400 watt system w/alternator questions

[Landon Ashby]

1. Do I need an inline fuse for each solar panel + before going into the branch connector or 1 after the branch connector?

2. Wills diagram shows 4 awg being used for just about everything. Even the solar wires coming in to the controller. The wire that comes off the branch connectors is 8 awg. Is the 8 awg large enough or should I be combining the 14 awg wires from the solar panels in a different method and using 4 awg into the controller?

3. If this system is placed at the rear of a minivan is 4 awg large enough to make the run to the starter battery or should I be looking at gauging up to a 2 awg for that wire?

4. I will definitely be limited to 400watts of solar on my roof. Can I increase my battery bank later on? I'm think 2 12v100a Battle Born Batteries will fit my needs of running a 12v fridge and a 600 watt microwave for 15 minutes a day. Buy if I find I need more Battery can I add a 3rd? If I can does anything change? Like the gauge of wire I need to join the batteries or any of the fuses or circuit breakers needed.

5. If by some bad luck I actually need to jump start my van, do I need to disconnect the wire that connects my starter battery to the system?

 

[Landon Ashby]

Answer to Question 1. I need 1 inline 15 watt fuse on each panel on the + MC4 connector before going into the 4-to-1 Y Branch MC4 Connector. The fuse needs to be on the solar panel side of the connection as close to the branch connection as possible to also protect the 14 awg wire of the solar panel and not just the solar panel. So, a total of 4 15-amp in-line MC4 fuses are needed in this application.

 

[Landon Ashby]

Answer to Question 2. 8 awg MC4 wire is adequate for the solar panels used in this application. The 4 awg in Will's visual aid for solar to the controller was only used as a representation in this application.

 

[Landon Ashby]

Answer to Question 3. 4 awg is the recomended wire and is adequate for this application. Using the Blue Sea app for 12v voltage 50amp load at 20 feet 4 awg is the recommended wire gauge.

 

[Landon Ashby]

Answer to Question 5. In the unlikely event I need to jump my battery it will most likely need to be replaced. Testing for to see if the battery is in need of replacement should be looked at first before jumping.

A simple circuit breaker or battety disconnect can be added on the + cable from the starter battery to the controller closest to the starter battery as possible in the event the battery does need to be jumped or could just remove the cable from the battery if it is easy to do.

I found no answer as to whether the battery actually needs to be disconnected from the system in the event it needs to be jumped. So this is the safest procedure to prevent any possible damage.

 

[snoobler]

Nice work. My thoughts.

1) 1 fuse or breaker for each series string, typically 15A as is typically recommended on the panel sticker.
2) 10awg per series string is more common. If you don't exceed 40A, you can use 10awg to the controller. Thicker is better.
3) Assuming you're running a DC-DC charger, 4awg is fine.
4) Adding more 12V is fine. Similar capacity and heavy interconnects at least as thick as the main leads is a good idea.
5) Surprised that's an issue unless it says so on the charger manual. Would expect you can just disconnect it AT the battery.

 

[Landon Ashby]

Thank you for confirming my homework. I really appreciate the help.

Question 4 was really stumping me.

Question 5 was one of those things my Dad said to me and I was like that will never happen. It's being charged all the time. Then he was like ya but what if you need to. So it was deemed worth investigating.

Thank You! ?

 

[GXMnow]

Most modern jump start setups will not exceed 15 volts and should not hurt anything for a short jump start. So many modern cars have a lot of electronics that are more sensitive than a charge controller, so anyone doing a jump start should know to watch the voltage boost. Some older engine/generator jump start units on old tow trucks of the 70's would top 20 volts, and could even spike higher when the started would stop cranking, and many cars had their ECU blow up from it in the early 80's. I sure hope no one is using those anymore.