I want to protect from dump, reverse battery and spikes. If I put the diode to the beginning then I should add 2A fuse, otherwise with reverse battery I can see smoke. Overcharging is not a problem, cause the diagram has voltage regulators NCV4275 (input voltage up to +45V) and NCV8774 (input voltage up to +40V). Rest of the voltages are not so critical and are solved with resistors/zeners.
Doesn't bidirectional TVS protect from negative spikes? I chose it to protect positive and negative spikes.
I added diode for reverse battery and 18V TVS is for secondary protection.
I can't use more complex devices for protection as they need more space and I have very limited space in my project.
If I had more space I would use triac, it would give nice protection. Even RBO40-40G is too big, cause I can only use 3 mm in height.
The details I chose are all available in Farnell and the SMD parts cost 1,2 EUR and that is only a small portion of the total cost of the project.