Johnny Kirkham Posted January 9, 2013 Share Posted January 9, 2013 Hi guys, after nearly 40yrs of IC flying on and off I have finally bought a first electric model. As I havent really got much of a clue about watts, amps, batteries, speedy controllers etc I opted for a foamie wot 4 where all these choices have been made for me and come complete with the kit. At the moment im using 3 cell, 2200, 25C batteries as reccomended but would like to give the model a bit more poke. Would using a 30C battery or larger achieve this? or would using a battery with a bigger C value damage the speed controller/motor? thanks John. Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted January 9, 2013 Share Posted January 9, 2013 No problem using a battery with a higher C value, generally the high C batteries hold their voltage under load better, so at wide open throttle you'll get slightly more power. Ideally you'd check the amps to make sure you don't exceed the ESC and motor amp rating, but staying with the same number of cells and using a "better" battery they will be within their capcity. The performance gains will not be significant, A larger mah battery will have the same effect, but the downside is that it will be heavier so the plane will need more power to fly so there is often no benefit. To get a real performance gain you'd need to look at a 4s battery but then you'd need to change the prop (smaller size) to keep within the ESC limits etc and if you don't have a watt meter then you could most likely let the magic smoke escape. If the wot 4 foamy is a bit tame for you, then try a Multiplex Dogfighter on your 3s battery they go like stink and fly as though they are on rails, one of my favourite planes on a 2200 mah 3s battery.up Maybe somebody will come on that has squeezed some more performance out of the foamy wot 4. Quote Link to comment Share on other sites More sharing options...
Johnny Kirkham Posted January 9, 2013 Author Share Posted January 9, 2013 Thanks for the info Frank you have been very helpful. I haven't got a amp meter as yet but i see they are cheap enough and look a worthwile investment....can you reccomend one? Dont get me wrong I love the Wot 4 as it is and as for £££'s to fun value you cant beat it i just thought a bit more verticle power would be nice. I'll take a look at the multiplex you never know i may become a leccy convert!! Quote Link to comment Share on other sites More sharing options...
Jon Laughton Posted January 10, 2013 Share Posted January 10, 2013 I agree with Frank re the Mpx Dogfighter: I fitted the optional rudder servo but it doesn't really need it Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted January 10, 2013 Share Posted January 10, 2013 I use an old Eagle Tree E-Logger with the live view display, but several people offer watt meters and any of them should be fine, the alternative is a clamp on meter which would be useful for other jobs as well, just make sure that it can measure DC current, Farnell are doing one at the moment for less than £25 My Dogfigher on the MPX standard set up has got unlimited vertical Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 10, 2013 Share Posted January 10, 2013 Johnny I am sure you can increase the performance of a foamie Wot 4 in more or less the same manner as you would for IC - add more power! The problem is you have to consider the complete battery/speed controller/motor/prop as the power package. It may be possible to increase the performance by altering one element but you need to ensure you do not overload any other, hence the use of a meter. With electric to keep weight down most things are run quite close to their limit and power electronics in particular don't like being overloaded by even a small amount for more than a few seconds. You may find a modest improvement can be achieved by simply changing the prop. Electric power is pretty efficient so increasing the current drawn by the motor by say a modest 5% may still be within the capabilities of the rest of the power train (but you need to be sure!) and with the right prop most of this extra power can be converted into thrust with no increase in weight. You don't get something for nothing so there would be a corresponding reduction in duration. The joys of experimenting with electric - but as others have pointed out it might be simpler to just move to a higher performance plane! Edited By Simon Chaddock on 10/01/2013 13:20:48 Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted January 10, 2013 Share Posted January 10, 2013 Johnny, electric flight is one of those areas where you need to understand what you are doing before you experiment.....once you move away from the factory settings then you can let out the magic smoke unless you are sure that the components are working within their limits. That isn't intended to put you off in any way.....but to make you aware that "Here be Dragons".....all electric set ups are to a certain extent experimental in that they involve a level of compromise.....a little bit of thought by you & advice from the good people on here will soon have you swapping props with carefree abandon..... Step1.....buy a wattmeter Step 2.....have you got that wattmeter yet? You won't get anywhere without it!!! Step 3....have a read through the Beginner Section on electric flight & get a feel for the topics & terminology Step 4......ask lots of questions & think carefully about the answers Step 5.....ask more questions to test your new knowledge Step 6......enjoy yourself.....its a hobby.... Edited By Steve Hargreaves - Moderator on 11/01/2013 09:25:12 Quote Link to comment Share on other sites More sharing options...
Johnny Kirkham Posted January 10, 2013 Author Share Posted January 10, 2013 Thanks Frank, Jon, Simon & Steve......wow it looks like ive really opened a can of worms here!! As you have all pointed out I really need to gen up on the subject before doing anything rash. Steve Im already at step 6 ......trouble is ive missed out on steps 1,2,3,4,5!! Back to school for Johnny for a while I guess lol Quote Link to comment Share on other sites More sharing options...
Former Member Posted January 11, 2013 Share Posted January 11, 2013 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted January 11, 2013 Share Posted January 11, 2013 Undoubtedly true Tom but wheres the fun in that?? Curiosity & experimentation is what drives the Human race forward.....its a well known fact that if Neanderthal Man had been equipped with a watt metter Homo Sapiens would have had a much harder time displacing him..... Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted January 11, 2013 Share Posted January 11, 2013 Posted by Tom Sharp 2 on 11/01/2013 01:20:49: I have been flying electric models for many many years, I have yet to use a wattmeter, I just do what it says on the tin. Using a wattmeter is venturing into totally unessesary territory and is best avoided. eg someone else has already done the sums. I think that works if you stick with the manufacturers recommendations, but if you want to squeeze a bit more out of an existing set up as Johnny does then a watt meter makes some sense, but I suppose a lot of people only get a watt meter once they've experienced white smoke for themselves.. But then again I'm one of those people who like to know whats going on. Quote Link to comment Share on other sites More sharing options...
PatMc Posted January 11, 2013 Share Posted January 11, 2013 A wattmeter is not really necessary for good results in electric flight but an ammeter is. A wattmeter & tachometer are useful. IMO the tach is the more useful of the two. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted January 11, 2013 Share Posted January 11, 2013 Much as I hate to disagree with you Pat I'm going to have to here..... A tacho will tell you revs which is nice to know but not critical. A wattmeter will tell you current, voltage & watts all of which ARE critical IMHO......too high a current will damage the motor or ESC or battery.....the voltage will tell you how well the LiPo is holding up & Watts will tell you the power to weight ratio which will give you a good idea of the performance. At the side of that lot a tacho looks a bit insignificant......in fact I don't think I have ever used a tach on my lekky models.....if I know my prop is spinning at 10,561 rpm thats interesting but nothing more. True you could use an ammeter as a basic minimum but an ammeter capable of reading over 10A is going to cost an arm & a leg....you could use a DC shunt but this is getting way over complicated......& you still don't know the voltage & hence the watts...... Wattmeters are so cheap & easy to use I really can't think of a reason NOT to have one..... Buy a wattmeter & be happy in my view..... Quote Link to comment Share on other sites More sharing options...
Bearair Posted January 11, 2013 Share Posted January 11, 2013 Couple of things if your new to electric. 1.You might find that the performance improves after youve charged the lipos a good few times. 2.Lipos hate the cold, if you keep your lipos warm (room temp) they will give you better performance. Ive flown alot of foamy wot 4s for people and the performance has always been good with the standard set up.Maybe not good enough for prop hanging but certainly good for extended verticals and squares. Quote Link to comment Share on other sites More sharing options...
FunnyFlyer Posted January 11, 2013 Share Posted January 11, 2013 Posted by PatMc on 11/01/2013 11:00:42: A wattmeter is not really necessary for good results in electric flight but an ammeter is. A wattmeter & tachometer are useful. IMO the tach is the more useful of the two. Eh? Have I missed something here? My watt meter goves readings of current, voltage and power in watts. An ammeter is useful - but you're missing the "V" bit in the equation P = VxI - so you can't even calculate power. Of course an ammeter will tell you if you're exceeding current ratings of motors and ESCs - but will not give you the whole picture. Edited By FunnyFlyer on 11/01/2013 14:07:43 Quote Link to comment Share on other sites More sharing options...
Johnny Kirkham Posted January 12, 2013 Author Share Posted January 12, 2013 Ok lads reading all your posts I gather it would be nice to know watts and amps etc.....can anyone reccomend a meter that reads both? or should I just buy on of those electricians multi meters? or do they do a dedicated meter that works out the power train? As im just dipping my toe into the electric flying obviously I dont want to waste money on expensive equipment that could be spent on other models. Btw I already have a tacho and a fusion battery checker that ive been using on my IC models. Regards Johnny Quote Link to comment Share on other sites More sharing options...
Wingman Posted January 12, 2013 Share Posted January 12, 2013 Johnny forget the multimeter it won't do the business. Have a look at this page and take your pick. this will do the trick but you will have to solder appropriate connectors to the input and output leads. Edited By Wingman on 12/01/2013 17:27:28 Quote Link to comment Share on other sites More sharing options...
Allan Bowker Posted January 12, 2013 Share Posted January 12, 2013 Johnny When I started with electric I thought I could get away with a watt meter (and I did for a while using prescribed manufacturer stock setups). However one manufacturer wasn't correct in some of their data and my stock setup caused my motor to smoke and Li-Po to dangerously swell up. I proved to myself that not buying a meter was false economy, I'd just lost £200 as I couldn't test the 'stock' system was within limits. I wish I'd at least borrowed one for 5 minutes. To answer your first question, the C rating on a battery indicates how fast you can discharge it without damage (amp draw from your motor, affected by prop size and pitch). The higher the C rating, the easier life your battery will have. You can think of it like a pipes diameter, a 1litre bottle with a 10mm opening will let out its contents slower than one with a 20mm or 30mm opening (unless you damage the bottle by crushing it and forcing the water out quicker). The same works with a Li-Po, a 10c battery will let out its electricity slower than a 20c or 30c pack (unless you damage the battery by drawing more current than it is rated for). The motor, ESC and battery all have their limits (data provided by their manufacturers). By using a watt meter you can ensure all components are comfortably within their limits and not near them, which will cause a failure. For example, don't run a 40amp ESC at its limit, it will get very hot and fail (like an engine in a car, don't run it at full revs). A 33amp max draw on a 40amp ESC should see you with a long lasting setup. Any basic hobby watt meter should be able to tell you the basic amps and watts that your setup is drawing, these are the important figures (asuming that the voltage of the Li-Po you have connected to your ESC and motor are within their limits). Be careful with your WOT4 Foam-E Johnny, they have quite a reputation for ESC failure (and I have experience of this). To get more 'poke' out of this model I would recommend a simple change of prop (but then you will need to know the spec of your motor and ESC..........oh and you will need a watt meter too! Of course, you could try a 4S Li-Po but then you will need to know if your motor and ESC can take the extra voltage (as per the manufacturers specifications). You also have the option of fitting a better motor and higher rated ESC for a 4S. Massive WOT-4 Foam-e thread, including Simon Chambers on Page 21 talking about fitting a 4S to his WOT. It seems that adding too much power to this model isn't good. I'd try a cautious prop change (ground tests) whilst recording the results and monitoring the temperature of the ESC. Good luck, keep coming back to us for help and let us know how you get on. Quote Link to comment Share on other sites More sharing options...
Johnny Kirkham Posted January 13, 2013 Author Share Posted January 13, 2013 Thanks Wingman for the link and to Allan for explaining in "lay man terms". Allan, ive just read the wot4 link you posted.....all 24 pages of it!! lol. Simons post was very interesting and like you say changing the prop for a decent APC looks the way forward to me at the moment......ill let you know the results when ive done so......thanks Johnny Quote Link to comment Share on other sites More sharing options...
Les Littleton Posted January 17, 2013 Share Posted January 17, 2013 Edited By Les Littleton on 17/01/2013 20:56:18 Edited By Les Littleton on 17/01/2013 20:56:40 Quote Link to comment Share on other sites More sharing options...
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