Re: first time using unprotected batts. advice please
Charge them when you notice dimming, right away. Unprotected are ok to use if you monitor the voltage periodically. When the voltage drops to 3.6, or so, per battery, then you know that they will be dropping below 3 volts pretty quickly under load. Usually a high drain incan will start to dim before the batteries are in any danger of being under discharged.
Bill