Coin Battery Hack ... my findings

[melott]

This is what I found in several days of playing around
with the Battery Backed Clock in my A2000 rev 4.4 MoBo.
I'm no Electronics Wiz so feel free to comment, debate
or dispute my findings.

I had intended to replace the barrel battery with a
coin battery. I stripped a battery mount from an old
PC MoBo and bought a new battery (a CR2025 battery).
What is the difference between a CR2025 and a CR2032 ?

I D/L'ed the coin battery hack from Aminet and followed
the instructions (not much to it).
What I found was the coin battery (3 volt) doesn't seem
to have enough power to hold the clock circuit.
I first thought maybe the circuit is bad so I installed
a standard Amiga barrel battery (3.6 volt).
The circuit worked fine. It held time and date for 24 hours.

Next I tried a cordless phone battery (3.6 volt). Again the
clock circuit held time and date for 24 hours.

My conclusion is the 3 volt coin battery doesn't have enough
power and the hack is a waise of time.
It seems that the clock circuit needs the extra point 6 volts to work.
 

[MskoDestny]

Perhaps this is a stupid question, but are you sure you installed the diode in the correct direction?

[melott]

MskoDestny wrote:
Perhaps this is a stupid question, but are you sure you installed the diode in the correct direction?

Yes... I installed the diode correctly and used the one
mentioned in the hack (RadioShack).
It starts loosing time as soon as the computer is shut off.
After about 5 minutes the time is gone but the date will
hold for about 10 minutes.

[vpcs]

I did the hack over a year ago and it has held perfect time.  I did this on a Rev 6.2 A2000

[Zac67]

A CR2025 is 20mm x 2.5mm and a CR2032 is 20mm x 3.2mm (slightly higher capacity)

I replaced the old battery in my A3k with a new NiCd battery of the same type (3GP-60 @www.reichelt.de, 1.75€), that'll do for at least the next 8 years or so. ;-)

[billt]

I think the voltage difference is the answer here. I did the coin battery hack a couple times. I never totally lost time or date, but it did slow down an dI had to reset it now and then if it bothered me.

I've taken to instead put a pin header somewhere and hook up a 3.6V rechargable telephone battery. Things seem to do better with these, and the plastic wrapping should help hold in leaking acids, plus you can put it somewhere less damaging if it does manage to leak, such as stuck to a solid metal piece of framing.

[MrZoon]

I'm about to try this on a parts machine before attempting it on my two in-use A3000s. Any other advice?

At least one of these machines has some acid damage, but just a little. Is there some kind of stuff I could put on the damaged area to stop further errosion? I'm thinking baking soda, or something like that.

Pete

[melott]

MrZoon wrote:
I'm about to try this on a parts machine before attempting it on my two in-use A3000s. Any other advice?

At least one of these machines has some acid damage, but just a little. Is there some kind of stuff I could put on the damaged area to stop further errosion? I'm thinking baking soda, or something like that.

Pete

If you go the coin battery route, I'd be interested
in your results....

As for cleaning ... I used electrical contact cleaner.
Can be bought at most any hardware or auto parts.
I sprayed the area then used a stiff brisseled small
paint brush to scrub the area then spray again to clean.

[Tomas]

is 3.6v phone batteries safe to use without a diode or a similar hack? Can you just solder it on and expect it to work?

[TjLaZer]

When I did this (see my gallery for pics), if I used a battery that was slightly used and the voltage dropped below 3V it would so as you desribed, but a fresh new one worked fine.  I did this on a A3000, A3000T, A4000 and a A501 with no problems.

[melott]

Tomas wrote:
is 3.6v phone batteries safe to use without a diode or a similar hack? Can you just solder it on and expect it to work?

I don't see why not........
Phone batteries are rechargeable and they are the same
voltage as the barrel battery.

I had another A2000 (sold it) with the phone battery
hack. I used it for almost a year before I sold it.
It worked fine. The only problem is finding a place
to mount the battery. On the A2000 I soldered 2 long
leads to connect the battery and then made a strap
that held the battery to the front of the machine case
between the Zorro slots.

[MrZoon]

So, anyway, I removed a couple of batteries and tried to affix a little tripod thingy made out of cordless phone parts - figured I could use the rechargeable battery pack - but it never worked (not sure why). So, instead, I just got a utility to grab internet time and everythings fine. One more machine to go, if I haven't waited too long...

[Oliver]

I've only ever used a 3.6V Li.  No problems.  Phone batteries are a bit expensive, aren't they?

If you drop the voltage, you risk running too close or below required logic thresholds.  Thresholds do vary a bit, so ymmv.