John Frum
Tell me your problems
- Joined
- Nov 30, 2019
- Messages
- 15,233
1s3p with a combiner box.
20 amp fuses per string.
Hopefully the voltage will be high enough to hit optimal power point.
I'm gonna step off now.
Best Way to Join Two 8S Packs With Two 8S BMS's
- Thread starter guidecca
- Start date
20 amp fuses per string.
Hopefully the voltage will be high enough to hit optimal power point.
I'm gonna step off now.
MisterSandals
Participation Medalist
2S3P (6 panels) works equally for same combiner box and same 20A fuses per string.
This doubles volts so still well below 150 max input volts (that was the target right?).
I have three panels; trying to keep cost down by skipping the Victron 250/60 SCC. But don't want to fry the 40A Epever SCC I have.
Attachments
John Frum
Tell me your problems
- Joined
- Nov 30, 2019
- Messages
- 15,233
He only has 3 panels.
The Epever Tracer 4215BN SCC maximum PV input current is 40A and the maximum PV open circuit voltage at 25 degrees C. is 138v. The SCC rated charge power at 24v is 1040v and maximum PV array power is 3x or 3120v. The three solar panels in parallel have a combined short circuit current of 32.07A which is about 8 amps less than the maximum PV input current of 40A. If the three positive wires are fused with 20A inline fuses and connected to 3 to 1 parallel / branch connectors with a 50A rating what other limitations do you see. The 32.07A combined short circuit current is less than the 50A rating of the branch connectors.
The Q-Peak solar panels use 12 awg wires for positive and negative. 12 awg wire has a 25A ampacity at a median of 75°C temperature. The parallel cumulative amps from all panels appears to exceed 12 awg wire rating. The three solar panels in parallel have a combined short circuit current of 32.07A. Does this affect the 12 awg wires connected to a 3 to 1 parallel branch connector? If so, is there any way to change the wire to 10 awg? If the combined current of the three panels exceeds the ampacity of the solar panel wires, does the 3 to 1 connector shield/protect them?
The Q-Peak solar panels use 12 awg wires for positive and negative. 12 awg wire has a 25A ampacity at a median of 75°C temperature. The parallel cumulative amps from all panels appears to exceed 12 awg wire rating. The three solar panels in parallel have a combined short circuit current of 32.07A. Does this affect the 12 awg wires connected to a 3 to 1 parallel branch connector? If so, is there any way to change the wire to 10 awg? If the combined current of the three panels exceeds the ampacity of the solar panel wires, does the 3 to 1 connector shield/protect them?
Last edited:
Will 20 amp inline fuses on the three positive wires protect the 12 awg wires on the solar panels, that have an ampacity of 25A? The three solar panels in parallel have a combined short circuit current of 32.07A. The object being to connect the PV wires with 3 to 1 connectors before connecting to the 8 awg wires in the van? If the wires are combined in a combiner box how are they protected?
Last edited:
MisterSandals
Participation Medalist
Combiner boxes usually have breakers or fuses for the incoming strings and an outgoing fuse of the combined strings.
As an example of a combiner box (not recommending any), here is a 4:1 combiner with 15A array breakers and an outgoing 63A breaker.
Might be able to build a combiner box with grounding busbars, 10 or 8 awg auto fuse holders, a plastic conduit box. But then that brings up the issue of how to wire the box inside, parallel or series. That Victron solar charge controller is looking better and better.
MisterSandals
Participation Medalist
Its a solid investment that should provide many many years of service.
MisterSandals
Participation Medalist
No there are quite a few options. You could use 3x cheap SCCs if you want. Everything is a tradeoff.
You have 3 very big panels. 49Voc and 10.7Isc is a lot for a system to handle on the cheap.
Good, simple or cheap. Pick 2.
The panels have a short circuit current of 10.69A, times 3 panels = 32.07A, in parallel. I checked the Epever SCC specifications yesterday against the solar panel specifications. The Epever charge controller can handle the panels' current. Even the 3 to 1 branch connectors can handle the current. The only weak link appears to be the solar wires which cannot handle the combined current of 32.07A. The solar wires are 12 awg with an ampacity of 25A. If there was a way to block the amps from frying the solar wires I could have electricity in the van without the 250/60 SCC.
For want of a nail a horseshoe was lost,
for want of a horseshoe a horse went lame,
for want of a horse a rider never got through,
for want of a rider a message never arrived,
for want of a message an army was never sent,
for want of an army a battle was lost,
for want of a battle a war was lost,
for want of a war a kingdom fell,
and all for want of a nail.
For want of a nail a horseshoe was lost,
for want of a horseshoe a horse went lame,
for want of a horse a rider never got through,
for want of a rider a message never arrived,
for want of a message an army was never sent,
for want of an army a battle was lost,
for want of a battle a war was lost,
for want of a war a kingdom fell,
and all for want of a nail.
MisterSandals
Participation Medalist
How about 3x Victron 75/15. $120 each. The bluetooth app is awesome. Probably necessary to get all 3 SCCs on the same settings.
So 410W panels charging at 28V
410W / 28V = 14.6A each
Lots of redundancy.
You could do this with a variety of smaller cheaper SCCs. Its more complex running 2 wires for each panel to a bus bar to the batteries.
Need big panels and a big battery to power a mini split bolted to the rear bumper. Drove 7,000 miles in Summer 2021 and the one thing I missed was air conditioning. That ain't gonna happen again. Nothing against Victron but I don't think they're made in the U.S.A.; $638.00 for a solar charge controller is way out of line. Way out there.
Last edited:
MisterSandals
Participation Medalist
I agree! I was in your shoes in 2010 and thought I was completely out of my mind spending $700 for a Morningstar MPPT 45. I mean completely out of my mind (i couldn't even break it to the wife how crazy it was!).
12 almost 13 years later its working everyday charging my batteries. I needed to upgrade firmware 3 years ago to be able to put in a LiFePO4 profile which was a pita with a PC and a RJ-45 to DB9 cable i had to make.
Best investment for solar I've ever made.
So if you go another route I completely understand. Its a long thread and I've looked back 20 times. If you currently have an SCC that will accept 2 panels, maybe get a 75/15 for the third. You can mix and match solar systems charging your batteries as long as settings are close.
Solar energy, especially with LiFePO4 is not a cheap sport!
Thank you for the alternative design (for a happy marriage).
I sketched a homemade combiner box idea. It fuses the 12awg solar panel positive wires with MC4 inline 20A fuses, it combines all the solar wires into a "combiner box", it runs a positive and negative 6 awg wire to the inside of the van to a 63a two pole breaker and it runs from there to the solar charge controller. I think it will work. What do you think? Correction: 25a not 25v (ampacity for 12 awg wire)
I sketched a homemade combiner box idea. It fuses the 12awg solar panel positive wires with MC4 inline 20A fuses, it combines all the solar wires into a "combiner box", it runs a positive and negative 6 awg wire to the inside of the van to a 63a two pole breaker and it runs from there to the solar charge controller. I think it will work. What do you think? Correction: 25a not 25v (ampacity for 12 awg wire)
Attachments
Last edited:
MisterSandals
Participation Medalist
Did you see the thread relevant to what you are proposing?
My read on it is that it will clip input amps to the rated output amps (40A). When over amped array coming in, there is no reverse polarity protection.
Jump in there with your own questions, especially if you think i misinterpreted.
Epever Over Paneling; how much is too much?
Setting the stage I have intentionally bought too many watts of panels not because I need the watts- but rather because I wish to have enough voltage to create usable charging in poor sun /overcast conditions. Overcast conditions are a consistent problem here in the Northeast Kingdom of...
diysolarforum.com
Can you really build a 3P combiner box and breaker (and 3 inline fuses) cheaper than $90?
Last edited:
As far as cost, I am kind of shooting from the hip. I had the two 63A breakers laying around and just found out that 12awg can be fused at 20A, thus the inline fuses. A junction box and grounding busbars at Home Depot and the 6 awg wire and MC4 on 12 awg wires would be the next thing to buy. I wanted the panels fused on the roof but I wanted the breaker to be inside the van. Can the reverse polarity issue be fixed with blocking diodes? They sell MC4 blocking diodes. The expense is rising. Let me read that thread.Did you see the thread relevant to what you are proposing?
My read on it is that it will clip input amps to the rated output amps (40A). When over amped array coming in, there is no reverse polarity protection.
Jump in there with your own questions, especially if you think i misinterpreted.
Epever Over Paneling; how much is too much?
Setting the stage I have intentionally bought too many watts of panels not because I need the watts- but rather because I wish to have enough voltage to create usable charging in poor sun /overcast conditions. Overcast conditions are a consistent problem here in the Northeast Kingdom of...
Can you really build a 3P combiner box and breaker (and 3 inline fuses) cheaper than $90?
Your output breaker should be 20% over your expected load (63A) to prevent nuisance tripping. 75A or 80A?
The output breaker is 63A. Not sure what the output load is. The SCC has a maximum PV input current of 40A. 32.07A is the combined short circuit current of these three solar panels. So, the array is not over-amped. In other language the amps do not exceed the maximum amps that the SCC can handle.
Similar threads
