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-Adam
Thanks !
The current draw vs speed reminded me of the formula for hull speed of a displacement hull it is HS = 1.34 x the square root of the waterline. If a 10 ’ kayak has a 6 foot water line the formula predicts a top speed of 3.3 knots. More power usually means pushing more water in front of the vessel in the form of a bow wave.
Thanks a lot for the information.
with regards,
It’s too bad the T 200 wasn’t able to be designed to handle 24 volts, it is so easy to put two 12v batteries in series.
Mark you mentioned automated control and guidance using a Pixhawk setup, did you have an idea for actuating directional control of the thruster?
Steve, your 144 amp hour lithium packs are impressive. Could you sometime go into how you make them, cost and who the suppliers are. I was planning on using a Trojan 24TMX.
Hi Patrick,
I’m using CALB 72AH cells http://en.calb.cn/product/show/?id-630 with a WATE 4S 50A PCM Protection Circuit Module ($21) I found on Aliexpress. CALB USA is in Southern California and I was able to get dealer pricing without too much trouble, saving me 30%.
LiFePO4 has a lower cell voltage than Li-Poly, but much better longevity and safety. The CALB 72AH can put out over 200 AMPs.
4 CALB cells gives me 72AH 14.4V. My craft is a catamaran and I use two battery packs (144AH at 14.4V). Each pack powers a pair of T200s with BlueESCs. My cost for each pack is less than $500.
I’d have liked to up the voltage, but a 5S LiFePO4 PCM is really hard to find as is the charger. As Phil mentioned, a non-planing hull has a max speed and I hit it without needing 18V. Can’t stress enough how important it is to measure hull speed at various throttle settings to maximize battery life. I put code in to re-normalize the throttle to not go beyond the max. More wattage than you need is just wasted.
Steve
Thank you Steve, the CALB 72 is out of my price range, thanks for the tip on hull speed I have looked it up and understand it. My little project will be for this coming summer and I will post how things go.
Thanks again
Pat