oddities with the electrical system

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Zacke
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oddities with the electrical system

Post Zacke »

Hey guys,

today I tried to bring the battery of the P-40 down intentionally. I switched all electrical consumers on (all internal and external light, radios, pitot, hydraulic pump etc.) and triggered the intertia starter several dozen times over about 20 minutes. The battery seems not to discharge. Even when I go to the hangar there's absolutely no message concerning the battery (or the starter).

Then I used the apu and it seems to be weaker (with starter) then the battery after doing all the things mentioned above.

Does the P-40 have a battery like a diesel uboat or is something wrong here? Maybe it has something to do with that one: viewtopic.php?f=82&t=70258

Thanks in advance,
Zacke

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Scott - A2A
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Re: oddities with the electrical system

Post Scott - A2A »

Hi Zache,

I will test this today and monitor the battery power (volts, amps, etc.) and see what is going on.

Scott
A2A Simulations Inc.

Zacke
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Joined: 27 Sep 2018
Location: EDNY

Re: oddities with the electrical system

Post Zacke »

Hello Scott,

sorry - don't want to plague you with this electrical stuff. But I discovered it and wanted to share it with you just to make that bird even better...

Regards,
Zacke

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Scott - A2A
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Re: oddities with the electrical system

Post Scott - A2A »

Hi Zacke, I tested the battery today using the pitot heat, nav and landing light. Under this load it took approximately 1 hr for the battery to discharge. I was actually running and holding the starter inertia wheel and as the battery neared a complete discharge the wheel ultimately stopped as it should as the drag overcomes the dropping current available from the battery.

Also batteries power to charge isn’t linear meaning the battery will keep putting out pretty good power until it’s close to being dead. If you were to do this test and come back over an hr later you would have a completely dead battery. They are this way by design.

Your electrical dependent gauges will die somewhere under 12 volts and if you go into the maintenance hangar with this dead battery your mechanic will charge it and leave a note for you.

I hope this helps,
Scott
A2A Simulations Inc.

Zacke
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Joined: 27 Sep 2018
Location: EDNY

Re: oddities with the electrical system

Post Zacke »

Thanks a lot for coming back with this, Scott!

Good to hear there's nothing wrong with the "simulated wiring" (except the ammeter :wink: ).

But is it actually realistic the battery keeps the starter running an hour with the other consumers mentioned online? I thought the battery should be much weaker respectively the starter should draw much more battery power. With a battery like this a gpu should be obsolete...

With the civ P-51 even with only the instruments and the nav lights on you can see the battery droping quite fast via the volt meter. Can't prove that with figures but it seems the civ P-51's battery is much weaker (seems to be more realistic) than the P-40's. Maybe I'm wrong.

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Scott - A2A
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Re: oddities with the electrical system

Post Scott - A2A »

Zache most of the energy for an inertia wheel is to spool it up. Once it's moving to keep it holding at the same speed only takes enough current to overcome any friction drag. The friction cost of the inertia wheel may be a bit low, not having one to test directly I can't say for certain. If this was a direct drive starter the battery would die very fast.

If you use the headlight alone, the battery should keep this on for roughly two hours based on the draw I'm seeing.

Scott
A2A Simulations Inc.

Zacke
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Re: oddities with the electrical system

Post Zacke »

Thanks for the clarification, Scott. Overall very good news!

Compared the the direct crank starters are the inertia starters even at risk to to overheat and do they wear slower overall? How is that modelled with Accu-Sim?

Zacke

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Scott - A2A
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Re: oddities with the electrical system

Post Scott - A2A »

That's a good question on the inertia starter. I don't know. The direct crank starters will definitely overheat in rather short order too so we do model the heat generated with our direct starters and subsequent breakdown if you let it get to that crazy high temp. Just because this is where we have experience.

Scott.
A2A Simulations Inc.

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