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Casey Pries avatar image
Casey Pries asked

Multiple questions about the FET Isolator

I'm getting ready to install an Argo FET Battery Isolator - 200AMP/2 Batteries on my 20' pleasure boat and I have a few questions.

1. Because the batteries straddle the engine in the rear of the boat and require fairly short cable runs that can be secured is there any reason to install fuses in the lines? Currently the boat has no fuses to the alternator or starter or 1/2/Combine switch. If I need to install fuses what size would you recommend? I'm installing 2 awg wire and the current alternator is 55 amp with cable runs less than 10 ft.


2. Does the Isolator get too hot to mount directly to the fiberglass?


3. I currently have a 55 amp alternator but because I plan to install some stereo amps there is a possibility of up-sizing the alternator in the future. With this in mind I ordered the 200 amp unit rather than the 100 amp unit. Is there a downside to being over-sized?


Thanks for any advice you can provide.


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jwfrary answered ·

There’s no problem with being oversized aside from cost.

If your going to install a larger alternator you may as well size the cables for that rather than changing them out in the future. No negatives apart from cost when looking at this.

You can mount directly to the fibreglass no problem, or you could pop a couple of washers behind the screws to leave an air gap should you be worried.

Fuses protect the cables not the device. I have used DC rated breakers, but more to allow easy isolation of the unit if anything needs changing or renewing. MEGA fuses work well and are cheap. A small DINN rail will also work well. With breakers on (ensure they are dc rated though)

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Casey Pries avatar image Casey Pries commented ·

Thanks a lot for the detailed reply, it's very helpful. I was considering using a resetable breaker, similar to what would be used in car audio, maybe a 100amp unit per line.

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