It's normally no need to replace these fuses as they could be recovered.

But if you still want to replace it, AliExpress is full of offers, just enter "12AH3" for example in the search engine.

https://a.aliexpress.com/_9up0zh

If your fuse is of 3-legs type, then check this topic on how to recover it.

How to repair a 3 legs thermal fuse

Posted by: @yura-compshop

Hello! Tell me who solved the problem. After unlocking the battery, the fuse is often defective, which blocks the output voltage. What can replace it? Maybe there is a link to aliexpress or another online store where you can buy such fuses? Thanks for the answer!

Take a picture of your actual fuse and we will help you how to repair the fuse step by step.

Thanks for the answer. Basically, I do not have working fuses on acer batteries, most often there is such a fuse.

This type of fuse is very easy to restore. Just put a very small amout of solder on your sodering iron tip and just touch the top of the fuse for 1-2 seconds and fuse is restored. I prefer to use low melt solder because the melting temperature is very low around 150 degrees celsius and if  the firmware decides to melt the fuse again there are no problems at all. But this type of solder is expensive and if you don't have it just use normal 60/40 type.

@torture @djibattworkshop

Could you please attach some pictures and short description how to restore a 3 legs type fuse ? To have both fuse restoration in the same place.

I guess it was somewhere on the forum a picture with 3 legs type, a good one.

The link is here above, in same thread.

https://www.laptopu.ro/community/postid/2432/

There is also another type of 3 leg fuse used mostly on Lenovo batteries. The restoration is a bit different. The power contact legs are not parallel to each other. But I will describe that when I get home soon since I'm out of the country right now and combine all of them in one tutorial. 

So I don't need to put d same kind of fuse that is in side. I should use solder flux to make d fuse 

or ChipQuik  Alloy

Posted by: @torture

There is also another type of 3 leg fuse used mostly on Lenovo batteries. The restoration is a bit different. The power contact legs are not parallel to each other. But I will describe that when I get home soon since I'm out of the country right now and combine all of them in one tutorial. 

I am talking about this fuse type. I remember we had a very clear picture with this fuse both good and bad posted by you or @djibattworkshop.

Posted by: @djibattworkshop

The link is here above, in same thread.

https://www.laptopu.ro/community/postid/2432/

 

Now I got it.

We need to put all info together.

Have sticked that thread as Tutorial as well so customers could navigate there directly from main page depending on which fuse type they have and not to scroll through unrelevant posts.

Anyway crosslinks from one tutorial to another is available as well.

I will also add the other type of 3 leg fuse as soon as I have a chance. So we cover all of them.