WingsOnWheels
Well Known Member
I am currently running one Mag and one EDIS-Based Electronic Ignition. In the future I am going to replace the mag with a second EI, but I first need to ensure that the electrons keeps flowing in the event of an emergency.
Goals for the system:
1) Ensure that the EI receives power in the event of a main buss or battery buss failure (or both), including a battery buss short to ground or battery disconnect.
2) Provide a minimum of 30 minutes reserve plus significant margin in the event backup battery condition is less than ideal.
3) The backup system should engage without any human intervention
4) Integrate with my existing electrical architecture without a significant rewire.
According to what I have read and been told on this forum, a backup battery of the same chemistry (lead-acid in this case) does not require a separate charge controller and that internal resistance is sufficient to limit charge current (please let me know if this is incorrect). Nominal current draw is ~1.5-2amps per ignition at cruise RPM. The battery I selected is a PC 1250 4ah SLA. This should provide at least 60 minutes of reserve. In the event that 60 minutes is insufficient, I can shutdown one ignition system and double that reserve.
The only downside I see with this arrangement is that the ignition buss is always hot, so it is extra critical for ensure the ignition switches are turned off after shutdown (of course that is always critical). Not included in this schematic, but in-work is a warning system for backup battery condition and a warning for leaving the ignition on with the main buss off (this can also act and the "backup in-use" warning.
Schematic (excuse the poor drawing, does the job though):
Goals for the system:
1) Ensure that the EI receives power in the event of a main buss or battery buss failure (or both), including a battery buss short to ground or battery disconnect.
2) Provide a minimum of 30 minutes reserve plus significant margin in the event backup battery condition is less than ideal.
3) The backup system should engage without any human intervention
4) Integrate with my existing electrical architecture without a significant rewire.
According to what I have read and been told on this forum, a backup battery of the same chemistry (lead-acid in this case) does not require a separate charge controller and that internal resistance is sufficient to limit charge current (please let me know if this is incorrect). Nominal current draw is ~1.5-2amps per ignition at cruise RPM. The battery I selected is a PC 1250 4ah SLA. This should provide at least 60 minutes of reserve. In the event that 60 minutes is insufficient, I can shutdown one ignition system and double that reserve.
The only downside I see with this arrangement is that the ignition buss is always hot, so it is extra critical for ensure the ignition switches are turned off after shutdown (of course that is always critical). Not included in this schematic, but in-work is a warning system for backup battery condition and a warning for leaving the ignition on with the main buss off (this can also act and the "backup in-use" warning.
Schematic (excuse the poor drawing, does the job though):
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