Capacitive current limiting may be used for electrolyzers powered by rectified AC. It is based on putting a capacitor in series between the AC source and the bridge rectifier. The reactance of the capacitor will limit the current to a certain value, but will not dissipate any power like a current limiting resistor.
The capacitor must be suitable for AC use (not an electrolytic capacitor). For mains-powered operation power-factor correction capacitors are the best. This is best suited for welders operating on mains power (no heavy transformer needed) or hydroboosters running on modified alternators (diodes removed). You can use any number of cells (even one), but you need to figure about 2.0V per cell minimum. For 230VAC 50Hz you need about 14uF for each Amp.