There has been a lot of exchange over just where you can place the battery protect fuse. In most cases it is on the Positive (red) side just off the battery and in some cases it is on the negative (black) side.
The theory is applicable in both cases and the preference is usually the owners choosing as long as it is protected.
The link-10 operates on the principle of monitoring the current flow through the negative leg. AMPLE POWER bases their design and safety on the fusing the negative leg to protect the battery, wiring and anything that might come in contact with the wiring.
I know that in all of the Navy contracts I've worked, the ships AC electronics are fused on both high and low sides because of poor grounding and return currents. That's AC I know.
Any thoughts on this? I'm not hard over but electrically it makes no difference.
"We wish to achieve safety with a minimum cost, which fusing on the negative side of a battery permits. If someone were to give you a sealed box with a battery and a fuse inside it, you would not be able to determine which side of the battery was fused by any kind of electrical measurement. That being a fact, why not put the fuse where it will be most economical? If you put the fuse on the negative side, it will not need to be insulated. Even if you do drop a wrench on the fuse, shorting it to your metal hull, no electrical damage will result. "
"A fuse on the positive side must be enclosed inside an insulator of some sort, which adds unnecessary cost to the system. Should you fuse on the positive side? If you need Coast Guard certification, then you will have to put the fuse in the positive lead of the battery. "
From the CG at www.uscgboating.org/safety/boatbuilder/downloads/ELECTRICAL.pdf from section 183.460 Each ungrounded output conductor from a storage battery must have a manually reset, trip-free circuit breaker or fuse, unless the supply conductor is in the main power feed circuit from the battery to an engine cranking motor. The circuit breaker or fuse must be within 72 inches of the battery measured along the conductor, unless, for boats built prior to August 1, 1985, the circuit has a switch that disconnects the battery.