[Arceenut]

Monitor the voltage at the battery terminals as the load is applied. The voltage will drop somewhat but should not drop more than a volt when the starter is run with no load. If the voltage drops drastically, it could indicate a fault with the starter motor or the battery. If the voltage drop is moderate at no load on the starter but drops drastically when a load is applied to the starter, it would indicate that the internal resistance of the battery is high. A dead battery.

Most starter motors will tolerate 24 volts for short duration without any ill effects. The weak point is the switch which may not be able to withstand the higher voltage and arc when the switch is released. I am using a 4s LiPo on a starter and have had no problems starting a 180 Saito but I have had to repair the switch once in 2 years due to arcing.