Sam Thomas Posted February 6, 2010 Share Posted February 6, 2010 You very kindly gave me a APC 8x3.8E Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 6, 2010 Author Share Posted February 6, 2010 Ah well in that case it should be fine and dandy on that motor with a 3s lipo. Quote Link to comment Share on other sites More sharing options...
Mike Downs Posted May 30, 2010 Share Posted May 30, 2010 I have seen on a 4 max website advice on how to wire up multi motored brushless power motors. It states that it is advised to cut the red (power) wire to one of the ESC. Does anyone know if this applies to jeti ESC's as well? I have 2xmega motors with 2xJeti 30-3 p powered by 3800 3cell Lipo.(11.1V) The site is www.4-Max.co.uk Cheers Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted May 31, 2010 Author Share Posted May 31, 2010 Yes. Quote Link to comment Share on other sites More sharing options...
Mike Downs Posted May 31, 2010 Share Posted May 31, 2010 Thanks!! Quote Link to comment Share on other sites More sharing options...
simpson j Posted February 6, 2011 Share Posted February 6, 2011 HI CAN I RUN 4 NO SPEED 400 BRUSHED MOTORS ON A 50 AMP Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 6, 2011 Author Share Posted February 6, 2011 Yes....maybe It depends on the current drawn by all four motors - which in turn depends on the battery cell count and prop size. Its quite possible( by using a particular combo ) to get a speed 400 to pull 15 -20 A - so four of those would be 80A.I assume of course you are using a brushed ESC Quote Link to comment Share on other sites More sharing options...
Steve Houghton Posted February 8, 2011 Share Posted February 8, 2011 I'm about to fit out my first electric model and would appreciate a liitle ESC help before I buy. 1) Can I use an ESC with BEC if I want to use a separate RX/servo battery, or must I buy an OPTO? 2) If I can use the BEC ESC, will I need to cut the red wire coming from the BEC? 3) If the red is cut, the ESC has no positive voltage reference for the throttle signal from the RX, so can this cause any problem if the RX battery voltage dips below the ESC's own positive supply, which I assume is regulated from the flight battery? I understand Timbo's preference for not doing this, but I want to understand the options available before I decide what to buy. The model will be a JP Fox electric glider with JP C35-26 1000KV brushless motor. Thanks for any help offered. Steve Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 8, 2011 Author Share Posted February 8, 2011 1) Yes, and then no you need not.2 ) Unclear of question3) No On a model like the fox, I would simply use the ESC BEC unit. Quote Link to comment Share on other sites More sharing options...
Tom Wright 2 Posted February 8, 2011 Share Posted February 8, 2011 Hi Steve i think Tim is right .A 40 to 60a esc with a 3 to 5a bec should be ok ,have you got a watt meter yet? this is essential to get the correct prop for the set up. Edited By tom wright 2 on 08/02/2011 18:28:54Edited By tom wright 2 on 08/02/2011 18:33:38 Quote Link to comment Share on other sites More sharing options...
Steve Houghton Posted February 8, 2011 Share Posted February 8, 2011 Tom & Tim, Thanks for your replies. Tim; my question 2 should have been clearer: If I buy an ESC with a BEC but want to use a separate RX battery, will I need to cut the red wire in the RX supply coming from the BEC (as I know you have to when using a UBEC)? Tom, Yes I have a Watt Meter ready for use. I bought the recommended JP 14 x 8 folding prop. The JP instructions recommend a 60A ESC with 3S LiPo - the motor is rated up to 45A. If the optional electric spoilers are fitted (don't know if I can afford them!), making a total of 4 servos + 2 spoiler motors, JP recommends using a separate RX battery or UBEC, hence my question. However, given the infrequent use of spoilers I would have thought a BEC would have enough power. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 8, 2011 Author Share Posted February 8, 2011 Yes...but rather than cut the wire, I would just lift the small retaining tab in the plug, and gently pull the pin out of the plug - tape it back up against the cable. That way, its still easily replaced should you wish to use the ESC BEC in future models. Quote Link to comment Share on other sites More sharing options...
Tom Wright 2 Posted February 9, 2011 Share Posted February 9, 2011 The cost of UBECS capable of delivering 5A or more is a small price to pay for the added reliability ,and piece of mind,although i am using several cheap ESCs that have 5A BECs. all have been very reliable,but i always allow 30 percent or so on the ratings. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 9, 2011 Author Share Posted February 9, 2011 I agree, and still prefer them to separate batteries for the reasons stated in other threads.Summary1) One less battery to remember to charge2) Constant and steady supply voltage3) Lighter wieight 4) LVC will still be effective in warning of low battery - if using separate battery, then that pack could "go low" whilst main battery is still good, and then you would receive no indication of that ...until the model goes in! Quote Link to comment Share on other sites More sharing options...
Steve Houghton Posted February 9, 2011 Share Posted February 9, 2011 Thanks for the further comments, Tim and Tom. I think I shall re-read the other threads dealing with UBECs as the possible solution. However, with regard to Tim's points: 3) The prototype JP Fox model needed 8oz of nose weight, so I could use an extra battery instead of dead weight. 4) The LVC is certainly a great indicator of a low battery, unless I catch a booming thermal and turn the motor off (it is a powered glider, after all)! Many thanks again for the useful feedback - bedtime now! Quote Link to comment Share on other sites More sharing options...
Tom Wright 2 Posted February 9, 2011 Share Posted February 9, 2011 Steve catching a thermal 4) is a very good point ,with most esc you can programme the motor cut off point high enough to leave bags of reserve for the RX ,unless you intend to use a small lipo,then RX power reserve could be a problem if you get away in a good one. Quote Link to comment Share on other sites More sharing options...
Steve Houghton Posted February 9, 2011 Share Posted February 9, 2011 Thanks Tom. This begs one final ESC question (trying not to drift off topic too much): If the LVC cut-off point is reached and the motor cuts, does an ESC with BEC: a) allow a LiPo to be flattened through the BEC by the RX and servos, since it is getting dangerously near to its minimum discharge voltage but probably has enough voltage to continue powering RX and servos? b) have a secondary LVC cut-off point for the BEC as well? I suspect the answers are (a) yes and (b) no, since it's probably better to loose a LiPo than lose the whole model if the RX power was suddenly cut. This could be an argument for fitting a separate RX battery. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 9, 2011 Author Share Posted February 9, 2011 A) It could, but it would take an awful long time to do so - the usual 3v per cell cut off occurs at high current draw, so the pack is "artificially" depressed as it were. Once the LVC kicks in, and that large current draw is removed, the voltage will rise almost immediately to a level way above that needed for the BEC circuitry to work.I have never timed it, but you would need to be up for a long long time I suspect. B) No Its no argument for a separate battery for me I am afraid, especially as we are not discussing a purpose built duration thermaling machine here - or are we ? Quote Link to comment Share on other sites More sharing options...
Tom Wright 2 Posted February 9, 2011 Share Posted February 9, 2011 Hi Steve If you know what your esc motor cut setting is you could get a good idea how much capacity will be left to power the rx and servos,again this depend on the size of the lipo.as a rough example say you use a 3a lipo and set the cut off point at 50% you would have more than 1amp available which should give you at least 2hrs before the lipo voltage gets near critical.In theory you could even more than that as i have built extra margins into the example. Quote Link to comment Share on other sites More sharing options...
Richard Wood Posted February 9, 2011 Share Posted February 9, 2011 Be wary of an LBEC in an ESC if using more than a 2S LiPo. The BEC rating of the ESC should be stated more clearly on some makes. For example - my nice shiny Scorpion 55A ESC states 5V/4A BEC on the case. Check the catalogue & the large print says it works at 6 - 15V. Further on in small asterisked type it states that the full rating only applies to a 2S & to derate by 50% for a 3S & to use a seperate UBEC for 4S. A bit misleading. Scorpion are probably not the only one - best to check ratings before using a BEC. Quote Link to comment Share on other sites More sharing options...
Tom Wright 2 Posted February 9, 2011 Share Posted February 9, 2011 Steve following on from the above ,four of us had a thermal soaring season last year flying 3and4m bubble dancer / avia type formats,We all retired so got out every day when it was not blowing a gale or raining .Over 400 flights were achieved with no separate batts ,no brown outs ,or critically low lipo voltages.We did use digital battery checkers,before each flight,and got many 40min flights after after motor cut off. We did make a rule not to follow thermals above 1500 ft after Pete got disoriented at 3000ft! Quote Link to comment Share on other sites More sharing options...
malcolm woodcock 1 Posted November 26, 2017 Share Posted November 26, 2017 Quick question on this old thread, I've several old ESCs without any markings on them, can anyone tell me if I can run a check on them to find out what amps I can run through them? Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted November 26, 2017 Share Posted November 26, 2017 No way Malcolm If they were yours as original You can only try to recall the type of plane they were in As unmarked stuff is usually from ARTF Quote Link to comment Share on other sites More sharing options...
Geoff S Posted November 26, 2017 Share Posted November 26, 2017 You'd probably be safe using them with a 3S LiPO then all you need to know what current they can draw safely. You can check that using a Watt meter and monitoring the current and temperature as you increase the load say by fitting different props to the motor you're using for the test. Unless they're very small, they're probably good for 30 amps perhaps even more. I woudln't be too keen using them on a model I treasure Geoff Quote Link to comment Share on other sites More sharing options...
Romeo Whisky Posted August 10, 2020 Share Posted August 10, 2020 There is a lot of useful information for beginners with electric flight here ... **LINK** Quote Link to comment Share on other sites More sharing options...
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