esc shutting down, what is cause please?

[pmdevlin]

Running a ripmax seasrprint water cooled esc,this will handle 280a, max peak current 940a (according to the instructions!, which seeem very high, here is the link http://www.ripmax.com/item.asp?itemid=P-XTRA-SESPRINT&Category=010), with a Graupner 12v 700bb turbo motor, 12.5a, 43a stall. I have 12v nimh, or two 7.8v (15.6v wired together). After a few mins running the esc shuts down,which is restricting me to a very small lake!
The above figures do not mean that much to me, but my novice experience would suggest the esc should be able to handle what the motor is giving it. THe boat is an old wood hull 48" huntsman. Whilst it does not need to be very fast, it needs to hav a nice scale speed, the real boat was actually used for racing, and the above combo works well, until the esc throws its hand in!!
I also have a 12v Graupner 600 turbo, far higher revving than the 700, would that be a better bet (PS.. The prop is 2 blade 40mm, I have tried a 35mm, but the boat stood still!)
Thanks
Paul

[pompebled]

Hi Paul,

Do you have a link, featuring the ESC you mentioned?

In general, the values you/ripmax give, are absolute nonsense; these are the factory specs for the Fets used in your ESC, completely disregarding the fact that the copper traces on the print would simply evaporate if these currents would ever be applied...

My guess is the ESC shuts down thermally after a few minutes, because the 700 draws too much current, turning the 40mm two blade.(high pitched?)

Without pictures it's hard to say if the set-up is sound, but I would not use a (relative) small, amphungry motor for such a large hull, if the boat has to move at hullspeed and beyond (half-glider).

My first thought would be a 800 or 900 motor, but the cell count would be quite high to get the boat moving for any length of time.

A much more economical motor would be a surplus from a copier, or a fan motor from a car.

I have had a 700 motor and a fan motor turn an 8"-6 airplane prop on 12V and the 700 motor pulled nearly 30 A continuously!
The fan motor turned the same prop without any problems drawing only 1,5A...

I do realize that turning a 40 mm prop in water will draw considerably more by the fan motor, roughly five to eight times as much, depending on the prop selected, but the 700 will do the same, leaving your ESC with the impossible task to provide such huge currents.

I added a few pictures of the fan motor and copier motors I use in hulls over 40".

The fan motor has been reduced in weight and fitted with watercooling on can and brush holders, a must when used in a closed hull.

Regards, Jan.

[pompebled]

[quote paul]:thanks for the photos and info Jan.the esc is a ripmax sea sprint, and can be seen in the ripmax website
http://www.ripmax.com/item.asp?itemid=P-XTRA-SESPRINT&selectedtab=060&Category=060-050

This is the page, with the spec, as I detailed above. When I read it back, it did seem ridiculous, but please have a look and see what you think. I feel as though I have wasted a fortune on these parts, £28.00 for motor, £35.00 esc etc etc!, thinking thast I was buying quality! that would do the job, when really a visit to the local car wreckers would have done the job for a lot less money!
Paul [quote]

Hi Paul,

If I read the info correctly, the ESC is designed for 12-36T motors.

If memory serves me well, the 9,6V 700 motor is a 7 turn motor, my guess is the 12V version will be 11, or maybe 12T

In combination with a submerged prop, this draws too much current.
I'd say the ESC in the link isn't suitable for this set-up.

Options:
- run a smaller prop (didn't work, as you mentioned)
- get an ESC that can handle the 700 motor (+ prop)
- change the motor for a fan motor (which has more than 12 turns)

Regards, Jan.

[Shaun Hendricks]

You can get a 700 with a higher winding value. Should be in the 20+ range for boat work. The other option is to put a gearbox on the 700 since it's not getting into its power band anyway. Maybe 1.33:1, 1.5:1 or 2:1. A variable gear/belt drive would be nice too... that way you can change out the pinion and spur to whatever you want. However, the gearbox will probably run you as much as a different motor.

I wouldn't cash in on the 700 just yet. 800 & 900 series motors aren't cheap... You can also go outrunner brushless but that would take a new motor AND new esc...

[pmdevlin]

Cant afford anymoe money!!!!! Anyway thanks Jan and shaun, this is the motor
https://shop.graupner.de/webuerp/servlet/AI?ARTN=6317
and I have this also
https://shop.graupner.de/webuerp/servlet/AI?ARTN=3302
Back to the amps thing Jan, I ran it on monday evening, without the tops on the cabins, to keep cool, and let the water cooling pipe trail into the water,thinking it might "syphon" water through coil. It did to a point. The esc seemed ok, I didnt run it flat out, however after about 15 mins, on inspection, the inline fuse holder I had fitted had melted! combined with all the above probs, does that mean the wires are too thin? Another problem, I'll have to get the rc helicopter back out at this rate!!!

[LtDoc]

I don't know why 'Ripmax' would even suggest that this ESC would handle upwards of 280 amperes, it certainly won't. [(280a x 280a x .003)/12V = 19.6 amperes. I would consider a 20 amp draw as maximum. With water cooling maybe 25-30 amps.]
The 'quick-n-dirty' answer is that the ESC is too small for the motor. I think you would be very lucky to get a continuous 20a draw with it. Hate to think of 'Ripmax' going that route with advertising, too bad. They did tack on that "*" on the ratings! To bad they didn't give an explanation for it.
- 'Doc

[green-boat]

the inline fuse holder I had fitted had melted! combined with all the above probs, does that mean the wires are too thin?
Those inline fuse holders are the worst thing to use. They have small wires crimped to buttons that have a domed end that presses against a fuse. Not much of a contact area for current to flow (resistance).

Resistance = heat= meltdown

Use a fuse holder that will mount to a flat surface, solder the wires to it and clip the fuse in place.

[Shaun Hendricks]

That puppy is spinning 11,600 rpms on 12v... waay too fast for direct drive on a cruiser hull. You need to gear it down or go to a smaller propeller. Maybe 35mm. That will decrease the pitch and allow for the higher rpms, but you might still be cavitating at that point. That's the only things I can think of to drop your amp draw down.

[pompebled]

Like Greenboat already mentioned, that kind of fuse holders are not suitable for the current you draw.
I must admit I never use fuses in my boats, they have to keep running during the races and not whine about every little amp-surge...

In your much bigger hull it's another matter, you wouldn't want things to get so hot they might catch fire.

General concensus seems to be that you either need to gear down, or use a motor for direct drive, that has more turns, to bring the amps down.

Did I mention fanmotor...?

Regards, Jan.

[pmdevlin]

Thanks to all for this info, great advice. First I will get the fuse holder sorted, and increase the wiring to handle more amps. Then as its the cheapest option, change the prop to a smaller one. Originally it was a traditional 3 blade, would this be better if smaller to the x blade on it now?
With the gearbox (this is new territory for me!) will this drop down reduce speed?
Thanks,
Paul
PS... Will give ripmax a call, I am interested in their explanation of the amps thing......

[green-boat]

I must admit I never use fuses in my boats, they have to keep running......
I like your thinking, I never use fuses either. The only time I used one was because it came with the ESC. It was one of those inline jobs and melted down with the motor pulling 3 amps. Finally got the boat back to shore, cut it out and wire nutted the wires back together. That was over 6 years ago and it is still that way.

[pompebled]

Originally it was a traditional 3 blade, would this be better if smaller to the x blade on it now?

If you take the same diameter; NO (the ESC will shut down even earlier)
If you start with a smaller on and work your way up, it might work, but you'll still draw too much current if you get to the propsize to get the boat going the way you want it.

With the gearbox (this is new territory for me!) will this drop down reduce speed?
Thanks,
Paul
PS... Will give ripmax a call, I am interested in their explanation of the amps thing......

With a good seleced gearbox the motor can turn the prop you need to get up to speed and draw less amps in the process.

Personally I'm no fan of noisy gears, a belt drive works much quieter.

(did I mention a fanmotor...?)

Regards, Jan

[pmdevlin]

yep, you mentioned the fan motor! I suppose I am hanging on for the inevitable after spending another load of dosh on the Graupner motor, thinking I was doing right! I think I will try the smaller 12v Graupner 600, the revs are higher, but the stated amp draw is a bit lower. Will also re wire, and get a better solution for the fuse holder, and try a smaller prop.
I think I Have a small 12v water pump from a car screenwash working in tandem with the motor, wired on the motor poles, so faster the motor, faster the pump, but will have to monitor battery drain, Failing that, another esc!

[pompebled]

My guess is the 600 in direct drive will make thing worse, short of burning up it might take the ESC with it due to shorting out.
Higher revs without a reduction isn't the solution.

Regards, Jan

P.S. go find a scrapheap...

[ernest2]

pmdevlin, is buying a new esc not an option right now? certainly there are some esc that can handle the load which might not costs an arm and leg.
the fan motor certainly is a cheap but great option but the esc might still not be able to handle it.

[pmdevlin]

Ernest2 I just seem to be continously spending money, until the advice on this forum, spending blindly with bad advice from certain suppliers. THe graupner motor for example, seems to be the root of the problems. I would say the esc is a good one, but the motor is amp hungry ihn this heavy boat, which needs to have a nice scale speed. Looking at previous comments, I would be better getting a motor from a scrap "white goods" or office etc! What esc would you recommend?