http://www.ebay.com/itm/231412173116?_t ... EBIDX%3AIT
it is origianlly supposed to be for a rechargeable battery pack, but is shipped without the batteries.
I have tested the voltage and it comes out at a little over 4v. Is that safe for an ESP-01?
if 4v is a a litthe to rich - what is th ebest way to shave 0.7v of?