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>> Home > Forum > Boat Specific Chit Chat! > BRUSHLESS ESC
Author Message
(Fleet Admiral!)

Forum Posts: 120
17th Jul 2018 22:02  
>> Permalink

Has anybody heard of, or have, a "rule of thumb" for the sizing of brushless ESCs?
Am new to brushless motor powertrains and have been using ESCs that nominally exceed the current draw capacity of the motor.
Have heard that they should substantially exceed the motor capacity and wonder, if that is the case, by what percentage?

(Fleet Admiral!)

Forum Posts: 133
18th Jul 2018 10:39  
>> Permalink

Hi RHBaker
If the ESC exceeds the motor draw that's all is required.
I only use two sizes in my boats, a 45A for small boats and 100A for the larger boats.
The both use the same program card !!!
These are the Hobbyking car ESCs because they have an on/off switch, small and have an electrical fan on top.
Very good for low speed running and no water plumbing required.

(Fleet Admiral!)

Forum Posts: 29
18th Jul 2018 12:51  
>> Permalink

From my experience I would suggest 2-3x your motor current rating especially cheap ones from china, I have found that a brushless motor can rapidly draw high currents with fouling of the propeller by weed etc.

I would check the current drawn with the propeller you intend to use with a watt meter in the test tank (bath) held stationary increase power and monitor the current drawn this must be well within the limits of your ESC this should show a 10-15% higher power consumption than when moving.

The best bit of advice (which I often don't follow myself) is to put a fuse in line

Please note some ESCs are not waterproof (avoid) or seal them with silicon sealant, go for a quality manufacturer and the highest current rating your can afford.

Cheap 30A ESCs can be ok for low power motors under 10Amps
my racing boat pull 60 Amps and is fused at 80Amps and has a 200Amp ESC

(Fleet Admiral!)

Forum Posts: 2548
18th Jul 2018 14:31  
>> Permalink

Also check the STALL current of your motor!
If the prop gets blocked the current drawn from a LiPo can rise so much it melts the motor and ESC if it can't withstand very high current.
Worst case - you have a boatfire instead of a Fireboat! 😡
Better still; fit a fuse of much lower rating than the stall current so that that blows and not the motor 😉
On normal running the ESC should have a continuous current rating of at least 50% more than the max running current of the motor.
As advised above, check this with a 'Wattmeter'👍
Attached an extract from the instructions of a typical unit as I have.
Only costs a few quid but can save hundreds 😉
Happy sailing, cheers, Doug

Attached Files - Click To View Large

Young at heart - slightly older in other places 😉 Cheers Doug
(Fleet Admiral!)

Forum Posts: 120
18th Jul 2018 23:02  
>> Permalink

Thanks for the advise.
Think if my latest set burns out, will increase ratings substantially.
The point about stall current is relevant, suspect that is why one of my last ones burnt out.

(Fleet Admiral!)

Forum Posts: 2548
18th Jul 2018 23:06  
>> Permalink

Hi Rowen, that's what often gets overlooked and why the Main fuse is so essential! Good luck with the set up👍
With multiple screws put a fuse in each ESC supply then if one screw blocks and the fuse blows everything else should still work so you can get back to port 😊
That's also a reason for NOT using the BEC on multiple screw boats; applying Sod's Law the one that blocks will be the ESC supplying the RX via the BEC then ..... U R Stuck!! 😡
A separate RX battery or UBEC off the main drive battery is safer 😉
Doug 😎

Young at heart - slightly older in other places 😉 Cheers Doug
(Fleet Admiral!)

Forum Posts: 120
18th Jul 2018 23:42  
>> Permalink

Thanks Doug. Agree with your suggestions. Have already implemented the multiple fuse idea. Hope to try it soon