foghorn757(at)gmail.com
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 Posted: Mon Jun 08, 2020 8:31 am Post subject: Physical construction of Z101 engine bus & battery bus |
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Bob,Here is what the SDS EFI manual suggest. I didn’t hit every point in my email to the group. I personally have the 2 ALT/1 BATT option.
Backup Electrical Power Considerations
Electrical power is necessary to keep the ECU, fuel pump, coils and injectors running so it’s important to think about having a backup power source available. In the case of Lycoming engines, a small backup alternator like the B&C SD8, SD20 or BC410-H SD can be fitted to a vacuum pump pad. On other engines, a small second alternator could be fitted.
If you don’t have a second alternator, you should have a small backup battery. Sizing would depend on your typical/ maximum distance between airports. Current draw of the pump, ECU, injectors and coils would be around 12 to 14 amps. A 12 amp/hour battery should give you a solid 30-40 minutes of flight time, just running the engine electrics. An 18 amp/hour one, around 1 hour. We want to be able to sustain at least 10 volts to the electrics.
We’ve found the most reliable, simple and light way to get backup battery power to the engine electrics is a single 12 to 14 gauge wire running from the backup battery, through a 30 amp ATO fuse, to a heavy duty switch, to an emergency buss where all the engine electrics can receive power. Simply charge the backup battery every 30 days and load test annually.
If you have the recommended check engine light fitted, it will warn you any time the battery voltage falls below 12.5V. You can monitor battery voltage in Gauge 3 mode.
Jeff Parker
| Quote: | On 8Jun, 2020, at 11:18, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
At 09:20 PM 6/7/2020, you wrote: | Quote: | | SDSEFI recommends 2 alternators and a battery. If you have a single battery and alternator they recommend an additional battery that is only connected to the ENG BUS for an emergency. The recommended procedure is to charge that battery on the 1st of the month and load test yearly. |
Not a particularly definitive battery management philosophy. "Charging once a month" whether needed or not? "Load test" is not specific . . . what kind of load and for discovery of what condition? Internal impedance (cranking) or capacity (endurance)? How would that knowledge augment the pilot's prospects for dealing competently with an alternator failure? How would these batteries be selected and configured in the architecture? What would the plan-b checklist look like? Recall that the ultimate goal for crafting a failure tolerant architecture is to prevent any single failure from becoming an emergency. That goal cannot be realized without first knowing the ENERGY requirements for the TOTAL constellation of hardware necessary to conduct a comfortable termination of flight within some ENDURANCE value determined by the BUILDER . . . not by some 'authority from afar' who will never ride in the airplane.
Bob . . .
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