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How do you decide what battery should be used in your pride & joy? Either made from a kit or one you've refurbished as a project? Is there a way of working out running hours etc? Any advice gratefully received.
Strangely no one has answered an important part of your original question !? 🤔 How to calculate running time! Simply put; divide the capacity of the battery in amp-hours (AH) by the current in amps (A) drawn by the load. AH/A = H !! Step 1; measure the max current drawn A(max) by the motor under load; i.e. full speed ahead in water - hang on tight!. If not possible then use the max current data of the motor at the voltage you intend to use. Step 2; check the capacity of your battery; usually given in mAH for some peculiar reason! Divide by 1000 to get AH. Divide the capacity in AH by the max current in A =A(max). Result is the theoretical time that the fully charged battery can deliver the current required; i.e. runtime at full speed. Theoretical because in practise the usable capacity will be a bit less than nominal depending on the age and condition of the battery, ambient temperature etc. Also you won't want to completely discharge the battery; it won't like it 😡 Step 3; measure current at a mid-range throttle setting 'cruising' - A(cruise). Again divide capacity AH by A(cruise). result is 'cruising time in hours. If measuring not possible use the motor current data given at maximum efficiency. Should give a reasonable approximation. Example: motor current at full speed = 10A. Battery capacity 7000mAH = 7AH. Max theoretical runtime at full speed = 7/10Hr. Approx 42 minutes. Cruising current; 5A. Cruising time = 7/5Hr = 1.4Hr. Approx. 84 minutes. Use the highest capacity batt. you can get in without upsetting stability etc.! If you need ballast use a bigger battery; then you have 'payload ballast' instead of JUST ballast. Minimise current drain by; ensuring drive train is perfectly inline, well lubricated, prop is as small as possible for the desired performance (trial and error!). Hope this lot helps, not space science but a few basic rules! 😉 Happy sailing and lots o' fun. Cheers Doug 😎
Young at heart - slightly older in other places 😉 cheers Doug