Horus RTC battery

[Geoff S]

Just had a warning on switching on my Horus X10 that the RTC battery is low. I checked through the system hardware option and it's ).46v. I'm guessing it should be around 1.2v so it is certainly reading low.

I've never taken the case off the Horus but I don't suppose it's all that much of a problem. Has anyone replaced the battery (or even needed to)? I don't suppose it prejudices the tranmitter as a model controller but warning as you switch on are always a little unsettling.

Geoff

[flight1]

The rct battery is a CR1220 coin battery 3v on the x12s whch i have replaced on mine . Its on the mainboad under the battery holder ,easy job Not seen a battery listed for the x10 i would contact t9 and ask

Edited By flight1 on 13/06/2020 23:36:28

[Dickw]

Posted by Geoff S on 13/06/2020 21:07:11:

Just had a warning on switching on my Horus X10 that the RTC battery is low. I checked through the system hardware option and it's ).46v. I'm guessing it should be around 1.2v so it is certainly reading low.

I've never taken the case off the Horus but I don't suppose it's all that much of a problem. Has anyone replaced the battery (or even needed to)? I don't suppose it prejudices the tranmitter as a model controller but warning as you switch on are always a little unsettling.

Geoff

A guy on RC Groups has just done it in an X10s. His comments are here.

Dick

[Geoff S]

T9 don't list a battery but I'm sure it's the same as the X10 which Dick's post points to. I found a video on YouTube where someone replaces the RTC batt on a X12S - different but similar and the same battery, I'm sure (CR1220).

Ny Horus is just over 2 years old so it's not lasted alll that well. I'll replace it with a quality item - I don't want to be doing it too often.

Thanks, both.

Geoff

[Frank Skilbeck]

Quick question, why does the set have a RTC battery? the only set I have that has one is a 1990s Multiplex 3030, isn't a RTC battery a bit of a throwback? Or am I missing something?

[Tim Ballinger]

Similar question from me. What does it power ? I did not even know I had one. I can not remember it being mentioned in the manual.

Tim

[Gary Manuel]

RTC = real time clock. It's to keep the date and time even if the transmitter battery goes flat or removed.

[Peter Christy]

It will be doing the same job as the one in your computer - maintaining the cmos RAM that stores things like the clock & date settings. Remember, any "computer" transmitter needs memory, and more sophisticated ones need to be able to keep the time when the main power is switched off.

Some JR transmitters need them too, notably the 388 (and similar). Also the PCM-10, if memory serves me correctly.

If your computer loses its time settings and any changes you have made in the BIOS, its because the cmos battery is flat. Some computers won't boot when this happens. I have no idea what happens to a FrSky transmitter in this case. My X10 is too new to need one yet, and my Taranis is still going strong after 7 years!

Cmos batteries typically last around 5 years in a computer, I'm not sure why they should fail so soon in a transmitter. I've recently changed one in a JR 388 that was donkey's years old!

Usually, once the Tx is turned on, the cmos battery is redundant. It only takes over when the Tx is powered down. Of course, the Horus family use a software switch to turn them on, and the power for that has to come from somewhere, so maybe if the cmos battery fails, you won't be able to turn it on!

Usually, the cmos battery will be backed up by a capacitor, which will keep things running while you change the battery, but not much longer. My advice would be to change the battery as soon as you get the warning!

--

Pete

 

Edited By Peter Christy on 14/06/2020 09:27:49

[Geoff S]

I've replaced batteries in my (desktop) PC a couple of times but they're easily accessible on the motherboard once the case is opened (I prefer desktop PCs because I can easily update/repair them and I like a proper keyboard and a big vdu!) but, from the video of a X12 battery replacement it seems the Horus batteries are more difficult.

I've never needed to replace one in either of my Taranis transmitters and the oldest is a very early one but the one in the Horus is only just over 2 years old. Don't know how old Peter Christy's Horus is but he may find the battery is nearer the end of its life than he realises. Perhaps worth checking its voltage. Perhaps the original battery is of poor quality and also could have been on the board long before I took delivery of my Horus.

On the positive side, there doesn't seem to be any other effects apart from the loss of the time, as you'd expect. the RTC battery is down to <0.5v, which is very low for a nominally 3v battery. I'll order a new CR1220 and wait before I start pulling the case apart.

Geoff

[Bob Cotsford]

The X10S case back comes off much easier than the X12, only 4 screws and the back lifts away (remove the SD card first!). I did it to adjust the stick tension. Apparently the RTC battery is under the motherboard and can just be reached by lifting the board without unplugging the aerials. Oddly the X9D and X12 were both a pain to get the backs off but easy to reach the RTC holder once that was done.

[Mike Blandford]

The RTC battery only supplies the real time clock, nothing else.

The spec. for the RTC battery supply is 1.65V to 3.6V, so the battery is OK down to around 1.7V, but will drop from there very quickly.

The capacity of a typical CR1220 is 37mAH. The typical current consumption of the RTC (at 25 C) is 0.75uA, so it should last for 5.5 years.

On the Horus, it could also be used to supply 4K of RAM, which about doubles the current it has to supply. At present, neither erskyTx not openTx do this, I don't know about FrOS.

As the circuit that is used to measure the battery voltage adds an extra load on the battery, the battery voltage is only measured at power on, then the measuring circuit is disabled.

Mike

[Bob Cotsford]

One side effect of a flat RTC battery that you may want to avoid is that you lose the timestamps of any logs that you may have recording. I have a great many stamped 01-01-2000!

[Geoff S]

Posted by Mike Blandford on 14/06/2020 11:42:54:

The RTC battery only supplies the real time clock, nothing else.

The spec. for the RTC battery supply is 1.65V to 3.6V, so the battery is OK down to around 1.7V, but will drop from there very quickly.

The capacity of a typical CR1220 is 37mAH. The typical current consumption of the RTC (at 25 C) is 0.75uA, so it should last for 5.5 years.

On the Horus, it could also be used to supply 4K of RAM, which about doubles the current it has to supply. At present, neither erskyTx not openTx do this, I don't know about FrOS.

As the circuit that is used to measure the battery voltage adds an extra load on the battery, the battery voltage is only measured at power on, then the measuring circuit is disabled.

Mike

Thanks for that, Mike. From you last paragraph, can I assume the very low reading of 0.5v I get when I access it via the system hardware option isn't very useful as the measuring circuit is disabled?

Geoff

[Mike Blandford]

The value should be fine. It is read (and stored I believe) at power on, so just after it comes off load.

Even if it was measured later, it would be the voltage off load, so not very useful.

Mike

[Geoff S]

My new batteries arrived this morning (I ordered a spare). I chose Panasonic CR1220 as known reliable product - at least I hope so.

It was a bit traumatic but ultimately successful and I thought it might help others with X10 Horus (and presumably X10s) if I described the process with a few photos.

The back comes off easily with just 4 screws. There are several sizes of screws to remove so be careful to keep them separate. Here's what it looks like with the back off. Unlike the Taranis, the back is a completely separate part and can easily be put on one side out of the way.

 

 

Remove the main battery and the SD card as I think it will catch on the case when the board is removed. Then take out the 4 screws holding the battery holder - keep them separate from the case screws. The holder also carries a PC board with connectors but you can just fold it back clear of the main board.

There is enough length in the black wire that (I think) is an internal antenna feed to keep it clear without disconnecting it. There are 6 screws that appear to be holding the main board down and I removed them all but I think it may only be necessary to remove the 4 near to the outer edges. The 2 in the middle of the board hold a plastic structure associated with the screen mounting/connection and could probably be left in place.

The reason I couldn't lift the board clear is the return/select knob on the rhs at the front which needs to be pulled off. I managed to get a finger nail under it to prise it gently away (it reminded me of my time as a teen repairing radios in the Murphy Radio service dept when getting plastic knobs off could be a challenge. At least then I had access to a store full of spares if I broke anything - not the case here!).

Once the main board is lifted you can see the rtc battery in its holder. Why it isn't on the top of the board only Frsky knows but there seems to be room and it would make the job a lot less hassle.

I found releasing the dead battery from the holder tricky but, using a small flat blade screwdriver I levered it out. There may well be a proper way but I've never seen a battery holder quite like this one and access is limited. I eventually succeeded in pushing the new battery in place and reassembled everything.

It all worked initially, except the 3 knob controls at the top, which I hadn't touched so I took the case off again to look for dislodged connectors. I tried again and nothing worked! It wouldn't even switch on. That was a bit worrying but further investigation revealed that the ribbon cable connector to the main board had becom detached. I hadn't noticed because the way the cable fits into the connector is unfamiliar to me (I have been retired for 30 years so it's hardly surprising).

If you look at the 3rd photo you'll see a ribbon cable with a blue end at the top of the main board. Tha's the one that became detached in the operation. A catch on the board connector holds it in place - just make sure it's firmly home before full ressembly. Despite the fact that everything seemed to be working OK (I even reset the clock) except the knobs, it could have disconnected at any time with potentially bad results if you were flying.

Hope this helps.

Geoff

Edited By Geoff S on 17/06/2020 16:02:42

[Peter Christy]

Thanks for that, Geoff! It looks a bit fiddly, so an "idiot's guide" is very useful!

I do wonder why manufacturers make consumable items so hard to change! I recently did a JR-388 which doesn't even use a battery holder - it uses a battery with tags welded to it, which is almost impossible to find! I ended up soldering some thick-ish solid copper wire straight to the battery. Worked like a charm, but again, dead fiddly to fit!

And don't even ask about the CNC milling machine where we had to dismantle most of the control unit to get at the board with the RTC battery on it.....!

--

Pete

[PatMc]

Posted by Geoff S on 17/06/2020 15:56:26:

My new batteries arrived this morning (I ordered a spare). I chose Panasonic CR1220 as known reliable product - at least I hope so.

Hi Geoff, snap !
But I had ordered 4, also Panasonic CR1220.
My Taranis & Horus X12S both needed their RTC batteries renewing (+ 2 spares). The cost of the 4, including postage, was 25p more than a single Energiser CR1220 would have been from Halfords!

The Taranis is one of the first batch into UK. I changed the battery about 2 years ago so the original lasted a reasonable time but the replacement was dubious quality one that happened to hand.
The Horus is only about 2 or three years old so no a good life span for the battery.

Changing the Taranis battery was simple & I followed John Salt's Youtube demo for the Horus without any problems.

I notice in both the Taranis & Horus radio setup menu the GPS sub section has a tick box option "Adjust RTC".
Do you know what this option does ?
(I've been playing about with the option with mixed results.)

Also in the opening post you mentioned that you checked the RTC battery through the "system hardware option". I can't find this option in either the Taranis or Horus X12, can you give me any pointers please ?

Pat.

[Geoff S]

In the X10: Press 'Sys', then page through to 'Hardware'. It has 'Calibration' at the top but scroll down and you get 'Battery Calibration' followed by RTC Batt and it shows the voltage (mine's 3.04v now but was about 0.5v with theold one).

I'm sure the option must be there for the X12 as well. Never checked either of my Taranisae . The oldest was bought from Giant Shark IIRC and is so old it won't bind to S6R receivers because the RF board is an early version.

My X10 is just over 2 years old so I'm surprised the battery failed so quickly. It really is a faff to replace; I just hope it isn't needed every 2 years and that the Panasonic last longer than the original. The annoying thing is that the main board looks empty on the top where the battery is tucked away out of sight underneath and it would be a trivial job to swap if it was there.

I would think having it replaced professionally would be quite expensive what with postage etc.

Geoff

[Peter Christy]

GPS signals contain a very high accuracy time signal, so maybe the "Adjust RTC" option allows it to update automatically from a known source. The standard clocks do drift a bit.

A PC can also do this using a timing signal from the internet, so this would make sense. However, I don't have a GPS unit so I can't confirm.

Your mixed results maybe to poor GPS reception indoors? You probably need a good signal for it to work properly.

--

Pete

[PatMc]

Posted by Geoff S on 17/06/2020 22:34:23:

In the X10: Press 'Sys', then page through to 'Hardware'. It has 'Calibration' at the top but scroll down and you get 'Battery Calibration' followed by RTC Batt and it shows the voltage (mine's 3.04v now but was about 0.5v with theold one).

Geoff

Geoff, that's where I looked. There's nothing after "Battery calibration", in fact the battery reading is changing & flickering continuously making any adjustment impossible.

Seems a little odd but the battery calibration is done in the "Radio Setup" page with no sign of RTC Batt on that or the "Hardware" page.

I have both Tx's on version 2.2.2 maybe when I upgrade "RTC Batt" will appear at least on the Horus.

BTW my Taranis is very old, it was one of the first batch that T9 imported.

Pat.

[Geoff S]

I'm on version opentx-X10-2.3.2 (a97962c5). dated 2019-11-16.

In Hardware, Battery Calibration (which currently a steady 8.13v) is followed by RTC Batt (currently 3.03v), then Check RTC Voltage (just a check box, which I have checked) then Max bauds (400000 - a bit up on the 110 baud teletypes we had at work )

So I don't know about your X12. Perhaps Mike Blandford can explain.

Geoff

[PatMc]

Posted by Peter Christy on 17/06/2020 22:37:47:

GPS signals contain a very high accuracy time signal, so maybe the "Adjust RTC" option allows it to update automatically from a known source. The standard clocks do drift a bit.

A PC can also do this using a timing signal from the internet, so this would make sense. However, I don't have a GPS unit so I can't confirm.

Your mixed results maybe to poor GPS reception indoors? You probably need a good signal for it to work properly.

--

Pete

Pete, I was guessing that's what it might be about, my car's clock also uses the time signal from the GPS. The first time I tried the Adjust RTC option on both Tx's when switched off then back on the time & date actually reverted to the low battery default T&D. I then unticked the option on both Tx's re-set the time & date & all was OK.

The Taranis doesn't have GPS but the Horus has so - tried again later this evening with the option ticked - set the correct D&T on the Taranis - it's held the setting OK.
Deliberately input wrong date & inaccurate time on the Horus - so far it hasn't corrected either but this is indoors, will see if it makes corrections tomorrow.

Pat,

[PatMc]

Posted by Geoff S on 17/06/2020 23:49:40:

I'm on version opentx-X10-2.3.2 (a97962c5). dated 2019-11-16.

In Hardware, Battery Calibration (which currently a steady 8.13v) is followed by RTC Batt (currently 3.03v), then Check RTC Voltage (just a check box, which I have checked) then Max bauds (400000 - a bit up on the 110 baud teletypes we had at work )

So I don't know about your X12. Perhaps Mike Blandford can explain.

Geoff

I'm hoping to find time to upgrade to version 2.3.n in the next few days. As mentioned in another post we've had some family health issues ongoing since last October so making time for model activities isn't a high priority.

Pat.

[Andy48]

Posted by PatMc on 18/06/2020 00:16:17:

Pete, I was guessing that's what it might be about, my car's clock also uses the time signal from the GPS. The first time I tried the Adjust RTC option on both Tx's when switched off then back on the time & date actually reverted to the low battery default T&D. I then unticked the option on both Tx's re-set the time & date & all was OK.

The Taranis doesn't have GPS but the Horus has so - tried again later this evening with the option ticked - set the correct D&T on the Taranis - it's held the setting OK.
Deliberately input wrong date & inaccurate time on the Horus - so far it hasn't corrected either but this is indoors, will see if it makes corrections tomorrow.

Pat,

As far as I know it is only the X12S Horus that has the GPS, the X10 and X10S don't.

[PatMc]

The Horus hadn't corrected overnight or when left on for about 20 minutes in a bedroom this morning. However left it switched on in the garden sun lounge the time & date were correct when checked after about 30 minutes.
Since the Taranis doesn't have GPS I've switched off the RTC adjust option.

I'm now wondering if selecting this option increases the drain on the RTC battery a) when there's no GPS b) when there is GPS.
If the drain is increased in b) it may be best to de-select the option once the clock has been updated.