NigelH Posted June 21, 2011 Share Posted June 21, 2011 I’m looking for power options for two different models 69” with an E-Flite Power 46, a 60 amp ESC (unknown BEC rating - disconnected), four DS821 digital servos and an AR6200 82” with two E-Flite Power 25s, six JR NES591s, two HS 85MG servos and an AR7000, which still needs two 60 amp ESCs I’ve looked at the Eneloops but they seem complicated (false peaks, over-charging and maybe even memory issues). The other consideration would be UBECs but it seems to me that it wouldn’t be sensible to risk very expensive 6.5lb or 12lb models to a budget £10 import. Things are complicated further having read only today that the JR servos don’t seem to like 6 volts. Informed advice required thanks. Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted June 21, 2011 Share Posted June 21, 2011 The simplicity of a standard 4- or 5-cell NiMh receiver battery is attractive to some. I haven't heard of any problems with Eneloops (maybe I haven't searched enough, because I don't use them), but my standard Sanyo packs, as supplied by Ripmax and others with their radios, have never let me down. My models (5lb to 12lb weight) all used opto ESCs and standard NiMh receiver packs when I was on 35MHz, to reduce the risk of interference. Since switching to 2.4GHz I've replace all the receiver packs with stand-alone BECs powered from the main flight batteries. I'm using a couple of the original UBECs, from USA, but more recently I've been using Hyperion Cool BECs. If you need more power, as might be the case with digital servos, Castle Creation's BECs seem to have a loyal following. I think only you can decide whether the failure risk of a BEC exceeds that of an NiMh battery -- or even of the receiver itself. For me the big advantage of BECs is I don't have to decide which model's receiver pack to charge the night before -- my A123 power packs are always ready to go, so I can decide which model at the last minute. Quote Link to comment Share on other sites More sharing options...
NigelH Posted June 21, 2011 Author Share Posted June 21, 2011 The risk of failure is the big consideration, along with cost. I also don't like the idea of charging before I fly. I don't think that you can even top up the Eneloops anyway. I meant to add that for the twin, HH told me that two E-Flite 60 amp Pros can be plugged in without the BECs being disabled to deliver more current for the radio. However, they're £70 each which I will not be spending. I wonder if other ESCs (e.g. Turnigy Plush 60 amps) can be connected that way. I was looking at the CC 10 amp BEC and they had the comment about servo connectors being rated at 5 amps but how are you supposed to connect it to an RX ? I've read the article showing that the leads got hot at 10 amps. There's something else I also meant to add but I've forgotten it again Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 21, 2011 Share Posted June 21, 2011 Im with Allan on the summary. Personally, I have never had a UBEC fail, and I use a lot of them - almost all are "budget" units from either H King, or Giant Cod. They are normally switchable between 5 or 6V output, and most are switch mode regulators these days, which are more efficient, and with 2.4Ghz gear, interference free.This is the one I use most. Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted June 21, 2011 Share Posted June 21, 2011 Posted by NigelH on 21/06/2011 12:09:35: ... I was looking at the CC 10 amp BEC and they had the comment about servo connectors being rated at 5 amps but how are you supposed to connect it to an RX ? I've read the article showing that the leads got hot at 10 amps. ... I don't know what current digital servos need, but if the total consumption is more than the 5 amps that the receiver's circuit board can allegedly handle (don't quote me on that figure either), you can feed each servo direct from the BEC without going through the receiver. The way to do it is to splice in another -ve wire to each servo lead, so that you have four leads coming from it. One -ve lead and the signal lead go to the appropriate receiver channel, and the other -ve lead and the +ve lead go to the BEC to get power. The BEC can also power the receiver, as usual, but by having no servo +ve wire going into the receiver, and having the servos tap directly into the BEC supply, the receiver circuit board won't have to carry the servo currents. Quote Link to comment Share on other sites More sharing options...
Olly Giles Posted June 21, 2011 Share Posted June 21, 2011 Two options That i would consider. 1. LiFe batteries 2. Powerbox Systems Digi switch Both of these do the same job as a NiMh battery without the weight penalty. I use the digi switch on a small 2 cell lipo and it is faultless. (you need to disable the BEC in both cases)Edited By Olly Giles on 21/06/2011 20:19:10 Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 21, 2011 Share Posted June 21, 2011 I would be VERY surprised if the radio system was consuming anything like 5A - closer to a couple of amps at most I suggest.Perhaps this old thread may interest? Quote Link to comment Share on other sites More sharing options...
NigelH Posted August 11, 2011 Author Share Posted August 11, 2011 Thinking about the Twin Otter with six standard NES591s and two HS85MGs, one of these should be perfectly good enough ? At what rate can you draw from them ? Running two of them to two different RX sockets with Y-leads would also give me double the current output and also provide resilience. The only other question would be whether the NES591s can run on 6 volts. I've read that this may not be possible. Anyone know ? Thanks Quote Link to comment Share on other sites More sharing options...
NigelH Posted August 11, 2011 Author Share Posted August 11, 2011 Ok, those servos don't run at six volts. MacGregor Industries suggested this one. Would it be suitable ? What could current drain could it sustain ? More than 1C ? Thanks Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted August 11, 2011 Share Posted August 11, 2011 The current the servo(s) pulls will be what ever it draws under particular load - this will be factored in by the manufacturer.Those sub C cells will be good for many amps....certainly way above the servo requirements.Edited By Tim Mackey - Administrator on 11/08/2011 19:32:33 Quote Link to comment Share on other sites More sharing options...
NigelH Posted August 11, 2011 Author Share Posted August 11, 2011 Tim, to use extremes to make my question clearer, we know that something could draw 100mA without, more than likely, affecting the battery voltage at all and we know that something trying to draw 100A (besides not getting very far ) would have a quite a big affect on battery voltage. So, is it clearer what I meant ? Interestingly, I just went mad and looked in the instruction manual I'd not bothered with the IC option so didn't notice their recommended flight pack They recommended these servos - Spektrum A6000 Digital Servo (6) SPMSA6000 JR SPORT MC35 Micro Servo (4) JSP20030 with this - Receiver Battery, 6-volt, 2300mAh JRPB5006 It's not even a sub-C and a lot less capacity than I was thinking about. It is a 6 volt pack though. And that's with digital servos instead or standard ones. I'm now feeling more comfortable about using the Overlander NiMH. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted August 11, 2011 Share Posted August 11, 2011 Just confirms then that this sub C large capacity pack will not even sniff at the current its required to deliver - and the example in your last post was for a 6V pack, so the current will be even lower than that on 4.8V. Quote Link to comment Share on other sites More sharing options...
NigelH Posted August 11, 2011 Author Share Posted August 11, 2011 Higher voltage = lower current but the Overlander is a higher capacity. Now I'm confused. The Overlander will or won't be suitable ? Thanks Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted August 11, 2011 Share Posted August 11, 2011 It will be fine.The 6 v pack recommended would be pushing more current than the 4.8v pack you intend to use. Quote Link to comment Share on other sites More sharing options...
NigelH Posted August 12, 2011 Author Share Posted August 12, 2011 I finally placed an order. I already have a new Overlander 4.8v 1600mAh Premium Sport NiMH so I've ordered another. That will give me 3200mAh when connected in parallel and when connected via two receiver ports, they will ease the load on the connections and give me a little resilience. I can also install a volt spy and then switch on each pack in turn to get an idea of where I am with them. I also intend to fit a TM1000 which should give me an overall voltage report and a low voltage alarm. Edited By NigelH on 12/08/2011 13:04:41 Quote Link to comment Share on other sites More sharing options...
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