Amplifier, Battery & Fuse Question

I have Wetsounds SD2 and SD6 Amplifiers. Also, I have a Dual Battery set up (both Deka AGM Group 31 batteries) with a Perko switch (1-Combine-2-Off Positions). The main battery is for the boat and other factory installed boat accessories while the second battery is STRICTLY for the sound system. The reason why I have this Perko switch is so when engine is running, the alternator will also charge the ‘Sound System’ battery while in ‘Combine’ position.

1) I am running 1/0 AWG Marine Grade Battery Cables from the Battery to the Perko Switch. For the ‘Sound System’ battery, should I install a 300A ANL fuse right after the +VE terminal of the battery or should I have this ANL fuse right after the Perko switch terminal? I guess my question is, would the 300A ANL fuse interfere with normal operation/ charging of this battery while in ‘Combine’ engine running position?

2) From the Stereo Head Unit, I will be running a remote trigger wire for the 2 Amps and WS-420. So I believe I definitely need a SPDT relay. What size fuse on the 12 Volts relay power would be adequate to support the 2 amps and WS-420 without circuit interruption?

Thanks in advance

I'm assuming that your amps are wired to your dedicated stereo battery terminals either directly or via distribution blocks. If this is the case, put your fuse along the positive lead between the battery and the amps. Place the fuse close to the battery (12 to 18 inches)

As for the remote turn on lead, the amperage through that line will be minimal. A 5 to 10 amp fuse should be all you need.

1) It depends on how close the Perko switch is to the batteries. If the switch is very close to the batteries, as it should be, then the fusing can go between the Perko and the amplifier distribution and as close as possible to the Perko switch.
Note, if using a dual battery manual switch, everything (alternator/starter feed, helm buss & audio supply) should access power/batteries only through the Perko switch common out post and not battery direct. The exception would be the float switch/bilge pump on a moored boat.
Now an ACR/VSR scheme is different.
2) It's about protecting the boat from the supply wire based on it's gauge (14 ga.?), length and current flow. Each one of those three devices may require 1/20th of an amp to trigger on. So 1 amp should do it. I don't want to ever replace that fuse unless something more catastrophic happens so I would probably run a very safe 3 amp fuse.

Russ & David,
Thank you very much for your responses. The Stereo Battery Cable to the Perko Switch is about 11 feet long. So I will definitely fuse it right at the battery terminal.

Also, I will be using a 3 amp blade fuse for the remote trigger Relay power.

Thanks.