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Replace 770x NiMH CMOS battery with lithium ion?
Posted: Wed Dec 12, 2007 12:49 pm
by virge
Hopefully this isn't a silly question...
I pulled the CMOS battery from my 770x and noticed it's NiMH. Can I replace this with a standard lithium ion CMOS battery similar to what's used in the TP600 series?
I had an old Packard Bell desktop that used a NiMH CMOS battery and I remember it couldn't be replaced with a lithium ion one because the NiMH battery would actually be charged by the motherboard. I'm not sure whether this also applies to the 770. It seems like it would because a NiMH battery would discharge pretty quickly if it weren't charged...
Andy
Posted: Wed Dec 12, 2007 2:10 pm
by rkawakami
What's the part number of the old (NiMH) battery? My understanding is that the CMOS battery in those systems should be a standard coin-type CR2025. Those are lithium (non-rechargeable), not lithium-ion (rechargeable) so your concern about the motherboard providing a trickle charge is appropriate. I don't believe that IBM used any rechargable backup batteries, but I could be wrong.
If you do have a nickel metal hydride battery in there, it would probably have a 3.6V rating. If it says 3V, then I'd have to assume it's lithium.
Posted: Wed Dec 12, 2007 2:38 pm
by virge
I don't have the part with me right now (at work), but doing an ebay search, I'm pretty sure its 05K4652. Here's a picture of what it looks like:
http://cgi.ebay.com/CMOS-BATTERY-FOR-IB ... 0202726124
Thanks for the clarification of the difference between lithium and lithium ion.
Posted: Wed Dec 12, 2007 3:04 pm
by rkawakami
Strange... The 770X HMM says the backup battery is part number 12J0453, which if you search on eBay yields this among other similar CR2025 batteries:
http://cgi.ebay.com/ws/eBayISAPI.dll?Vi ... 0181258336
Of course, searching for that FRU also turns up the memory bay cover
. I'm stumped... maybe the HMM is in error or there was another motherboard design which uses the battery pack you have.
Posted: Wed Dec 12, 2007 3:35 pm
by SMA
The 770 series has 3 batteries.
The purpose of the one in question here, is - as I recall it -
to make it possible to swap the main battery without having to reboot.
It is not the cmos battery.
The cmos battery is located next to the memory slots and it is a standard one.
My advise would be not to replace this third battery and leave it out of the machine.
I have recently seen one of these which had been leaking.
Posted: Wed Dec 12, 2007 4:10 pm
by rkawakami
Ah, thank you SMA! Yes, the "standby battery" is listed in the HMM and appears to be an FRU 12J0428. This would seem to have nothing to do with the battery which is supposed to keep the real-time clock (RTC) and the CMOS information alive.
Posted: Thu Dec 13, 2007 1:15 pm
by virge
doh! Thanks for clearing that up SMA. This is the first time I've been in a 770 series Thinkpad and I've never seen a standby battery in another of my other models.
Also, thanks for the tip about removing it. I didn't think about the leakage issue. I had a 701C where the main battery leaked...
Andy