Small battery as solar-to-laptop (USB-PD) buffer


New Member
Apr 7, 2021
I've got a 120 watt (at 18 volts) unregulated solar panel. It also has a (presumably, regulated) USB-C-PD output which can connect directly to a MacBook Pro. However, this connection isn't stable--the laptop will continuously connect and disconnect, and it seems like a risk to the laptop to use it.

I'm looking for a simple way to buffer the solar panel (via the unregulated 18 volt barrel connector) without adding much weight, bulk, or complexity, ideally without needing to cobble a full kit together from individual parts. The small (100 wh -ish) external all-in-one batteries would be ideal, but most of them don't accept charge through the barrel connector, and even when they do they seem to charge very slowly (e.g. 60 watts or less), which wastes a lot of solar capacity.

I found this item, and the manufacturer claims it'll work with my setup, charging at 90 watts max, which is as close as I've been able to get to 120 watts in something this size. There is an adapter I could use to achieve USB-C-PD output from the battery. However, this product is not designed for a solar panel, and I'm fairly sure the battery lacks a solar charge controller. Is this a critical issue, or will it charge fine? I am not educated enough to know.

Or if there's a simple alternative that would be better, I'm all ears.


Swears he didn't start that fire.
Sep 12, 2020
You could get a cheap solar charge controller for under $15 ( ), some 3s 18650 holders ( ), and a cheap BMS ( ).

Grab some 18650's from batteryhookup or eBay, go with a 3s2p setup, and it will act as a buffer for a drop in panel current / voltage.