Thinking I am smarter than the engineers...Redpill me please.

[Michael T.]

So I bought a big 12 volt lithium battery(300 ah). I bought 6, 160 watt 12 volt solar panels, and a morningstar TS-60 PWM controller. 

I want to wire the panels in parallel, but I do not want to bother with all the weird Y-branch connector nonsense and have a hoard of wires on my roof... I am considering taking two 10 gauge MC4 extension wires and running them along the roof of my van all the way to the front most panel in the array, then splicing into the wires at 5 places on the positive, and 5 places on the negative and connecting all my panels in a parallel circuit matching this configuration...but with bigger watt rating a bigger inverter and bigger battery.

Am I just young and dumb? Will I catch fire? please help me, I have no idea what I am doing. 

 

[jonyjoe303]

My advice is to go to solarpaneltalk.com the people in that forum are experts on hooking up multiple panels. That's where I go when I can't find answers anywhere else. They would know if its possible to do it that way.

 

[jimindenver]

Is Solar King still over there? Hooboy can he get testy. lol

There is also a forum for Northern Arizona wind and solar.

 

[jimindenver]

10 gauge is going to be at its limit at 30a. Some of the connections are going to be carrying a lot of current. Going 3 sets of two series/parallel and a MPPT controller would raise the voltage and reduce the number of connections.

Your diagram shows a 220v inverter. Will you need another for 120Vac? Also I would only plan on turning on the 10a load once the batteries had only accepted 20a or less.

 

[Optimistic Paranoid]

The usual practice is to use a waterproof combiner box on the roof, and run a single pair of wires from that down to the controller.

http://amsolar.com/rv-combiner-box/20-roof

 

[BradKW]

At 960 watts, you're actually going to be exceeding even the TriStar 60's maximum input at 12v... 960/12 = 80 amps. Which means you've got a few choices:

1) roll the dice and hope you never actually hit conditions where you maintain max input from panels for a period of time,

2) step up to a bigger CC ... iirc, the Outback 80 is about alone in the options.

3) split the input between two CC's ...two TriStar 60's @ 48amps each for example.

4) when faced with same choices, I opted to move to a 24v system which gets you all sorts of headroom... 960/24v = 40 amps.

 

[John61CT]

Larger Victrons get pricey but IMO worth it.

 

[MrNoodly]

960W to charge/maintain a 300Ah battery seems like overkill unless you're in someplace that's always overcast. Are you in the PNW or something? Rain forest?

 

[John61CT]

Overkill on panels gives great flexibility, it's only money if he can afford it why not?

Nice to have the freedom to boondocks in more places, or be able to move more quickly to a shady spot.

Again assuming money's not a problem, better to say, you could get a bigger bank.

 

[BradKW]

Plus can add more lithium as funds allow...

 

[John61CT]

Yes, with thousands of cycles lifetime rather than hundreds, the "don't mix new with old" rule gets a bit more flexibility.

 

[Spaceman Spiff]

I want to wire the panels in parallel, but I do not want to bother with all the weird Y-branch connector nonsense and have a hoard of wires on my roof... 
Am I just young and dumb? Will I catch fire? please help me, I have no idea what I am doing. 

I agree with Optimistic Paranoid:  use a combiner box.  From the combiner box use the wire size that will give you less than 3% voltage drop (1% is better).  http://circuitwizard.bluesea.com/#

As to size of your system: 3 to 1 is overkill for the desert Southewest, good for Pacific Northwest and will allow for adding battery capacity later or running more during daylight.

Parallel vs. series connection:
Other panels in parallel will continue to supply max current if one is shaded.  Panels in series will revert to the output of the shaded panel(s).
The higher voltage of series panels require smaller gage wire and smaller controller amp rating.  I don't like to go closer than 3/4 rated capacity (in amps) on a controller.

Do you have a good understanding of how much power you are going to be using in a day?

 -- Spiff

 

[John61CT]

I don't like to go closer than 3/4 rated capacity (in amps) on a controller.

With many quality vendors they usually build in a solid cushion between the stated max vs what the unit can actually handle.

Plus, if you are using the totaled panel ​Short Circuit Current (Isc) rather than ​Max Power Current (Impp) then you're already building in a cushion there.

I believe it's stacking Voltage where you need to be more careful about damaging the controller; that's definitely true for the victron mppt units.

 

[jimindenver]

Always leave a buffer when dealing with the Voc limit of a MPPT controller. Some conditions like high altitude and cold weather can push the voltage of a panel up and fry a MPPT controller.

 

[Michael T.]

Thanks so much for all the quick replies everyone!

But The diagram I posted was a bit misleading, I am actually using an AIMS 2000 watt inverter(continuous with 4000 watt surge.), I am running a (very) small AC, (either a frigidaire 550 watt 5000 btu unit like this one, http://www.frigidaire.com/Home-Comfort/Air-Conditioning/Portable-Air-Conditioners/FRA053PU1/ , or a zero breeze ) A triple monitor dockable laptop that draws about 250 watts when running absolutely maxed out and  maybe a Fan and small DC refrigerator like a dometic CF-25.  I will also be charging my phone. I designed my solar power system to allow me to survive with full comforts of home anywhere in the continental united states, if I ran everything but the AC/heater for 8 hours per day every day. That is why I made it so large... I also wanted the additional head room to outlast those overcast places and times, As I will likely not be a snowbird and will be urban camping near my work place. I am a physicist so I need to be able to remain stationary for extended periods regardless of weather.

For you who mentioned the maximum current of the controller, my panels tell me that they output about 9 amps maximum current at 12 volts. 9*6 would be 54 amps, which is within specs for the morningstar ts-60.

Additionally, I am not super wealthy here, I have a limited budget, I merely decided to dedicate more resources to what I cared most about, Electricity to run my comforts and computers. I want a system that will last and be as close to ZERO maintenance as possible. I did not buy electrical systems to have to fudge with battery and electrical system maintenance.

I have examined the combiner box method, but I am not sure which box to purchase, or how to select one.


Can any of you tell me if running two #4awg wires as main leads back to the charge controller, and then connecting all 6 panels to those two mains in parallel would work? has anyone tried a setup like that? 

Just the panel connection part of the previous diagram is what I am interested in discussing. As below... but with 6 panels instead of 4 and with #4 awg wire running straight back to the charge controller for the main positive and negative leads of the parallel circuit. I would be adding my own MC4 connectors onto the leads to allow the panels to connect to the main leads. I am wondering if such a system is safe. I have examined many other systems, and the use of multiple branch interconnects, and combiner boxes always seems so complicated, I dont want to hassle with all the boxes and combiners, I just want to run two heavy leads back to my solar charge controller and be done.

I can move a thread to the other forums if the mods here would prefer it. I just thought I would start here since you guys are so active and friendly lol.

Thanks again for all the help. Ill be listening for your advice and suggestions.

 

[Michael T.]

960W to charge/maintain a 300Ah battery seems like overkill unless you're in someplace that's always overcast. Are you in the PNW or something? Rain forest?

For the record, yes I do live in a rainforest at the moment. The temperate rain forest of east texas.

Compared to the battery, the panels were super cheap. They are the 160 watt panels from hightec solar. I bought them on ebay.

 

[Michael T.]

I agree with Optimistic Paranoid:  use a combiner box.  From the combiner box use the wire size that will give you less than 3% voltage drop (1% is better).  http://circuitwizard.bluesea.com/#

As to size of your system: 3 to 1 is overkill for the desert Southewest, good for Pacific Northwest and will allow for adding battery capacity later or running more during daylight.

Parallel vs. series connection:
Other panels in parallel will continue to supply max current if one is shaded.  Panels in series will revert to the output of the shaded panel(s).
The higher voltage of series panels require smaller gage wire and smaller controller amp rating.  I don't like to go closer than 3/4 rated capacity (in amps) on a controller.

Do you have a good understanding of how much power you are going to be using in a day?

 -- Spiff

I did calculate my power usage, but i opted for a worst case scenario, I chose to build a system as close to being able to run all my comforts and entertainment for 8 hours per day every day as possible. Realistically, I am unlikely to be using more than 630 watts for more than 4 hours per day.  630 watts for 4 hours per day is likely near the maximum usage this system will see most of the time. But, I am relying on my electrical system to run everything in the van, so I decided to max it out as much as budget and space would allow, I just did not count on my ignorance of relatively simple electrical work lol    live and learn i suppose.

 

[Optimistic Paranoid]

I'm not quite sure what you plan to do here.  AFAIK, mc4 connectors don't take wire bigger than 10 gauge,  so I'm not sure how you are going to hook them up to a 4 gauge wire.

The only way I can see to do what your diagram shows is to strip some insulation off the 4 gauge wire, wrap the bare wire from the panel around it, solder it and insulate it with tape.

Frankly, looks like a whole bunch of potential failure points compared to using a combiner box.

If I'm misunderstanding how you plan to do this, maybe you could explain it a little better.

 

[BradKW]

For you who mentioned the maximum current of the controller, my panels tell me that they output about 9 amps maximum current at 12 volts. 9*6 would be 54 amps, which is within specs for the morningstar ts-60.

Can any of you tell me if running two #4awg wires as main leads back to the charge controller, and then connecting all 6 panels to those two mains in parallel would work? has anyone tried a setup like that? 

Just the panel connection part of the previous diagram is what I am interested in discussing. As below... but with 6 panels instead of 4 and with #4 awg wire running straight back to the charge controller for the main positive and negative leads of the parallel circuit. I would be adding my own MC4 connectors onto the leads to allow the panels to connect to the main leads. I am wondering if such a system is safe. I have examined many other systems, and the use of multiple branch interconnects, and combiner boxes always seems so complicated, I dont want to hassle with all the boxes and combiners, I just want to run two heavy leads back to my solar charge controller and be done.

So your error here is thinking that your panels will produce 12v...they won't, they produce more like 18v, thus the 160 watt = 9 amps x 18v. Which puts ya over the 60 amps.

#4 awg is big, no reason to use anything bigger than #8 I believe, and even that is probably overkill to the CC.

Your diagram is fine, the problem comes in each of those branching connections needing to be weatherproof. It's doable using MC4 Y-branch connectors (is how I did it), but this is not the "easy way". Buying a MC4 crimper and learning the ins and outs of manufacturer variable MC4 fittings is much more effort than running to a combiner box. You'll need the box anyway (actually I used a Blue Seas puck) for water tight penetration through roof.

Sounds like you've got a fun build ahead, hope to start a build thread and keep us posted with pics  

Edit: OP is correct, #10 is max for the MC4 connectors I used...

 

[highdesertranger]

I vote a combiner box but I wouldn't use the screw pinch type terminals I would use standard ring terminals on a standard terminal strip. highdesertranger