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Old Jan 09, 2015, 04:56 AM
genesisrc is offline
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Help!
Keep blowing ESC's?

Hi guys,

hoping you might be able help? I recently bought a Himoto Genesis RTR and I seem to be going through ESC's lately? Im new to RC boats but have other RC's. If theres anything Im missing, please let me know.

Everything was going fine until I bought a new LiPo as I wanted to extend the running time (10 minutes was way too short for me). Basically - The initial set up was working fine for months and the only LiPo that I was using was a Turnigy (Nano-tech) 4s / 4500mAh / 35-70C

Boat was running standard internals:
125A ESC
2075Kv motor (not sure of brand) Water cooled
6Kg Himoto Servo
Himoto Rx and Tx

In the hope of extending my running time, I purchased a Zippy 4s / 30-40C "8000 mAh" (High discharge LiPo) and this is where the issues began. I ran it for the first time fine. New Batt lasted about 20 - 25 min. Brought it in after 10 Min to cool down and check temperatures, then sent it back out for the remaining 10 / 15min. Battery and ESC's get warm to touch but not burning hot.

Once Batt cut off, placed the original Turnigy back in and it ran for about 3 min then died. (Had to go for a swim)

Servo works, but no throttle. Again, not burning hot?

Brought it home and tested both the ESC and motor with another RC and narrowed it down to the ESC. Motor would throttle with a different ESC but boat ESC would not power any other motor.

Went out and bought a Swordfish Pro - 120 A - S BEC - as the guy at the hobby shop seemed to think the original, even though mentioned 125A, would be luckily to be a 60A (because it was a cheaper ESC) and mentioned that the Swordfish was a guaranteed 120A with 150A peak.

I found somewhere that the 2075kv motor would be about 100A so presumed that 120A was to be sufficient? not sure if this is correct.

I replaced and programmed up, took it out for the first time and it lasted about 15min with the 800mAh - and now - No throttle again, but servo movement.

Does anyone know if its the 8000mAh that is killing the ESC's or if there is something else that I may be missing? Is it in fact the ESC's failing as they dont seem to be burning hot? Well under 100 degrees Celsius.

Is there a simple fix to the no throttle that Im missing?

Thanks guys and appreciate any help
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Old Jan 09, 2015, 06:10 AM
ivaylo goranov is offline
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What propeller you use?
what is the weight of the boat
Did you measure any speed( GPS)?
Any pictures with propeller shaft angle and position will help us as well.
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Old Jan 09, 2015, 08:20 AM
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Hate to say it but sounds about right for a Genesis, just about everybody burns them up then replaces the electronics (motor and esc) with something better after a very short time.
Motor and esc are cheap no name chinese junk basically. Too bad because the rest of the boat is pretty good.
Swordfish esc isn't much better than what the boat came with, Seaking 180 would have been a better choice.
Also you can't go by any kind of "rating" an electric motor will draw as much amperage as it needs until it either goes or burns something up. The prop is what determines the load, not the motor.
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Old Jan 09, 2015, 10:15 AM
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What were your temps when checked...personally I think you are running things to long a heat is an issue...also, are you running mostly full throttle or partial...partial will kill an ESC.

Just re read your post "well under 100C!!!!!!!!!!!!!" how much is well under, and how soon after the boat died did you take this measurement?

Also, don't swim after a boat...becoming a statistic is dumb.
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Old Jan 09, 2015, 03:31 PM
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Your runtime is your main problem is you
are killing the esc and the batteries by running them down to the cutoff
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Old Jan 09, 2015, 11:00 PM
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Thanks all for your feedback. Some answers to your questions:

Propeller - Standard 2 blade Nylon
Weight - According to Himoto website - 2200g Plus Lipo's I assume
No speeds recorded at this stage
Will add some pics

i have heard a few people mention the Seaking 180A. If I get a 180A - 200A would this help relieve the issues instead of having the 120A?

Run times - the recent run time wasnt very long at all - about 5 - 6 min. Boat sputtered then stopped. Grabbed it and checked and nothing was very hot at all. Barely warm to touch. Unplugged batt and back in (leaving Tx on) but no music tones from the engine? Servo works but no throttle.

Running to cut off - i set my Low voltage alarm to 3.3v and once the ESC cuts off I use my Battery Tester to check all cells and they are usually about 3.1 - 3.3v each.

When I charge, Lipo's are about 3.3 - 3.4v per cell. I store at 3.8 and charge to 4.2v only charging at 1c max. The recent 8000mAh batt is only a few weeks old and have used twice so far. Each time, kills the ESC

I have heard people running to 3.8v per cell but that is literally about 3 - 4 min for my 4500 mAh.

What does everyone else run their batts down to?
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Old Jan 09, 2015, 11:52 PM
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the motor may be the culprit. I set my lvc at 3.2v and have never had an issue with the batteries.
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Old Jan 10, 2015, 12:13 AM
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Is there anyway to check the engine or tell if its faulty and is the reason for burning the ESC's out.

I havent changed the prop or Flex Shaft from stock.

I think Im going to get a 200A ESC. Has anyone used "Mystery RC 200A 2-6s Brushless ESC"? They are cheap but assume you get what you pay for?

http://www.ebay.com.au/itm/Mystery-R...item5af545418d
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Old Jan 10, 2015, 05:33 AM
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Hi genesisrc,

You didn't mention how you ran the boat when the ESC gave up.
A fast electric should be run at full throttle, 80-90% of the runtime, running in large ovals with sweeping turns.

If you start and stop a lot, or run a lot of partial throttle, the ESC and motor (particulary if it's a two pole) will heat up to no end; even if it doesn't feel hot after retreiving the boat the excessive amount of switching may/will kill your ESC.

My son runs the Himodel 200A ESC in his Arowana with this motor on 4S:
http://www.hobbyking.com/hobbyking/s...ess_Motor.html , turning a 42 mm narrow blade metal prop, nothing gets beyond handwarm after a 7 minute full throttle run (he only throttles down for a turn).

http://www.himodel.com/electric/HiMo..._GX200A-B.html
The Himodel is similar to the Mystery ESC and suffers from the same lack of craftmanship as all cheap ESC's.

If you want to be able to draw a lot of current, you'll have to remove the shrinkwrap and check if all Fets have contact with the watercooler.

As an example one of the Mystery ESC's I've checked, the light patches in the picture show where the Fets actually touched the cooler...:



I sanded the Fets into one plane, using a flat piece of hardwood with 120 grid sandpaper, the width of the Fet board (so you sand all fets simultanously).
Clear the dust and refit the watercooler, using a new piece of shrinkwrap.
Make sure not to cause a short between the input leads (and/or capacitors), when putting the cooler back on.

All my sanded ESC's still work after many years, waterproof the board if you want, because they don't like water (poof).

Regards, Jan.
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Last edited by pompebled; Jan 11, 2015 at 08:39 AM. Reason: Text corrected.
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Old Jan 10, 2015, 07:33 AM
Sibe is offline
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I completely missed the 100C part! That is way way too hot, 120F is getting close to the limits. Thought it was 100F!
Long runtimes, cheap electronics, did you recheck your CG after doubling the battery weight?
If your motor was near 100C you may very well have demagnetized it, would be much hotter internally.
Get her fixed up and go back to the original batteries. Better quality ones would also help, go for 5000mah. Try Dinogy or Revolectrix, The Zippy you bought is actually a much better battery than the nano techs, all 4 of mine puffed up and failed in my heli when the stock e-flite 20c packs are still going, and they aren't very good!
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Old Jan 10, 2015, 05:36 PM
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Thanks heaps everyone. definitely learning a lot!

Maybe it was "user error" that contributed as it was quite choppy out and I was not running at 80% - 90% constant because of the waves. Didnt actually realise that this also has a huge impact to the ESC, but know I now.

I'm definitely hearing the better way to run these boats is to have smaller mAh Lipo's (up to 5000mAh) and run them down to about 3.5v and bring it in. Ill just get a few smaller Lipo's instead of 1 x 8000mAh

Im going to head down to the hobby shop today where I bought the Swordfish ESC and see if they can test the set up and see whats going on. Will let you know how I go
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Old Jan 10, 2015, 06:21 PM
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Set it up and run it for 2mins and see how many mah you take out of the batteries then you can adjust from there
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Old Jan 10, 2015, 09:05 PM
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Quote:
Originally Posted by dobydog6507 View Post
What were your temps when checked...personally I think you are running things to long a heat is an issue...also, are you running mostly full throttle or partial...partial will kill an ESC.
That's a myth. Its fine to run an ESC at partial throttle... I don't know how that particular myth got started, but its definitely not true...Notice no MFG cautions against doing it, also, think, have you ever had an ESC go bad where it could definitely be pinned on being due to partial throttle? Do you know anyone that has? I haven't and I don't.... In fact I almost never run full throttle on any ESC I own.... Various vehicles run anywhere from 20-80% average throttle for most of the run...
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Old Jan 10, 2015, 09:07 PM
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1. You cant supply TOO much amperage to your ESC, the 8000mah 'high output' lipos(40c or better i hope) are plenty, too little amperage is what takes out ESC's.

2. What diameter is this mysterious "standard Nylon" job? 42mm or less is all that motor can handle in that hull. Its a cheapo 2 pole amp hog that probably runs in the 75% efficiency range.

3. Get a 4074 or 4082 Leopard or similar 4 poler which a decent 120a ESC like Turnigy 120 will power just fine................with an appropriate prop.

4. if you are not confident in your setup abilities and have amperage concern get a 180a ESC, Turnigy, Seaking or Swordfish.

5. A 2200kv 4074 Leopard on 4s with an x642 will need a 180a ESC for that "room" we need, but will get you close to 50 mph.................
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Old Jan 10, 2015, 09:12 PM
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Quote:
Originally Posted by dacaur View Post
That's a myth. Its fine to run an ESC at partial throttle... I don't know how that particular myth got started, but its definitely not true...Notice no MFG cautions against doing it, also, think, have you ever had an ESC go bad where it could definitely be pinned on being due to partial throttle? Do you know anyone that has? I haven't and I don't.... In fact I almost never run full throttle on any ESC I own.... Various vehicles run anywhere from 20-80% average throttle for most of the run...
Your ESC's arent taped airtight inside a hull with a hot motor and zero airflow, they most likely lie beneath a rotor, which is providing airflow, in ambient air temps. Water flow can greatly decrease or cease when a boat is run too slow.......which would fall into the mid throttle range or less.
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