# Regulation of current at constant voltage, 2kW

Hello

I need to regulate current which is pulled by high power devices connected to constant voltage 12V PSU. PSU is about 2kW.

So voltage is always around 12V(11.5V - 12.5V), but when I connect my devices, the full current needed for devices is pulled. I need to regulate how much current is available to those devices, either via PWM or analog voltage.

Thanks!

Why do you want to regulate the current? If you will take the time to explain the real question, you will probably get better advice.

Great, I like guessing games :confused: I think they are peltier elements. Or else they can be lights or heaters or motors or linear actuators.

Please give more information. It depends if the devices are inductive or not. How many devices are there ? What is the current per device ? It is okay if the grounds are connected ? Are long wires involved ?

(jremington asked the same thing while I was typing this)

Very importantly what voltage overhead are you envisaging for the constant current
drive?

Wow, sorry that I missed the important info. I am not really a pro

So devices are generators for water electrolysis. They work at 12V and I plan to connect 8 of them. Maximal current for them is about 20A. I can also use higher voltage PSU, but then I would combine series and parallel of those devices. They are not inductive(they are made of inox 316L). Grounds can be connected together and wires are fairly short(50cm).

I want to regulate the current so I can control how fast the process of electrolysis will go.

Hopefully this electrolysis is for some useful purpose, and not for something as completely misguided and phony as "HHO gas".

You could vary the amount of salt you add to the water. This will vary its resistance and hence the current flowing in the electrolysis process.

You do realise that the 2kw of energy will be mostly dissipated as heat in the water

I have done that as a kid. The larger the current, the more the fun

I think a PWM control will be not the same as a smooth analog controlled current. It’s just my opinion, I think that pulses of high current is chemically not the same as a smooth analog current.
However, An analog current control will require big transistors and a very large heatsink.
Controlling the current is even harder.

It can be done with a shunt resistor as a feedback for an Arduino. And very big mosfets or transistors for a PWM control. It needs to be very big. To control 20A is no problem, but the PSU could supply much more current, a current limiter is almost impossible when the Arduino is used as control unit.

Perhaps a controlled switching regulator is the best option. I assume that something like that can be bought. Perhaps there are even devices like that with current control instead of voltage control.

Having a big PSU and controlling the current afterwards doesn’t seem the right solution.

For a test perhaps you can buy a used variac together with a 12V battery charger (a simple one, with only a transformer and rectifier diodes) could be used. Perhaps it will cost 100 or 200 dollars.

I have a very old welding power supply. Inside is a transformer and a moveable core to select the current. With 4 diodes of 250A it would supply a large current and the core can be used to control the current a little. Perhaps that is too big, you don’t want to boil the water :o

There are 12V 20A power supplies with current control for leds. Search Ebay for : 12v 20a led

My conclusion: It is not easy, buy something.

One interesting question is the capacitance of an electrochemical cell - is it true capacitance or is directly coupling the current to (reversible) electrochemical change at the electrodes?

The electroplating industry probably has the knowledge about how PWM affects electrode behaviour.