I designed and built this charger when I was resident in Ecuador, as an example of what their armed forces could easily make after they expressed interest in fabricating accessories for tactical radios which we had supplied.
It consisted of 10 identical charging ports. The power supply was conventional (transformer - bridge rectifier - reservoir capacitor) running on the local 110Vac (nominal) supply.
I can't find the English version, assuming it was amongst the dozens of items stolen during a house move. This (Spanish) document is a copy of the one submitted to the Ecuadorean Army. I learnt the language during my many trips to, and residences in, South America. Not grammatically correct as I didn't have lessons, but good enough to satisfy a contractual requirement to teach their technicians in Spainsh.
The following is just a small sample of the drawings I made. Unfortunately they didn't scan very well so don't reproduce well here.