IPA is bad for some plastics and can make some acrylics crack. Even if it won't melt down most plastics it might remove details like structures on the materials, leaving behind a shiny surface. It can also discolor some plastics. If you don't want that I'd be careful. It's sadly impossible to say in which cases it will happen and it which it wont as there are about a gazillion of different plastics. Test at some corner. Honestly, for most plastics some soap and warm water is fine. If you can't clean off whatever you want to clean off with that, my experience has shown anything harsher to finally get it off will also usually damage the plastic.
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To a tech tip: If you want to replace a worn out lithium-polymer battery for a device, don't search for <device name> battery but search for the batteries specifications. Many lithium-polymer batteries are not custom made for specific devices but actually off-the-shelf standard items. You'll get the battery probably easier and also much cheaper. The whole business model of some sellers on eBay etc. is to find out what a battery some device has and then price gouge people who use google to find them.
In the same vein, hard plastic case shell rechargeables (for laptops for example) often also just contain standard battery cells that can directly be replaced if you can open the shell carefully and can solder a little. This is becoming increasingly less true in the last few years though as trends towards thinner and smaller devices actually lead some of the big manufacturers to custom-design batteries for their devices. Beyond an original part, you're often out of luck there. (frankly, this should be illegal because it causes an enormous pile of trash)
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There's an two component epoxy made by different manufacturers that's like putty. You knead it to activate it and then have a few minutes to form it and then it hardens into a plastic-like material. (wear disposable gloves while you form it, you don't want that stuff to have contact with your skin while it's reacting. When it's hardened it's fine) It can then be sanded and even painted. This stuff is incredibly useful for misc. repairs, from deep scratches with pieces missing in wooden surfaces you plan to paint over to broken off plastic nubs and even cracked plastic cases. If you roughen up the surface you want to put it on with coarse sandpaper, it holds on very well to it.
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Many cheap chinese electronics in recent years come with a rubberized surface as you might have noticed to make the device feel more fancy and look more expensive. That stuff is cheap and you can buy it in spray cans. It's very easy to apply and you can even take it off again mechanically. If you have some device (old keyboard case etc.) that looks ugly but you want to keep using you can give it a paint job with that and it'll look good and even feel nice to the touch. You can easily remove the paint-job and reapply a new one later.
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This one is a bit advanced: Acetone dissolves many consumer item plastics but when the acetone vaporizes the plastics actually turn hard again. If you have plastic devices that got shiny and ugly over the years from touch use but are worth something (e.g. retro electronics) you can make a plaster impression of the surface structure from an undamaged part, then slightly coat the shiny part with acetone and press the plaster impression into it to get a structure again. Good as new! Practice this on something you don't mind throwing away as it is hard to get right. You can also fuse broken off plastic parts back together again with acetone. This works best with ABS. Not all plastics dissolve in acetone.
I repair old stuff often.
