I literally found my powerbank in storage 2 years after I last used it and it had 3/4 charge indicator.
I think powerbanks with integrated solar are garbage - leaving it out on a sun and thus heat for extended periods of time is probably a bad idea, and the solar cell they have is far too small and shitty to make any difference anyway. But I am not an electronics expert, just my opinion.
edit:
sorry typo in original comment:
"I got one without solar and remote charging" - just plain powerbank without any additional crap.
I think I have this one
https://www.amazon.com/Anker-PowerCore-Portable-Double-Speed-Recharging/dp/B01JIWQPMW/ref=sr_1_3?keywords=power%2Bbank&qid=1639691592&sr=8-3&th=1
Just charge it at home once and leave in car for emergency, or buy solar cell on its own like this one https://www.amazon.com/25000mAh-ADDTOP-Portable-Waterproof-Compatible/dp/B07FPHHNDL/ref=sr_1_4?crid=2VFXM4PVQN52W&keywords=solar%2Bcharger&qid=1639691737&sprefix=solar%2B%2Caps%2C187&sr=8-4&th=1 and charge off of that.
I literally found my powerbank in storage 2 years after I last used it and it had 3/4 charge indicator.
I think powerbanks with integrated solar are garbage - leaving it out on a sun and thus heat for extended periods of time is probably a bad idea, and the solar cell they have is far too small and shitty to make any difference anyway. But I am not an electronics expert, just my opinion.
edit: sorry typo in original comment: "I got one without solar and remote charging" - just plain powerbank without any additional crap.