As John stated you can use those cheap chargers BUT ! you must correctly test them with a meter to verify one that it does output a direct current voltage, two that it exceeds the final charge voltage app. 1.45V per cell and third doesn’t exceed C/10 current unless you are willing to watch the charge the whole time. Next connect it up with amp meter in series plug in and verify C/10 then set back and wait, check if wall charger not getting to warm. The first time I check every hour the current and voltage until done, that it did not over charge by exceeding Vpk and that battery or wall charger did not get to warm. Then tag the charger with a note on what battery it’s good for.