frockin five second rule

[amo123]

so got a swordfish 120 and an 8xl and running 4s2p. first run the other day and the from the time you hit throttle it only goes for five seconds....let it off and repeat...this goes on for a while....any ideas?

ao

[Steven Vaccaro]

Is that on the bench or in the water? Which prop are you using? what are the pack specs?

[LiPo Power]

If you hit full throttle and hold, how long will she run?

[keithbradley]

What batteries are you running and with what prop and boat? That 8XL is a pretty amp heavy motor especially if its turning a decent sized prop. If your batteries arent up to the task maybe you are hitting the cutoff?

[BakedMopar]

I run the swordfish (aquastar) 120 with 8xl's in several boats. One thing I noticed about all three of mine is that the "Auto Caculate" on the LVC always reads it one cell higher. You can verify this by listening to the number of beeps on start up. What this means is under load, if your batteries aren't up to the task it will hit the cut-off. Make sure to manually set it for your cell count.

[amo123]

using 5000mah 25c batts 4s2p. 642 prop. and yes in the water. five seconds of run time only and then it stops.

[Fluid]

George's explanation is the most likely answer. That setup can draw over 150 amps on acceleration, dropping pack voltage below 3.7 volts per cell. If the ESC thinks the pack has 5 cells, it will shut you down at around 15 volts. Your 4S pack under load will drop below that voltage to 14.5 or less - that is why the boat stops. Just manually program the ESC to 4S and the problem should go away.

BTW, you will get better cooling if you can position the water inlet/exit at the top of the motor. Right now only the lower half of you motor is being water cooled.



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[Steven Vaccaro]

I ran at the nats with 2 4s packs in parallel, but forgot to parallel the second pack. I had a similar issue with the esc hitting the lv cuttoff. Until the pack heated up. And ended up running for the entire race heat without another issue.

[LiPo Power]

Maybe ESC caps???

[amo123]

dammit! i win for biggest tardo today.....had it set for 6s....when i originally got this esc was planning on running 6s so that is how i set it up....problem solved....check yo self and do it again!

[sailr]

Manually set the cell count like the man said! You are hitting LVC because the auto cell-count is off. Nothing really wrong with the ESC. There's a reason for it, but too lengthy and complicated to explain here.

[amo123]

George's explanation is the most likely answer. That setup can draw over 150 amps on acceleration, dropping pack voltage below 3.7 volts per cell. If the ESC thinks the pack has 5 cells, it will shut you down at around 15 volts. Your 4S pack under load will drop below that voltage to 14.5 or less - that is why the boat stops. Just manually program the ESC to 4S and the problem should go away.

BTW, you will get better cooling if you can position the water inlet/exit at the top of the motor. Right now only the lower half of you motor is being water cooled.



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so just rotate the can around?
on a side note the water flow sucks.....has a rudder pickup with inlets on both sides. but just barely tinkles out. is this inherint to this type of pickup? on my bj26 i made the custom pickups that attach to the brackets for the rudder...since that one only has a pickup on one side..am using large i.d. tubing...

[Fluid]

The easiest would be to rotate the can 90 degrees as long as there is room for the water lines under the hatch. I use single rudder pickups on most of my boats and the water discharge is plenty. You probably have a restriction in the system somewhere. Unscrew the discharge nipple on the top of the rudder (if it has one) and check for trash inside the rudder. Make sure there are no kinks n the flexible lines. You do not need the water to be shooting a foot out the exit, a small stream is plenty.



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