Bidirectional USB-C PD Charging


Has anyone looked in to this for DIY packs? The best I can find (for boards/modules) are 18/24w max USB-PD modules that only work for 3.7V lithium batteries, 1-series.

I've bellyached about this in recent years on here but now there are so many portable power station 'solar generators' out there that offer it (with 3S 3.7v / 4S 3.2v lifepo4 inside) that I can't imagine it's proprietary and these no name companies have rolled their own.

For the power stations I guess it's possible they're negotiating 20v from the PD source and piping that in to their MPPT. I know some power stations with 120V input have a 24v PSU inside to do exactly this. I just kind of doubt it though, since no name power banks are doing it too and they lack MPPTs. Somehow Monoprice's Obsidian 26800mah power bank offers 87w charge/discharge, and while I'd be happy with 60w, 87 would be cool too.

Reason: I just bought a spot welder and am assembling my third portable 12v pack, 12 cells in parallel * 4 series for an estimated 640wh. Plugging in for ~12 hours assuming it was dead wouldn't be the end of the world, it'd in fact be my preferred method of charging before a trip.

Would allow me to charge from a wall charger, my 90w USB-PD car charger, or even B2B house bank to portable pack.

Also, has anyone found a source for 8mm panel mount jacks? Those are featured on damn near every power station but I can't find any to save my life. I know they also go by 8.0x2.5mm or 7.9x2.5mm, all dead ends. If no name brands have these components, where the hell are the modules and jacks on ali/banggood/amazon/etc?!

Chris Boyd

Maybe this could work for the USB wired to an MPPT or BMS?

Mentions needing an I2c to configure, but maybe there is another reason to have a small microprocessor onboard. If nothing else, it hints to what it’s using: standalone controller from STMicroelectronics, the STUSB4500.

I’m try to do some similar stuff and was also looking at this as an intelligent SoC and Lifepo4 charge manager. Hadn’t thought about the USB PD angle to charge, which is interesting.

This what I cam across which might help certain other areas:

If you look at the technical docs, it has a number of use cases(pg 24) for monitoring charging. You’d have to use a BMS in conjunction to manage the pack balance and overall cell health. In general this is limited to device is limited to 60A, so maybe too small for your use case of welding, but definitely works for some things I’m thinking about and average overlanding loads .

Chris Boyd

A blog I found on the STUSB4500 controller that might be interesting

There is a reference in there to a flashing utility for one time programming of the device via I2c

Edit: and following the rabbit hole, a link to a device you can purchase with optical programming via screen from a web page. Too cool. Out of stock at the moment, but worth hitting up the maker if there is interest.

I might try this tied to an MPPT on my small 60Ahr DIY portable pack!
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I think the things you linked are just decoys/spoofs/triggers and negotiate the voltage from the power supply. These aren't bidirectional :( I actually have several in 20v and 12v. 12v have powered a home router and some other gadgets, and the 20v I've used many times to charge my existing portable batteries. Probably 10kwh charged through a single one @ 20v with no issues at all. Doesn't even get warm.

I added a 2.1x5.5mm metal bodied "10 amp" panel mount jack that goes straight in to a Victron MPPT PV input. It works great charging from my 87w macbook brick with the max charge current set low on the mppt to keep brick happy. When I want to fast(er) charge I just use a 10 amp 24v power brick which has a robust 2.1x5.5mm jack as well, with charge current set on MPPT to not exceed 7 amps -24v at the "10 amp" jack (168w). They're only like $5 a pop for these adapter-decoy-spoof-trigger things and they're much harder to break than the programmable ones. My 100w folding (non suitcase) solar panel also has a 2.1x5.5mm plug so it's all very convenient. This MPPT is in its own pelican knockoff case with temperature controlled exhaust fan and intake vents connected to the load output.

Trying to make the new pack as compact and self contained as possible so that's where the bidirectional appeal comes in to play, no tag-along MPPT box, or stuffing one inside. One port on the side for charging and discharging, no cig socket even. A PD USB hub if I want to charge multiple things at once. The highly critiqued Apple approach - a dongle for every need 😄 building this specifically to charge my laptop while I work, because building a 640wh power bank (I think I'll be in about $200 with case and BMS) sounded a hell of a lot cooler and cheaper than buying a bunch of PD power banks rated at 100wh or a 240wh clown company power station.



Active member
I think you would want something the the capability outlined here.

Input range of 2.85V to 80V and output range of 1.3V to 80V. I doubt you'll find this complexity on the typical little DIY consumer boards.


With the PD standard, you have a Source that "offers" a set of standardized voltages (at different Watt capabilities)

and a Sink that signals what it wants

which the Source then supplies best it can. Usually the target (sink) does the flow control regulation and charge termination.

I cannot visualize how that standard can be adapted to "bidirectional" without putting in path-switching relays or something.

John Shaffer

New member
You might want to checkout

8mm 3 pole power connector
From Newark NJ. Electronics
Lumberg 1614.07 dc7909 8mm male 3 pole 10amp.

1636.07 female panel matching 10amp

I’m working to create a custom cable to alternately power my Bluetti ac50s to it proprietary 8mm input plug.

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