Fuse size before and after Tristar 45 PWM

[kp_utah]

So, I had another question before this around chargers. I decided to just upgrade my tracer to a Morningstar Tristar 45amp. Thank you to those who responded there. This forum is very active and responsive. Thank you!

First off... All this electrical stuff is sometimes confusing to me. When I installed my solar panels 1 year ago, I researched alot then, but now I struggle to recall some of the setup. Like parallel or series panels, etc.

I think its overkill, but the Tristar accepts 2AWG wiring. So, from the controller to the batteries, I will use 2AWG, just because I can, and its not too expensive for a 3 ft run of it.

From the panels to the controller, my 5th wheel came prewired with 8AWG wire. The run is about 12ft, I think. As its above the hitch area on the roof, down to the battery compartment, which is at the front of the 5th wheel, just behind the the hitch.

I really don't want to rewire unless it is really needed. So, I plan to leave the 8AWG wiring to the controller, which is in the battery compartment. Its well ventilated and a very open area. I believe this isn't ideal, but perhaps next year I upgrade the wiring. Is there is a significant difference to upgrade the wiring to something bigger that was be interesting to know.

Panels: two 100Watt renogy panels. I have measured the volts with the previous setup at 17volts. I don't recall if they were in parrellel or series. I would have to get on top and peek under the panels. They are rated at 12volts, I think. So maybe that answers it.

My questions:

• Panels to the controller: Wire is 8AWG. What size fuse and what type of fuse? I have a 8awg maxi inline 20AMP fuse already with my previous setup. Is that fine? Suggestions??
  
  
• Controller-to-Battery: I was leaning towards a 2AWG wire from controller to battery. What size (amp) and type of fuse do you suggest? I was considering an ANL. I sorta liked the air conditioner disconnect mentioned by Jack Mayer in a blog, but he said they are "slow blow time delay" fuses. I think I read that you need 1.25 times the controller rating. The charge controller is rated at 45amps. So I assume 60amp fuse is it. Correct? Any harm in going bigger? Like 100amp fuse?
  

[time2roll]

No fuse needed from panels to controller. You can short the wires all you want and they will not get hot or do any damage to the solar panels. Although you may want a switch to cut solar power from the controller for service. A removable 30 amp fuse would be fine or a resettable 30 amp circuit breaker.

If the connection to the battery is protected and in plain view I would skip the fuse. If subject to damage or goes through hidden areas then about any fuse is fine but 60 amp rating would be normal. This fuse should be close to the battery positive terminal.

Controller install instructions have this info.

[Njmurvin]

I've read Handybob's site. He actually has an entire blog extolling the virtues of the Trimetric meter and SC controller .. https://handybobsolar.wordpress.com/2015-the-trimetric-2030-perfect/

No question about the quality of Morningstar. Glad to see it's doing the job. I currently have a Go Power controller and it doesn't seem to work properly. It may be good for maintaining the batteries when in storage. But, for dry camping, it doesn't seem to keep up even with minimal usage. Like your Tracer, it doesn't have the capability to adjust the charging parameters. That's why I'm looking elsewhere.

[kp_utah]

I went w that Tracer mppt since it was less then the nicer PWM's. But I think you get what you pay for.

Tracer brand you can't tweak much, and it wasn't fully charging my batteries (Trojan T105's) at the 14.8 they call for.

Today, I just put in the Morningstar Tristar 45. I am excited to see it work. Went w that mainly because various forums speak highly of it. Google Handbob's Blog - Making off grid RV electrical systems work. Good stuff. But i don't understand it all, just learning this. Its interesting.

[Njmurvin]

I'm going through some of the same thought process upgrading my solar charging system. It will be interesting to see what the experts say.

From what I've read, with only two 100W panels and that short distance to the controller, 8awg should be fine. Also, it appears that your panels are wired in parallel if your voltage at the controller is only 17V.

Just curious why you chose an MPPT controller for such a small system instead of something like the Bogart products (Trimetric meter with its companion PWM charge controller)? My brother just installed those in his trailer with 4x100W Renogy panels and they really do a nice job both monitoring and charging his dual 6V battery bank.

[GordonThree]

A fuse protects the wire, not the load. Check out this chart for fuse sizes.

http://assets.bluesea.com/files/resources/newsletter/images/DC_wire_selection_chartlg.jpg

Each fuse (or breaker) is going to cost you some voltage, so don't go overboard putting them everywhere, especially where a simple disconnect switch would serve just as well.

If you have multiple gauges of wire connected together, the fuse needs to be sized for the smallest wire gauge that's on the circuit.