Why would a DECT Panasonic cordless phone keep losing the wi

[Oren]

On Tue, 7 Jan 2014 04:29:19 -0800, "William Sommerwerck"
<grizzledgeezer@comcast.net> wrote:

>Why hasn't someone suggested changing the WiFi channel?

I was thinking about it

>That's a great place to start testing.

Even suggested when installing a home router. Change the channel if
there are problems.

 

[Danny D'Amico]

On Tue, 07 Jan 2014 08:19:18 +0000, Geoffrey S. Mendelson wrote:

There are three kinds of interference that can happen in this case.
The first is direct interference
The second is intermodulation
The third is desensitization, where a strong signal on a relatively near
frequency overloads the receiver in a device. So a WifI router can cause
DECT phones to stop receiving, even though WiFi is 2.4gHz and DECT is 1.7gHz.

This is very useful information, an applicable to the WiFi group as well.

My DECT Panasonic KX-TG6441 phones & handsets apparently operate at
1.9 GHz, according to page 6 of this PDF:
http://service.us.panasonic.com/OPERMANPDF/KXTG6431-MUL.PDF
"The product operates in the frequency range of 1.92 GHz to 1.93 GHz,
and the RF transmission power is 115 mW (max.)"

 

[Danny D'Amico]

On Tue, 07 Jan 2014 14:52:02 -0500, Percival P. Cassidy wrote:

Our Panasonic DECT phones are on 1.9GHz, I'm almost certain -- not on
the common 2.4GHz WiFi frequency.

My problematic Panasonic KX-TG6441 cordless phone is also on 1.9 GHz,
as described on page 6 of this PDF:
http://farm4.staticflickr.com/3786/11829460325_b34ca30a30_o.png
http://service.us.panasonic.com/OPERMANPDF/KXTG6431-MUL.PDF

 

[Danny D'Amico]

On Mon, 06 Jan 2014 22:21:07 -0800, Jeff Liebermann wrote:

Nope. If it's a loose antenna connection on the base, the handsets
close enough to get a minimal signal from the base would still work,
while those far away would loose the signal.

This is a good point!

 

[Danny D'Amico]

On Mon, 06 Jan 2014 23:24:45 -0700, Tony Hwang wrote:

One base and many handsets?
Then logic tells me radio in the base unit is suspect.

This makes sense.

What I did today was I pulled the batteries out of the five handsets
and pulled the power from the base, and let it sit that way all day.
http://farm6.staticflickr.com/5506/11829276385_b88f6d65c7_o.gif

Then, I performed the re-registration procedure as outlined on p27
of this PDF:
http://service.us.panasonic.com/OPERMANPDF/KXTG6431-MUL.PDF

Here's just the Panasonic cordless phone re-registration procedure:
http://farm8.staticflickr.com/7353/11829263895_ac761cd5cf_o.gif

Hopefully, re-registering all five handsets may help with the
problem of the Panasonic KX-TG6441 dropping calls after a while:
http://farm8.staticflickr.com/7331/11829272305_f01a1c8679_o.gif

I'll let you know what happens...

 

[Danny D'Amico]

On Tue, 07 Jan 2014 07:53:03 -0500, John Grabowski wrote:

*The last time my Panasonic phone did that, I replaced the batteries with
new ones. Problem went away. If yours are four years old I would think
that it is time for a battery replacement. Home Depot has them and I think
Wal-Mart does also.

This might actually be the problem!

After removing all the batteries and allowing the handsets and base to sit
for about five hours today ...
http://farm6.staticflickr.com/5506/11829276385_b88f6d65c7_o.gif

When I put the batteries back, I noticed that all five handsets said to
"Charge for 7 Hours" ...
http://farm8.staticflickr.com/7331/11829272305_f01a1c8679_o.gif

So, I put them all on a 3.5 hour charger:
http://farm8.staticflickr.com/7341/11829684174_606aa41376_o.gif

And, when I put them back into the phone, they *still* said to
charge for 7 hours!
http://farm4.staticflickr.com/3756/11830061806_447da87566_o.gif

So, maybe it's that simple - that the Ni-MH batteries, which are a
few years old, are bad.

One problem though, is that I put the new Ni-MH batteries that came
with the charger in, after charging them on the charger, and the
handsets *still* said to charge for 7 hours.

So, something fishy is going on ... with the charge message on the
handsets ... but I don't know what yet.

 

[Danny D'Amico]

On Tue, 07 Jan 2014 13:43:39 -0500, Jeff Urban wrote:

> If they're 2.4 Ghz, wifi could be interfering too much.

They're on 1.9 GHz ...
http://farm4.staticflickr.com/3786/11829460325_b34ca30a30_o.png

 

[Danny D'Amico]

On Mon, 06 Jan 2014 22:28:25 -0800, Jeff Liebermann wrote:

In the USA, there's no GAP support, which means that phones from
different manufactories not only will not talk with each other, but
also can interfere with each other. You might try your problem phone
with the other DECT phones and base turned off.

That's a great suggestion Jeff.

Maybe these other DECT phones in the same house:
http://farm3.staticflickr.com/2873/11811729095_cafdd2467b_o.gif
Are causing the problem with this DECT phone:
http://farm4.staticflickr.com/3779/11811980883_f540a29bee_o.gif

It might also be the batteries, although you can see in the previous
photo that they are fully charged - yet - I charged them today off
the Panasonic base:
http://farm8.staticflickr.com/7341/11829684174_606aa41376_o.gif

And, strangely, when I ran the registration procedure, they showed
up as being discharged! ?????????
http://farm8.staticflickr.com/7331/11829272305_f01a1c8679_o.gif

So that makes absolutely no sense. I chalk it up to "confused
electronics" at this point - because I can't imagine what happened
to make a fully charged battery indicate almost discharged.

Anyway, as a precaution, I ran the re-registration procedure,
which is described on page 27 of this PDF:
http://service.us.panasonic.com/OPERMANPDF/KXTG6431-MUL.PDF

This is a snapshot of the re-registration procedure:
http://farm8.staticflickr.com/7353/11829263895_ac761cd5cf_o.gif

Since the menus don't show up until *after* you run the procedure,
I post below sequential screenshots so others who run the registration
procedure can see the cause and effect on the phones:

Press LOCATOR on base 4 sec. Then press OK.
http://farm4.staticflickr.com/3708/11829267845_c9363aba09_o.gif
Call from Base:
http://farm8.staticflickr.com/7392/11829686934_e1799e3098_o.gif
Base regtr'ing
http://farm8.staticflickr.com/7331/11829272305_f01a1c8679_o.gif

 

[Danny D'Amico]

On Tue, 07 Jan 2014 20:03:55 -0800, mike wrote:

Since about zero percent of people are gonna do that, they might have
concluded that a timer inside the device would determine
that the device had charged all it could and the display was in
terms of "do this" instead of any actual measurement, and be adequate to
direct 99.9999% of users to perform the operation.

That might be the case Mike, because I know two things.

The batteries were showing fully charged initially:
http://farm4.staticflickr.com/3779/11811980883_f540a29bee_o.gif

Then, I removed them and let the phone sit for a few hours:
http://farm6.staticflickr.com/5506/11829276385_b88f6d65c7_o.gif

When I then ran my first re-registration procedure, I was surprised
to see that all five phones suddenly showed low battery indications:
http://farm8.staticflickr.com/7331/11829272305_f01a1c8679_o.gif

That made no sense because pulling the batteries and letting them
sit disconnected for a few hours couldn't possibly have discharged
them from full to near zero. But it was easy enough to charge them
independently on a Ni-MH charger:
http://farm8.staticflickr.com/7341/11829684174_606aa41376_o.gif

Yet, I was again very surprised to see, after 3.5 hours on the
charger (the lights stop blinking on the charger to indicate full
charge) that, back in the handsets, they *still* said they were
low on charge!
http://farm4.staticflickr.com/3756/11830061806_447da87566_o.gif

Something doesn't add up - but all five handsets acted the same
way, even with the four new batteries from the charger put into
two of the handsets.

All five phones are now in their respective holders, and, I just
checked the charge, and they went from one bar to three bars, so,
that's just weird.

It's almost as if they'll only charge from their Panasonic
holders, and not from a separate non-Panasonic charger. But,
that makes no sense - so - I really don't know what to make of
this inconsistent data other than to ignore it.

 

[mike]

On 1/7/2014 7:48 PM, Danny D'Amico wrote:

On Tue, 07 Jan 2014 07:53:03 -0500, John Grabowski wrote:

*The last time my Panasonic phone did that, I replaced the batteries with
new ones. Problem went away. If yours are four years old I would think
that it is time for a battery replacement. Home Depot has them and I think
Wal-Mart does also.

This might actually be the problem!

After removing all the batteries and allowing the handsets and base to sit
for about five hours today ...
http://farm6.staticflickr.com/5506/11829276385_b88f6d65c7_o.gif

When I put the batteries back, I noticed that all five handsets said to
"Charge for 7 Hours" ...
http://farm8.staticflickr.com/7331/11829272305_f01a1c8679_o.gif

So, I put them all on a 3.5 hour charger:
http://farm8.staticflickr.com/7341/11829684174_606aa41376_o.gif

And, when I put them back into the phone, they *still* said to
charge for 7 hours!
http://farm4.staticflickr.com/3756/11830061806_447da87566_o.gif

So, maybe it's that simple - that the Ni-MH batteries, which are a
few years old, are bad.

One problem though, is that I put the new Ni-MH batteries that came
with the charger in, after charging them on the charger, and the
handsets *still* said to charge for 7 hours.

So, something fishy is going on ... with the charge message on the
handsets ... but I don't know what yet.

Since about zero percent of people are gonna do that, they might have
concluded that a timer inside the device would determine
that the device had charged all it could and the display was in
terms of "do this" instead of any actual measurement, and be adequate to
direct 99.9999% of users to perform the operation.

Some people are "overthinkers" ;-)
Hmmm...I resemble that remark.

 

[William Sommerwerck]

Don't you have a voltmeter? You shouldn't be depending on the base to inform
you as to whether the batteries are actually being fully recharged.

 

[Geoffrey S. Mendelson]

Jeff Liebermann wrote:

Two independent but incompatible DECT systems, on
the same frequency, are going to cause mutual interference. The
reason the problem is intermittent is that both bases have be on the
same channel in order to cause mutual interference. With 5 (US)
channels to use, you're chances are 1 in 5 of having a collision.
Unplug one base and see if the probleem goes away.

Part of the DECT standard is that a device listens before it transmits. If the
channel is in use, it changes the channel. What happens when all channels are
busy I have no idea.

What you describe was the problem with the old 2.4gHz cordless phones. They
just picked a channel and transmitted on it. The later ones were spread
spectrum, so as far as WiFi was concerned, it interfered on ALL of channels.

Or in plain English, when my upstairs neighbor's phone rang, my WiFi
crashed.

DCT phones work the same way as DECT phones, but on the 2.4gHz or 5.8gHz
band. Again, what they do when all channels are busy I do not know.

This is also why cell phones do not need to be licensed. They only
transmit when asked to by a cell, which in most places is licensed.

If for example, you were to bring a 1900mHz GSM phone to Europe, or a
900/1800mHz EU GSM phone to the US, it won't start transmitting and
interfere with whatever is using those frequencies.


Geoff.

--
Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379

 

[Jeff Liebermann]

On Wed, 8 Jan 2014 03:41:46 +0000 (UTC), Danny D'Amico
<danny@is.invalid> wrote:

What I did today was I pulled the batteries out of the five handsets
and pulled the power from the base, and let it sit that way all day.
http://farm6.staticflickr.com/5506/11829276385_b88f6d65c7_o.gif

Ummm... was the phone designed to use NiMH or NiCd batteries? I'm too
lazy to check.

NiMH batteries can be a problem due to high self discharge and
possible overcharging. I suggest that you charge a few of the
batteries in the phones for a day and then remove the batteries.
Measure the voltage which should be about 1.2V when fully charged.
Just let them sit outside the handset for at least 12 hrs (or more).
Then measure the voltage again. 1.1V to 1.2V is fairly normal. 1.0V
is borderline. Anything less than 1.0V is a problem. What you're
measuring is the self-discharge rate, which tends to get worse as the
batteries get older. It's particularly bad with NiMH which can lose
1% to 5% per day depending on temperature and age.

Besides dubious batteries, I'm beginning to suspect you may have
multiple problems. Two independent but incompatible DECT systems, on
the same frequency, are going to cause mutual interference. The
reason the problem is intermittent is that both bases have be on the
same channel in order to cause mutual interference. With 5 (US)
channels to use, you're chances are 1 in 5 of having a collision.
Unplug one base and see if the probleem goes away.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Danny D'Amico]

On Wed, 08 Jan 2014 02:50:41 -0800, William Sommerwerck wrote:

Don't you have a voltmeter? You shouldn't be depending on the base to inform
you as to whether the batteries are actually being fully recharged.

I was remiss in not mentioning that I tested the voltage with my fluke
but the problem, as always, with testing open circuit no-load voltage
is that without a load, a battery that tests good isn't necessarily good.

However, all the handsets are now reading full bars in battery voltage,
so, I'm inclined to assume that the battery-charge indicator on the
handsets isn't really a voltage indicator - but some sort of integrator.

The good news is that it hasn't happened since re-registration; but I also
haven't been on the phone a lot either. I will report back in a few days
to let you know if the problem is solved by the re-registration or not.

 

[Danny D'Amico]

On Wed, 08 Jan 2014 10:26:04 -0800, Jeff Liebermann wrote:

Ummm... was the phone designed to use NiMH or NiCd batteries? I'm too
lazy to check.

Hi Jeff,
The batteries are the original, and, they're all Ni-MH batteries.
I noticed a set (white paint) was of a different amperage, so,
I reassembled all the sets with like-amperage batteries (to
prevent reverse voltage situations).

NiMH batteries can be a problem due to high self discharge and
possible overcharging. I suggest that you charge a few of the
batteries in the phones for a day and then remove the batteries.
Measure the voltage which should be about 1.2V when fully charged.
Just let them sit outside the handset for at least 12 hrs (or more).
Then measure the voltage again. 1.1V to 1.2V is fairly normal. 1.0V
is borderline.

I ran that from yesterday, Jeff, and they came back at 1.2 volts.
So, I must tentatively conclude that the phone itself has a
summative charging icon, where it might be "timed" in the charger,
rather than checked at the battery.

All five handsets, with the same batteries that read nearly dead
after charging, now read full. I haven't extensively tested yet,
but, all seems well now (tentative assessment).

With 5 (US) channels to use, you're chances are 1 in 5 of having
a collision. Unplug one base and see if the probleem goes away.

This might be the reason for the intermittence!

What I *should* do is buy a DECT system with 9 handsets instead
of two DECT systems for a total of 9 handsets.

 

[Jeff Liebermann]

On Fri, 10 Jan 2014 15:22:06 +0000 (UTC), Danny D'Amico
<danny@is.invalid> wrote:

On Wed, 08 Jan 2014 10:26:04 -0800, Jeff Liebermann wrote:

Ummm... was the phone designed to use NiMH or NiCd batteries? I'm too
lazy to check.

Hi Jeff,
The batteries are the original, and, they're all Ni-MH batteries.
I noticed a set (white paint) was of a different amperage, so,
I reassembled all the sets with like-amperage batteries (to
prevent reverse voltage situations).

I don't believe it. The phones look at least 8 years old. If the
NiMH batteries were that old and left on continuous charge, they
should be nearly dead by now. I have a discharge tester (West Mtn
Radio CBA-II) that can test them. Send me one cell and I'll run a
test (time permitting).

NiMH batteries can be a problem due to high self discharge and
possible overcharging. I suggest that you charge a few of the
batteries in the phones for a day and then remove the batteries.
Measure the voltage which should be about 1.2V when fully charged.
Just let them sit outside the handset for at least 12 hrs (or more).
Then measure the voltage again. 1.1V to 1.2V is fairly normal. 1.0V
is borderline.

I ran that from yesterday, Jeff, and they came back at 1.2 volts.

Ok, the batteries are not totally dead.

So, I must tentatively conclude that the phone itself has a
summative charging icon, where it might be "timed" in the charger,
rather than checked at the battery.

Dunno. I've used a few Panasonic handsets around the house. The one
with individual cells ate batteries about every 3-5 years.

All five handsets, with the same batteries that read nearly dead
after charging, now read full. I haven't extensively tested yet,
but, all seems well now (tentative assessment).

Offhand, I would say a bad battery or charger connection. The chrome
plated connections on both the handset and charger base don't make a
reliable connection and must be cleaned carefully. Same with the
internal battery contacts.

With 5 (US) channels to use, you're chances are 1 in 5 of having
a collision. Unplug one base and see if the probleem goes away.

This might be the reason for the intermittence!

What I *should* do is buy a DECT system with 9 handsets instead
of two DECT systems for a total of 9 handsets.

Just buying some additional handsets for your existing base might
be a better and cheaper idea. The data sheets list the maximum number
of handsets a base will accomodate. I know of one system with 12
handsets. This might help:
<http://cordless-phones-review.toptenreviews.com/>
Oops. Looks like Panasonic is limited to 6 handsets.


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Danny D'Amico]

On Fri, 10 Jan 2014 09:17:11 -0800, Jeff Liebermann wrote:

I don't believe it. The phones look at least 8 years old. If the
NiMH batteries were that old and left on continuous charge, they
should be nearly dead by now. I have a discharge tester (West Mtn
Radio CBA-II) that can test them. Send me one cell and I'll run a
test (time permitting).

Hi Jeff,
The phones *are* old. I agree.

And, those yellow Ni-MH AAA batteries are the originals.
So, I must have done the voltage test wrong.

Let me explain what I did, so we can see what I did wrong.

1. Here are four of the handsets, with full battery indicators:
http://farm3.staticflickr.com/2886/11882484886_4839174995_o.gif

2. Flipping them over, only two currently have original batteries:
http://farm4.staticflickr.com/3797/11882074284_ee4763c59f_o.gif

3. Opening one, I find the battery open-circuit voltage is 1.4VDC:
http://farm6.staticflickr.com/5498/11881637505_1ba94a31d5_o.gif

4. Likewise, the other battery is 1.4VDC, with no load on it:
http://farm3.staticflickr.com/2810/11881914203_f2b50e19ea_o.gif

5. Yet, putting them back, the phone now indicates a low battery:
http://farm4.staticflickr.com/3742/11882073034_b75d2d560e_o.gif

Conclusion?
A freshly charged battery (hot off the phone cradle), reads good;
but the phone charge indicator reads full at first, and then almost
empty after merely removing and then replacing the batteries.

6. Similar voltages were found for the other handset batteries:
http://farm3.staticflickr.com/2824/11882072184_59ba294c4e_o.gif
http://farm8.staticflickr.com/7377/11881635665_24a4718078_o.gif

7. The replacement batteries read slightly higher voltages:
http://farm8.staticflickr.com/7392/11882071034_45f3c6231e_o.gif

8. Yet, all read low when immediately put back in the handset:
http://farm6.staticflickr.com/5482/11881635265_a2ba55592c_o.gif

I'm not sure what to make of this data ...

 

[Tony Hwang]

Tony Matt wrote:

On 01/07/2014 10:48 PM, Danny D'Amico wrote:
When I put the batteries back, I noticed that all five handsets said to
"Charge for 7 Hours" ...
[...]
So, something fishy is going on ... with the charge message on the
handsets ... but I don't know what yet.

Been there, done that, should have posted sooner. These/some Panasonic
cordless handsets display a "Charge for 7 hours" message (and a single
bar on the battery gauge) whenever batteries are installed, regardless
of the state-of-charge.

Details:

Last spring I attempted to set up a used KX-TG9341S system and got this
message on all of the handsets. Old batteries, new batteries, Panasonic
batteries, externally charged batteries, didn't matter (other than
alkaline cells, which it detected: "Wrong battery type"). Measured
voltages, currents, took apart a handset to look for damaged components,
double checked that full battery voltage was actually getting to the
PCB. Googled it, read a bunch of head-scratching, generic battery
advice, and speculation. Got frustrated and moved on to other projects.

A few months later I saw some of the Panasonic NiMH cells at the local
recycling center and decided to take another run at it. I charged
(externally) all of the cells and tested them. Then I got another idea
- I don't normally use AAA NiMH cells, but use lots of AA cells, so
jumpered over a pair of known-good, freshly charged AA cells to the
battery terminals of one of the handsets. Still got the 7 hour message.
That seals it - it's not the batteries. I picked the best six
Panasonic cells, let the handsets go through their 7 hour charge cycle,
and have been using the system ever since.

Panasonic apparently decided to override the charge sense/termination
circuitry with the 7 hour timer when batteries are installed in order to
reduce product returns (from customers who neglect to read the fine
manual and discover that their brand-new handsets and batteries don't
work right away). I did find some weak cells over time, but that's
unrelated to the 7 hour message.

Recommendations:

1. If you put charged cells into the handset, ignore the message and
leave the handset out of the charger for a few days (while using it, of
course). Otherwise, the batteries will be overcharged by the forced
7-hour 'initial' charge.

2. Test for good cells in the handset by trying the speaker phone
option. A weak cell will result in a power cycle (no audio, blank
display, then display with no backlight). If both cells are weak, it
will power cycle when the backlight comes on (i.e. whenever a button is
pressed). Check the cells under load with a meter to determine if one
cell has dropped out, or they are both at low charge. Keep pairs of
cells matched wrt state-of-charge.

3. Look elsewhere for the solution to your link issue.

Good Luck,
Tony Matt

Hmmm,
Maybe I am dumb or simple minded. Manual says charge 7 hours B4 using. I
just left it over night out of box. Ever since they all have been
reliably working. At home and at the store.

 

[Tony Matt]

On 01/07/2014 10:48 PM, Danny D'Amico wrote:

When I put the batteries back, I noticed that all five handsets said to
"Charge for 7 Hours" ...
[...]
So, something fishy is going on ... with the charge message on the
handsets ... but I don't know what yet.

Been there, done that, should have posted sooner. These/some Panasonic
cordless handsets display a "Charge for 7 hours" message (and a single
bar on the battery gauge) whenever batteries are installed, regardless
of the state-of-charge.

Details:

Last spring I attempted to set up a used KX-TG9341S system and got this
message on all of the handsets. Old batteries, new batteries, Panasonic
batteries, externally charged batteries, didn't matter (other than
alkaline cells, which it detected: "Wrong battery type"). Measured
voltages, currents, took apart a handset to look for damaged components,
double checked that full battery voltage was actually getting to the
PCB. Googled it, read a bunch of head-scratching, generic battery
advice, and speculation. Got frustrated and moved on to other projects.

A few months later I saw some of the Panasonic NiMH cells at the local
recycling center and decided to take another run at it. I charged
(externally) all of the cells and tested them. Then I got another idea
- I don't normally use AAA NiMH cells, but use lots of AA cells, so
jumpered over a pair of known-good, freshly charged AA cells to the
battery terminals of one of the handsets. Still got the 7 hour message.
That seals it - it's not the batteries. I picked the best six
Panasonic cells, let the handsets go through their 7 hour charge cycle,
and have been using the system ever since.

Panasonic apparently decided to override the charge sense/termination
circuitry with the 7 hour timer when batteries are installed in order to
reduce product returns (from customers who neglect to read the fine
manual and discover that their brand-new handsets and batteries don't
work right away). I did find some weak cells over time, but that's
unrelated to the 7 hour message.

Recommendations:

1. If you put charged cells into the handset, ignore the message and
leave the handset out of the charger for a few days (while using it, of
course). Otherwise, the batteries will be overcharged by the forced
7-hour 'initial' charge.

2. Test for good cells in the handset by trying the speaker phone
option. A weak cell will result in a power cycle (no audio, blank
display, then display with no backlight). If both cells are weak, it
will power cycle when the backlight comes on (i.e. whenever a button is
pressed). Check the cells under load with a meter to determine if one
cell has dropped out, or they are both at low charge. Keep pairs of
cells matched wrt state-of-charge.

3. Look elsewhere for the solution to your link issue.

Good Luck,
Tony Matt

 

On Tue, 14 Jan 2014 23:57:25 -0500, Tony Matt <tonym@theworld.com>
wrote:

On 01/07/2014 10:48 PM, Danny D'Amico wrote:
When I put the batteries back, I noticed that all five handsets said to
"Charge for 7 Hours" ...
[...]
So, something fishy is going on ... with the charge message on the
handsets ... but I don't know what yet.

Been there, done that, should have posted sooner. These/some Panasonic
cordless handsets display a "Charge for 7 hours" message (and a single
bar on the battery gauge) whenever batteries are installed, regardless
of the state-of-charge.

Details:

Last spring I attempted to set up a used KX-TG9341S system and got this
message on all of the handsets. Old batteries, new batteries, Panasonic
batteries, externally charged batteries, didn't matter (other than
alkaline cells, which it detected: "Wrong battery type"). Measured
voltages, currents, took apart a handset to look for damaged components,
double checked that full battery voltage was actually getting to the
PCB. Googled it, read a bunch of head-scratching, generic battery
advice, and speculation. Got frustrated and moved on to other projects.

A few months later I saw some of the Panasonic NiMH cells at the local
recycling center and decided to take another run at it. I charged
(externally) all of the cells and tested them. Then I got another idea
- I don't normally use AAA NiMH cells, but use lots of AA cells, so
jumpered over a pair of known-good, freshly charged AA cells to the
battery terminals of one of the handsets. Still got the 7 hour message.
That seals it - it's not the batteries. I picked the best six
Panasonic cells, let the handsets go through their 7 hour charge cycle,
and have been using the system ever since.

Panasonic apparently decided to override the charge sense/termination
circuitry with the 7 hour timer when batteries are installed in order to
reduce product returns (from customers who neglect to read the fine
manual and discover that their brand-new handsets and batteries don't
work right away). I did find some weak cells over time, but that's
unrelated to the 7 hour message.

Recommendations:

1. If you put charged cells into the handset, ignore the message and
leave the handset out of the charger for a few days (while using it, of
course). Otherwise, the batteries will be overcharged by the forced
7-hour 'initial' charge.

2. Test for good cells in the handset by trying the speaker phone
option. A weak cell will result in a power cycle (no audio, blank
display, then display with no backlight). If both cells are weak, it
will power cycle when the backlight comes on (i.e. whenever a button is
pressed). Check the cells under load with a meter to determine if one
cell has dropped out, or they are both at low charge. Keep pairs of
cells matched wrt state-of-charge.

3. Look elsewhere for the solution to your link issue.

Good Luck,
Tony Matt

If the power to the master is disrupted while the remotes are not on
charge it is possible for the remote to loose connection to the base
on SOME Panasonic phones. Mine are KXT5433 5.8ghz units and it has
happened to me. Don't know about DECT