Stephen Stockwell Posted August 3, 2007 Share Posted August 3, 2007 I Was thinking of converting the hanger 9 thunderbolt to Electric there was an artical in qfi magazine in feb2006 where they useda 6cell 10C pack with the improvments in cells is this still neededor can I use a 4-5cell lipoy say 4000mamp or has any one got a bettersolution. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted August 3, 2007 Share Posted August 3, 2007 The improvements in cells does not include them increasing their voltage - they are still 3.7V nominal. If the original conversion used 6s thats 6 X 3.7 = 22V. If you use 5s thats only 18.5V NOMINAL.Now I know that the higher C rate packs available today SHOULD hold their volts better under load than the lower rated, early gen cells, but now assume this if you will, just for a minute.....lets say the old 6s packs held only 3.3V per cell under load, that makes almost 20V for the 6s pack. Now assume the better cells of today hold say 3.5V - thats 5 X 3.5 = 17.5V.Further assumptions now, as I dont have the figures to hand, but lets say the current on the particular motor prop combo was 30A.The old pack combo therefore had a power input of 600Watts(20V X 30A)Your proposal of 5 cells on the same combo gives only 525 Watts( 17.5V X 30A ) - over 12% less!Personally I would stick with 6S, and accept the fact that the higher C rate packs of today will result in a slightly better wattage,( 630Watts ) AND will have a longer life because you will only be pushing them to a small degree, compared to the old 10C jobbies. Nothing worse than an underpowered electric plane, and the best way to get the power up is with more volts not just more anmps. Quote Link to comment Share on other sites More sharing options...
Alan Scarlett Posted June 19, 2009 Share Posted June 19, 2009 Can any one help me I got a vulcan on the plans it got a Marco 61 ic in the back I like to put 2 Brushless outrunners in it. It will be 12lb spread over 9sq ft. I like to run it of 3cell packs for each motor,will 600w on each motor be ok Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 19, 2009 Share Posted June 19, 2009 Should be - after all its not a speed machine. Motor Kv and prop selection will be more important than out and out power. Quote Link to comment Share on other sites More sharing options...
Alan Scarlett Posted June 19, 2009 Share Posted June 19, 2009 Hi Timbo I can only get a 11in propeller on it as to big will hit the fuselage, the motor kv about 1100 or 900 kv i do not but know which kv or pitch for the propeller. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 19, 2009 Share Posted June 19, 2009 If you are planning on using 3s Lipo for 600watts then your current draw will be very high ( 600 /10.5 = 57A ) so dont expect long flights! You will need very high capacity packs. If you MUST use 3s packs then you will probably need the 1100 Kv motors in order to get even close to 57A, and even then you will need a high pitch. Why not use the 2 batteries in series as one 6s pack? That way, you could maybe use the lower Kv motors ......and for the 1000 watts or so that you need, you would only be at 46A or so. What capacity batteries are you planning, and just exactly how much experience and knowledge of electric powertrains do you have ? Quote Link to comment Share on other sites More sharing options...
Alan Scarlett Posted June 20, 2009 Share Posted June 20, 2009 Hi Timbo I have got about 10 modle all electric this is my frist twin I have got 6 3cell 4000ma batteries all 20c like to put in it. If I do 2 batteries in series as one 6s pack can I run the 2 motor of the 6s pack,the esc are 60amps each the motor i got get. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 20, 2009 Share Posted June 20, 2009 Hi Alan. You can run both motors off the one 6s battery ( but use 2 x ESCs ) and this will increase the RPM considerably of the motor. However, both motors in parallel will draw twice as much current as one motor on one battery each. They are quite large capacity though at 4Ahr each, and with a 20C rating they are good for around 80Amp maximum. The problem with using a battery for each motor is that one battery could easily run down a little more than the other, causing the ESC to shutdown the motor - never nice on a twin, so personally I would use one large battery to feed both ESC and motors. TBH 3s is a little low on volts for 1000+ watts. If you join 2 in series, that will give you around 21 Volts (under load ) and for 1000 watts from 21V you will be pulling 47A....which is do-able off the 4000 mahr packs. Remember of course that doubling the voltage by connecting in series does NOT double the capacity - or C rate - of the packs. HTH Quote Link to comment Share on other sites More sharing options...
Alan Scarlett Posted June 20, 2009 Share Posted June 20, 2009 Hi Timbo I will keep you posted on how i get on. The motor I hope to get at wings and wheels next weekend. (The photos one of my modle which lose on a acro wot on 3cell for 3.5lb and 450watts.) Quote Link to comment Share on other sites More sharing options...
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