Old Laptop CMOS Battery

Ok so i received an ancient laptop from a client to repair, and the first thing i noticed upon booting was the cmos battery had failed. I cracked the laptop open, and realized it used a button cell array of rechargeable batteries, what i assume at one time also functioned as a reserve for safe shutdown. The battery pack was 7.2V and was unavailable anywhere i looked.

Now, i have tons of CR2032's for bios battery replacements, and i know full well if you try to charge one of those, it would burn or corrode the clients laptop, so I had an idea.

Since i do not need the batteries charged, but the laptop needs the charge, i would allow the laptop to get juice without giving juice, using a diode. So i stacked two CR2032 (I know, slightly under volted) ran an inline diode and hooked it up.

It seems to be working flawlessly, and these CR2032's last years, but is there something I am not thinking of that might make this solution undesirable?

 

I guess no one could think of any ill effects? I surprised this solution is not widely known, seeing as the old rechargeable reserve+cmos batteries were so widely used and now near impossible to find. Maybe this will help someone else if nothing else.

This project is pretty safe for anyone, even tho the CR2032's have an exploding risk, the diode prevents that possibility entirely. And if the diode is backwards, it is obvious as the battery will not allow the bios settings to keep a charge, and will reset upon removing external power.

 

Good DIY work! It sounds safe to me.

 

Sounds like a waste of time to me But also, whilst the diode should prevent charging those 2032's, the initial lower voltage of the 2x2032's combined with the voltage drop across the diode will surely lead to the bios prematurely reporting that the CMOS is corrupted due to insufficient voltage....

Seriously, I've never commented on somone's icon before, but yuck! Do I really need to see a pierced tongue? It's not that uncommon and not that impressive IMHO

 

Yes timfountain, I thought of that, and initially i tested it with a couple of half dead CR2032's and the bios was still not reporting lost bios settings after an hour of no external power supply. If anything, i suppose it might need battery replacements faster than normal, but if that is the only side effect, i suppose it is worth it to get it back in running shape.

Thanks for the input.