You do realize that the stall current on 2 550's is over 160A? Check the specs, and you will see the stall draw on a 550 is about 85-90A per motor (the newer ones have an 85A spec for the 12v - used to be 86 or higher for both 12v and 6v). www.mabuchi-motor.co.jp/cgi-bin/catalog/e_catalog.cgi Cheers,
Not really. In my Derf, my pair of Mabuchi 550s that pull about 80A at stall (I may just test that one day for giggles), they each run around 4-6A while driving my ship around. I have each fused with 15A fuses, for a maximum possible continous draw of 30A, on a 40A mtroniks ESC. 12A continous limit would be really tight, and the moment you hit pond snot that slows your prop rotation, you'd threaten to cook the thing. Which raises a point to comment on Wreno's warning, yes 550s can draw 80+amps at stall, but why would you let them get that far when you can stick a 15A fuse between your drive motor and your ESC?
550 is a size desigination, it has very little to do with motor specs, different 550 sized motors can & do have different stall currents. For instance a Stinger and a Titan are both 550 motors but have different stall currents than the standard drive motor that BC sells as well as eachother.
I'm going to stick a 60a fuse inline between each battery, thats two... from my conversations with Stephen, that should work ok. I will use a Viper40 for the esc...
I will again suggest that you fuse each motor individually. Multiple reasons... 1 -a 60A fuse upstream of the ESC won't protect your 40A ESC. Yes the mtroniks are suppose to shut themselves down in an over-draw scenario, but why risk a 60$ ESC over a pair of ten cent fuses? 2 - If you lock up one motor and pop its fuse, you still have another to limp home on. 3- if you fuse at your batteries and pop that fuse, you will be 100% dead in the water. No pump, no drive, nothing to do but sink.
There are differing opinions on how to fuse a system. -Some go over kill and design the ESC to handle a locked drive motor. This is expensive but usually works well. -Fuse before everything. Works but you are dead in the water if it goes. -Single large fuse before the ESC. Protects the ESC but if your radio is powered by the ESC then you are still dead in the water. -Smaller fuses for each motor. The most complex but offers the best odds of something working if a motor locks up. I usually go the lazy route of a single 30amp fuse before the 40 amp ESC (with the motors in parallel a single locked motor is no big deal). Being an easy kill when a fuse blows is no fun but it beats having to buy a new ESC (fuses are cheap). Always pick an fuse rated for less than your ESC.
I use 30-amp set-resetting thermal circuit breakers, intended for automotive headlight circuits. If a motor stalls, the ship stops for a second or two, then comes back to life. You can then carefully limp to port, as long as you dont push the throttle too hard.
Yes banebots.com/pc/ELECTRONICS/BB-1245 is what I use but there are no more to be had. I use 1 per motor.
Hahahaha In my long and glorious history (okay, inglorious but fun), I've only fried one motor/ESC brushless combo, and one Titan motor met its end from overcurrent being run at 12V vice 6V (design error from the get-go, eh?) (back when I was young and didn't do much testing). Not a bad record. Of the two incidents, the Titan could've been saved by a fuse, I'll admit. But overall I don't feel gravely compromised by a lack of fuses. You young people, don't blow off bench testing!! Won't solve everything, but I'd have heard that Titan sound like it was going to die
Your mileage may of course vary, I doubt my boat would have burned to the waterline at any point without fuses, but it has possibly saved me time and money and allowed me to remain on the pond in some cases.
Fuses aren't there primarily to prevent a fire. That is a rare issue in a properly designed and maintained boat. The primary use for a fuse is to protect your ESC. The circuitry can self destruct nearly instantly (much faster than a thermal resetting circuit breaker).
I have been running ESC's since March 2012 (banebots and Mtroniks) without fuses and have not lost an ESC yet. I do try to keep within specs as far as motor draw to ESC limits and such. Another thing I learned.. if you boat is not moving when it should be... then STOP trying to drive it.. I had a plastic shopping bag from walmart wrapped around my prop and I had been trying to drive. I didn't burn anything up but at that point I learned to just stop and get it to shore and check it.
I have run ESC's since 2004. No problems either as long as I paid attention to the specs. For example: -2 Maxon brushed motors that stall at 8A a piece run off a single 20A Mtroniks ESC -a brushless outrunner motor that stalls at 9A run off a 15A ESC I heartily second the notion of being a conscientious ship captain.
