Thinkpads Forum

I am currently working with the 701C and will open it up as soon as I get the T1 bit I bought on eBAy. The main goal is to replace the soldered-on CMOS battery with a regular 600 CMOS battery, and clean out light traces of oxidation on the main battery contacts. I don't know why it has oxidized, as the main battery wasn't leaking at all. Those cells are out now anyway, as I will recell it with regular AA rechargeable ones.

Then the question: I also took out the standby battery, (The one that's accessible through the lid on the bottom) and it obviously didn't do much, as the black cable had become detached from the battery. As far as I have found here on the forum, that's a 1.2V 30mAh NiMh rechargeable battery. Has anyone tried to replace it? And if so: What kind of battery did you use? Would one like this work, if it gets the cables and plug from the old battery soldered on to it? http://www.ebay.com/itm/220574302704?_t ... EBIDX%3AIT According to the HMM, the standby battery's purpose is to give you a 1 minute time frame to swap the main battery while the laptop is in suspend mode. And as the one cable on my battery was detached, it seems like the laptop works just fine without it. So maybe no reason to put a big effort into it, but we'll see.

Thanks for any input on the issue. Also feel free to share other useful 701C battery related issues, if anyone has any.

After doing some research, I am pretty confident that the battery IS a 1.2V 30mAh NiMh battery. So I might want to rephrase my question:

Is there a problem using a 1.2V 80mAh battery, as long as it physically fits inside the machine? The only ones I find on eBay are the 80mah ones, the link is in the previous post. If I search specifically for a 1.2V 30mAh battery, I come up with a NiMh battery from a website in France http://jr-international.fr/storage-batt ... glish.html, and a NiCd battery on a different site http://tronic.manufacturer.globalsource ... n-Cell.htm. The advantage of the NiCd battery is that it has solder tabs that are more suitable for my application, but this is a different type of battery. All of these batteries will no matter what need an extra shrink tube around them, as the solder tabs are so big. I definitely don't want those to touch anything in there..

What do you guys think? Is the charging circuit for this battery so fragile that I should go only with what's correct when it comes to both mAh capacity (30mAh vs. 80mAh) and battery type (NiMh vs. NiCd)?

I worked on batteries for a 701c about 4 years ago: http://forum.thinkpads.com/viewtopic.php?f=6&t=115043

Thanks. That link points back to this thread, but I have actually read some of your posts about this subject, and you were the one who mentioned the voltage / capacity of the standby battery. But I don't think anyone has ever written anything about replacing this battery with an universal battery, unless you have once posted something I have missed.

Norway Pad wrote:After doing some research, I am pretty confident that the battery IS a 1.2V 30mAh NiMh battery. So I might want to rephrase my question:

What do you guys think? Is the charging circuit for this battery so fragile that I should go only with what's correct when it comes to both mAh capacity (30mAh vs. 80mAh) and battery type (NiMh vs. NiCd)?

I've been meaning to look into this battery for a little while now. You seem to be correct the internet description is IBM 04H8345 1.2 Volt 0.03 Amp NiMH.

NiMH and NiCD can be used interchangeably, charging circuits won't care which type you use, but you should prefer NiMH I'd say due to its enhancements over NiCD.
I would say that the slightly larger capacity *shouldn't* create any problems, I mean people are rebuilding their main battery packs with larger nimh cells, same concept. The nimh battery you found actually looks almost identical to the original, just missing the wires!


I've managed to find comparable 80 mah ones on ebay, shipping from china as 3 packs.
Two pronged version
http://www.ebay.com/itm/3X-Ni-MH-Button ... 0923020350

Three pronged version
http://www.ebay.com/itm/3X-Ni-MH-Button ... 0574302704

AND this may be one of the best solutions too:
http://www.ebay.com/itm/1-2V-20mAh-New- ... 1167693770
Now, I know, this is only rated at 18 mah but I believe this batteries purpose is to keep the clock functioning while the machine is in sleep mode, and if the power cord or a working main battery are installed, this battery shouldn't in theory drain until after they are removed.

Thanks for that last link. The plug doesn't seem to be the same, which is no problem as I can put the old one back on and use tiny shrink hose. And with this one, there are no worries about the additional mAh capacity. One other thing to consider is if I really *want* the standby battery back. One extra source of future leaks, and I'm not very likely to use the sleep function much anyway. Even less swapping the main battery while it's sleeping. The main priority will no matter what be the CMOS battery, as that causes errors when not working.

We'll see, but I think I have gotten the answers and options I was looking for when I started this thread. Thanks all!