Powering the Rx

[Erfolg]

As a long term electric flyer, I now wonder how IC aircraft Rxs are now commonly powered. Electric models the Speed Controller commonly powers the Rx, as most will know.

 

In the distant past a small Nicad would be used to power the Rx. I wonder if it is now the practice to used a Lipo or are Nimh now the preferred method?

[Paul De Tourtoulon]

What sort of plane, size and servos, I still prefer Ni-hm on 5 cells = 6 volts.

[Stuart Z]

Still using Nimh as it suits the voltage of the receivers I use.  Haven't got around to trying a UBEC between RX and Lipo.  Seems another thing I don't need inside the fuselage. 

[Erfolg]

It is an old DB Mascot, a trainer type model, about 56" span.

 

Being an electric flyer I normally undertake 6-10 minute flight, probably 4 off. Say 40 minutes in total. 

 

In the past I would fly 10-20 minute flight, say 3 off, which would be about one hour. I am not sure concentration or boredom would fail that long now.

 

I have started flying electric glider recently and find that by 20 minute flight I am totally board, often having cramp from holding the Tx.

[GaryW]

I had an ESC take a total dump and fail on me about 12 years ago causing a model to pile itself into the ground and oblitorating itself so ever since thenI always use a separate ( nimh ) 4.8v RX battery to power the Rx in all my electric models ( as shown in the photo below ,,,,, which is very easy to do,, simply by removing the red wire from the servo lead that goes from the ESC to the RX isolating the power the ESC wud normally send to the RX then connect the RX battery through a swithc in the same way you would with a glow/petrol powered model,, then the lipo only powers the motor

Edited February 15 by GaryW

[Erfolg]

Stuart, I just happen to have a few UBECs, God only knows why, just seem to have them.

[leccyflyer]

It depends on the model.  For my slope soarers, which can be viewed as similar to IC models as only the radio gear is being powered by the RX battery, I mostly used NiMh packs, as they can be left in the model, charged in the model when needed and provide a bit of weight where needed for ballast. For ease of operation, with the battery pack often buried in the fuselage, it's NiMhs all the way.  I'm tending to favour 5 cell 6.0v packs these days, rather than the previous packs of 4xAA NiMhs or Eneloops.  Just replaced a possibly quite old pack of 4xAA Nimhs with a 5 cell NImh pack with more capacity this morning in a PSS model that I'd been gifted.  IN a minority of soarers I am using a 2 cell Lipo pack, through either a voltage regulator or and old brushed ESC to provide a stable 5.0v power supply. In those models the Lipo RX pack is not stored in the model, is kept at storage voltage with my other lipos and is only inserted in the model when it is time to fly.

[GrumpyGnome]

NiMhs in most of my ic planes - old technology but works!  All 5 cell.

 

LiFe in a couple - just 'cos I had a couple and no spare NiMhs.  I don't find much advantage tbh.

 

Did use LiPos once, via a voltage regulator.  Totalled the aircraft as it failed....... I happily avoid another thing to go wrong now. 

[Dickw]

For models that have a BEC I mostly use that.

For models that don't have a BEC (or I don't use the BEC) I think everything I have now has 2s Lipo and HV servos.

 

Dick

[Nigel R]

4 cell Eneloopp nimh for all my IC airframes.

 

Quality cells, technically simple answer, right volts for my JR servos, pack weight is not an issue at .40 size glow and upward.

 

I use a simple trickle charger.

 

2 cell lipo would also work if you are kitting out with new servos that cope with the voltage.

[Frank Skilbeck]

Note all modern receivers are fine on 4/5 cell nimhs or 2s lipo/life batteries, but unless the servos are HV you can't use a 2s lipo to power the servos without an BEC to drop the voltage. Some older servos, e.g JR 517s are only suitable for 4 cell nimhs.

 

I typically use 4/5 cell nimhs or 2s life batteries in my IC models. Note we used to go flying all day on a 4 channel sports model with a 600  mah 4 cell NiCd.

[leccyflyer]

Is it safe to presume that the servos are okay with 5 cell 6.0v Nimhs too - don't they receive a regulated suitable power connection from the receiver?

[GrumpyGnome]

A word of caution, not all rx can handle the full 8.4v of a fully charged Lipo..... check first!

Edited February 15 by GrumpyGnome

[Engine Doctor]

28 minutes ago, leccyflyer said:

Is it safe to presume that the servos are okay with 5 cell 6.0v Nimhs too - don't they receive a regulated suitable power connection from the receiver?

 No the power to the servo is as per battery unless a regulator is fitted , usually fitted when a lipo pack is used. Most servos are fine on 5 cell Nihm check the servo spec . JR servos were well known for letting the magic smoke out if powered by a freshly charged 5  cell pack. 

Erflog. If using  NiMh battery try to get the pre charged cells as they dont self discharge like ordinary NiMh . Dont buy anything with capacity higher than 2,300mah . 2000mah is ample for a few flights The cells with higher capacity are not as robust and drop voltage more under load . If using digital servos then think about Sub C pack as digital servos can draw a higher current than AA cells can handle.

Edited February 15 by Engine Doctor

[Erfolg]

As part of the process of starting to ready, I found this piece of kit, hard to miss, on top of the tank hatch.

 

https://www.turbines-rc.com/en/testers-checkers/451-7-led-tower-pro-receiver-48-6v-battery-low-voltage-indicator.html

 

I have no instructions, I am assuming that the plug is plugged into a spare Rx socket. If non is available I guess it is OK to "Y" lead with the power supply.

[GrumpyGnome]

Yup. I used to use those but they caused me more angst as the displayed level changed than they were worth. In the end, I just started to jeep an eye on the battery voltage with a stand alone checker after the first few flights, maidens, remaidens, or servo changes.

 

 

YMMV of course.

[Jon H]

8 hours ago, Erfolg said:

I wonder if it is now the practice to used a Lipo or are Nimh now the preferred method?

 

I personally use Nimh as they are quick, cheap, and simple. I am also not a fan of burying lithium based batteries in foam and then whacking them on charge. A lipo with a regulator also has more points of failure within the system so is technically less reliable. 

 

I use 4.8v 1200-2200mah for my smaller stuff (up to about 70 inch sport/scale) and 6v 3000-3300mah for my big scale stuff. In your mascot i would expect a 1200mah battery to be good for at at least 20, and more likely 30 flights of the duration you mention. As Frank points out, we used to use 6 and 700mah nicads and not think anything of it. Modern 2.4ghz radio use less power than the old 35 meg stuff as well and i noticed this on a model i swapped from 35 to 2.4. 

 

As with many things, there is a perception that 'bigger number better'. Where a 40 2 stroke used to do fine we now use a 55. Where a 3kg torque servo used to do we now use a 9kg digital for some reason. 5% nitro was fine but we now use 10 or 15. Batteries are the same. If 700mah is good 3000mah is better, 6v is better than 4.8, so a lipo or life at 7.4v or whatever is better? 

 

I dont really subscribe to that sort of thinking myself and select the minimum spec equipment that will do the job and have a required margin so it is not pushed to its limits. Buying bigger number equipment often comes with a bigger number price, and this is not ideal. Clearly you can buy a bigger number piece of equipment at a low bangood price, but i have seen more than a few models bite the dust as their cheap and nasty gear let them down. 

 

In the case of the DB Mascot, i would use bog standard 3kg servos, a 4.8v1200 nimh battery and a 35 or 40 2 stroke. Even an old 35fp plain bearing engine would be more than enough. It would be most civilised and have more than enough performance for a little fun.  

[Paul De Tourtoulon]

The tower pro voltage tester is well worth the couple of £, I have one in my more expensive models, when the radio is

turned on, a quick bit of stick movements will tell you if your battery is on the way out, or if a servo is binding.

[Cuban8]

I know we've been round this so many times before but..............with a four cell nimh it only takes a single cell to develop a weakness leaving only a three cell pack, that if not spotted by regular testing (be honest who does?) will spoil your whole day at some point. I've found several that could have given trouble if I hadn't noticed. People run old RX packs for years and years and they happily power their model for their usual three of four Sunday morning flights - until say a really nice day and four flights turn into six or seven or the battery is forgotten to be recharged and......oops!

A five cell pack does give a significant degree of redundancy and will power a model quite happlly with a bad single cell.

Test 'em regularly folks - note the dicharge capacities and act if you discover a significant change. Dead easy to do. RX battery - one of the least expensive components in a model but super critical to safety.

Edited February 16 by Cuban8

[Stuart Z]

18 minutes ago, Cuban8 said:

I know we've been round this so many times before but..............with a four cell nimh it only takes a single cell to develop a weakness leaving only a three cell pack, that if not spotted by regular testing (be honest who does?) will spoil your whole day at some point. I've found several that could have given trouble if I hadn't noticed. People run old RX packs for years and years and they happily power their model for their usual three of four Sunday morning flights - until say a really nice day and four flights turn into six or seven or the battery is forgotten to be recharged and......oops!

A five cell pack does give a significant degree of redundancy and will power a model quite happlly with a bad single cell.

Test 'em regularly folks - note the dicharge capacities and act if you discover a significant change. Dead easy to do. RX battery - one of the least expensive components in a model but super critical to safety.

Echo that- new Nimh packs every year two at the most, and write a date on them so you know how old they are.  Same goes for TX pack.  Small price to pay.

[Jon H]

I think cell death in nimh and nicad packs is an overstated problem these days. In the old days of trickle charging and nicad memory etc it was much more of an issue that it is today with a peak charger monitoring what is going on. The memory issue is absolutely the root cause of the issue Cuban points out where just topping the thing up every week didnt do it any favours at all. 

 

My batteries are all due a cycle to check their health and i tend to do this every year (missed it last year as i hardly went flying at all), but just keeping an eye on things is well worth while. My Sea Fury battery was detected as faulty as it would discharge more than all its mates in other models when stored over winter giving me a red light on the battery checker when all of the others were still in the low end of the green. Still, this battery had on two occasions been run stone dead flat as the switch got bumped and the model ran flat, before remaining so for weeks at a time. This likely killed the cells so that battery has a knot tied in its lead to mark it as non airworthy and i use it for things like bench work and/or driving electric retracts. 

 

I have never had a battery fail in flight and i am still using some packs which are more than a decade old. I delta peak them in the morning before i head out to the field and make a mental note of the time taken to recharge. In regular use i know that i have time to put it on, have breakfast or whatever and then it should be ready in X amount of time. if not, or it peaked early, there might be an issue that needs investigation. 

 

Dating batteries is a good idea, and i put that sort of thing under generally paying attention to your gear and just being attentive. It still surprises me that people have absolutely no idea what their gear is, when they last did maintenance (if they ever do any), what fuel they have, what prop etc. Just knowing your gear inside and out is more than half the battle.

 

Oh and i do not consider fixing something broken as doing maintenance. Maintenance is preventative work to stop something before it happens. Fixing a broken thing after its failed is a repair. 

[Cuban8]

I'm not talking about 'memory effect' per se - my concern is that single cells in nimh packs do deteriorate and lose their  capacity before the others and need to be detected before they cause an excessive voltage drop across the whole pack in use, with all the ramifications that might lead to. 

Quite rare for a single  cell to deteriorate very badly, it's true, but it does happen and I've seen it in a few occasions in my own batteries over the years. Easily picked up by regular voltage and capacity checks.

[GaryW]

Ive been using 4.8v Nimh Rx pack for as far back as the 90's and never once had a cell go down or any situation that would cause a " brownout " even in helicopters... Only time I wud go upto a 6v ( 5 cell ) pack is if a model is fitted with high power/torque or digital servos whether its an I/C glow or petrol model or an electric model which I have had it myself with an electric model where the ESC took a total dump and fail causing the model to pile itself into the ground which I've also seen others over the years have the same thing happen....

 

I must admit my current helicopter being a shuttle plus is fitted with a 2S lipo as it is also fitted with an Align 2 in 1 Regulator feeding 5v to the rx & 1.5v to the glow plug and is fitted with JR digital servos and the TT Raptor 30 im about to take delivery of will have a 6v rx pack simple as its also fitted with JR high torque digital servos... Other than that all my current models all have 4.8v rx pack 3 are electric with separate rx packs .. 6 are glow engine powered and 1 is diesel engine powered

 

All my rx packs are 2000 & 2300 mah which i know will easily give me 6 to 8 ,, 8-10 minute flights any given flying day without the need to worry that they may suddenly go flat on me..... as a regular routine battery maintenance every couple of months i will give all of them a complete charge/discharge cycle specially during the winter months when certain models dont flying over the winter months and dont get used for a few months.. and I never fast charge an RX pack although I do have 2 chargers for lipo/lilo/pb/nicad/nimh  I only charge my rx packs with  mains powered Futaba TX/Rx chargers for the full 12-14 hrs which i have 4 of these chargers

 

 

 

 

 

Edited February 17 by GaryW

[GaryW]

I have also had many people over the years including people behind counters in model shops tell me with 2.4ghz radios i shud using nothing less than 6v ( 5 cell ) rx packs as 4.8v rx packs are not sufficient enough for current/modern 2.4ghz rx's and will most deffo fail ie: voltage drop ( brownout ) ........ I say what a total load of BS unless you are  using high power/torque or digital servos  .... Only reason they say that in model shops is they want you to spend money you don't need to spend on items and batteries you dont want let alone need

[Jon H]

9 hours ago, GaryW said:

I have also had many people over the years including people behind counters in model shops tell me with 2.4ghz radios i shud using nothing less than 6v ( 5 cell ) rx packs as 4.8v rx packs are not sufficient enough for current/modern 2.4ghz rx's and will most deffo fail ie: voltage drop ( brownout ) ........ I say what a total load of BS unless you are  using high power/torque or digital servos  .... Only reason they say that in model shops is they want you to spend money you don't need to spend on items and batteries you dont want let alone need

 

In fairness, spektrum rx's are (or at least were) vulnerable on 4.8v packs even using standard servos. I worked at a model shop and the advice we gave about using 6v packs came from Horizon themselves. While it is not unheard of for model shops to flog you something more expensive than you need we were under instruction to do it in this case. There clearly was an issue as they sold that plug in capacitor thing to help guard against voltage drops. 

 

Admittedly this was all 10-15 years ago and a great many things have changed since then so it may not be true today. My only spektrum rx's have operated off of bec's in electric models so i have no first hand experience with them on a battery. All of my futaba 2.4 rx's have been fine on 4.8v so i have no worry there. A club mate had some hitec 2.4 rx's that flat out refused to work on 4.8v for some reason, but i have a sample size of only 3 so that is hardly conclusive.