Sciencemadness Discussion Board

Electrolysis in series cells?

Pumukli - 28-7-2015 at 10:36

I was wondering if it was possible to use series connected electrolysis cells with higher voltage?

Reason is I have a beefy lead acid battery charger but it outputs at least 14-15 V when charging the 12V battery.
It can output 40-50 Amperes continuously but I only need say 5-6V to make the desired electrolysis going. The excess voltage just heats the electrolyte and means energy loss and low efficiency.
What if I connected two (or maybe three) such cells in series? The net current would be the same through all the cells but the voltage would be divided (more or less evenly).

Do I overlook something obvious? :-)

Sulaiman - 28-7-2015 at 10:50

You certainly can put electrolysis cells in series,
this is precisely what you do when you charge your 12 V battery
which is six cells in series.
for efficiency and plating quality lower current density (A/m2) is better,
and higher than necessary cell voltage is a waste of energy,
which as you noted, turns to heat.
so more cells in series is better up to the point where the combined cell voltages required is more than the power supply voltage.

[Edited on 28-7-2015 by Sulaiman]

Pumukli - 28-7-2015 at 11:55

Arrrgh, the car battery is really six cells in series!
I felt that I may just overlooked something obvious... :-)

Thanks for feeling like a real dumba...s. :-)

hissingnoise - 29-7-2015 at 01:29

Quote:
What if I connected two (or maybe three) such cells in series? The net current would be the same through all the cells but the voltage would be divided (more or less evenly).

Do I overlook something obvious? :-)

Yes you did. That voltage is unaffected by inserting multiple cells but current density is lowered by each extra cell!
If you're electrically minded you could try taking a centre-tap off the output transformer . . . ?


Fulmen - 29-7-2015 at 02:04

Hissingnoise: I think you've gotten it backwards. In a series circuit the current will be the same for all cells.

Pumukli - 29-7-2015 at 02:57

I think if I used the same geometry for electrodes then the current density would be the same in each cell.

What flows in should flow out in a series of cells (resistors, lamps, etc.)

j_sum1 - 29-7-2015 at 03:31

This is exactly what is done in an aluminium smelter. A pot line may be a couple of hundred cells in series. There is about 4 volts drop in each cell. The whole thing is DC (and un-grounded). Currents are huge.

Aluminum-Smelter-Production-Line.jpg - 72kB

hissingnoise - 29-7-2015 at 04:28

Quote: Originally posted by Fulmen  
Hissingnoise: I think you've gotten it backwards.

Fulmen: I think you've misconstrued my meaning . . .

Only an idiot could assume that current density is variable for any circuit!


hissingnoise - 29-7-2015 at 04:34

Quote:
This is exactly what is done in an aluminium smelter.

In chlorate/perchlorate production, too, cells are used in cascade!


annaandherdad - 29-7-2015 at 09:11

Quote: Originally posted by hissingnoise  

Only an idiot could assume that current density is variable for any circuit!


The current through each cell is the same but the current density depends on the geometry of each cell. Current is amperes, current density is amperes per m^2.

Fulmen - 29-7-2015 at 13:03

Hissingnoise: So it seems, I really don't understand what you're getting at. Why bring up current density at all?

aga - 29-7-2015 at 14:58

It sounds good !

Why bother with facts when even quantum paticles indulge in Spin ?