Dual EI require dual battery?

[macwolf]

Hi, I'm getting contradictory info from several sources about the need for a backup battery on a dual EI installation. Perhaps someone can clarify?

I do want to have a backup system, so if something quits in the air, things must still keep going.

1) Yes, you do need a second battery because: The EI gets energy from the battery, so if the battery fails or the wiring from the battery fails, a secondary battery (small one on the firewall) with alternative wiring wil kick in and keep the sparks firing

2) No, you do not need a second battery because: The EI gets energy from the alternator, so if the battery fails, the alternator will continue to support the EI. If the alternator fails, the EI will get power from the battery.

Which one is accurate here? Appreciate the help.

Stuart

 

[Neil]

 

[Beej]

 

[Skybolt31]

 

[user 38]

 

[darylat8750]