Tim Mackey Posted August 24, 2009 Share Posted August 24, 2009 I did do a thread similar to this a while back but cant find it since since the forum platform change - the issue raises its head often, so here's my take on it - and this time I shall bookmark it The following is of course, only my personal opinion and not based on science, engineering degrees or anything else quite so sophisticated, but will doubtless cause "debate" . " BECS are actually better than a separate battery" Let me explain why I think this could be so . BECs ( whether separate or part of the ESC ) usually get their power from the main flight battery - a relatively meaty great big powerful beast. The ESC also features a low voltage cutoff circuit ( LVC ) designed to give visual but safe indication that the battery is running low. However even if the battery approaches this low level, it will still have more than enough juice left to continue powering the BEC / UBEC which in turn powers the receiver and brown out should therefore not happen ( assuming the BEC circuitry is "up to the job" ). A separate Nixx battery pack on the other hand has the following potential problems. 1) It needs to be capable of supplying the correct voltage and current necessary - and many are not, especially smaller cell AA type. 2) It needs charging ( and by different means to that of the flight pack ) and this could be / has been forgotten with disastrous consequences 3) Nickel based cells have a bad reputation for black wire disease - which most decent evidence seems to point to the chemistry of the electrolyte used. No such BWD has been found in Lithium cell based packs. 4) Perhaps most critically of all - if, for whatever reason, the separate pack runs low, or stops altogether due to a bad connection etc there will be no prior warning via the motor stopping / slowing / pulsing or whatever the ESC would normally do. The first signs of trouble will be the receiver stopping working altogether - including the flight controls! This will not be a "failsafe" situation - this can only occur with RF signal loss / interference, not a power loss. This of course is dependant on the BEC / UBEC being reliable and capable enough for the job...which frankly these days the majority of them are. A separate circuit UBEC should indeed run cooler ( provided it is within capability and has airflow around it ) than one built onto an already warm, hard working ESC PCB So in order of preference I will go for - in true Miss World fashion EG: in reverse 6th place- the separate 4 cell NiXX battery 5th place- the separate 5 cell NiXX battery 4th place - the ESC BEC combo unit 3rd place - the UBEC powered by Nixx battery 2nd place - the UBEC powered by seperate LiPo Ist place - the UBEC powered by main flight pack Quote Link to comment Share on other sites More sharing options...
Merlin spit Posted August 24, 2009 Share Posted August 24, 2009 good info tim ,i like first place best as wel,l i think it works out the cheapest option alot of the time ,you can get a opto esc's and ubec's very cheap on web ,also you can get some good esc with a 3a-5a switching bec built in ( 4th place ) these are a bit more expensive ,what do think about them tim ? Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted August 24, 2009 Author Share Posted August 24, 2009 I have sussesfully used the inbuilt switch mode BECs on ESCs on several models without problem. Of course, it all depends on what sort of loads are being palced upon the servos via flight styles and surface areas etc...as well as the total number of servos themselves, and their type . Digitals and mini /micro jobs are usually thirstier than their standard analogue brothers. Quote Link to comment Share on other sites More sharing options...
Garry G Posted August 30, 2009 Share Posted August 30, 2009 I'm a little confused about all this, is a UBEC a separate piece of kit that can be used with an ESC with BEC or only with one that has OPTO as I thought that this type of ESC must operate with a separate battery. Also in passing why do most ESC's not have an ON/OFF switch like a Jeti? RegardsGarry G Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted August 30, 2009 Author Share Posted August 30, 2009 IMO the "on-off" switch is a waste of time - prefer the absolute security of knowing that when the main battery is disconnected nothing can start up, and whenits plugged in I treat the model as "live". Now the UBEC. It ( or a separate battery ) can be used with an OPTO ESC...but TBH in order to retain full opto isolation, a separate battery is required not a UBEC.If you wish to use a UBEC with an ESC which has a BEC onboard, then remove the red pin from the ESC servo lead which plugs into the throttle port. This cuts off power from the BEC but still allows the throttle commands to be communicated. Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted August 30, 2009 Share Posted August 30, 2009 TIMBO-you are the man-i take my hat off to you for all the info you are putting on the forum for us apprentice sparkie's-should you cross the border to the centre of the world(geordie land) you will def get a pint from me.......... ps-get young ashby to get it all(the info) into one book-you'll be a millionaire asap..... ken anderson............. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted August 30, 2009 Author Share Posted August 30, 2009 Thanks ken - nice of you to say so, and I shall definately look you guys up when we next venture oop norf. Millionaire?....naaa, dont think so mate Quote Link to comment Share on other sites More sharing options...
Garry G Posted August 31, 2009 Share Posted August 31, 2009 Many thanks Timbo, understand where you are coming from re. the ON/OFF switch. If I am using a UBEC with a ESC that I have removed the +ve red pin, this is still plugged into channel 3 ( throttle ) where do I plug the UBEC into the RX ? the normal battery socket? I remember when the most demanding technical decision was wether to use 6 or 8 strands in the rubber motor. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted August 31, 2009 Author Share Posted August 31, 2009 Yes, or indeed any spare port on the Rx - they are all connected internally to battery pos and neg Quote Link to comment Share on other sites More sharing options...
Merlin spit Posted October 15, 2009 Share Posted October 15, 2009 i was just wondering if it is possible to use a ubec with a 7.4 v lipo without a esc (i.e on a i.c model as a reciever pack) ? forgive me if youve already anwsered this elsewhere tim Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted October 15, 2009 Author Share Posted October 15, 2009 Absolutely...thats the main purpose of them TBH Quote Link to comment Share on other sites More sharing options...
Merlin spit Posted October 15, 2009 Share Posted October 15, 2009 thanks tim ,i dont need to buy another 6v NiMH (lost my only one)now and ive found a use for some 2s lipo ive got . .my main reason for asking was i was thinking of getting a glider (i live near ivinghoe beacon and it seemed rude not to) so i thought i could use a 2s lipo and ubec for convenience. Quote Link to comment Share on other sites More sharing options...
Olly P Posted October 15, 2009 Share Posted October 15, 2009 I have just bought the gubbins for converting my trainer to electric, and as soon as I've sold my IC bits SWMBO will let me access them... either way, according to the UBEC diagram the UBEC is connected from battery to reciever and the esc from battery to motor, in a sort of parrallel (but different output) set up. This now makes sense, especially when coupled with the LVC function of the ESC. right, now to find some cheap(ish) deans ultra connectors and banana clips. Thanks Tim! Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted October 15, 2009 Author Share Posted October 15, 2009 Posted by austen rover on 15/10/2009 15:16:15:thanks tim ,i dont need to buy another 6v NiMH (lost my only one)now and ive found a use for some 2s lipo ive got . .my main reason for asking was i was thinking of getting a glider (i live near ivinghoe beacon and it seemed rude not to) so i thought i could use a 2s lipo and ubec for convenience. Its the method I use in all my gliders too AR Quote Link to comment Share on other sites More sharing options...
Peter Roberts Posted October 23, 2009 Share Posted October 23, 2009 Does the use of Twin Motors make a difference as to whether you are able to use BEC or not? I'm thinking of buying a YT International DHC-6 Twin Otter with 2 x 1250 kv motors 2 x 60A esc's and drawing from 2 x 3200 or 3700 3s lipos. Are there issues with using the BEC's built into the 4-Mac escs? How should I wire these? Do I Y lead the connection to the Spectrum receiver? Do I need to disconnect one of the red wires from the ESCs? Can one leave the lkeads from the esc's intact to provide redundancy to the receiver for power? Any help or experience with this kind of set up (and the Twotter) gratefully received. Thanks Peter Edited By Peter Roberts on 23/10/2009 16:58:51Edited By Peter Roberts on 23/10/2009 16:59:16 Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted October 23, 2009 Author Share Posted October 23, 2009 Generally speaking, its best to disconnect the BEC power ( red lead ) from one of the ESC BEC units that are connected to the Rx throttle channel ( usually with a Y lead ).It is not uncommon for two BECS to "fight" one another. Quote Link to comment Share on other sites More sharing options...
Lee Smalley Posted October 23, 2009 Share Posted October 23, 2009 have used BEC and UBEC on all my light foamies and even on my blizzard never had a problem, a few at our club have had problems when using BEC on bigger full house models, but thats their fault for ignoring recommendations in my opinion!! Quote Link to comment Share on other sites More sharing options...
Lee Smalley Posted October 23, 2009 Share Posted October 23, 2009 Posted by Peter Roberts on 23/10/2009 16:58:22: Does the use of Twin Motors make a difference as to whether you are able to use BEC or not? I'm thinking of buying a YT International DHC-6 Twin Otter with 2 x 1250 kv motors 2 x 60A esc's and drawing from 2 x 3200 or 3700 3s lipos. On a model this size should you not put a small seperate rx battery in? its not like the extra weight will be an issue and it will give you piece of mind, i think your pushing it on that current draw and i would think 4 rather large servos?? Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted October 23, 2009 Author Share Posted October 23, 2009 I think my OPclarifies where I stand on this matter. Quote Link to comment Share on other sites More sharing options...
Dusty Posted October 23, 2009 Share Posted October 23, 2009 Nigel hawes did a article on this in October 08 RCM&E issue? Was self explanitary! I was considering a OPTO or BEC esc for my new bird, I am undecided on what to do... grrr Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted October 23, 2009 Author Share Posted October 23, 2009 Give us a clue as to what the bird is, how many servos, what flight pack etc, etc Quote Link to comment Share on other sites More sharing options...
Garry G Posted October 25, 2009 Share Posted October 25, 2009 I have been looking for that article that Nigel wrote but it does't seem to be in the Oct 2008 issue,anyone know which month it was in? Quote Link to comment Share on other sites More sharing options...
Dusty Posted October 25, 2009 Share Posted October 25, 2009 Tim Sebart Sukhoi 50, 4 servo's (Graupner 5077) 5kg torque, they going to busy on this plane ! I have a opto esc that I could fit, however I did order a Turnigy Plush 80a that its BEC can handle 6s input! Assuming this is a discouraging option then i will go the opto way and consider a seperate RX pack, however the object is to keep the model as light as possible as will be using 6s 3700 packs wich is the heavier option of Lipo choice, I could stretch into the pocket and get some lighter lipo's, but I prefer the 3700's as they are used in other models. So 3700's plus the extra weight of a rx pack might tip the model a tad heavy for the performance I am aiming to get out of this model! Quote Link to comment Share on other sites More sharing options...
Dusty Posted October 25, 2009 Share Posted October 25, 2009 Garry, the mag cover has a Hawker Hurricane on the front! Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted October 25, 2009 Author Share Posted October 25, 2009 Dusty... I would use separate UBEC, plenty around from the likes of Grant, and Rob ( GC ) Quote Link to comment Share on other sites More sharing options...
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