Need help on charging the battery??

[Steven]

I’m also interested if this works to charge a dead battery.

[Mjwatlanta]

I’m not having any success getting the Schauer 24 V portable power supply/charger to deliver power to my 2019 DA 40 NG so that I can play with the avionics without draining the battery. I followed the directions provided by Schauer and restarted multiple times to no avail. Instead, I simply watched the battery voltage drain slowly but surely instead of either staying the same or going up as I expected / hoped it to do. I did note that the lights on the charger were on but the fan was not.

I did try multiple ways of turning on the electricity including turning the engine master as well as the electric Master ( key). When I turned on the engine master the battery drained so fast I could see it move on the engine screen. So, I did not try that for very long.

Perhaps I have a defective charger/power supply. But, before I go to the trouble of turning it back I would appreciate any ideas as to how to solve this problem.

Thanks in advance. Michael

[dmloftus]

Hi Michael,
If you have a voltmeter, check that the smaller pin has 24V on it. That is needed to energize the APU relay. Call me if you still have questions.

[dmloftus]

Reading back through this thread and I had a few questions. It's mentioned that you just have to kick the 24V EPU relay for a short period to get it to activate connection to the battery. The way I read the schematic is that you need to power the small pin on the Cessna connector continuously to keep the solenoid energized. I do not see a feedback loop that would allow it to self-energize. What am I missing?

Also, the schematics show a link between ALT and BATT switches, which would imply a double pole switch that works in unison. My 2008 DA40 XLS allows me to split the switches, and switch BATT on independently of the ALT switch. Is that not the case on some aircraft?

Is anyone charging and conditioning through the Cessna connector? Is it legal to do so? As an electrical engineer, I could not see paying the hefty price for an aircraft GPU. I bought a 10A 24V Omron power supply off EBay and a Cessna plug from Aircraft Spruce and wired my own, just tying both positive pins together. I originally created that to load databases and play with the G1000. I recently bought a charger/conditioner and I'm currently direct connecting to the battery occasionally to desulfate. But I'd like to do so more often without pulling the cowling. I also bought the permanent direct connect kit and plan to have it installed by my A&P during my next annual or service (ridiculous that I can't legally do myself). In the meantime, I can easily modify my homemade GPU to break the line for the larger + pin, power the EPU relay on the smaller + pin from that unit, and connect the charger/conditioner to the larger + pin on the Cessna connector, tying the grounds together. Anyone see a problem with that?

[Rich]

Is anyone charging and conditioning through the Cessna connector? Is it legal to do so?

The attached picture shows (schematically) a way to use the GPU connector in both roles. It does exactly what the specialty connector does. The side-effect is that the (+) pin on the jack s always hit, hence the fuse. One could also fashion an insulating sleeve for this pin when not connected to the GPU or BatteryMinder. It'd be legal if you can get an IA sign-off.

[CFIDave]

You have to turn the key to Electric Master ON position to get GPU power to a DA40NG (unlike the DA40 XLS, or even a DA62, where all you need to do is power up the GPU). Do NOT turn Engine Master switch ON.

The 3rd pin on the external "Cessna connector" must be energized to close the plane's GPU relay, otherwise GPU power will not be supplied to the aircraft. Some GPUs have an additional 2-way switch labeled something like "GPU vs. charger" to energize the 3rd pin, so you might want to check for this.

Assuming you're able to close the plane's GPU relay, if the GPU is then putting out a higher voltage (e.g., 28V) than your DA40NG's 24V battery, the battery will charge. So yes, that will permit you to charge the battery through the external GPU connector.

[AuRod]

Ever thought of putting a diode in series with the fuse? Then the middle pin wouldn’t be live when disconnected.

[Rich]

Ever thought of putting a diode in series with the fuse? Then the middle pin wouldn’t be live when disconnected.

Yes, but there is a wrinkle with that. Specifically, when using a BatteryMinder, the forward bias voltage drop for diodes is significant enough to compromise the effectiveness of the various BM operating modes.

[dmloftus]

Are people connecting battery minders through the GPU pins? Any downside? Probably a bit more resistance than direct-connect to battery, but BM's don't usually drive a lot of current.

[Mjwatlanta]

Dave, this comment relates to the NG where the battery is in the back so it might not have any meaning to the 180. I posted about this elsewhere on DAN too. I wanted to connect a battery minder through the GPU (Cessna connector) pins. At least on the NG, that will not work. So, my idea was to insert a switch into the circuit between the GPU plug and the various relays it connects to before it gets to the battery. The plan was to make is so position "ONE" was no change to the GPU path and position "TWO" would go direct to battery minder pigtail that would be connected to the battery directly. Diamond said - wait for it - NO. So, if I want to comply with Diamond, to have a minder on my battery, I'm going to have to disconnect it from the airplane and then hook up the minder. I did discuss this with Southtec and they want to see the various parts that would be involved. I'm in the process of sending Glenn and Chris battery minder instructions and photos of the parts. Stay tuned as I have not given up on this plan. Michael