diy solar

diy solar

The more I learn, the less I know….

Mrmikek

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Joined
May 22, 2022
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How do I determine appropriate fuse size for a lynx shunt 1000 and the lynx distribution panel. I’m in a fifth wheel with 2 SOK 205Ah batteries.
 
You choose wires to safely carry needed loads. You pick fuses to protect those wires.

If you need help with either then post details about the loads and/or equipment involved and which fuse location you need help with and someone can help you work out the details.
 
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Well your SOK batteries are capable of 100A discharge so if they are in parallel no more than 200amp fuse.

But agree with rmaddy
 
Thank you. I have 4 320 W Heliene panels. SCC 10.2 A, OCV 40.5. My thought is to put 2 panels in series to a victron 100 / 30 charge controller. Then controller to links distribution box, 6 guage wire and 40 amp fuse. From there to lynx 1000 shunt and 2 205aH in parallel. The other end to Victron Multiplus II 3000W inverter/charger. Shunt to Batteries 2/0 cable and 200 A fuse. To inverter, 4/0 cable, 250 A fuse.
sound feasable? Is using panels in series and only 2 charge controllers a decent idea? Or am I bending over a dollar to pick up a dime?
 
The Victron 100/30 provides up to 30A of charge current. 30A x 13.5V = 405W. But you plan on using 640W of panels. A 40A or 45A controller would be more ideal for 2 of those panels. But the next step up is the Victron 100/50. That would let you make full use of the 640W from 2 of the panels. Another option would be the 150/85. You only need one of those and you could put all 4 panels on it in a 2S2P setup. But it appears that two Victron 100/50 is a little cheaper than one Victron 150/85. You could use two of the 100/30 instead of two of the 100/50 and save about $200 but you end up giving up about a 1/3 of your potential solar power.

If you go with the 100/30 then you only need 10AWG wire from the SCC to the Lynx with the 40A fuse. This assumes the two wires will be under 5 feet long. If you do go with the 100/50 then you would want 6AWG and a 60A fuse.

The MultiPlus II 3000VA is 3000VA, not 3000W. 3000VA is about 2400W. This is clearly shown in the data sheet.

2400W / 10V / 90% = 266A. You should use 4/0AWG wire between the batteries and for all wires leading to the MultiPlus battery connections. The main battery fuse should be 350A.

However, the SOK 12V 206Ah LiFePO₄ battery has a max continuous discharge current of either 100A or 130A depending on which one you have. The heated version is 100A and the unheated is 130A. If you have the unheated version then your two in parallel will barely handle a full 2400W load from the inverter. If you have the heated version then you can only power about 2000W of loads. Either way you need to add a fuse to each of the two batteries, in addition to the main battery bank fuse. I'd use a 150A fuse if you have the unheated version and a 125A fuse if you have the heated version.
 
Why the difference between heated and unheated?
I'm going by the specs shown by SOK. They list the unheated battery as 130A and the heated as 100A. They must be using a different BMS in the two batteries.
 
Here is what I have penciled out. 2-206AH SOK heated in parallel. Pos to a bus bar then 350A fuse in the Lynx 1000 shunt. Neg to isolater switch, then bus bar then Lynx 1000 shunt. Shunt to Lynx distribution box. Multiplus inverter/charger to distribution box and 2-100/50Victron MPPT SCC’s To distribution box. Multiplus AC out to my AC panel. DC panel powered from the bus bars.
Am I going to burn my RV down? Electrocute someone?
 
A 350A main battery fuse seems rather large considering your two batteries can only provide 200A total. Your two batteries can't fully power the 3000VA MultiPlus as I pointed out in post #3. You really need 3 batteries in parallel to fully power the inverter. Don't forget to fuse each battery in addition to the main battery fuse.

I would also move the isolator switch to the positive wire between the main fuse and the Lynx.

I assume your use of the bus bar is just for connecting the batteries in parallel.

The DC panel can be connected to the bus bars but make sure you put an appropriate fuse between the DC fuse box and the bus bars. But why not connect the fuse box to the Lynx like everything else?
 
I tend to agree with rmaddy except for the size of fuses. Fuses are there to protect the wire. I use the largest fuse that will protect the wire. My reasoning is a larger fuse has less voltage drop than smaller fuse. Yes, I know, anal. Solar panels are very limited in the power harvested and batteries are limited in capacity.
I design system current so the BMS will never trip, except in the true emergency that is its purpose.
 
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