Jump Starting a DA-40

[Jean]

I'm not sure if it is the same in a DA40, but you definitely can jump start a DA20 from the EPU. There is a procedure for it in the flight manual. I did it a couple weeks ago.

Yes, there is a relais for the EPU as well, if I remember that correctly. But not in the DA40. And there is nothing in the flight manual about jump starting or starting from an EPU. So if the battery is low because of a long winter, what do you do? Just turn on the master switch, plug in an external battery in parallel, and crank the propellor with the starter, then, after the engine runs, unplug the external battery?

There is a relay for the EPU in the DA40 too. See page 7-37 in the AFM. The relay is powered by the third pin (the smaller one) of the EPU Cessna type plug.
I bought a jump plug at Aircraft Spruce. If you want to start the engine with a flat battery, you just hook the external battery to the jump, switch Battery on and start.
I use it mainly for avionics supply with a CTEK 24V charger I bought from accubat.fr. You just need to plug the external power and all the avionics starts. You don't need to have the battery switched on.
There is also a charging mode. I tried to get it on this afternoon (it was the first time since november that I could reach the hangar, too much snow) but I couldn't get it work allright. I didn't have time enough to sort the problem today. I will do that this WE. Normally, with the Battery switched on and the Battery Breaker pulled off it should work and I could leave the charger plugged as long as I want (like the Battery Minder). There is also a temperature sensor for current regulation.
The Battery Minder requires a hard wiring. I guess it requires a shop sign off.

[Kyle]

Hello all, reviving an old thread here...

After discovering that I had a dead battery, I followed the procedure to start with external power. Everything went as expected and the engine started normally. After running for several minutes, I turned off the "ALT" side of the master switch to make sure that the ammeter reading dropped per the procedure and that the battery continued to power the devices. When I did this, I lost all electrical power. Turning the "ALT" switch back on did not restore power so I shut down and removed the battery with plans to charge or replace it.

I just reviewed the schematics and it looks to me like it is not possible for a dead battery to be charged by external power or even the alternator after starting with external power. It looks to me that the coil of the battery relay can only be pulled in using power from the battery. So if the battery voltage is lower than the voltage required to pull the relay in, then the battery can't be charged without removing it or connecting a charger directly to the battery as the battery relay would never connect the battery to the bus.

It seems odd that the circuit would be designed this way. Maybe I'm missing something as there are several different versions of the schematic but I'm pretty sure that's what happened to me and would also explain why switching the "ALT" switch back on did not restore power as there was no power on the bus to switch the alternator control back on. Has anyone else experienced this?

[blsewardjr]

My battery went completely dead recently on a trip in 2003 steam gauge DA40. I was told by my Savvy help desk that we needed to remove battery and re-charge so that's what we did. A couple of days later, I attempted a start. Battery was too low to start but still had some power. We then used external power and it started right up. Ran it for about 30 minutes on the ground to get fully charged. No problems since. Battery is two years old.