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Author Topic: Fuse requirements for Big Brushless?  (Read 6662 times)

boaterjim

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Fuse requirements for Big Brushless?
« on: February 22, 2016, 02:53:39 PM »

Hi all, I have just got a HK Princess speed boat and it will be using a 3 cell lipo battery, power chain is a 3660 1604 kv motor and a 125 amp esc, both water cooled. total boat weight around 2kg

My question is, what size fuse do I use?

       Jim
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Martin [Admin]

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Re: Fuse requirement
« Reply #1 on: February 22, 2016, 04:28:38 PM »

 
Hi Jim,

HobbyKing state that the motor's Max Current is 94 Amp, so fusing it may be a bit tricky.
Lets ask the high power race boys?!

Martin    :-)


http://www.hobbyking.co.uk/hobbyking/store/__25091__Watercooled_Brushless_Inrunner_3660SL_3180kv.html
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inertia

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Re: Fuse requirements for Big Brushless?
« Reply #2 on: February 22, 2016, 04:36:15 PM »

Maybe??
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Bill D203

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Re: Fuse requirements for Big Brushless?
« Reply #3 on: February 22, 2016, 04:48:51 PM »

Hello Mayhem land. Its been some time since ive been on here.
Now what size fuse ?
I have not yet seen a fuse fitted in this sort of set up. Im not even sure if a fuse that size would be able to fit in a boat as with that type of current its going to be BIG. Maybe the Car boom boom type radio boy might have something that will do the job.
This sort of set up relies on the ESC doing its stuff, GOOD connectors on the motor and batterys. However if it all goes wrong the old magic smoke will so be visible.
Take care all. :-))
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martno1fan

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Re: Fuse requirements for Big Brushless?
« Reply #4 on: February 22, 2016, 04:52:01 PM »

You dont need a fuse,what im looking at though is your motor it only has 1604 kv ? on 3 s thats only a tad over 14 k rpm loaded which isnt much in a fast boat using a smallish prop.Usually the fast electric guys run them at 30 k rpm for surface drives,not sure what your princess has but im thinking 14 k isnt enough rpm . That kv is more suited to 6 s setups .What does the boat come with ?.
My thinking is the boats under powered id fit it with a 40 mm motor and 6 s and a stronger esc and it will be much happier but you might need to also upgrade the driveline.If you want you could try your setup with 4 s 2 p setup for longer runtimes and a bit more speed.
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boaterjim

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Re: Fuse requirements for Big Brushless?
« Reply #5 on: February 22, 2016, 06:41:12 PM »

Blimey lads wot a can of worms. The Hobby King Princess has been purchased of the shelf ready to run, I was going to start with a 3 cell lipo to get used to running the thing and then upgrade later.
The blurb on the boat by HK says the motor is a 3660 1604kv motor, which on some of the videos on u tube looks pretty fast,
wonder if they got the kv right?
Has anyone got this boat and could tell me how it runs with stock set up and help sort me out? I don't think a fuse will be much good and will go with the advice of esc, wiring and connectors.
Jim
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andrewh

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Re: Fuse requirements for Big Brushless?
« Reply #6 on: February 23, 2016, 02:18:59 AM »

Hi, Jim

Worry not!  You are doing the right thing, and all will be well.

Your original post was about a fuse rating.  Generally its a good idea to fuse a system capable of high power  - and Lipos certainly come into this category.

The motor you have will take only a nominal power if you don't fit a prop! :}
Neither the motor or the battery govern to power required - hence the fuse rating - its the prop that does that
All the power figures come from aircraft use where there is a near-infinite range range of propellers available to load the motor exactly as you choose.

So:  I didn't know the boat till now - I see that the motor is fitted and it seems to have an outdrive, possibly surface-piercing prop.  The motor (as martinno1fan) said will be spinning about 17000 rpm (if the prop allows) and you will get to know it (remembering Hailwood's law "the throttle goes both ways".

If it were mine I would just try it as it comes, and feel the motor after a 5 minute run.  I suspect it will not be warm in the slightest (with 3 cells).  Probably a 50A fuse would do the job - that would suppose about 500W power.  that's half a kW and roughly 3/4 horsepower.  Sounds about right!

I see that the standard blade car fuses seem to be available up to 60A, with in-line holders to suit.  Suggest you get a small selection from 30A to as big as you can find and see if you can blow one. If you have a fuse which is spot on for the running power it will probably blow if you hold the boat and give it full welly.  So go up a size till it doesn't! (note - if the speed controller has a very soft start it might not blow on this test)  You actually want it to blow if the prop gets snarled to protect everything else.

Just for info - low voltage fuses go up to about 1000A  - they are called fork-lift fuses and are fitted to fuse base  - can be home-made.  I have seen (and used in my Espace) car fuses up to 175A  - there is a very neat one available from RS which fits over an M8 bolt and has a ceramic body -  http://uk.rs-online.com/web/p/automotive-fuses/3377993/

I hope this gives you the confidence to proceed - its for fun :}

Andrew
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canabus

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Re: Fuse requirements for Big Brushless?
« Reply #7 on: February 23, 2016, 03:30:10 AM »

Hi
1604kv x 3s(11.1 volts) = 17,800 rpm.
Prop 40 to 45 mm.
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martno1fan

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Re: Fuse requirements for Big Brushless?
« Reply #8 on: February 23, 2016, 08:25:36 AM »

 1604 kv on 3 s is 14777.652 rpm loaded and thats what matters not the unloaded rpm which is why i said 3 s is not enough ,i doubt the boat would go more than 20 mph on 3 s.Even 4 s i think performance would be nowhere near the videos they show,that is most def not a 3 or 4 s setup most likeley 6 s minimum or a much larger motor and 10 s which is more likely. You dont need a fuse the esc just needs to the right one for your setup.
Mart
http://www.radiocontrolinfo.com/information/rc-calculators/rc-boat-calculator/#Brushless
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TugCowboy

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Re: Fuse requirements for Big Brushless?
« Reply #9 on: February 23, 2016, 08:26:53 AM »

Not sure if this thread is relevant: http://www.modelboatmayhem.co.uk/forum/index.php?topic=49962.0

My understanding of these setups is that the ESC is designed to handle any overvoltage protection so I've never personally fused one. Quite happy to learn I'm wrong though if anyone has any references?
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boaterjim

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Re: Fuse requirements for Big Brushless?
« Reply #10 on: February 23, 2016, 09:50:00 AM »

Hi all, thanks for all your comments, I will go with the stock set up to start with and then do some tweaking if required.

 It has occurred to me that quite a few people have questions about power set up requirements, would it be an idea for a section on MBM to submit say your boat type, weight, battery, motor type, prop type and size, approx speed / performance. to provide some form of data base to start from ?
     
       Jim
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TugCowboy

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Re: Fuse requirements for Big Brushless?
« Reply #11 on: February 23, 2016, 10:46:00 AM »

submit say your boat type, weight, battery, motor type, prop type and size, approx speed / performance. to provide some form of data base to start from ?

That's quite an interesting idea! I wonder if others would be interested?
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martno1fan

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Re: Fuse requirements for Big Brushless?
« Reply #12 on: February 23, 2016, 10:53:53 AM »

Check the online boat calculator tool i posted earlier   ok2 .
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boaterjim

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Re: Fuse requirements for Big Brushless?
« Reply #13 on: February 23, 2016, 07:25:25 PM »

Battery arrived today 3c 4 amp, I will report back on performance when I get and fit the 125a  esc.
Some of the vids of the boat state that they are using 3c batts, and they look pretty fast to me, so it would appear that someone is mistaken or telling porky pies on them?
we shall see
Jim
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martno1fan

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Re: Fuse requirements for Big Brushless?
« Reply #14 on: February 23, 2016, 09:19:25 PM »

Now come on Jim are you trying to say our Chinese friends would tell porkies  :o {-) %% . 3 s with 1604 kv motor 40 mm prop =14777.652 loaded rpm and speed of around 21 mph,probably speed will be less due to size of this boat .
Mart
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nick_75au

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Re: Fuse requirements for Big Brushless?
« Reply #15 on: February 28, 2016, 08:01:21 AM »

Never seen fuzes in most brushless boats, fasties anyway, scale stuff its pretty standard


http://www.amazon.com/IMC-Audio-Inline-Holder-Gauge/dp/B007WX0NMS


but this might work. :-)
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boaterjim

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Re: Fuse requirements for Big Brushless?
« Reply #16 on: February 28, 2016, 10:04:45 AM »

Looks like a good compact solution better than blade fuses anyway, thanks
Jim 
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sparkey

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Re: Fuse requirements for Big Brushless?
« Reply #17 on: February 28, 2016, 11:45:57 AM »

I use a Component shop current monitor,goes up to 150amps and logs max current, power and volts, I have used this on all my brushless boats to closely fuse them,I was surprised how little current they used even flat out,it is alright sitting down and working out the current on paper but until you get the boat on the water in running conditions you will never know,a 500kv 1300 watt outrunner on 5s lipo with a 60mm 4 blade prop was pulling a max of 12 amps only and I have fused it at 15 amps with no problems,so until you measure the current on the water you will never know what size fuse to use,and lastly I would never run a boat without a fuse, never,I have seen a boat burst into flames and sink,modern batteries can deliver a lot of current and can soon turn your pride and joy into an expensive hand warmer.......Ray.

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inertia

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Re: Fuse requirements for Big Brushless?
« Reply #18 on: February 28, 2016, 12:28:24 PM »

I've long held the opinion that Chinese Amps are a lot smaller than those we use. This is yet another little piece of evidence to back that up. I used a similar meter to check the 2817 1050kv Turnigy in my Huntsman and found it was pulling just over 1A flat out under no load. You only have to look at the thickness of the cables fitted to these motors and ESCs to know that they wouldn't carry the large continuous currents claimed without melting.
I think Ray's approach is the most sensible one i.e. measure it under actual operating conditions, then fuse to suit.
DM
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Steve Dean

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Re: Fuse requirements for Big Brushless?
« Reply #19 on: February 29, 2016, 05:36:06 PM »

Hi Boaterjim,

Our humble leader Martin sent me a PM and asked me to comment on this thread. That's because I have boats that are capable of going over 100mph, use custom built German Lehner motors and MGM Compro ESC's.
Generally the advice you're getting on the Forum is sound. Remember that the motor is under the most load when the prop is nearly in a stalled state and the hull is moving slowly, i.e. with lots of it in the water causing maximum drag.
For the combination of motor and batteries you're using fitting a fuse will be fine. The value is best determined by experimentation. The time you are likely to 'pop' a fuse is when you're just cruising along nice and gently and then give it full throttle ...... lots of load on the prop and lots of drag on the hull ..... therefore lots of Amps. Car type blade fuses are ok. Start with something around 3 to 5 amps and then go from there. If hard acceleration pops the fuse then go up to a 10 Amp fuse or even 20 Amp.

There is some wise words written on here by Inertia and others so take note of what they say.

For your interest 20 Amps on 11.1 Volts is only 222 Watts ..... I have boats that can pull over 6 kilowatts !
Happy boating.
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martno1fan

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Re: Fuse requirements for Big Brushless?
« Reply #20 on: March 01, 2016, 09:43:49 PM »

Steve do you use fuses on any of your fast electrics ?.
Mart
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Steve Dean

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Re: Fuse requirements for Big Brushless?
« Reply #21 on: March 02, 2016, 06:00:53 PM »

No my high end boats do not have fuses. The speed control controllers I'm using have all manner of protection built in. However I am playing at the high end of the game and to use an analogy from the world of motorsport, it's a bit like top fuel dragsters .... very expensive, staggering performance, exciting but terrifying ..... and when it goes wrong, it goes wrong BIG TIME.

My current 'toy' is a big catamaran hull moulded from carbon & Kevlar, running twin surface piercing drives with a pair of custom built Lehner motors and twin high end MGM controllers. It runs 6S lipo's  (5100mAh with a 50C rating) each side. In layman's term that's a potential for over 5KW per side (the motors can handle more).

Definitely NOT for beginners! But I enjoy the engineering, both mechanical and electrical of it all. Either that or I'm just plain nuts!
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martno1fan

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Re: Fuse requirements for Big Brushless?
« Reply #22 on: March 03, 2016, 08:26:37 AM »

Thought as much which was why i said he didnt need a fuse,im a hull manufacturer and none of my customers that im aware have ever used fuses on their fast electric builds of my Apache or my Thunderbolt cats.I have one planned for me this year single 5692 motor on 8 s .
Mart
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inertia

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Re: Fuse requirements for Big Brushless?
« Reply #23 on: March 03, 2016, 09:46:50 AM »

Thought as much which was why i said he didnt need a fuse,im a hull manufacturer and none of my customers that im aware have ever used fuses on their fast electric builds of my Apache or my Thunderbolt cats.I have one planned for me this year single 5692 motor on 8 s .
Mart

Mart
I suspect this is because, like Steve, you know exactly what you are doing; what your equipment is capable of, and how to install and connect it up. It looks like that attitude has brushed off onto your customers, which can be nothing but good. I know another nationally-known modeller who admitted to me that he has never fitted a fuse in any of his models, but he is also the sort of bloke who understands and researches the equipment and its limitations. My old friend and mentor Craig Talbot (the original ACTion man) had no time for fuses, either. For lesser and/or lazier mortals, however, the use of a strategically-placed fuse can prevent serious damage to the electrics (and often the model itself).
Dave M
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Charlie

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Re: Fuse requirements for Big Brushless?
« Reply #24 on: March 03, 2016, 12:57:18 PM »

This has probably been asked before, but where should the fuse go - between Battery and ESC or ESC and Motor?
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