I purchased a buck/boost voltage converter on ebay for under £15 which upped my 12 volt cheap wall plug in PSU to 38 volts. It is meant to regulate the amperage but it was never sensitive enough at keeping the current low enough for making Colloidal Silver therefore I only used it for the higher voltage. Because it could not regulate the current well enough I instead used a current regulating diode while testing and had planned on building a better device but when I discovered the ineffectiveness of silver against bacteria and yeast/fungi I stopped using it.
Bacteria have several mechanisms for defeating silver. Gram negative bacteria such as Pseudomonas aeruginosa can reduce silver using Pyocyanin which stops the ionic silver from damaging them by reducing it. That makes silver totally ineffective. Reducing Silver using Green Tea or other Efflux Pump Inhibiting substances can make it more effective because it can still ionize making it active but while bacteria are constantly reducing it it cannot work. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4135871/
We report that the Gram-negative bacteria Escherichia coli 013, Pseudomonas aeruginosa CCM 3955 and E.coli CCM 3954 can develop resistance to silver nanoparticles after repeated exposure. The resistance stems from the production of the adhesive flagellum protein flagellin, which triggers the aggregation of the nanoparticles. This resistance evolves without any genetic changes; only phenotypic change is needed to reduce the nanoparticles’ colloidal stability and thus eliminate their antibacterial activity. The resistance mechanism cannot be overcome by additional stabilization of silver nanoparticles using surfactants or polymers. It is, however, strongly suppressed by inhibiting flagellin production with pomegranate rind extract. https://www.ncbi.nlm.nih.gov/pubmed/29203912 https://sci-hub.se/10.1038/s41565-017-0013-y