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Spektrum DX6 Tx battery alarm

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brokenenglish13/02/2018 19:34:41
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307 forum posts
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Gentlemen, I have an "idiot" question (sorry!).

I've been flying with a DX6i for the last few years, powered by 4 eneloop cells that are always charged before every session. I've never had the slightest problem, so I intend to continue like that.

However, I've just "upgraded" to a DX6, so I now have a Tx low voltage alarm. The instructions are very clear on setting the type of battery used, but no actual voltage level is given...

So, my obvious question is: when operating a DX6 on 4 eneloops, what would be a reasonable and, above all SAFE, voltage value at which the low voltage alarm should be activated?

I have to say that I'm surprised that I haven't found an answer either in the Spektrum instructions or in any of our threads, which leads me to suspect that I may be particularly stupid and missing something obvious ...

Denis Watkins13/02/2018 20:31:15
2716 forum posts
137 photos

This has been discussed recently, for the RX and for telemetry alarm too, and the consensus is 1.1v per cell

Which could have the alarm going off very frequently. I leave mine at 4v, but is never gone to alert as I charge frequently

**LINK**

Edited By Denis Watkins on 13/02/2018 20:35:33

brokenenglish13/02/2018 20:44:59
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307 forum posts
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Thanks Denis (again). I think I found that link, but it seems to mainly discuss Rx cells.

I was thinking not in terms of cell voltage, but in terms of the minimum safe voltage needed by the transmitter to operate properly.

Frank Skilbeck13/02/2018 20:55:56
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3991 forum posts
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Broken, your Dx6i has a low voltage alarm at 4.3v, I don't know what it is on the newer Dx6, but 4.3v is pretty low and means land immediately. I never ran my Dx6i that low, but recharged when the on screen voltage hit 4.8v. The setting options on the newer Tx which does different battery types are to cater for that.

As regards the minimum voltage for the tx to work, the main chip will run at 3.3v, my Multiplex Profi which uses the same chip runs on a 1s LiFe cell and the fully charged voltage on that is 4.2v!

John Robertson 313/02/2018 21:15:10
119 forum posts
1 photos

It seems that "Eneloop" is basically a trade name for, essentially, a brand of NiMh cells, so I'd be inclined to set the alarm to the NiMh level.

See https://en.wikipedia.org/wiki/Eneloop​.

What should THAT level be?

A charged (but not recently) AA cell shows around 1.364v.

See https://www.youtube.com/watch?time_continue=110&v=z9Uz9oNcT-8

I would think an alarm setting of 1.15vor even 1.2v per cell would be appropriate from looking at

https://web.archive.org/web/20141129145504/http://www.panasonic-eneloop.eu/home/whats-eneloop.html

1.1v looks like the critical figure for the "cliff edge",

As usual, it is probably worth NOT screwing the maximum capacity out of either Tx or Rx power packs. The loss of a plane surely outweighs the economic benefits of doing so! Setting the limit higher is certainly safer than going too low. If the higher value gives too little flying time then it can be reviewed.

brokenenglish13/02/2018 21:22:40
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307 forum posts
22 photos
Posted by Frank Skilbeck on 13/02/2018 20:55:56:

Broken, your Dx6i has a low voltage alarm at 4.3v, I don't know what it is on the newer Dx6, but 4.3v is pretty low and means land immediately. I never ran my Dx6i that low, but recharged when the on screen voltage hit 4.8v. The setting options on the newer Tx which does different battery types are to cater for that.

Thanks Frank. You've hit on what sparked my question.

I thought that if I set "battery type" to NiMH, then the Tx software would automatically set a low voltage value.
However, I think this isn't so. I think you still have to set an actual voltage value... Hence my question.

As you suggest, 4.8V sounds reasonable and safe, but I have zero knowledge and I'd appreciate knowledgeable confirmation!

Frank Skilbeck13/02/2018 22:17:04
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3991 forum posts
96 photos

On my other Multiplex set which uses a 6 cell Nimh pack the alarm is set at 7.2v, or 1.2v per cell, i.e. 4.8v for a 4 cell pack, so I would go with 4.8v. BTW I never used to charge my Dx6i after every flying session but only when the indicated volts dropped below 5 volts and I would stop flying if it got to 4.8v.

trebor14/02/2018 07:39:39
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1549 forum posts
191 photos

I thought the tx was supposed to set off an alarm and flash when alkaline battery got to 4.3v, lipo / lion battery 6.4v. Have you run it down to test it ?

Denis Watkins14/02/2018 07:50:05
2716 forum posts
137 photos
Posted by trebor on 14/02/2018 07:39:39:

I thought the tx was supposed to set off an alarm and flash when alkaline battery got to 4.3v, lipo / lion battery 6.4v. Have you run it down to test it ?

Spot on Trebor,

Non of us operates at low TX battery level, and we usually fly near or at full charge, but I still had full control,

On the ground (he he), at a display voltage of 3.3v

It would be complete madness to operate anywhere near this voltage, and non one would, this is just a test

Masher14/02/2018 08:10:40
1073 forum posts
160 photos

Here is a plot I took of a 4 cell, 2AHr NiMH Eneloop battery under load of about 1A (deliberately heavy to stress the cells). This is just a typical​ plot, they will vary between manufacturers, age etc etc. Note the 'Voltage no load' values which show how useless battery checkers are if the battery is not under load

batt discharge.jpg

 

Edited By Masher on 14/02/2018 08:12:05

brokenenglish14/02/2018 09:26:20
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307 forum posts
22 photos

Thanks for all your opinions and advice.

On my old DX6i, as mentioned, I always charge before every session, and I don't ever recall seeing a displayed voltage of less than 5V. So I'll go along with the consensus and set an alarm value of 4.8V.

Thanks again!

Frank Skilbeck14/02/2018 09:37:41
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3991 forum posts
96 photos
Posted by Masher on 14/02/2018 08:10:40:

Here is a plot I took of a 4 cell, 2AHr NiMH Eneloop battery under load of about 1A (deliberately heavy to stress the cells). This is just a typical​ plot, they will vary between manufacturers, age etc etc. Note the 'Voltage no load' values which show how useless battery checkers are if the battery is not under load

batt discharge.jpg

Edited By Masher on 14/02/2018 08:12:05

Masher, bear in mind that a TX will draw less the 0,2A in operation, so the above curve is misleading, but it dos show why a 4 cell high capacity AA pack isn't a good choice for a larger model with more powerful servos.

Masher14/02/2018 10:01:17
1073 forum posts
160 photos

Agreed Frank. The test was actually done to show performance in a high current drain model scenario - sparked off by the inexperience of a chap who lost 2 models in a short period. He was adamant that he had charged his batteries and checked (with a no-load battery checker) that all was good at 4.8V...................................... trouble is he was on a 5 cell pack! He may​ now understand that 4.8V is wrong even for a 4 cell battery when fully charged

TJ Alexander15/02/2018 10:20:52
95 forum posts

Ah. I had assumed that it set the low voltage level automatically. As I have the battery pack fitted (why didn't they make one the battery cover could fix over?), I need to check what the range of acceptable voltage is.

Thanks for the prompt.

phil alvirez09/06/2018 12:58:57
46 forum posts

facts

the DX6i has the transmitter battery alarm at 4.3 for nicads. nevertheless, i keep an eye on the charge so try to avoid hitting this figure. usually, when i hit 4.8 i replace it with a fresh charged pack. as i fly electric sailplanes, sometimes i stay up there in a thermal for a long time, but have never hit 4.3v, even on a long day, as i check the battery charge before every flight.

now that i got a DX6G3 radio with telemetry, i learned that the alarm for nicads is set at 4.3 too, and, from bench tests , i have learned that from the moment the alarm goes off, to the moment the radio stops working there are 9 minutes.

for flights when the plane is no higher than 200 meters it gives me enough margin for bringing it down at a reasonable rate. still, when sometimes it happens to be that my plane is high up there at 400 meters, as when a very strong thermal drags me strong, it may take longer to bring it down without the wings colapsing, so i have the alarm set at 4.6v.

problem with the radio is that it discharges way faster than what the experts say at the forums. on the other hand, the figures i provide are from tests, and not from theory. what i have learned (again, from tests) is that the radio battery reaches the alarm level after only 45 minutes of use, so this has to be timed to avoid this situation, and/or carry another fully charged pack too.

and i have problems programming this radio, as the "manual" does not provide the necessary details.

but that, my dear sahib, is another story...to be pursued at another forum.

if someone reads this, and could provide help on dealing with the manual's shortness of instructions, will be highly appreciated. just reach me. thanks.

Edited By phil alvirez on 09/06/2018 13:15:38

brokenenglish09/06/2018 14:48:03
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307 forum posts
22 photos

I'm very surprised by your "short duration" Tx batteries.

In Europe, not many people are using Nicads. Regulations force us to use NiMH, although I'm still using Nicad Rx packs.

Anyway, a typical flying session for me is around 2 hours. I start with four fully charged eneloops in the DX6 Tx, showing an initial voltage of around 5.4 or 5.5V. After a couple of hours flying, the reading has dropped to around 5.1V, but I don't ever recall seeing a battery reading of less than 5V.

Edited By brokenenglish on 09/06/2018 14:49:14

phil alvirez09/06/2018 16:17:12
46 forum posts
Posted by phil alvirez on 09/06/2018 12:58:57:

here i come again:

(it is nimh eneloops)

facts

the DX6i has the transmitter battery alarm at 4.3 for nimh (eneloops). nevertheless, i keep an eye on the charge so try to avoid hitting this figure. usually, when i hit 4.8 i replace it with a fresh charged pack. as i fly electric sailplanes, sometimes i stay up there in a thermal for a long time, but have never hit 4.3v, even on a long day, as i check the battery charge before every flight.

now that i got a DX6G3 radio with telemetry, i learned that the alarm for nicads is set at 4.3 too, and, from bench tests , i have learned that from the moment the alarm goes off, to the moment the radio stops working there are 9 minutes.

for flights when the plane is no higher than 200 meters it gives me enough margin for bringing it down at a reasonable rate. still, when sometimes it happens to be that my plane is high up there at 400 meters, as when a very strong thermal drags me strong, it may take longer to bring it down without the wings colapsing, so i have the alarm set at 4.6v.

problem with the radio is that it discharges way faster than what the experts say at the forums. on the other hand, the figures i provide are from tests, and not from theory. what i have learned (again, from tests) is that the radio battery reaches the alarm level after only 45 minutes of use, so this has to be timed to avoid this situation, and/or carry another fully charged pack too.

and i have problems programming this radio, as the "manual" does not provide the necessary details.

but that, my dear sahib, is another story...to be pursued at another forum.

if someone reads this, and could provide help on dealing with the manual's shortness of instructions, will be highly appreciated. just reach me. thanks.

Edited By phil alvirez on 09/06/2018 13:15:38

 

Edited By phil alvirez on 09/06/2018 16:22:17

Edited By phil alvirez on 09/06/2018 16:23:40

phil alvirez09/06/2018 16:19:45
46 forum posts

sorry. it is nimh eneloop cells. posted it again, as i dont know how to edit the original post. so the alarm goes off after 45 minutes anyway.

Edited By phil alvirez on 09/06/2018 16:22:45

Frank Skilbeck09/06/2018 22:19:05
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3991 forum posts
96 photos

Phil, the Tx should run for way longer than 45 mins on a full charge, the typical operating current is around 200 ma, so a 2,000 mah set of enelopes should run for 10 hours or so not 45 mins. This suggests that he batteries are not being correctly charged, a faulty battery or the Tx is faulty, but for it to go flat in 45 mins it would be consuming over 2 amps and you'd notice it getting warm.

How are you charging the batteries, by the internal charger, what is the pack voltage straight off charge.

gangster09/06/2018 23:16:13
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765 forum posts
7 photos

Frank You might be a bit ambitious expecting a 2000 mah battery to deliver 200ma for 20 hrs but I agree 45 mins might be a bit short and would expect at least 5hrs

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