so, I want to install this motorbike battery (just like a car battery, but smaller) to give my pc power while starting the motor.
Problems: the diode. It can't be a normal one cause, imagine the little battery is really dry and then I start the engine and the alternator really gives a lot of power to recharge the little battery... well, i found out i need a power diode. They dont have them anywhere around, but in a ship shop. thats right, not at any car dealer or machanician, but a stupid boat shop. it seems in boats they do that a lot, putting batteries in parallel with diodes. So this thing cost like 40E !! crazy! its go a dissipator and all.

You got any better solution? I mean, apart from using a non rechargeable batt or a bigass capacitor?

steels