SRAM Battery Replacement

[JackLeather]

Hello all, its been a while!

I just set my x68000 up for some fun and apart from the SRAM battery its still working fine. To make sure it stays that way the time has come for me to remove that evil battery and replace it with a coin battery and holder.

I have the X68000 ACE-HD (CZ-611C).

Questions:

- is the battery on the main board in the right hand tower or in the bottom (i/o?) board on my model?
- will a standard CR2032 do the job?
- does the battery need a diode or can i fit without - i seem to remember reading that the SRAM battery isn't rechargeable.
- any handy hints/tips when disassembling and fitting the new battery? should i fit it somewhere that's easier to get to via extension wires?

Many thanks.

[a24tanabe]

Hello.

ACE has it's battery on the bottom board.
And it's not recommendable to replace it with CR2032 because
(1) original battery is 3.6V.(CR2032 is 3.0V)
(2) original battery is rechargeable battery,so using CR2032 without diode may cause explosion.

Valta(German maker) sales compatible battery(3/V80H).Using it is very simple, I think.
Thanks.

[JackLeather]

Hello.

ACE has it's battery on the bottom board.
And it's not recommendable to replace it with CR2032 because
(1) original battery is 3.6V.(CR2032 is 3.0V)
(2) original battery is rechargeable battery,so using CR2032 without diode may cause explosion.

Valta(German maker) sales compatible battery(3/V80H).Using it is very simple, I think.
Thanks.

Thanks! Does seem a shame to remove a battery that's likely destroying the board to only replace it with the same tho.

I was also hoping that the battery would be on the easier to access mainboard. I replaced the PSU several years ago so I do remember some of the intricacies of opening a 68000 but would be good to have a guide. Is there a decent tear down guide anywhere?

[aarkay14]

Hello.

ACE has it's battery on the bottom board.
And it's not recommendable to replace it with CR2032 because
(1) original battery is 3.6V.(CR2032 is 3.0V)
(2) original battery is rechargeable battery,so using CR2032 without diode may cause explosion.

Valta(German maker) sales compatible battery(3/V80H).Using it is very simple, I think.
Thanks.

I dont understand why we are not replacing it with ML2032 rechargeable batteries.  With a nice coin cell holder.. I will do this and check..  I m 3v will work..

[JackLeather]

I have just dismantled my X68000 to get at the battery.

It is a lot easier than i expected. remove side panels. the two screws at rear (below image in and scsi connectors) that hold the bottom to the main chassis and the 5 screws from the underside - disconnect several cables and the board slides out - took 10 minutes! Respect is due Sharp!

Now i can see the battery I'm a little surprised and hugely delighted - because the battery looks like new and hasn't leaked! 

The photo attached shows battery as a Ni-Cd gb50h-3 3.6V 50mAh. I was expecting 3 pins but this only has two.

can someone confirm that this one on Amazon is a good replacement?

https://www.amazon.co.uk/Varta-industrial-battery-80mAh-Battery/dp/B00C2PEP1G

[JackLeather]

Just been reading up a little on Ni-Cd v NiMH, specifically concerning how each should be charged.

Found this:

The primary problem is that NiMH batteries do not like to be force-fed/overcharged, and
that is exactly what NiCd "low-end" chargers do: they are basically constant-current
"trickle" chargers (low current, takes many hours to charge, then keep feeding this
same charging current even after the NiCd is fully charged). NiCd batteries just shrug
off this excess charging current, but it will eventually "cook" your NiMHs.

http://www.candlepowerforums.com/vb/showthread.php?164059-Can-I-substitue-NiMh-for-NiCd

and this:

It is more difficult to tell when NiMH cells are fully charged than NiCds.  When NiCds are nearly fully charged, the voltage suddenly rises - and then starts to go back down again when an overcharge condition is approaching.  NiMH cells will do this, but the magnitude of this voltage rise is only a fraction of that of NiCd cells and, under many charge conditions, may go completely unnoticed, hence the need to monitor the temperature of NiMH cells as well as to limit the amount of time over which a charge is applied.

Charging a NiMH cell from the original NiCd "slow" charger should work, but it will probably take more than twice as long as it did with the NiCd charger.  Typically, "slow" chargers will charge a NiCd pack in 12-16 hours, but this means that the same charger will probably take 30-36 hours to charge the NiMH pack.  This extra charge time is required because the storage capacity of the NiMH cells are likely to have around twice the capacity of same-sized NiCd cells that they replace.

http://www.ka7oei.com/nicds.html

Does the X68000 slow charge?

Before I go ahead and buy the Varta NiMH (link in a previous post) I'd like to be sure that the X68000 wont cook it, ultimately ending up in leakage and the death of my beloved machine. Call me paranoid. 

[aarkay14]

I just replaced my NiMh battery with a rechargeable coin cell 3v 65mah battery and the x68000 is working super fine!

Pics:

[JackLeather]

I just replaced my NiMh battery with a rechargeable coin cell 3v 65mah battery and the x68000 is working super fine!

Good news - glad you found a solution!

I went with the Varta Nimh battery, linked in a previous post.

Just fitted it yesterday and it has passed it's first test; charged for 24hrs then the x68k was unplugged for a few hours - SRAM was still intact when i rebooted.

Will let it charge for another night and then unplug for 24hrs and see how it performs.

BTW. The Ni-Cd that i removed appears to be fine. I have just tested its voltage and its around 3.6v - cant say i expected that.

[JackLeather]

In conclusion the replacement battery is working well. the x68k was unplugged for 10 days and the content of the SRAM was there when i booted today.

I checked the old batteries (Ni-Cd) voltage one more time and it still reads fully charged!

[Pantman]

Hi there!

I'm having trouble finding a supplier of the 2 pin Valta 3/V80H. Are they still available? I can only find a 3 pin version :-(

Is there another alternative I can use?

Many thanks!