I also run my FF on Lipo polymer 4 cell batteries. These are 14.8 volts W/battery monitor.
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Hobby King Battery Monitor 4S
Accurate and easy to use, the Hobby King Battery Monitor 4S will give a warning buzzer when the Lipoly pack drops below 12v.
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These light weight batteries 5000mah will give me over 18hr of running time on the FF.
The yellow case is water proof. I made sure the outside connection are also waterproof. Running your FF and bait tank on lithium does have its inherent dangers, but the lifepo4 type batteries are much safer.