Delta Force build (bought part build

[MrBennett]

Hey guys, I finally got the chance to do a first proper test run today.

Setup with a 5S pack and on the fairly calm sea, my GPS picked up a recorded speed of 40mph but it subjectively looked faster. It was only running a few seconds each direction and I don't know if that was long enough for the GPS to pick up the full max it was getting to.
Only further tests on super calm surface will help verify that.

It did unfortunately end in a sinking which was my own stupid fault, after removing the temporary duct tape I was using on the hatch to let it cool before a second test run, it hadn't stuck down well on the damp hull, and when a too sharp turn flipped the boat, the hatch came off annoyingly.
Straight away rinsed in fresh water and blown out with air then left to slowly dry fully. All seems ok beside potentially my power meter. They're ?10 though so could have been worse.
I won't run it again until the proper hatch tape I've ordered arrives anyway!!! Lesson learned.

Anyway, I now am hoping for a further bit of advice.
The boat ran great for a first try, but the hobbyking 120A esc got pretty warm and I think went into thermal protect (limited speed until I left it a few minutes to cool).
What surprised me though is the power meter claimed it had pulled a peak of 179.31amps (it also displayed 2436.3Wp, 0.692Ah, and 8.1Wh).

Now the ESC is a 120a one with a temporary peak limit of 150a so I'm kinda surprised there weren't fireworks, and delighted it protected itself, but given the hardware I'm running I'm really surprised it drew so many amps since the prop is only 38mm twin blade and I understand that's not a huge size for this sort of boat/setup (going on other builds I've looked at for Cyber Storms anyway).

So just to recap here are the details, if any of you guys might be able to suggest why the amp draw would be so high as it is I'd appreciate the wisdom and experience thanks!

Delta Force Cyber Storm 33
Hobbyking 120A marine esc (rated for 3-6S)
Aquastar 2200kv 3974 motor (rated for 5S)
Some budget 5S 3000mah 30c pack
Prop - 2 blade 38mm diameter (14.5mm from front most point of blade to rear most point of blade if that helps to identify since I don't know actual pitch or type).

Max amps pulled = 179A
40mph max recorded speed.

Grateful for suggestions on improvements in respect of reducing that current drawer as it seems like an awful lot for a 38mm prop, but I don't know the spec of that.

Thanks!

[eehess81]

I don't think 120amp is enough for running 5s at 2200kv. That is about 41000 rpm..I wouldn't run that at over 4s. Try and bring rpms down to 35000 max. Or drop prop size to a 34 or lower to reduce motor strain. Surprised it only hit 40 with that high rpm..you may have triggered lvc quick and been running on half power. I have an external lvc I hook up to my battery so I can shut off lvc on my esc.

[eehess81]

My DF23 does 40 on 3s with 3000kv motor and 35mm prop on 90 amp esc. That's about 34000rpm. My lvc was kickin' in after a few mins..think my 2 25c 2200mah batteries aren't putting out enough juice.

[MrBennett]

Thanks for the suggestion.

I did wonder if it?s hitting more than 40mph but just not recording the full speed due to such short bursts and the gps lag etc.

It?s a shame I don?t have a means of counting the rpm in order to check to see if it is getting anywhere close to 41k.

I wonder if it?s possible that it?s not hitting its full rpm and a slightly smaller prop would allow it to, resulting in less load and amp draw but possibly the same or higher speed (if it did end up revving more than it currently is).

Worth a try to order a smaller one anyway thanks. I?ll have a look for a 34 or 36mm octura then run it again.

It still seems odd though as I?m sure I?ve read builds where people are running much bigger props but I assume they?re running on lower Kv motors.

So I wonder if something more like a 6s rated motor around 1600kv might be a more suitable option at some point?

[eehess81]

If you are gonna run 5 or 6s then yes I would drop the kv. Or you can keep the motor and try a 4s.

[eehess81]

If you were hitting 41k rpm with no lvc or thermal protection kicking in you would be probably hitting closer to 50 I would think. I'm guessing it's overloading. Lower the rpms and the 38 prop should be fine.

[MrBennett]

Ok cool thanks. Someone else suggested for something like this I should be using a bigger esc, but I feel like it?s an awful lot of amps for a boat this size so that?s not really the answer just yet.

I?ve orders some 4s packs and an Octura x436 so can try different combos of props and lipos and monitor temperatures and current draw etc.

Thanks!

[tebby2]

If I read your information correctly, you should be using XT90 plugs (not XT60) on your battery and ESC connections. The XT60 is rated for a nominal 60 amps and is not meant to handle anything close to 179 amps. The high amperage loading and LVC could be the result of undersized plugs.