Embedded Planet, Inc.
epConnected Vehicle | Product User Manual
Version: 1.0.0 | 25 Feb 22
Embedded Planet, Inc. | 31225 Bainbridge Rd Suite N, Solon, OH 44139 | 216-245-4180 | www.embeddedplanet.com |
Page 14 of 39
9.
Power
The epConnected Vehicle board is designed to be powered by 12V through an OBDII cable connected to J5. The
12V input on the PCB includes input protection elements designed to guard against egregious fault conditions and
withstand alternator load dump conditions. A 1.1A, 60V resettable PTC fuse (polyfuse) in line with the 12V input
protects against potential high input current levels. A series rectifier diode at the 12V input assures a one-way flow
of energy at the connector. There is a TVS diode positioned for transients at the 12V input with a reverse stand-off
voltage of 22V and a maximum clamping voltage of 35.5V. A capacitor bank provides conditioning & stability on the
system side of the protection circuitry.
9.1.
Power | Battery
The battery backup option for the epConnected Vehicle includes a small LiPo battery. This battery assists
in the safe & consistent shutdown of the system when the +12V system power becomes cut from the system
due to the vehicle turning off. If the system is in the middle of a transmission, sensor reading, or other sensitive
process, the backup battery can help ensure that the process is carried through to completion before the
system is fully shut down. A voltage monitor input to the epConnected Vehicle system monitors for the
presence of 12V power and alerts the system if the power is cut off, allowing the system to move into a state of
preparation for soft shutdown.
The battery provided with the epConnected Vehicle is a 3.7V, 500mAh rechargeable Lithium-Ion
Polymer (LiPo) battery. The output ranges from 4.2V when completely charged down to 3.0V. The battery
includes protection circuitry to keep the battery voltage from going too high or low; the battery will cut out
when completely dead at 3.0V. When power is applied through the 12V system the battery charging is active.
The battery is only meant to be charged using the onboard circuitry using the JST battery connection; never
charge the battery using a non-recommended charging method. For the epConnected Vehicle the battery
charge current limit is set to 450mA, and the charge termination voltage is set to 4.2V. The charge manager IC
used is the Microchip MCP73831. More on the Microchip MCP73831 can be found at
https://www.microchip.com/en-us/product/MCP73831
.
If the 12V input is cut (e.g., the vehicle that is supplying power is turned off), the PWR_STATUS GPIO line
will transition from high (3.3V) to low (0V) to indicate the loss of system input power. The system can then
finish its current operations using the battery backup and then do a safe power shutoff once ready. The
PWR_STATUS line corresponds to GP5 (pin 15) of the MCP23008 LiPo charger IC. This IC is connected to the
Agora over I
2
C bus using the address 0b01001110 (0x4E).
