CMOS battery replacement

H. Nikolaus Schaller hns at
Sat Dec 19 17:27:57 UTC 2015


Am 12.12.2015 um 03:06 schrieb Benjamin Deering <ben_deering at>:

> On Fri, 11 Dec 2015 15:38:54 -0800
> Andrew Schenck <andrew at> wrote:
>> That's a lot more work than I had hoped.  Thanks very much for the
>> info though.  If I'm going to be soldering I might as well try to fix
>> the USB port and GPS port at the same time.
>> -Andrew
>> On 12/11/2015 1:30 PM, Benjamin Deering wrote:
>>> The backup battery (supercap?) is welded to its bracket and
>>> won't push out.
>>> I replaced the backup batteries in my GTA02s with supercaps several
>>> years ago.
>>> The parts I used didn't match the original footprint so it was a
>>> little work.  If you get the exact replacement part, it would be
>>> easy if you have soldering experience.
>>> I vaguely remember a software problem causing the line that charges
>>> the backup bat/cap not being set high.
>>> Good luck,
>>> Ben
>>> On Fri, 11 Dec 2015 12:26:54 -0800
>>> Andrew Schenck <andrew at> wrote:
>>>> The secondhand GTA04 I have now is pretty beat up and can't charge
>>>> because the USB port is disconnected.  I've been using a spare
>>>> GTA02 as a charger, but every time I switch out batteries the
>>>> clock resets to 12/12/1999 16:00 and it's a pain to re-set it
>>>> since network time doesn't work.  I couldn't find any information
>>>> on the wiki about replacing the CMOS battery to solve this
>>>> problem; has anyone here dealt with this same problem before and
>>>> have recommendations?

The GTA04 already has a supercap in battery shape. They came to the market
in ~2011.

Since there is nothing to replace (a supercap rarely fails), it is most likely
a software issue that the charging current provided by the tpw65950 is not

So which OS&kernel are you using? In most systems I know, the RTC
"resets" to 1st Jan 2000.

> I was successful in fixing the USB port, but never tried the GPS port.
> The GPS port is under a lot of stress when the board is installed.

Should not be the case. You should move the USB+GPS socket as flat as
possible into or out from  the case. Then push out the case at the position
of the headset connector so that the latter snaps down a little in its hole.

This avoids breaking off connectors.

See also photos in chapter 4 (especially page 18) of the GTA04 system

> I ended up giving up on the traces and soldering thin wires to the ESD
> protection chip and to the leads on the jack.

That is fine and indeed sometimes needed if a socket was broken off.

> After getting the USB port connected electrically, I used JB weld epoxy
> to fix it mechanically.  The repair lasted years including some pretty
> rough use and being reflow soldered.

> Good luck,
> Ben
>>>> I disassembled a GTA02 enough to see the battery, but it didn't
>>>> yield to gentle pressure trying to slide out of its bracket and I
>>>> don't want to destroy things too badly in my attempt to fix them
>>>> so I didn't push too hard.  Because of this, I don't even know the
>>>> exact type of button cell to buy to replace it.  Any help would be
>>>> appreciated.

The GTA04 original part is a PAS414HR-VG1.

BTW: it should also work in the GTA02 (which has a real 3.3V LiIon cell
in 414 package).

>>>> Thanks,
>>>> -Andrew

BR and also good luck,

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