kick myself in the butt for not running ...

[Painless]

I'm thinking that taking an SS plate and reading across it isn't going to be an accurate test. You need to consider the conducting electrolyte between two plates. Current will take the path of least resistance, if the resistance to keep traveling through the plate is greater than the resistance across the electrolyte and onward to the opposing power terminal, then the current will say goodbye to the remainder of the plate path.

If you follow what I'm saying above, this should show why a larger plate may not make so much use of it's surface area other than to help absorb the heat of resistance.

Russ.

[alpha-dog]

I'm thinking that taking an SS plate and reading across it isn't going to be an accurate test. You need to consider the conducting electrolyte between two plates. Current will take the path of least resistance, if the resistance to keep traveling through the plate is greater than the resistance across the electrolyte and onward to the opposing power terminal, then the current will say goodbye to the remainder of the plate path.

If you follow what I'm saying above, this should show why a larger plate may not make so much use of it's surface area other than to help absorb the heat of resistance.

Russ.

Here's a better test --- when running your cell read the voltage between any two plates on the corner that you apply voltage, then read the same two plates on the opposite corner. Is there a voltage difference from one corner to the next. My guess is it would be to insignificant to notice.
I feel the plate size has more to do with fitting in your vehicle. Even on our dodges it would be hard to install a 24" x 24" electrolyser.

[BoyntonStu]

Here's a better test --- when running your cell read the voltage between any two plates on the corner that you apply voltage, then read the same two plates on the opposite corner. Is there a voltage difference from one corner to the next. My guess is it would be to insignificant to notice.
I feel the plate size has more to do with fitting in your vehicle. Even on our dodges it would be hard to install a 24" x 24" electrolyser.

A 1/4" SS bolt 1" long gets hot with 25 amps passing through it.

I have not seen this temp rise with non-stainless steel bolts.

BoyntonStu

[keiththevp]

I do have a 6" by 6" cell. and my old cell was a 4 neutral that ran about 3lpm at 40 amps. I bought this cell on ebay and it came as a 3 neutral, I just had no idea that is was going to make that much of a difference in amp draw and cell temp. I am going to change this cell to a 5 and 6 neutral setup just to see how many amps it draws in such a high concentration electrolyte. When I have results I will post them. Thanks everyone for your input!!

[daddymikey1975]

Just take your meter and read accross a S/S plate. I don't believe you'll read very much resistance. It's just BS to think that S/S will have a problem like that.

Alpha-dog..
i mentioned a few times that it was an 'untested theory'.. i never insinuated that there was fact behind it and certainly wasn't making an attempt to stir up yet another debate.

I was just offering help to the guy, and other pointers to keep in mind that he may not have thought of yet.

I hope this helps
mike