Have you seen any of those on Amazon, or a similar battery?
I can't really find a battery with that spec on Amazon.

I found a very good and very very cheap solution for battery.
I have bought an irobot braava 380 battery:
https://it.aliexpress.com/item/1005008959335050.html?spm=a2g0n.order_detail.order_detail_item.3.8b76582frptfuU&gatewayAdapt=glo2ita

It has 3 pin. Remove the cells from you old battery and connect this to the old battery plates (red for +, black for -, white for the upper -).
It recharge also with the original charger!
My pleo now stay up from more than one hour!

I hope I have help someone with this.

Bye

Good evening Dawn and Balletmom, I hope you were able to play with your Pleos again. I just found my beloved Pleo (Maris) after several years, still in her sleeping position, but haven't quite found her battery yet, and there's no guarantee she'll wake up after this time. And thanks for the suggestion, Chris.

I just pulled our original Pleo out for our grandson and found the batteries need replacing.  UGH...on a mission now.

Thank you for posting the battery information.  I want to revive our original Pleo for my grandson and realized one of the batteries has corroded.  I will try to order the ones you mention.  I will not be able to solder anything.  Does this mean I can leave the tabs as they are, fold them down, and tape them in place?

Thank you again!!!  I could not even find some overpriced ones online.

hmmmmm... He's not doing anything
And after he just does the same thing as before

-PleoLifeDino

Thank you for replying!
I’m 100% sure he is a ugobe not an RB, there’s no battery in his foot.
I’m going to try the 1.1.1 and the 2.0.1 now

-PleoLifeDino

A second thought just to be sure, when you do an update, you put the SD card in, start your pleo, and when the update is finished it says "Huh?".  You then have to turn the pleo off and remove the SD card. 

I would actually suggest using the OS 1.1.1 or 2.0.1, not the 1.0 for a non-RB pleos.  The POP OS and 1.0 are really more for trying to get a bricked or corrupted OS pleo functioning. 

Do you know for sure if your pleo is one of the original "classic" models, or the newer (but still old) Pleo RB?  It is very important to know this as using the wrong upgrade/downgrade can make a pleo non-functional.

one key way to identify if you have a pleo RB is to look at the feet.  Does one of them have a battery in it?  If so, it's an RB, and you might try replacing that battery.

So, I tried all the different versions but it doesn't do anything, Pleo just stays quiet.
And after, Pleo just does the same thing,
he makes a "HUH?" sound and moves a little.
I don't know what to do!!!???

-PleoLifeDino