Cable Selection & Critical vs Non-Critical Voltage Drop - Which Do I Use?

[HereWeGo]

I'm using the Blue Sea wire selection chart to determine cable size for the primary run from start battery to house battery in the bed. The run will be between 15 and 20 feet. I have a 120AH battery, 200W solar panel, Renogy DCC50S charge controller. I'm not sure whether to use the "non-critical" or "critical" chart specifications. I don't know how to determine if "critical" applies to my application. The cable size needed is different depending on that factor.

I have already purchased 6/2 AWG duplex marine cable, so I have that extra sheath to protect it. I just read that this duplex cable with the extra sheath will not dissipate heat as well. Yet another worry on which size cable I should use.

Any advice is appreciated.

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[sharpsicle]

I've only ever seen critical vs non-critical in boating applications, but I'm sure the concept can easily be applied here. The gauge wiring is decided to prevent voltage drop more than anything else. Minimizing that drop for critical equipment is where larger gauge wiring comes in such that an unexpected drop doesn't cause the equipment to fail or unexpectedly shut down.

Critical is really anything that must remain operational. Things like communications and safety-related equipment. If the equipment going out causes a safety issue, it's critical.

Non-critical is anything else, which really boils down to things that are more for comfort than they are for safe minimum operations. Radios, heaters, lighting, added accessories, that sort of stuff is non-critical. You can wire these up to meet critical standards if you want, but there's little reason to do so.

An added battery in the back like you're describing, to me, falls under non-critical.

 

[Mr._Bill]

Warn sells a kit that I used to connect the front and rear batteries.
WARN 32963 20' Quick Connect Power Cable https://a.co/d/8XOTa4T

I added a Smart Isolator and some other components. I installed a winch and a rear battery.

 

[HereWeGo]

I've only ever seen critical vs non-critical in boating applications, but I'm sure the concept can easily be applied here. The gauge wiring is decided to prevent voltage drop more than anything else. Minimizing that drop for critical equipment is where larger gauge wiring comes in such that an unexpected drop doesn't cause the equipment to fail or unexpectedly shut down.

Critical is really anything that must remain operational. Things like communications and safety-related equipment. If the equipment going out causes a safety issue, it's critical.

Non-critical is anything else, which really boils down to things that are more for comfort than they are for safe minimum operations. Radios, heaters, lighting, added accessories, that sort of stuff is non-critical. You can wire these up to meet critical standards if you want, but there's little reason to do so.

An added battery in the back like you're describing, to me, falls under non-critical.

That makes complete sense. Never thought about what was being powered. Thought it had to do with system integrity or something, IDK... Thanks for the reply.

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