Trade speed for run time?

[Test0055]

Hello
Perhaps this is a weird question to you all-out-speed FE boaters, but I'd like some ideas of preserving power to prolong run times on the SV27.
This is my first boat and now in the beginning I'd be happy to trade some speed for longer driving between charging the batteries.

I plan to try the boat with paralell 3s 2250mah LiPo's and later I order 4s LiPo's of larger capacity.




...And, I'd appreaciate to hear some run times you're getting out of 4s Lipo and if you go flat out or more conservative?

[motoxbob11]

You can't really "slow it down" to increase run time unless you put in a whole different setup. Most of the time I run everything stock with 2s lipo batteries in series for 14.8 volts. I don't think you will like running it on 11.1 volts and that won't really increase runtime all that much.
I use 4800 mah batteries and time my runs. A 5 minute run uses about 2500 mah running at close to 40 mph. I really don't know how long it will run because I don't trust the voltage cutoff that is built into the stock speed control. So my advice is go with a pair of 2s lipos and move them forward so the boat's cg is around 8.5 inches forward of the transom and have at it.

[cuzican]

I know what you mean about wanting longer runtimes. I came from larger gas boats that will run 30 minutes on a tank.
Thought a supervee looked pretty cool. The guy at my LHS said its just stupid fast. While I admit it is impressivly fast, what is the point of going that fast if its only for 4 to 5 minutes before your batteries start to drop off. It got a little better when I put on a balanced/sharpened octura x440 prop...but still. How lame compared to 30 minute run times.

[Electro]

You could in reality increase run time by decreasing the amp surge going into the motor, for example if you get lets say 2 cell lipos 5000mah and 15c each they will increase more run time because the battery is limited because it can only discharge at 15c but it will also have 5000mah capacity as in more runtime, Nothing big like 10 minutes but you might get 2 or 3 more minutes.

[Bill-SOCAL]

Bigger battery + smaller prop = longer run times.

[Fluid]

Bill is right, and by going down to 3S you will also gain run time because at the lower voltage the motor will draw fewer amps with the same setup. Using low-discharge cells (15C) is not the way to go as cell heat buildup will be greater - see below.

The biggest boat issue with extended run times is heat buildup. Water cooling will do only so much, and heat will steadily increase in the motor, ESC and cells. Not only do you need to avoid over-discharging LiPos, but keeping their temperature down is important. Any time they get much over 140F you risk permanent damage. Going 4S2P with 5000 mAh cells gives a 10,000 mAh capacity - considering an 80% discharge as safe, then to run 10 minutes your average amp draw can't exceed about 45 amps. That's fast enough to be rewarding, but watch the heat buildup.

I used to run nitro and a little gas, and call me silly but after 5 minutes of running a fast boat I get either bored or tired. Bored if the boat is slow enough not to require much attention while driving, and tired if it is really fast and requires intense concentration to avoid trouble. I just can't see why 30 minutes of driving in circles would be fun at all.....




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[RiverRat]

We are getting 12mins out of 2s 6000 polys with a 3.3v lipo cutoff installed.

[azjc]

you could try a higher voltage/lower motor kv this will also lower your amp draw and running a higher voltage setup will also allow you to run packs with a lower "C" rating

[ChaKane]

How is your wiring harness connected up?? If it is currently in series, you could change it over to parallel and that will double the runtime but will halve the voltage (ie make it slower). All you need do then it run a higher voltage cell and get your speed back with higher run times.