Q: Iphone 5 battery is stuck on 100%

is there any way of resetting the %?

I changed the battery due to it running out at 20-36% most days, since putting the new battery in it has been stuck on 100%, I even tried the original battery and another new battery but still get the same, it doesn't change.

Also when when the phone is switched off for any reason, once switched back and is used for what ever or put straight on charge it seems to crash and reset after around 3/4 mins, all 3 batteries do the same thing. I've found that if I plug it in to switch it on then remove charger for about 5 mins or I dont touch anything for 5 mins then when I go back to it it can be used/charged as normal.

I can deal with it but it's just annoying more than anything, does any one have any ideas as to why this has happened and can I sort it?

Changing IOS didn't help

Thanks in advance