Quote:
Originally Posted by supik
The Diode between MAIN BUS and ESSENTIAL is there just in case the ESS BUS Contactor fails.
Should the MAIN BUS Contactor fail open, ALT1 could still supply everything through the Deuce Schottky Diode incl. battery charge.
This should not happen normally;
-let's assume I have a flat battery (24Ah),
-the MAIN BUS Contactor has failed open
-ALT2 is OFF
-ALT1 (60Amp) would try to feed everything on MAIN BUS and ESSENTIAL + Battery charge
-what loads shall I expect to see across the the CB from MAIN BUS to ESSENTIAL? My concern is the 50Amp circuit breaker.
-opinions?
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Some thoughts:
- If your battery is flat, this is a hard ?ground the airplane? issue. Use a real charger to bring it back, or better yet replace it as most AGM batteries suffer permanent capacity loss if you abuse it (e.g. leave the master on).
- I suggest you eliminate the ground power jump connection. This is a left over from vacuum driven gyros and mags. In other words, never jump start your airplane. You will be launching into the ether with no clue of battery capacity, if any. On top of that, these are massively clumkly plugs with big fat wires - both are on the list of things to minimize in our airplane.
- On loads for each alternator, you will need to carefully adjust each voltage regulator to make sure you have current flowing as you think you do (for each of your primary and back up modes). Adding diodes complicates this as voltage drop across the diode needs to be measured to achieve the load balance you want.
- Running everything off the one 60 amp alternator is not an issue. Even if you have low charge lithium batteries they will not take more current than associated with the buss voltage, and buss voltage will drop under heavy current load. So unless you are doing something weird the alternator will carry the load and buss voltage will increase with time. Note however that 60 amp alternators will put out more than 60 amps, so upsize your current limiter to 70 amps. But again if you are trying to use the alternator to breath life into a dead battery, you are violating a prime rule as discussed above.
- On my planes I do add a ?shore power? breaker to the main buss. I use this to connect my 30 amp regulated power supply using a short #14 jumper cable to run the plane on the ground. 30 amps is more than enough to run the whole panel and to keep the batteries topped off (just like the alternator does). In practice with both (charged) batteries on line and all avionics up - current draw is about 10 amps.
Carl