Help with prototype-circuit protection

[brutl_force]

Hello. First off, I am not an electrical engineer, have no college education, just an inventive mind, and smart enough to get myself into trouble.

The project: I have a automotive computer I need circuit protection for. This computer draws a maximum of 30 (dual 15 amp fuses) amps at 12 VDC on 4 un-switched battery wires. I want to protect it from voltage spikes (up to lightning would be great), positive current shorts to ground (that do burn these computers), or welding on the vehicle chassis, and protect against hooking up the battery leads wrong (WILL burn these computers).

From what I can figure, I need some diodes on both positive, and negative (it uses 3 negative wires for ground) wires.

Question: being as I have limited knowledge of diodes, what type/ratings would I need for this project.

Trying to keep the cost under $50 in components.

Any help is appreciated.

Thanks
Dan

 

[anorlunda]

https://www.littelfuse.com/~/media/...utomotive_tvs_diodes_application_note.pdf.pdf