Emil Benson Posted September 21, 2011 Share Posted September 21, 2011 Hi Guys, I am just wandering what a UBEC does. Am I right in saying that you plug lets say a 2s lipo, into it and it converts the voltage into a more manageable voltage for your RX and servos. I have a model that could do with a new battery, and its a little on the heavy side. I'm thinking of making it a little bit lighter by using a lipo. Cheers, Emil Edited By Emil Benson on 21/09/2011 11:57:24 Quote Link to comment Share on other sites More sharing options...
Ben B Posted September 21, 2011 Share Posted September 21, 2011 Yes, that's exactly what it does. It changes the battery voltage down to a voltage that the servos and receiver can handle. Traditionally that was 4.8v (5v in reality) but some UBECs offer slightly higher voltages as some modern servos and receivers will happily take a higher voltage. Indeed if you're on 2S you might not need a UBEC at all (but check the specs for your servos and rx). Quote Link to comment Share on other sites More sharing options...
Emil Benson Posted September 21, 2011 Author Share Posted September 21, 2011 Thanks for the speedy reply Ben, well explained. one other question that you might know, when you charge a Lipo or Lifepo battery etc that has been made especially for a reciever, can you charge it on an ordinary lipo charger? Edited By Emil Benson on 21/09/2011 12:20:20 Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted September 21, 2011 Share Posted September 21, 2011 Emil, take a look here.A suitable entry into the search box will also show a few more threads on the subject.LIKE THIS Edited By Tim Mackey on 21/09/2011 12:30:41 Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 21, 2011 Share Posted September 21, 2011 Yes you can Emil (although your charger must have a LiFe setting as the voltages are different.) Rx Lipos tend to differ from motor Lipos in that they won't offer such a large discharge current. They generally have a much lower C rating...after all you're unlikely to want to put 20A through your radio now are you.... Things to watch with a BEC..... Tthey can often cause interference with 35MHz gear (in my experience) as they are usually switching regulators..... The little Volt Spy things we often use on NiMh packs are useless....the voltage output will stay pretty contant until the LiPo battery is completely flat Might be worth getting a unit with a low voltage alarm for the LiPo.....these will typically go off at around 3 & a bit volts per cell to let you know the LiPo is getting a bit tired but there will still be plenty of juice to keep your radio going.... The Big Fish have a good range in stock.... Quote Link to comment Share on other sites More sharing options...
Emil Benson Posted September 21, 2011 Author Share Posted September 21, 2011 Search box, duh! your Timbo I'm Dimbo! anyhow taking a good look at the article. Steve cheers for that, I use 2.4 GHz on that model, so that shouldn't affect it. Would sound advisable to get one, with the voltage monitor, I'll keep a look out for one. taking a look on Giant Cod now Thanks very much Guys Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 21, 2011 Share Posted September 21, 2011 Another option is to use a seperate low voltage screamer which plugs into the balance lead of yer LiPo....you can get these off BRC & others for about a fiver. Another point worth mentioning is to make sure you wire the UBEC up after the switch so you switch the power to the UBEC off rather than switch the power from the UBEC to the radio off (if you see what I mean...) A UBEC takes a small bit of current itself & will slowly flatten your Lipo right down to zero volts if you let it..... Quote Link to comment Share on other sites More sharing options...
Peter Beeney Posted September 21, 2011 Share Posted September 21, 2011 Steve, With the greatest respect, and absolutely no offence meant at all, I’m only being cheeky, but I’d have do disagree slightly with regard to the lipo voltage discharge curve. The amount of charge left in the pack is very predicable, when, for instance, the open circuit voltage of a two cell pack is 7.2V we can say fairly confidently that it is around half charged. (Or discharged). The longer term storage capacity can be judged on the voltage, in fact, the total performance is always based on it’s voltage. If the pack is allow to totally discharge to zero volts it might be rendered u/s.The GWS voltage monitor can be switched to a 8.4V level, I’m sure this would be perfect for monitoring the voltage level of a 2S pack. However, it would have to be installed in the loom between the switch and the regulator, if you connect it straight on the battery you would have to continually disconnect it otherwise it would eventually totally flattened the battery. As would an audio monitor also, you would have to switch in some way, although perhaps perhaps this has it’s own switch. When I get a mo, I’ll give the monitor a twirl, it’ll only take a couple of seconds.A standard 1 amp £1 linear regulator would be fine in this situation; simply because the voltage differential is so low. A 5V reg and a fully charged battery. 8.4 - 5 volts = 3.4; at a 1 amp load then 1 by 3.4 = 3.4 watts, max, are only ever going to to be dissipated across the reg as heat. It doesn’t even try to warm up, I proved this when the lipos first appeared. As it happens, most of the time it’s only conducting milliamps, the radio quiescent current. Plus no interference, and the regulator is unbreakable to boot. I’ve not studied this, but I suspect that up to now the difficulty has been the connections? Have any of the manufactures come up with a suitable set up yet? Certainly ok if you can customise your own, but perhaps many folks are not able to do this.PB Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 21, 2011 Share Posted September 21, 2011 Of course you are right Peter provided the monitor is plugged directly into the battery but I am thinking about a more practical situation where a, shall we say. less technically minded modeller might simply plug a voltage monitor into the Rx output as if using a 4 or 5 cell Nimh pack. In this situation the Lipo battery could be getting dangerously flat (down to 3 volts per cell say) whilst the regulator is still happily supplying 5.5volts to the Rx.... Thus we have a situation where the modeller checks his battery monitor...see's its fully green & takes off with a dangerously low battery..... Quote Link to comment Share on other sites More sharing options...
Peter Beeney Posted September 21, 2011 Share Posted September 21, 2011 Yes indeed Steve, if the rx supply is from a regulator then it’s impossible to monitor the battery voltage from the receiver. It definitely has to be from the battery.My friend is changing all his model to 2 cell LiFe packs, supplying the rx direct, but he’s using one of those cute little monitors that scroll through a menu and give you a constant readout of the individual cell and then the overall pack voltage. This connects to the balance lead, so at the moment he has this same problem of disconnecting on a regular basis. I think his best idea would be to extend the wiring from the monitor and incorporate a three pole switch at the same time. The very smallest would be sufficient. When he first used these cells he tried a standard monitor and I adjusted the slight voltage discrepancy with a diode. Actually a two pole would suffice, simply leave the centre wire common and switch the outside pair. Whilst I’m very much a supporter of monitoring the receiver battery I’m also quite happy to say that if you check the pack regularly for any signs of declining capacity, and make sure that it’s always fully charged before flying, (that’s nickel cells), or sufficient charge (lithium cells), then you will never have any problems. I never have, anyway. If you assume an average 150 mA/hour consumption for a standard sports model then you’d have 6 hours continuous flying from a 900 mAh pack. Even at 200 mA/hour you’d have 5 hours from a 1000 mAh battery; and some people seem to be using more than 2000 mAh as a source. I’m sure the present little drawback to the receiver battery monitor will undoubtedly be addressed, lithium batteries are becoming very popular for rx and tx supplies, but, of course, they all go flat eventually… PB Quote Link to comment Share on other sites More sharing options...
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