For various reasons, I keep several very large four cell lithium-polymer batteries in my vehicle. Each of these batteries is rated for over 100 amps of constant current, with 10 second burst ratings of twice that. Wired in parallel, they could easily provide enough power to start my vehicle.
However, a fully-charged 4s LiPo is normally 16.8 Volts and the electrical system on almost all of my vehicles is 12 Volts.
All of my life, I've been told that providing more than 12 volts to any modern car will damage the sensitive electronic components. Obviously, this can't be entirely correct, as a typical alternator can provide up to 15 Volts. I've also seen videos of people using 4s LiPos much smaller than mine to start their cars. I even know one shop mechanic who claims he used to jump 12 Volt vehicles with 24 Volt systems.
So, essentially, I'm wondering what the maximum safe voltage is for jump starting. Would 16.8 Volts be safe? What about a "storage charged" 15.28 Volt battery?