On Thursday, January 1, 2015 8:56:58 AM UTC-8, wrote:
For now, I hesitate installing a very large amp hour LiFePO4 battery required in starting a self launch glider engine. It is a lot of energy in case of a short circuit.

Just for clarity, I am not an expert on this matter, however, it is the advice I have received from people I respect.

Tom

A starting battery need not have a very large amp hour capacity, just the ability to supply a large current for a short time. Due to the cost of the materials, engine start LiFePO4 batteries generally have 1/2 or 1/3 of the amp hour capacity compared to the LA batteries they replace while providing more starting current longer due to lower internal resistance.

A lead acid engine start battery has plenty of energy itself to start a fire - it can produce at least 1500 watts for several minutes if shorted. I don't think there is much difference in safety in this application between LA and LiFePO4. In fact the Lithium is probably safer, since the better ones have a BMS that shuts the battery down in an over current situation.