Solar Power Newbie question

Fuse the battery cable, yes. It will work without the fuse, and so will you home wiring, until sh-t hits the fan, and then you have not a $10 fuse problem but something more serious.

I wrote in another thread about brands and off-brands - either one could come from China, but a brand like Morningstar or a brand-ish one like Landstar will have better literature. Could be a better efficiency as well.

Make sure you get a proper wire gauge for a given length to battery. With MPPT, thinner wire = more amp-hours lost. This is - assuming you have MPPT and not PWM. No kidding, but from time to time people are trying to run 24V panel via PWM.

Wow! Thanks for the video follow up! Nice work!

:B Thanks to this great forum for all the help. I have not only got my solar panel and installed it, but I also made a video of the whole process and posted it on Youtube.

Click here to watch the video.

RJ's controller must come from a different part of China than mine. I have a LandStar 20a PWM controller (costs $39 locally including tax)

Instructions are very clear. The fuse must be on the pos line within 150 mm ( 6 ")of the battery on the controller-battery wire.

In addition, there must be a fuse on a controller-load wire (if used)but in this case it does not matter if the fuse is on the pos or neg wire according to the instructions.

Only thing is I can't find anywhere what size fuse it wants on the controller -battery line. It says total load line fusing (each load needs its own fuse) should not exceed load rating of controller.

Remember the solar controller needs power to operate - that power comes from the battery not the panels. A fuse or breaker is a easy way to isolate the controller from the battery for extended periods of time while in covered storage without any sun for the array.

Me I always have a easy way to isolate the controller from the array and the battery as in removeable fuses, breakers or combination fuse and switch.

Fuse ? My elcheapo china controller never said nothing about no fuse ! It sure works good w/o one :)

I really REALLY like to see an ammeter reading 100% of the time that shows the amperage flow from the panels. Not what's going into the batteries, that's another ammeter, but one that can pinpoint whether a bird is building a nest atop a panel (or worse), or they just need to be hosed and squeegeed off. A cheap 25 amp needle type meter can do this just fine.

My 25 A MPPT controller calls for a 30A fuse.

Your 250w 8.7a with MPPT should get you an expected max amps of 16a plus 10% more for MPPT = say 18 amps. (panel pointed at sun mid-day) You should have a 20% margin for more amps at times, but ok for the controller at 20a if it is one of those that clips the amps at 20 so it won't overheat.

However, your controller battery fuse on the pos wire needs to have the margin in case the controller does not clip the amps, so you need a 25 to 30a fuse.

Since you already have a 30a fuse on a pos battery line somewhere, maybe more fuses than that of that size or more, just add the controller's pos wire to the outer end of one of those existing fuses and it will take care of both things.

Fuses are there to protect your wiring so I would just get one big enough to protect that OR, if that's too expensive, somewhere over 20 amps and under your max amps for the size wire you're using.