Considering that USB C can output up to 20 volts and 5 amps, what would be required to wire up a 12 volt battery to a usb type c female port?

I want to charge my phone using my motorcycle's 12 volt battery at full potential of usb c.

Assuming I purchase a simple IC for managing and negotiating the power delivery over usb c such as this: https://www.rohm.com/products/interface/usb-type-c-power-delivery/controller/bm92a50mwv-product

What would be my next step?

  • 1
    \$\begingroup\$ en.wikipedia.org/wiki/USB#Power_Delivery_(PD) You'd need some ICs to do the negotiation of the power mode and deliver the proper voltage, not just the raw battery output (which can range from 14V to 10V) \$\endgroup\$ – Wesley Lee Apr 3 '18 at 1:58
  • \$\begingroup\$ it's complicated. as of now, you can get almost as much for a phone (not laptop) from a beefy 5v source, but that won't be the case for long as more phone support the newer profiles. \$\endgroup\$ – dandavis Apr 3 '18 at 2:02
  • \$\begingroup\$ The phone expects only 5 volts to start with, then puts in a request for a higher voltage. \$\endgroup\$ – VTNCaGNtdDVNalUy Apr 3 '18 at 2:48
  • \$\begingroup\$ Solution: go to Walmart (or AliExpress) and buy a 12-V car charger with PD functionality. \$\endgroup\$ – Ale..chenski Apr 3 '18 at 14:28

Your next step (which should be your first step) is to figure out if "your phone" uses late edition of PowerDelivery and can negotiate anything above 5 V level.

If it supports PD and can use the elevated 12-V voltage profile, you can proceed with:

(2) Make a 12V-to-5V switcher, to provide the 5V source for default power path (because everything must start with 5V)

(3) Since you already made your selection for BM92A50MWV chip, you need to read carefully its datasheet, not just the matketing description of it.

(4) Then you will need to select any MCU that supports I2C interface, and write a program which will communicate to the BM92A50MWV chip which power profile you can/will offer, which would be obviously a 5-V (with whatever current you can manage with 12-to-5V switcher), and the 12-V profile with whatever current your battery can deliver. This will allow the BM92A50MWV chip to spill out its right capabilities to external cable and to the connected "your phone".

(5) upon successful completion of PD exchange protocol (done by BM92A50MWV ) and accepting the phone request for the 12-V profile, the chip will likely automatically switch from 5V to 12V path, although it is not clear from the datasheet.

(6) before doing all this, it is highly advised to procure a reference platform for the BM92A50MWV if you can find one, with code samples and internal register definitions. If the design doesn't exist, even after contacting ROHM engineering, change your selection of CC controller IC, and start over.

That't about it.

| improve this answer | |

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.