Will MPPT fail if main battery fuse fails while sun is shining?

[DamBuster]

Hi, first post on the forum, looking forward to using the forum as I learn more about DIY solar.
I am putting together a small system (12V 100Ah LiFePO4 battery, 40A MPPT controller, 1000W inverter, 2x200W PV, all from Renogy).
I am wondering if, should the main fuse to the battery blow while the sun is shining, will the MPPT controller be fried, as I have seen loads of Will's videos on YouTube and he always stresses that the MPPT must be connected to the battery before the PV is connected.
If the main battery fuse blows, the MPPT will have the PVs connected but no battery, so will the MPPT controller be fried?
Thanks!

 

[Wjm1964]

The reason the scc is connected to the battery 1st is so the scc knows what voltage the battery is. E.g 12v or 24v etc. Fuses protect wires, not equipment but if your main battery fuse blows the scc won't do anything as there wouldn't be a complete circuit. Just fuse correctly

 

[guidecca]

Wjm1964, here is another question that relates to unexpected consequences and will electricity fry my gear.

If the solar panel wires to my three panels is 12 awg with an ampacity of only 25 amps AND I have all three panels in parallel AND they have a combined short circuit current of 32.07A. How do I isolate the solar panel wires from the 32.07A?

First, 20A inline MC4 fuses are attached to the 12awg solar panel positive wires. Then, all the wires are inserted into a homemade junction box with two busbars; the positive wires go to a positive busbar and the negative wires to a negative busbar. Lastly, 6A wires (positive and negative) exit the junction box and connects to a 63A DC breaker inside my van and then the 6A wires goes to the solar charger controller.
Are the solar panel wires protected? * Correction on drawing: change 25v to 25A *

ADVICE WELCOME

 

[Wjm1964]

When you connect solar panels or batteries in parallel the voltage stays the same. However if you make a series connection the voltage is added e.g 12v connected to another 12v in parallel it's still only 12v. Series would add the voltages 12 + 12 = 24v
Your panels will only give 10.69 in parallel. You don't need 20A fuse nor 63A as they won't do anything. Just get a mc4 connector like this
PAEKQ Solar Connector Y Branch Parallel Adapter Cable 3 to 1, 3 Way Solar Panel Branch Cable 50A Waterproof PV Splitter Coupler Cable Connectors Wire Plug Tool Kit for Solar Panel(1 Paire) https://www.amazon.co.uk/dp/B09V2WYCP2/ref=cm_sw_r_apan_gl_i_A5708RMVET7VGTVMX6KB?psc=1
Run your cables to scc and your set. However do some reading about putting panels into either series or parallel and do what suits your needs.

 

[guidecca]

When you connect solar panels or batteries in parallel the voltage stays the same. However if you make a series connection the voltage is added e.g 12v connected to another 12v in parallel it's still only 12v. Series would add the voltages 12 + 12 = 24v
Your panels will only give 10.69 in parallel. You don't need 20A fuse nor 63A as they won't do anything. Just get a mc4 connector like this
PAEKQ Solar Connector Y Branch Parallel Adapter Cable 3 to 1, 3 Way Solar Panel Branch Cable 50A Waterproof PV Splitter Coupler Cable Connectors Wire Plug Tool Kit for Solar Panel(1 Paire) https://www.amazon.co.uk/dp/B09V2WYCP2/ref=cm_sw_r_apan_gl_i_A5708RMVET7VGTVMX6KB?psc=1
Run your cables to scc and your set. However do some reading about putting panels into either series or parallel and do what suits your needs.

But, the panels in parallel add amps; 10.69a x 3 = 32.07a which is higher than the ampacity of the 12 awg solar panel wires. The 12 awg wires won't stand that much current going through them will they?

 

[Wjm1964]

Oh I thought I read 2 panels @ 200w. Yes amps will go up volts stay same. What scc are you using. Its max voltage is what to look at. 40amp is its max output in peak.https://www.windynation.com/jzv/inf/choosing-right-wire-size

Sorry I'm using an old phone there's a good chart on that site. Is there a particular reason your choosing parallel over series? A combiner box should have its own breakers and diodes to protect things. 10awg is good for a run under 20ft. 6 awg from combiner is ok if less than 15ft from scc. Its easier IMHO you'd be better going series. I'm assuming the panels are 12v?