This has been bugging me since day 1, but i never really bothered looking into it. Im also not sure if this has been covered before.
So, there seems to be magic current battery current coming out of nowhere. I thought there was some weird configuration but ive come to conclusion that its a bug.
A simple explanation of how these simple battery circuits work. These are very basic and everyone should know this from preschool. Here are some basic rules(cases).
When the alternator is off, then the battery provides ship power.
When the alternator is on, then the alternator provides ship power + battery charging.
If the battery is fully charged then the battery current is 0 and the alternator provides ship power.
When the alternator is on, but the battery is disconnected, then the battery current is 0 and the alternator provides ship power.
When the alternator is on and the engine is off, then the alternator is not providing power and the battery provides ship power.
Using SimVarWatcher (provided in the SDK) you can see the current going in and out, even on planes without G1000s and premium planes.
For my testing i will be using a 172 (JTA) with an alternator that can provide 100A, a battery that does not drop voltage, and the 2nd battery disconnected to make the calculations easier.
- Case 1: When the alternator is off, then the battery provides ship power.
I have setup the lights etc to draw ~40A.
As you can see here, the alternator is providing 0 Amps, the Battery is providing 40A. Ship must obviously draw 40A
If I were to turn on the alternator, then the alternator should provide the 40A ship current however
- Case 2: When the alternator is on, then the alternator provides ship power + battery charging…
We can already see something funky going on. Alternator current is now 46A and the battery is charging at 54A. Meaning ship current is negative 8A?
Even if you were to ignore the 54A going into the battery, the ship power has increased from 40A to 46A?
46A (ship current) + 54A (Phantom battery charge) = 100A.
Those are the 100A that the alternator is providing. But the simvar shows the alternator only providing 46A.
What seems to be happening: The Alternator is providing ship power and the rest of the current that the alternator can provide is all being burned into the battery.
Also the 6A current increase out of nowhere. I cant explain this
- Case 3
Similar to case 3, but again this weird 6A increase on the ship load.
The main bus now seems to be burning the 54A out of nowhere.
- Case 4
Please ignore the readout on the G1000, this is custom code i have implemented to provide a current current readout on the JTA and Diamonds. Look at SimVarWatcher!
Now we are back to 40A ship current, which is correct. However the alternator is still providing 40A, except that its not. The battery is losing 40A, and the alternator simvar is broken. Eventually the battery will drain and die
So to sum up the problems that i have discovered.
- The alternator causes higher current over all
- “phantom” current is generated from nowhere and burnt into the battery or main bus
- The alternator displays that it is generating current when the engine is off, but actually isnt
I hope this wasnt confusing and that the devs can take a look at this