Engine Bench Power Supply

[chadjmccolm]

Context

The current power supply has some limitations that prevent it from being used full-time as well as some
unsolved problems. Ideally, both can be addressed.

The power supply is limited to 40A continuous however the starter requires somewhere around 110A
(at best estimate) to start the engine. A car battery could easily supply this so long as it was sufficiently
charged. A car battery however will not hold its charge unless it is wired into the stator on the engine
through a rectifier. A suitable (supposedly – should be double checked) rectifier is currently on the car
and the stator wires are the only wires coming off the engine which are unused.

The other issue has an unknown cause. When running off the current power supply, sometimes the
output drops to zero and the engine shuts off. This may be due to vibration, spikes in the current draw
from the coil, or something else entirely. The only solution found so far is to unplug the power supply
entirely and shake it.

The spark plug coil takes 14A in bursts, the fuel pump takes about 7, and the Microsquirt takes about 0.1A.

Outcomes

The outcomes of the project are as follows

• provide power to all the engine electronics for bench testing

Constraints

• the draw of the individual components cannot be changed
• the power supply must not be so large that it impedes safety around the engine when it is on the bench and engine dyno or causes a trip hazard

Related Issues

Related issues include:

• AFR/O2 sensor  #24 AFR/O2 sensor
• Switchboard Design #23 Switchboard design
• Wiring Schematic Fuses #18 Wiring Schematic Fuses
• Wiring Schematic Cleanup #17 Wiring Schematic Cleanup
• Bench Wiring Harness Cleanup #16 Bench Wiring Harness Cleanup

[chadjmccolm]

The power supply was elevated on a block of wood to dampen vibration and that solved the immediate problem. Issue closed.

Learning: power supplies need to be isolated from vibration.
Going forward: start using a battery to power everything or isolate the power supply from vibration.