Universal emergency phone charger

[maxkracht]

Most of the city I live in has been without power for going on a week due to an entirely unexpected hurricane like event. In the first few days there were no stores open, no gas stations, and if there were you probably couldn’t get to them. Cellphone and internet service was spotty, but still existed. There were limited options for phone charging to get critical information. After the second day of this, I figured out the DC adapter from my car doesn’t mind 18v from my drill batteries. This made me wonder if there were a simple circuit or chip(s) that could boost low voltage batteries to 5v+ and drop higher voltage battery packs to 5v. Any ideas? I plan to do a bit of research after the power goes back on. Curious if this already exists and would be easy to diy.

[pompeiisneaks]

They sell buck/boost converters on ebay/amazon etc all the time... they aren't expensive and can usually take in like 20v and output 5 etc

[maxkracht]

Thanks. I assumed I would need a Separate boost converter and a buck converter and would have to combine them in a cleaver way. I totally missed that combo boost-buck converters were a thing. Seems pretty obvious now.

[xtian]

I received some of these last week, seem to work very nicely:

https://www.ebay.com/itm/332711109230

Input Voltage 3.2V-40V
Output Voltage 1.25V-35V
Output Current 3A (Max.)
Conversion Efficiency 92% (Max.)