A battery with an ability to provide a large cranking current is more
important than the Ahr rating. Provided that you use one of these a17Ahr
battery should be sufficient. I started off with a standard sealed lead acid
battery but I soon found that cold starts after lengthy lay-offs were
marginal. Once I changed to the newer type it was obvious that much more
cranking energy was available. As it is not practical to hand prop a Rotax
it is wise to have an external power connection to allow for the day the
battery lets you down whether it is due to battery age or just leaving the
battery master on by mistake. The 912S is much more critical of battery
state then the 912 or the 914 due to its greater compression ratio.
Nigel Charles
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