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G/Day I have not got any idea about electronics. I have got a 47 inch Perkasa Patrol Boat running with a single Brush less Turnigy 3974-2200kv water cooled motor and a water cooled Turnigy 160A ESC running directly from a rechargeable sealed lead-acid battery RL1270(12v7.0Ah/20hr). My problem is when the motor is running at high reves it cuts out after a few minuets. Is this from low battery or wrong setup? All the help i can get to get my boat running smoothly would be much appreciated . thank you. Allan
A quick check on the specs of your motor /esc combo states its good up to 5s LiPo.
So step 1 get a watt meter ( cheaper than burned out motors )
Step 2 check with your bank manager ( or wife) for available funds
Step 3 buy the biggest 4s or 5s LiPo you can fit in the available space.
you will also need a LiPo charger do not attempt to skimp on that step LiPo batteries need special handling and can be spectacular if you do it wrong.
You have not mentioned the prop your using if you use the watt meter you can play around with different props so the current used by your setup heads towards the point you pick twixt performance / running time.
If you do go LiPo you will also need a battery monitor part of the careful handing includes not discharging them below around 3.3 Volts per cell.
3s =3cells 4s=4cells etc. So if you go 4s then you should not discharge below 13.2V.
some text on the care and feeding of LiPo batteries.
The reason for your problem is a simple case of battery chemistry a lead acid accumulator cannot deliver a high current for extended periods gasses on the plates prevent the electrolyte coming in contact so the battery loses power. After a while the gasses are re dissolved and the battery can then go on providing power. Nothing wrong with the battery its just a case of wrong tool for the job.
"that's not a bug its just an undocumented creature."
Sir Terence David John "Terry" Pratchett, OBE (28 April 1948 - 12 March 2015)
Hi Patto I agree with what has already been posted, but it would help if we knew the size and type of prop you are running with your brushless motor. Fast large racing props do not work well with brushless unless your battery can provide the very heavy sustained current required. As Haverlock suggests a Wattmeter will allow you to select the best prop for your set up. LiPo power will give you all the speed you need but at an initial high cost as they require special chargers and correct management. You could use NiMh batteries which are lighter than SLA and are more suited to high discharge currents. You can get these in 12v packs and 5000mAhr would be a good starting point. If your motor is cutting out it is more likely the ESC is the culprit due to too high current draw. Another possibility is that the propshaft is too tight, it should turn freely with no tight spots and have thrust washers at both ends. Dave
G/Day All Thanks for all of your advice. I have a 2 blade 40mm prop and the shaft is running free. i originally running a Johnson brushed motor with no problems with power except it and the esc i had got extremely hot. i could not find a water cooled brush motor so that is why I got the brush less motor. It is very hard to get model boat parts in Australia. Maybe it might be easier to put the old motor back in, i have now got a water pump so i maybe able to make a cooling system. Cheers Allan
Hi Allan The motor and ESC seem well matched which points to the prop being too coarse a pitch. You have a large scale boat not a fast racing boat and I suggest you replace the prop with a brass three blade of 35-40mm. As we have suggested a wattmeter will help you determine which is the most suitable for your set up. My Sea Queen with a similar set up (40mm brass prop) draws 30 amp at full speed so well within your ESC and motor spec. I see you have water cooling and am wondering if this is working correctly. You should see a good flow of water from the exit port at all but the lowest speeds. The inlet scoop should be immediately behind and facing the prop with a good straight pipe run to the ESC and motor cooling points. Dave
Thanks Dave I have a pump for the water cooling so it is running separately and has a good flow of water. I did have a 3 blade plastic prop but a blade broke off when i ran aground at high speed the 2 blade prop was doing ok when i had the old motor in.As you said earlier I will check out the lipo battery and see how it goes. Cheers Allan
Hi Allan You don't really need a pump with a fast boat as a simple scoop placed just behind the prop will give ample cooling water. Is it possible that your pump is becoming ineffective as the battery drains? Your prop was OK with the brushed motor because it was designed for this type of motor, brushless need much less coarse pitch propellers or very high capacity batteries and ESC's. Hope you can find a suitable set up Dave
Thanks Dave The pump is necessary as i was not getting any water threw with just the scoop. the pump is running on a separate battery.I have started looking into getting a new prop and lipo batteries. Thanks for your help i will keep you informed at how i get on. cheers Allan
Hi Patto, Sounds like you aught to be running on a decent lipo. The motor is probably taking more amps out of the battery than it can maintain. Lipos are much much lighter than lead acid and can give a higher discharge rate. The dicharge rate is the 'C' rating of the lipo, the higher the number the greater the discharge capacity. If the 'C' rating is too low the battery will start swelling up and its life expectancy greatly reduced. Go for the highest you can afford with the greatest capacity and always use an alarm with the battery, it plugs into the little white plug and can be set so when the battery gets to a set voltage an alarm sounds indicating to stop using it until it is recharged. A 3 cell will give you the required 12volts. The 'C' rating now goes up to 130 in the more expensive lipos but an 80 will probably suffice. The higher the amperage of the lipo the longer running you will get. A 2500 may only give you 8-10 minutes whilst a 4500 (cost just under £50) will give you up to 20 mins. You will have to check your speed controller to make sure it is compatable with lipos, a few are not. Remember you will need a balanced Lipo charger, I only spend about £20 or less but they only charge lipos, quite often the more expensive ones will charge a variety of battery types. I'm not an expert on electronics my knowledge comes through personel experience. With the lipo you will get better performance as the lead acid weighs the boat down. Good luck.
BIG MISTAKE I brought a 5300mha -50c-14.8v-4s1p-78wh LiPo battery yesterday. Bloke in hobby shop checked my ESC which is a TURNIGY AQUASTAR Watercooled ESC 160A. and said that it could handle that size battery. Giving the boat a test run this morning the ESC erupted in a huge cloud of black smoke. Not happy Jan will be ringing the hobby shop in the morning.
Hi Allan Was the boat in the water or on the bench? There are several posts online indicating that you cannot run this ESC without water cooling. You did say you needed a separate water cool motor. Is it possible the motor or ESC water jackets were blocked? Hope you can find a solution Dave
Yes Dave I had the boat in the swimming pool and holding it stationary. The water pump was running with a good flow of water before and after the fire. I just had a thought maybe there was to much turbulence from the prop around the water intake which is behind the rudder stopping the water flow when the motor was running at speed . I couldn't see the out let as it was on the side away from me. Maybe i will have to move the inlet or something. Cheers Allan
Hi Alan, following this thread, your last post might give it away, you were holding the hull stationary, that means it was loading the motor far higher than if it was moving. You said that the coolant was running before you started so it probably was all the time, that could mean the ESC was over loaded and then blew. How long did you hold the hull?? at the sort of power a lipo can give, cooking the ESC would not be hard, even with the cooling water. Dave M could give the proper answer but i think you held on to long. Haverlock also mentioned using a watt meter, i am almost certain that you overloaded the ESC by some considerable margin, i have re-read the other threads, what size prop are you using? with a 40000 rev motor if its loaded too heavily it will just use more power to get itself going, so we are back to the ESC overloaded.
Sorry if this has been long winded, it might not help, but less revs and more torque could be the answer
Thanks Jarvo Ihave a 40mm 2 blade prop and the motor was running at high speed for about 1 minute. My swimming pool is to small to run a large boat at speed in, that was why a was holding it. Yes it was very hard to hold the boat at the time there was a lot of power, as you said it my have been overload because the boat could not move. Next time i will take it down the pond where i used to sail. Cheers Allan
Hi Patto, forget the 'watt meter' and consequent P=IV -> I=p/V conversions! What you need to measure is the actual current drawn, especially the stall current, if you can manage that without getting any fingers chopped off 😡 On the lake anything can choke the prop so just testing 'free running' is not the whole answer. Sounds to me simply that your setup is drawing so much current that any battery or accu will go flat in a few minutes. Your example of a 5300mAH (i.e. 5.3AH) means that in perfect (!) condition, fully charged and almost zero internal resistance (int. cell resistance wastes power so buy the best quality you can possibly afford) it can theoretically supply 5.3 Amps for 1 hour. or 53 Amps for ~ 6 minutes (1/10 hour). and so no. LiPos with C values of 130 sound great BUT the discharge C value is related to the AH rating. So taking your example of 5300mAH = 5.3 Ah 130C = 130x5.3 = 689Amps! The Accu would supply that for ~ 27 seconds before departing to the great recycling centre in the sky! If you ever decide to try such an experiment PLEASE let me know in advance and I'll fly over the record the event for posterity 😉 Seriously though folks: I can't comment on the prop/motor setup, one of my weaknesses - I always check my stalled motor current draw with an ammeter before selecting the ESC - but as an electronics engineer I do have some idea about power supplies and circuit requirements etc. Can't imagine that your setup exceeded the 160A (short term remember!) rating of the ESC so that seems to be faulty, but you still need to find out what current your setup will draw under severe load i.e. stall. If just holding the boat cause blow ups then something else is fundamentally wrong 🤔 Bit long-winded perhaps, much of the above makes sense but not the whole story, time to cut to the chase I thought. MEASURE THE CURRENT! Good luck. Doug 😎 By the way the above comments about lead acid & hi current are OK. They are more useful for long term supply of low to medium currents. I still use them in some larger scale models (~ 1.5metre naval ships) as they provide useful ballast (i.e. payload) instead of JUST ballast! The 20HR of your lead acids refers to the Hourly charge Rate, i.e 1/20 of the capacity in AH, in your case 7/20 = 0.35A or 350mA.
PS Allan, there are several water jackets / spiral tubing available for cooling brushed motors, try Hobby King, or just get some alu and silicon tubing and make your own. Apply some heat conducting paste between the jacket or tubing and the motor casing (as used in the electronics industry for mounting power transistors, processor chips etc) available in tubes also in model shop site for a few dollars. Good luck
PPS Allan pondering the 'spec' of your LiPo "5300mha -50c-14.8v-4s1p-78wh" The wh rating = Watt Hours. i.e how many watts of power it can deliver in 1 hour. Since Power (P)= Volts(V) x Amps(I) (simple DC calc!) I=P/V i.e. 78/14.8 = 5.27, which is where the nominal capacity of 5.3AH (5300mAH) comes from. I don't think the battery is your only problem, i.e. a) the ESC was fundamentally defective, b) your setup is drawing too much current for more than a few minutes running on a 5 to 7 AH battery with no reserves. Good luck. I run a 1.3 metre destroyer on 2x540 brushed and 2x6V 4AH (4000mAH) SLA and it trundles around for 2 or 3 hours, and can still outrun several wannabee 'boy racers'! 😉
Hi Allan If you had water cooling and it was provided by your pump then it would seem the prop was far to coarse a pitch for you fast motor and very powerful battery which was quite capable of delivering well over 200 amps through the 160 amp ESC. Your comment re the power delivered rather confirms this, and holding a model at full speed to test is only possible for about 5-10 secs max. You need to get a much smaller and less coarse pitch 3 blade prop plus a wattmeter to measure the current to make sure you are no where near the max ESC current. Personal experience suggests this should be less than half the rated Max so say 70 amps for your ESC. Testing should be brief and stopped immediately if the current being taken is above 20-30 amps. Smaller props will reduce the current to an acceptable level and your model will go faster and for longer. As a guide 14 volts at 70 amps will be using 980 watts so you will perhaps appreciate why cooling is necessary. Also at such high currents the wiring from battery to ESC then motor will need to be capable of carrying such high currents. As there are three wires to the motor and the power is pulsed at high frequency they are usually not as heavy as the battery to ESC. Your battery to ESC connectors also need to be capable of high current such as Deans, Euro or bullet type. Having looked on U-tube it does appear that others have had similar experiences with this ESC. The specs say it is capable of running at 14.4 volts so when you buy a replacement I would ask your local store to run your motor with the ESC and your battery to ensure it works OK. If they have a wattmeter ask them to test the open current then also buy the wattmeter and a smaller 3 blade prop of slightly less diameter than that of the motor without the water jacket. Do a final brief test at home holding the model and see briefly what the wattmeter reads, this will be near the max current draw. If it's too high you need a smaller prop. There are several Perkassa builds on the site and some use brushless with success. If you search you will find details of their power train which may help you choose the best set up. I do hope you will soon have your model speeding round your lake. Dave
something is fundamentally wrong here, there is no way that motor/esc/battery combo should have fried the esc in your perkassa. I have a number of large scale boats with a fast brushless set up, I pull almost 90 amps with one of them, on the initial acceleration, using 6 cells, 120a esc and (here is the difference) a 900kv brushless motor. The racing guys use high kv motors, they need the high revs, with a heavier boat like yours, you need the revs, but also the torque, which is a lower kv motor Before you do anything else, buy something like this http://www.4-max.co.uk/wattmeter-budget.htm
really cheap, but saves you a fortune. As many of previous posts have said, you need to measure what is going on, for example, the specs of you motor say max current is 100amps, you need to measure your amp draw. You know the esc was 160a with a burst of 200a, so should have been well within the capabilities of your set up, but we cant see the prop. If its too big, and too coarse, particularly holding the boat, the amp burst would have had to exceed 160a to pop the esc, which is also well over the motor specs. I doubt the hobby shop will do anything, as the fault could have been a multitude of things, Personally, I think that motor is way too high KV, and I'm saying this from experience of large, heavy scale boats, with fast brushless set ups. I would have expected it to rev very high, but not deliver a really fast top speed, but I could be wrong. Shame really as its quite an expensive set up there. Are you sure about the facts, holding that boat, and max throttle must have been pulling your arm off, I cant hold any of mine😱
This triggered my curiosity! So have just ordered the Busing in-line 150A Power Analyser, €12 😊 Anyone looking for such a device can find several review videos here https://www.youtube.com/watch?v=Lxv9Rozs774 Happy hunting 😎
My knowledge of "elecy" stuff is pretty limited, but I see that the model boat world (excluding racing types) is in the dark ages compared to planes, helis, cars etc when it comes to motors, batteries etc
We have to reply a lot on testing, fiddling etc when it comes to gettingn a fast electric set up, in a scale heavy old wood boat😁 as there isnt much info out there. I tried testing over a long time, with one boat inparticular, and was lucky enough to have te use of eagle tree data logging, so could measure watts, amps, gps speed, voltage drop and so on, and analyse the resultsd on graphs etc back home on the pc. Its amazing to see that sometime s the fastest set up isnt always the best when you compare run time, amp draw, heat, voltage draw etc, and what "looks fast" sometimes isnt as fast as you thought😊
This boat for example, 6kg, ply construction will do 25mph, after that torque roll is kicking in, and it want to roll over. I tested props over a long time, using cheap plastic "X" props, and with the results was then able to get a more efficient and visually pleasing brass cleaver 3 blade one. Ranging from 50mm to 55mm the amp draw went from 45a to 90a using same batteries!, and teh highest amp draw prop didnt produce the fastest speed, all interesting stuff. The boat is similar to the OP perkassa. I also went from direct drive, to a geared drive, and can change the characteristics of the boat using different cheap gears, eg., small lake, dont need top speed, so change to acceleration, big lake, lets give up acceleration and have top speed, and so on👍