Connecting multiple solar panels and controllers to a single battery bank

I have 2 identical 100W solar panels each with a built-in PWM controller connected to 2 x 130Ah 12V batteries wired in parallel. The 2 panels connect to a bifurcated cable with Anderson plugs so that a single O ring connects to each battery terminal. I enquired with another solar panel supplier about adding one of their 300W panels which also has a PWM controller. They said that you must only use one controller per solar panel array / battery bank. My 100W panels each have their own built-in controller and they are hard wired so I can’t see how I could modify the wiring to make them both charge through one controller. The supplier of those panels didn’t say anything about using a single controller with both panels. I’d like some clarification about connnecting multiple solar panels and controllers to a single battery bank.
Comments
Multiple panels (an array) to a single controller is fine, providing wiring is done right for the controller used.
Multiple charge controllers (esp. mppt type) connected to a single panel/array can be an issue and should generally be avoided.
Multiple charging sources to a single battery/ bank is generally fine. A potential issue can be controllers changing charge state independently (eg one goes to float before others). In general, this isn't a big issue though.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
So each solar panel connected to a battery bank can and should be independent of the other and charge through its own dedicated controller?
I also have an inverter connected to the battery. If I connect more panels to the battery then I’m potentially going to run out of space on the terminals to fit the O rings and washers onto. Is there some kind of adapter available to solve this problem and create more terminal contact space or is the solution to use fewer and higher wattage panels?
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
In your case, the 300w panel with inbuilt controller may or may not work. A panel that size would typically have a working voltage of ~38v, and with a pwm controller would likely be for a 24v nominal bank. It may be wired internally as 2 x 12v nominal panels in parallel though, with a shared 12v nominal pwm controller. If so, it could be added in parallel with your existing 12v nominal panels.
Rather than stacking more on crowded battery terminals (inefficient and potentially unsafe), what's often done is to have a single pair of heavy wires going from battery/bank to a positive and a negative buss bar. These can be bought premade (eg from our hosts), or can be DIY from copper bar or tube stock and SS bolts. Controllers, inverters, etc are connected to the buss bars (with wire and breakers/fuses sized for the particular device).
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
These are the specifications for the 300W panel. I believe it’s designed for 12V battery systems.
It does appear to be 12v nominal panel(s). Not sure about a 10a max series fuse with Imp of 16.6a though?
Adding fridge/freezer to a system generally moves system size up a notch or two. A typical AC fridge is ~1500wh/day, and needs an inverter big enough to start it. A single 300w added panel is unlikely to support this addition on a daily, year-round basis. It may work for something like a weekend summer cabin though.
Boosters can also use a fair bit if left on 24x7 (I think mine would be on the order of 5-600wh/day + inverter losses). I turn mine off when not in use.
As @mcgivor suggests, you may be getting to a point where it's worth thinking about what a future ideal system might look like. Alternatively, you could go ahead with some extra pv for extra loads, and maybe a generator for now.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
This is not the easiest task on a mobile application, usually means parking in an open area, or by using a movable array, either way it's prudent to not build too conservatively based on proposed useage, most successful off grid users have more capacity than needed to not only get through times of poor sun, but also to recover from these times.
From the information provided regarding panels with their own controllers I'd be inclined to use multiple modules in parallel with a single controller, rationale is there would be a single charging algorithm which is more precise than multiple sources.There are excellent PWM controllers available at reasonable costs, some of which can be programmed to suit specific needs of the battery, naturally cost is relative to the individual but a professional unit can be had for less than $200, down to a generic one for $50 or less.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Overall consumption varies a lot with box insulation, ambient temp, etc. My boat unit isn't all that well insulated, and uses ~750wh daily. A similar sized but heavily insulated unit I built in the cabin uses ~150wh/day.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Given I already have panels each with their own built-in controller that I can just plug in and go, is the benefit of using a single controller worth the potential additional cost of another unified controller (not sure whether I could just use one of the existing ones) and the time to research how to rewire the system to make sure I know what I am doing?
To help with power consumption we sometimes get a block of ice and put it on the bottom of the chest fridge/freezer. It lasts quite a while.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
@MattY said
Given I already have panels each with their own built-in controller that I can just plug in and go, is the benefit of using a single controller worth the potential additional cost of another unified controller (not sure whether I could just use one of the existing ones) and the time to research how to rewire the system to make sure I know what I am doing?
Can you provide a link to the panel with integrated controller, as well as the 300W controller, or do you know the specifications? There are different charge algorithms for different battery types, whilst it is possible to have multiple controllers work if all follow the same charge profile, not knowing the the specifications makes it difficult to say definitively one way or another. Having a single controller with a display, can provide information at a glance wether the battery is charging, discharged, in float or some other state, they also provide low battery cut out to protect against completely discharging the battery.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
In short it depends entirely on expectations, saving money is often more expensive, in the long run.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
on the referigerator , I am using two Grape Solar GS-5 units. These have a Chinese knockoff of the Danfoss compressor , The Colku. I am using 200 -250 watt hour per day per unit. Have Chinese volt/amp/watt meter on each unit for data logging. Use is in 38 foot fifth wheel travel trailer which is used as a house in mountains. Heated space at 65 degrees. Grape Solar has since exited the referigerator business, too bad , these are great units. Purchased at Home Depot Online for about $800 / one unit.
Hope this info is useful
david
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
I have 25 panels, wired properly into 2 controllers, and all works fine after 10 years.. no need to have 25 controllers
Remember - these are SOLAR panels, not shade panels. A panel in shade, produces next to nothing..
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,