Hi,
My name is Dennis and I am an electronics engineer. The low cost and high current way to go is this;
1. Buy a cheap digital multimeter(the max current rating is NOT important). Believe me on this.
2. Buy a current sensing resistor. See this link. It is a 0.005 Ohm, 7 Watt resistor and it's real cheap($4.16).
http://www.mouser.com/Search/Product...KYZDPMxg%3d%3d
3. Put this resistor inline with the +12V against the electrolyzer.
4. Use the voltmeter to read the voltage across the sense resistor. Whatever value is displayed, multiple it by 200 for the true current value. This calculation is due to the resistor being 0.005 Ohms.
This gets your cheap DMM an effective maximum current measurement of about 37 Amps.