Rx battery

[James Humphreys 1]

OK silly question alert? 

Does the rx battery affect range in any way ??

[Shaun Walsh]

6 minutes ago, James Humphreys 1 said:

OK silly question alert? 

Does the rx battery affect range in any way ??

Only if it's flat?

[Allan Bennett]

.... and if you put it in a location that affects the efficiency of the antennae.  With a 2.4GHz system, the antennae should be clear of any metal, cables, battery, etc., and at 90 degrees to each other.

[Denis Watkins]

A motor, a battery, servos

Are very effective in putting the RX antenna in a shadow, screening the signal from being complete.

However, 2.4gig is designed and effective able to re-aquire connection.

[Frank Skilbeck]

If the question is does the Rx voltage affect range? then the answer is no, as long as it is above the minimum operating voltage of the receiver, drop below that and it just stops working.

 

What will be affected as voltage drops are the servos as the voltage decreases the power and speed drop off, exceed the maximum rated voltage of a servo and it may burn out.

[James Humphreys 1]

OK I'll add some more info flyin ic engine 5 servo's including throttle. I'm trying to to work out what caused it to crash I went from down wind into wind into a landing approach so I either stalled it or the battery was the cause,

I was using a 5 cell ni-mh rx pack 6v

After crashing with no control the battery was at 4.5v or bellow. As I'm still abit nervous with ic I opted for a very long approach.

[gangster]

Ah you have added a useful bit of info. a 6 volt battery at 4.5 volts is bad news. It either indicates a duff cell of a flat battery. Since you have got a voltmeter you can prove pre

tty conclusively. Reconnect all the servos , put the voltmeter on and waggle the sticks , does it drop further? Also you need to determine that any fro is due to a dud battery or switch harness or leads. Black lead corrosion is a strange one. As far as battery voltage affecting range is concerned, no the receivers have regulators in and run a bit over 3 volts. 

[Denis Watkins]

You are Going to get further advice James, so read them all, as there are many reasons for your post.

 

Back to antenna in a shadow

The largest antenna shadow is on landing.

You are low, and transmitter pointing at the receiver

Your big aluminium I/C motor and nimh are usually in front of your RX, maybe momentarily loss of link.

 

You can mount the RX higher or lower

 

As above, you can swop your nimh for a new one

And check that you have 6 volt servos

Edited August 30, 2021 by Denis Watkins
Mis-spelling

[James Humphreys 1]

I did a range test later when I got home battery started at 4.5v with just waggling the elevator probably ten times as I walked to the end of my road the voltage had dropped to 4.2v I think it was 

[Martin Harris - Moderator]

A 5 cell NiMH battery would be considered fully discharged at 4.5V so this is the likely cause of your crash - your servos will pull the voltage lower than the resting voltage especially when under flight loads. Even if the receiver is still functioning, the servos themselves may become erratic. 
 

The first question is how the battery got to this condition. Was it fully charged before the session, how long did you fly for, what is its capacity, age and type?

[Dale Bradly]

Expand on this:

"I went from down wind into wind into a landing approach so I either stalled it..."

 

I could easily imagine going quite slow downwind, (so very slow airspeed trying to stop it getting away) then the turn was enough to stall it completely.

 

 

[Martin Harris - Moderator]

While a flying error is always a possibility, the fact that the battery voltage was so low needs to be explained and resolved. 
 

James, please supply the info requested in my previous post as there may be a simple explanation - several possibilities come to mind which I have encountered over the years…and not always from inexperienced pilots either!

[gangster]

Just to be certain I assume the 4.5 was measured at the battery. If so you need to heed Martin’s advice and work out why it’s low. Duff?  Forgot to charge? Long day?  Also remember there is no such thing as a smart charger they can peak detect when there isn’t a peak

[John Muir]

In what manner did it crash? If it dropped a wing and went in or even just fell out of the sky on your final turn on the downwind leg, then I'm afraid, as so many before you have done (including me), you stalled it.

4.2-4.5V is still plenty to run both your receiver and servos and if your radio has been performing perfectly well up until the incident then it's unlikely (though not impossible) to be a radio problem. You would know if your receiver had shut down because the plane would carry on doing what it was doing for at least a moment or two and, depending on your radio, you'd have had a 'telemetry lost' message.

And, by the way, your battery was very low.

[James Humphreys 1]

OK so a update 

Tested the battery on the bench while putting a right aileron turn in with slight up  elevator to simulate the turn the battery dips to bellow 3v ( below the recommended min volts) so with the possibility of a stall in the turn also put into the equation and the frantic inputs put in by me would of kept the volts below 3v 

 

As for the reason the battery was low I'm afraid pilot error is the cause on that point not doing pre flight checks properly ?‍♂️

[John Muir]

Oh dear. 3V is very, very low and in 'nothing works' territory. At least now you know.

[Graeme White]

I killed a 4.8v nimh recently by leaving it switched onto the receiver. My charger still charges it but because it is now knackered it thinks it is fully charged after a few minutes, peak detects a good voltage and if my charger didn't record the current added I would be a plane down. Voltage after "charging" shows a good 5v but the moment any load is added I drops down 4v instantly which is obviously too low for anything to work. Even leaving on trickle for a day so I know it has had a lot of current added the voltage still drops instantly on load. I guess batteries can just die but sometimes appear good.

[Mike Chantler]

Have you tried trickle charging it with an old fashioned (dumb) charger?

[Martin Harris - Moderator]

How did you charge your battery?  Disaster was only narrowly avoided when a pupil’s battery was found to be almost flat after one flight…he had confirmed that it had been fully charged before coming to the club. Further questioning revealed that he had put it on the standard wall charger for “the full hour”…?

[gangster]

The moral of the story is that it is pointless measuring the open circuit voltage of a battery. A battery must always be measured on load

[gangster]

The other thing this shows is that it is certainly not a silly question, no such thing. If this post prevents just one flyer from having a nasty it will be worth it.  Hope you can repair the model

[Peter Beeney]

Hi James,
 
As with a number of other forumites that have posted here I would agree that your battery state was 99.5% responsible for your crash. An open circuit voltage reading of 4.5 volts for a 5 cell nickel pack says that is well and truly exhausted and under load could not sustain even a light current flow for probably more than just a few seconds.

 

I would give the pack a standard charge, that's 14 - 16 hours at 0.1C  and then a discharge test at say 0.25C, nothing too drastic to start with, and if I found I had lost less than about 8% of the capacity I’d just carry on as normal; 8 to 12% needs a little think about and anything beyond about 15% I’d definitely be doing a bit more digging before anymore air time.

 

One small item I’ve not flown without consulting on a regular basis is a LED Receiver Voltage Monitor. This is just a little voltmeter with a scale of probably about one volt and in my experience they are ultra reliable and accurate with it. I’m not really interested in the top end, when I’m in the green carry on up the cavortings as they say, it’s only if I see amber or red would get a bit concerned. I’ve extensively bench tested these in the past, both the nickel and lithium types and I personally think they are impeccable. When I’ve ganged say four together and run up and down the scale with a variable voltage bench supply particularly at the lower end where it really matters they are always perfectly in harmony, most likely to the millivolt… Also it’s worth noting that even if the last red has been lit for a while and the pack voltage has dropped even lower there are still enough watts left in the remaining capacity ‘safety net’ not only to enable a safe landing but a few touch and goes in between as well!

 

Not that expensive either, £2:35 from Hobbyking or £1:81 courtesy of ebay.

 

They can be useful in other ways, too, if the leds run up and down when you waggle the sticks on the ground there is certainly a good chance there could be a problem coming down the track sometime. This is an indication there is possibly a high resistance point in the rx supply circuit somewhere causing a momentary volts drop when the servo motors start up, from wire corrosion to a dodgy connection in a plug and socket, or even the pack itself starting to fail, and is definitely worth sorting before it becomes a rather more obvious ‘black bin bag required, please’ open circuit.

 

Just my take on it all, certainly not intended to be any sort of instructions, but when you watch a large model totally destroy itself at full speed a couple of minutes after take off due to a flat battery very close to where someone is standing in a spot where they have every right to be it does become quite thought provoking…to say the very least…

 

Good luck.

 

PB

[Martin Harris - Moderator]

Or the flying friend who charged a 5 cell pack and checked it with a dedicated tester before handing me the model to test fly. 
 

After three circuits, I lost all control and the newly built model re-kitted itself terminally. During the post-mortem I discovered that the receiver battery was completely discharged - and that both his charger and checker were set to 4 cells…

[Alan H]

15 hours ago, Martin Harris - Moderator said:

Or the flying friend who charged a 5 cell pack and checked it with a dedicated tester before handing me the model to test fly. 
 

After three circuits, I lost all control and the newly built model re-kitted itself terminally. During the post-mortem I discovered that the receiver battery was completely discharged - and that both his charger and checker were set to 4 cells…

What was the charger in this case? all the intelligent chargers I have seen that can handle NiCad and NiMh are of the peak detect type and do not require the number of cells to be set.

[Martin Harris - Moderator]

Unfortunately his was not one of these - a case of the charger being a bit too complex for the owner. I can find out if you’re really interested. 
 

My ISDT chargers require the cell count - I haven’t tested them but I assume they have an over voltage protection built in to guard against a missed delta peak detection.