SOLUTION CONCENTRATION

[weggl]

The latest cell I’ve built is a 7-cell job and I have a puzzle with it and there may be someone on the site who can answer the puzzle.
After conditioning then running it on 24% sod/hyd cold start temp 22d/c 14v would only draw 5 amps. After an hour the amps increased to about 5.75 and the temp went to 29d/c.
I emptied the cell ran it on distilled water with the residual sod/hyd that remained in the cell, ran at 3 amps. I ran it for 2 hours emptied it and re-filled wit 20% sod/hyd temp 29d/c 14v and it started at 9 amps. So the question is why did it draw more amps at a lower concentration?
The other unit I have in the car wont get above 6 amps because I cant get the temp up.
The unit is in the boot (trunk) so it is not in a warm environment and because the vacuum is removing HO gas that is warm the unit cant get its temp up. What to do?
Because all of my trips are for short distance I have a temp problem, who can solve it?

Weggl

[kumaran]

Hi Weggl,

1) What power source are you using, battery or power supply?
2) What is the voltage readings between first plate and last plate of your cell?

Voltage readings between first plate and last plate of the cell must be at least 13V (1.85V per cell) in order to generate good amount of gas (3mm gap between plates). The best probably near to 14V and not more than that (loose efficiency).

More KOH (best 28% strength), more current goes in and not the other way round. I believe you are using battery as power source for your cell. If yes make sure battery charger connected to battery when powering the cell. If not the voltage from battery will drop and causing less current flow.

If source voltage is lower than stated above, no matter how much KOH added on, current flow will not go up.

[weggl]

G‘day Kumaran
I am using a 40 amp charger through a variable resistor setting the voltage at 14v across the terminals.
I am using sodium hydroxide, the only type that I have been able to obtain.
The plates are 8 of at 6’x6â€

[Looking In]

[quote="weggl"]G‘day Kumaran I am using a 40 amp charger through a variable resistor setting the voltage at 14v across the terminals. I am using sodium hydroxide, the only type that I have been able to obtain. The plates are 8 of at 6’x6â€

[kumaran]

Hi Warren,

[quote="weggl"]G‘day Kumaran
I am using a 40 amp charger through a variable resistor setting the voltage at 14v across the terminals.
I am using sodium hydroxide, the only type that I have been able to obtain.
The plates are 8 of at 6’x6â€

[weggl]

Hi Kumaran,
Thanks for your assistance. The reason I am using a variable resistor is so I can control the voltage. If I use one battery the voltage is below the 14.3 volts my car runs at. If I use the charger, which puts out 15v I still have to use the resistor to get the required voltage drop to achieve 14.2v.
I ran the unit this morning cold at 10C, 20% s/h 14.2v, started at 2.5 amps.
Where you live the temp might not get as low as it does here in Sydney, last night down to 9C. As you are aware the temp makes a big difference to current flow.
I then went to a 28% solution 84gms s/h 216 water which makes a 300gm mix.
Here are the results with temp rise. 28%

TIME VOLTS TEMP AMPS
11.20 14.2 12 3
11.30 14.2 12.5 4
11.47 14.2 20 6
11.52 14.2 23 7
12.03 14.2 25 10
12.05 14.2 26 12
12.08 14.2 27 15
THE TABLE WONT PRINT BUT THE AMPS WENT TOP TO BOTTOM
3,4,6,7,10,12,15
However a problem I have encountered when using concentrations higher than 24% is that the black coating that accumulates on one face of the plates comes off causing the water to go a dark blackish colour. The SS steel I have been using is 304, which gets a black to brown coating unlike 316 that goes a golden colour. This happened again with this mix. So I have gone back to 24%. Will let you know how I fair.
All the above were on the charger.
I then went to 2 bat in series through the var resistor to get 14.2v which was straight DC.
The temp when I switched to the batteries was 32C surprisingly at 14.2v the current was only 10 amps the time was 12.20 but by 12.27 the temp had gone to 32C and current to 15amps.
If you compare the table above with the charger putting out 14.2v the current was 15 amps at 27C.
It appears that to reach the same current on straight DC requires a higher temp than the pulsing DC on the charger?
Maybe I wont have this problem when the overnight temp stays above 20C.

Regards Warren.

[kumaran]

Hi Warren,

I don't have temperature problem here. Just some clarification. According to Bob, optimum solution with Sodium Hydroxide (NaOH) is 24% and Potasium Hydroxide (KOH) is 28% by weight ratio. The table shows clearly that the amps linear increase with temperature. Probably find someway to heat up solution before electrolysis (not practical).

I did some testing with 13 plate series cell (with 3mm hole at bottom of each plate) few days back. I didn't measure exact amount of KOH (very less) which added into solutions but the current goes beyond 20A using battery as power supply because of current leakage due to 3mm hole at bottom of the plates.

After few testings, I dismantle the cell to place into acrylic housing and notice the plates turned into gold in colour (evenly). I'm using 304 and not 316. I believe the higher electrolyte solution causes black to brown coatings on the plates.

[weggl]

Thanks Kumaran,
I have reverted to 24% and am getting higher currents at same voltage than 28%. Haven't had chance to do any yield test yet. the water staying clear at 24%. So it looks like Bob may well be right.

I think that maybe you should have made the holes 1mm and staggered them over different areas of the plates. Say - on bottom + near the top and the others as far away from each consecutive plate as far as possible.
Warren

[kumaran]

Hi Warren,

I always follow Bob's guide. I really inspired with his years of experiments and experience. Best of all he share his findings freely to public. Always respect his knowledge when comes to alternative energy technology.

Well the 6" x 6" plates with 3mm hole are arranged in zig zag pattern. It took me about nearly 3 weeks to measure, design and almost complete the housing construction. Will update some photes into my project area soon.

Update your result once you put your cell for test. LPM and power consumption.

[van]

Kia ora

I am about to try and fill/run my booster cell with KOH and distilled water. My supplier, a local science teacher, is dubious that an electrolyte at 28% by weight is feasible. ie Making up 4l would require 1 kg of KOH to be dissolved which he doubts is possible. Am I on the wrong track? I have no idea what the purity of the KOH will be, but given his background expect fairly pure. Any advice/suggestions are welcome. Thanks

[glenn_aircooled]

Gooday Bill,
Yes you can mix that concentration of Potassium Hydroxide.
You will probably want to go a little lower though.
The concentration rises as water is used up, the output will fall
when concentration goes above 27 %.
I would be mixing 26% solution by Weight with Distilled Water.
- Please Note; there are Very Serious Safety Warnings when mixing
Potassium Hydroxide solutions.!
- Do not mix if you havent read the Warnings.
Glenn.

[glenn_aircooled]

On this Page, 1/4 way down the Page. "Looking In" wrote it in RED.
http://oupower.com/phpBB2/viewtopic.php ... c&start=15
-
Glenn.

[van]

Kia ora Glenn

Thanks for the confirmation. Yes I have read all the safety warnings, part of the reason that so far I have confined my activities to using baking soda .
At the back of my mind I have a cunning plan, a plan so cunning you could put a tail on it and call it a rat, which would be much safer but the question is will it work? If it does I will make it known, but don't hold your breath

[van]

Kia ora

Well, got the KOH and made up a 10% solution. Given that in the past I have used caustic soda and seen its violent reaction, this one was a cinch. No noticable reaction with minimal temp rise. Which brings me to another question. When I explained all this to my supplier (science teacher) he asked why not use Sodium Hydroxide? Quoting from a catalogue, KOH is $20 + per kg , whereas Sodium Hydroxide is about $3 per kg. Anybody?
By the way I can appreciate now the difference between Baking Soda and KOH
Have to check things out, as 2 cells are going like the clappers while the 3rd appears to be idle, perhaps a short as in path of least resistance.
In brief, I have 3 tubular cells in series in one container. The possiblity exists that one is bypassed via leakage? Will look into isolating the 2 most active cells via pvc/nylon shield next week. Meanwhile the whitebait season beckons!

[van]

Kia ora

Sodium hydroxide/ caustic soda/NaOH