Interesting AMP control issues - Any Ideas?

[scopemaster]

For the last 2 weeks I have managed to build a simple lexan box with plates. I first began with 1 gallon distilled water then started with adding electrolite (Sodium Hydroxide).

A couple attempts I added the sodum to get a 15amp draw. Then watched it. I returned an hour later to find the solution boiling like crazy and the AMP gauge pegged at over 60amps. Needless to say wires were red and seals melted down.

Next I repaired and then this time I took 1/4 tsp and mixed it in 20ml of distilled water. This time I used a syringe and added 2ml. Amps immediately went to 10amps but went down within a min or 2. I then added another 3ml to total the solution at 5ml. (Again solution was 1/4 tsp to 20ml water. Mixed and dispensed as discribed from a syringe).

After adding the total of 5ml soultion I waited. the first hour seemed steady around 6-7amps. But then it began to climb. 2 hours later I stopped the process when the amps grew to over 30amps. Thinking it was the heated water I ended this for the day. The following day however right when I connected the Amps jumped right up to 30 amps immediately. I let it go but had to pull the plug when the terminals began to heat up. I can assume heated solution was not the sole answer.

Why did this happen? What could have changed when temperature was ruled out?

Is there a way or method to limit the current going to the generator so no matter what the concentration level is the predetermined amperage will not be exceeded?

[pertyfly]

Is this a sealed series cell unit? It sounds like it from what I'm reading, but I don't see a mention of that. How many cells are you running, and what voltage?

Also, are you emptying the electrolyser when you add the NaOH, or are you adding it to the unit with it filled?
If you are doing this, it may be that the lye is not mixing in the whole electrolyte fully for some time. (possibly, if they are sealed cells)

Also, maybe the cells are not sealed all the way, and there is current leakage. This could have that sort of affect on this, and it would be extremely inefficient

[Bob Boyce]

You don't mention what metal you used for plates. If not an inert metal, it could have eroded into solution and increased solution conductivity through contamination.

If you are using inert metal plates, the initial current drop is quite normal. An electrochemical reaction first starts out as electrolysis, then as the metal reacts with the electrolyte solution, electrochemical films develops on the plates and thicken. These films contain trapped atoms of hydrogen on the negative plates, and oxygen on the positive plates. Once these films are fully formed and the electrolyte temperature rises, current will rise again as the electrochemical reaction becomes more pronounced.

Normally, each time you power down, allow to cool,and re-apply power, current draw reduces until the electrolyte warms up. It does not seem to take near as long for the reaction to get fully under way after the unit has been in use for a while. It's almost like the plates need time to get conditioned before they will perform their best.

Without knowing the construction details, it's kinda hard to try to troubleshoot what may be happening with your unit.

Bob

[scopemaster]

Its a single cell 4x7 16ga 316 Stn Stl plates. 18 total in the sealed box. The box has been leak tested ad can hold 30psi min as tested. Thinking of eventually working with multiple cells but only after I figure out what is happening all together. (New at this and learning). Each plate is spaced arond 1/8" apart. Each plate is 4.5" x 7".

I am using a typical 12v x 675 Cranking Amp marine deep cell battery with a 10amp charger with 50 amp booster. (Battery seems to continually take around 5-8 amps consistant draw from the charger.)

Once I figure out how to accurately control the AMPS and limit the amps to lets say 10 amps per cell and never exceed the determined draw then I will look at multi cell unit.

I have total access to machine shops and materials. (People oweing favors) So I need to be pretty much on target on what I am asking for.

[Bob Boyce]

Oh heck, no wonder. That many plates in a parallel configuration is gonna suck down loads of amps at 12 VDC. You only need less than 2 VDC on a single cell, anything more than that is wasted in making heat.

You can use a heavy duty PWM (12 VDC motor speed control) to regulate the current, which will also drop the average voltage applied.

Bob

[duke401]

[adam666]

[kevinsatterfield]

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