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Old 04-20-2018, 02:09 PM   #1
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Wink An unlikely issue - current from solar is out of control(lor)

This sounds weird but for real -

I have two sets of solar panels, and I am using two MPPT controllers. One of them is Midnite Classic 150, which has a limit of 96A on 12V system. In the past few days in sunny Cal I have seen that the charge current flared in 95-96A area. We are just in April now, it could only go up when summer comes.

The circuit breaker between the controller and battery is 100A, but has already been tripped a few times due to overheat (i think). i ordered a 150A circuit breaker to take care of that.

But the controller is an issue - I need one with 150A limit. I called Midnite they said they have no plan to make it bigger. I googled, ebayed, amazoned... nothing came up. I consider splitting the panels as the last resort as leading more wires from roof to my battery bay is a pita.

Does anyone, especially those in the solar industry, know if there are higher powered MPPT controllers out there, or a way to bundle multiple controllers onto the same wire?

Any suggestions are highly appreciated.
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Old 04-20-2018, 02:21 PM   #2
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It would be helpful if you fully described your solar and battery system. How many panels of what wattage rating and voltage output, are they in series and/or parallel? What is the second solar controller? What is AHrs at 12v of your battery system?
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Old 04-20-2018, 02:24 PM   #3
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So both pair of solar panels comes together on the inside of the breaker? If so, put a second 100A breaker, and split the pairs one each. Then you can add a second controller.

We have five 240W 48V panels coming in individually, each thru their own breaker, before moving on to feed the Classic 150.

Or, is it the feed from the breaker to the Classic 150, and then from the 150 to the batteries that is the PITA to run?

(Sorry I do not know the answer of splitting the output side of a single breaker to feed two controllers via one cable... So, will tag along for leaning opportunities off of someone else's dime!)

And talk about a great problem to have!

Best to you, and all,
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Old 04-20-2018, 02:26 PM   #4
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Originally Posted by rarebear.nm View Post
It would be helpful if you fully described your solar and battery system. How many panels of what wattage rating and voltage output, are they in series and/or parallel? What is the second solar controller? What is AHrs at 12v of your battery system?
Thanks Fred! Actually I have a little writeup here.

The said controller is on the circuit of 8 panels in parallel, 250w each.
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Old 04-20-2018, 02:40 PM   #5
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Originally Posted by Smitty77 View Post
So both pair of solar panels comes together on the inside of the breaker? If so, put a second 100A breaker, and split the pairs one each. Then you can add a second controller.

We have five 240W 48V panels coming in individually, each thru their own breaker, before moving on to feed the Classic 150.

Or, is it the feed from the breaker to the Classic 150, and then from the 150 to the batteries that is the PITA to run?
Hi Smitty,
Two sets of panels are on separate circuits. The smaller one is 128v (3 panels in series) with its own 60A charger controller; this one is no problem. The circuit having problem is the larger one consisting of 8 46v panels in parallel, each having its own breaker inside the combiner. From combiner to controller is a pair of single wire. Before and aft Midnite Classic 150 controller, a circuit breaker is on the leg; the output leg is with a 100A breaker which is overheating now.

If there is/were a way to bundle two Midnite Classics onto the single set of input wires, 46v, each controller would be carrying half of the total current, that would resolve my problem. To my knowledge, it's not viable. Could new technologies be out there to make it happen?
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Old 04-20-2018, 03:27 PM   #6
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I have 1500w of panels in three strings of 500w each - each string to a midnight solar combine box with circuit breakers - then onto a midnight solar classic 150 - and a 150a inline circuit breaker yo the battery bank. So a similar system.

Your 100a breaker is not enough to provide any margin - I would suggest a 150a.

Are your panels tilted or flat? If tilted you have little headroom for oversubscribing the Classic 150. Flat you could be pushing it in optimal sun.

You could simply drop out a panel or two in the summer with good sun days. Easy to do since you have individual string circuit breakers.

You could also rewire a panel to the other system with the 60a controller.
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Old 04-20-2018, 03:32 PM   #7
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Sounds like you might have to do what "Wheeling it" did when they upgraded their solar. Would that even be enough for yours?
https://wheelingit.us/2016/03/06/the...-installation/
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Old 04-20-2018, 03:50 PM   #8
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I noticed that its is cheaper to get a pair of Victron SmartSolar 100/50 MPPT controllers than buying the 150/100 version. I may not have enough roof space but will consider bringing down a pair of 8 AWG wires from a larger combiner box down to my storage area that will house the controllers. Each one would support a pair of 300 watt 24 volt panels.
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Old 04-20-2018, 03:54 PM   #9
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Originally Posted by vsheetz View Post
I have 1500w of panels in three strings of 500w each - each string to a midnight solar combine box with circuit breakers - then onto a midnight solar classic 150 - and a 150a inline circuit breaker yo the battery bank. So a similar system.

Your 100a breaker is not enough to provide any margin - I would suggest a 150a.

Are your panels tilted or flat? If tilted you have little headroom for oversubscribing the Classic 150. Flat you could be pushing it in optimal sun.

You could simply drop out a panel or two in the summer with good sun days. Easy to do since you have individual string circuit breakers.

You could also rewire a panel to the other system with the 60a controller.
My panels are flat mounted. I want to use as much power as possible though it outputs more than what i originally unexpected .

The other charge controller is 60A with max voltage of 175V. I initially tried to use 4 panels in series, but during the test ran I found out sometimes the voltage could shoot up to 190V, way higher than that allowed for the controller, thus I settled with 3 in series. Since the wires are very thin at 14ga, series/parallel 2 x 2 isn't quite desirable.

Vince, you just opened a window - I could go back to do 4 in series, and replace the controller to Midnite 200, which allows voltage up to 200v. Bingo! .
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Old 04-20-2018, 03:58 PM   #10
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Sounds like you might have to do what "Wheeling it" did when they upgraded their solar. Would that even be enough for yours?
https://wheelingit.us/2016/03/06/the...-installation/
I read her post when it was just posted, now I read it again. Tina uses 3 groups so 3 controllers. I could do the same but that would be my last resort.
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Old 04-20-2018, 05:08 PM   #11
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Originally Posted by astrocamper View Post
I noticed that its is cheaper to get a pair of Victron SmartSolar 100/50 MPPT controllers than buying the 150/100 version. I may not have enough roof space but will consider bringing down a pair of 8 AWG wires from a larger combiner box down to my storage area that will house the controllers. Each one would support a pair of 300 watt 24 volt panels.
since you are using 24v system, 8ga wires are good enough for the panels you plan to install. i use 6ga wires for the larger array but on 12v system. the smaller wires were installed by the previous owner, i was merely to make use of it trying to squeeze out the last drop of water :-).
i don't have hands on experience with victron controllers i suppose the model you choose meets your needs well.
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Old 04-20-2018, 06:05 PM   #12
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I have put in a couple of smaller (100 and 180) watt solar systems on my sons and my truck camper shell. I like the Victron SmartSolar MPPT controllers because they have bluetooth buit in and can be programed by a phone, tablet or laptop app. The app has a great live information and historical data. The app also works with the BVM-712 battery monitor for larger systems with a shunt. The systems range from 75 volts - 10 amps to 250 volts - 100 amps. The 20 amps or less versions have a 3rd set of terminals for load controll. These are completely programable with tenth of volt settings for charging voltage, float voltage and battery low voltage disconnect.

You can mount them out of sight near LiFePO4 batteries since there is no gassing from these batteries. With lead acid they should be in a compartment away from the gassing.
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Old 04-20-2018, 10:43 PM   #13
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I have put in a couple of smaller (100 and 180) watt solar systems on my sons and my truck camper shell. I like the Victron SmartSolar MPPT controllers because they have bluetooth buit in and can be programed by a phone, tablet or laptop app. The app has a great live information and historical data. The app also works with the BVM-712 battery monitor for larger systems with a shunt. The systems range from 75 volts - 10 amps to 250 volts - 100 amps. The 20 amps or less versions have a 3rd set of terminals for load controll. These are completely programable with tenth of volt settings for charging voltage, float voltage and battery low voltage disconnect.

You can mount them out of sight near LiFePO4 batteries since there is no gassing from these batteries. With lead acid they should be in a compartment away from the gassing.
I heard a lot of good things about Victron stuff, no wonder many people chose it.
Yup, my controllers are in the same bay the battery cells are in. About 4 years no problem.
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Old 04-20-2018, 10:51 PM   #14
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You could convert to a 24 volt battery system and put your panel strings in deeper series to deal with your smaller wires between the panels and the controller.

There are MPPT charge controllers that can handle up to 250 volts and 100 amps.

You would need to add a DC - DC power supply for your 12 volt needs and buy a 24 volt inverter.

I thought about doing a 2 parallel 2 series 4 battery system but could justify the added costs even if I could reduce wire size in the inverter/battery part of the wiring.
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