UPS / 12v car power for raspberry pi

A project log for Off-grid GPS (race) tracker client and server

GPS tracker map server and client for use in remote locations with no internet coverage or mains power.

stevesteve 12/01/2016 at 16:110 Comments

Every man and his dog needs to power their Pi from a battery, and deal with filesafe shutdown, but I can't get one that works!

I'm now on Pi UPS number 3 in trying to find a system that will work - I want 'idiot proof' power - plug it in to cigarette lighter socket and it starts up. unplug it and it gracefully shuts down without corruption. Plug it back in and it reboots automatically.

With the LoRa board and the LCD display as well as fairly processor intensive operation and wifi, the power requirements of the setup are over 1.5A@5V.

I tried first an early generation UPSPico from modmypi, but this had pin conflicts with the LoRa module.

I then tried a LiFePO4weredPi UPS, but the version available at November 2016 was limited to 450mA. I could just about get it to work if I isolated the LCD backlight 5V power from the Pi power, but then the battery still drained as there was about a 50mA deficit. I might wait for the 18650 version... the form factor is great.

I then tried an ebay CPT 12V to 5V 15W (3A max) power supply, but this was atrocious - voltage at no-load was a healthy 5.15V but dropped to around 4.75V under >1A load.

I then tried a new UPSPico from modmypi (HV3.0A Stack). This works fine with an official mains-to-micro USB adapter, but with anything else I struggle with current draw brownout over any of the USB to micro USB cables I have tried, and any of the 12V to 5V USB cigarette lighter adapters I use, even though they claim 2.1A output. When the UPS Pico charger kicks in, even the 2.1A output droops to ~4.7V and causes the UPS pico to brownout.

Next to try:

1) homemade USB micro cable to reduce cable loss

2) LM2596 adjustable buck regulator to homemade USB socket to boost USB voltage available.

3) UPS Pico HV3.0A stack PLUS, which has an external 7-24V input that I will wire to a 12V cigarette lighter socket directly (fused!)

4) LiFePO4wered 18650 version.