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John, I am sorry, but aren't you the one who uses unapproved, for starting, LiFePo4 batteries in your ASH-26E for engine starting? I am surprised you seem to lecture others while you do questionable things yourself, just saying.

Andrzej, the Schleicher maintenance manual (which specifies SLA batteries for both engine AND avionics) was written in 1995, and is not likely to consider a battery technology invented in 1996. Anyone flying an ASW 27 or 29 should similarly not use an LFP battery for avionics as they are not an approved type. Yet nearly every glider supply outlet sells them for this purpose, and I note that Schleicher ships LFP batteries for both start and avionics in many of their current gliders.

I'm not lecturing (or even recommending) people to use or not use anything. I educated myself on what was required and acted accordingly based on facts, not questions. I AM asking that they use precise language, where precise language is important. Schleicher does not say "use a lead battery", rather they say "use a maintenance free lead-dry-gel battery" - because installing a flooded lead acid battery on its side near your butt is a bad idea. Even then they are imprecise - the battery they call out is an AGM, not a gel and these have different charge requirements. The terminology matters.

From 'Fiddler On the Roof' (not to be confused with Sean Fidler):

Tevye: He is right.
A Jew: He is right and he is right? They can't both be right!
Tevye: You know, you are also right!