Where to put fuse on solar/regulator/lights

So far as your connections go, a lot depends on the type of regulator you have. Some have a connection for the solar panels, the battery and also the load, while others don't have a load connection. If yours has a connection for the load, you should use it, as many regulators calculate the amount of charge they need for the battery based on the load current as well as the voltage of the battery.

The fuse locations should be planned to place them so that they protect anything that can't protect itself. If you have a separate Load connection, you should have the fuse at the regulator end. This will then protect against a problem with your load AND the cable that connects it.

With a connection to a battery under the above scenario, it is probably wise to have a fuse at the regulator end AND the battery end. This is because a pinched cable could be fed with current from either end, the battery or the regulator and fusing just one end will not necessarily immediately protect the other. Don't forget, fuses don't just protect equipment, they also prevent fires caused by cooking cables!

If your load is connected in parallel with your battery, it is often wise to have some sort of distribution system whereby each individual load device has its own correctly rated fuse and you have one larger rated fuse between the battery and the distribution point. A rough rule of thumb is to use a fuse that is the equivalent of the sum of all of the individual loads for this purpose.

You can never overdo fusing, but the consequences of underdoing it can be expensive and dangerous. Always err on the side of underrating fuses when selecting which fuse to use.

Cheers

Russ.

When you parallel batteries make sure one battery supplies the negative to the load and the other battery supplies the positive to the load, this way both batteries share the load equally.

Quote "Usually I would put the fuses close to the batteries but the problem is that everything is paralleled so reg can also power the lights without the batteries even being there." - There is not much use powering the lights from the regulator, you don't need the lights when the sun is shining.

Forget all the talk about fuses protecting your equipment. When the current drawn by any equipment blows properly rated fuses, that equipment is already buggered. Fuses are used to prevent fires, either started by the buggered equipment catching fire or the wiring overheating due to excess current (possibly from excess current drawn by buggered equipment.)

Connect your 12 V distribution directly to the battery. This allows you to temporarily disconnecting your solar system (for service etc) and you are still left with your lights still operating. Place your fuse block near your battery. If the heavy battery lead to the fuse block passes through a metal battery enclosure then use a good insulating bush where it passes through the metal enclosure. Locate your solar controller close to the battery, the leads to the solar panel does not need fusing as the current from the panel is too weak to overheat the cable.

The fuse ratings should be no larger than half the cable current rating. If you think you need larger fuses then your cable is too small in cross section area. In the lengths employed in caravans if the cable current rating is not several times the current they supply you will experience too much voltage drop. For an excellent dissertation on this subject see Site Link

Wiring in the compartment where the fuses, solar regulator and battery charger does not usually need protecting by fuses. The protection is needed before the cable exits this compartment and disappears into the walls. This is where the cable is more likely to overheat and people installing after market items in the vans spike the cable with nails and screws.

PeterD

The principle is simple - the fuses must be sized and located so that a short circuit or overload anywhere will stop a high current flowing that could cause overheating and a fire.

Batteries can supply huge currents in a short circuit so they need a fuse that is rated at LESS than the rating of the thinnest cable fed from it.

Solar panels do not need fusing because they are constant current sources. An 80 watt panel will deliver 4.5 amps into a 12 volt battery and 5 amps into a shortcircuit.