How do I match up portable/foldable solar panels for my power station when buying different brands?
Posted by muddbone46@reddit | preppers | View on Reddit | 16 comments
I know the easiest way would be to just buy the exact same panels but I see deals all the time. My first set are 220w so can they be paired safely with 200w panels?
TacTurtle@reddit
Voltage, amperage, connector
IGetNakedAtParties@reddit
Voltage are important but so is the device you're charging or powering from the panels.
A 12V solar panel will actually output anywhere from 0 to 14V depending on the sunlight and angle.
A 12V lead acid battery will be anywhere from 11.6V to 12.8V depending on state of charge.
If the solar voltage is higher than the battery voltage, the battery will charge up. If not it will do nothing. These are both called 12V because they work together without control systems. A voltage higher than 14V will damage a battery like this. All battery chemistry has different voltage tolerance.
A charge controller can take a low voltage and "boost" it to a higher voltage to charge the battery making more use of the sunlight, it can also "buck" down high voltage to protect the battery. A "portable power station" (terrible name for a battery) often have these boost/buck controllers built in to the battery management system BMS.
So basically without information about the exact components you want to connect nobody here can answer your question. Share the links and I'll have a look.
muddbone46@reddit (OP)
I currently have the Oupes Mega 2 along a set of Renogy 220w Solar Suitecase Panels. There’s currently a deal on Renogy E.Flex 200w Panels that I’d like to get, but the advice I’m asking for isn’t just about these components. I do want to know if these will work properly and efficiently together but I also want to know how to figure out what other components will work together for future reference. I don’t just want the answer, I want to know how to answer my own question.
IGetNakedAtParties@reddit
The oupes mega 2 looks like a great piece of tech. It has internal BMS and even has a MPPT on one of the solar inputs. This is the best way to extract maximum juice from the sunlight by basically "pretending" that the battery is exactly as flat as the sunlight is strong. Their website has the input and output specs and claims the following:
So it seems any 12V+ solar panel can go into the normal buck charger, but to use the MPPT you need higher voltage panels.
The renology panels are 20V and 18.6V respectively, so either of these connected to the MPPT should give you the most optimum use of sunlight. However they are not the same voltage architecture so putting both in series will see the 20V do all the work and the 18.6V panel doing nothing. That might not make sense let's visualise it like water pressure. The 20V panel can pump up 4 storeys, the 18.6V pump can only pump up 3 storeys. When you connect them together the pressure of the 20V just pushes back on the 18V pump, making it worthless.
Unfortunately this is always true of solar panels, have two identical single line panels at the same angle and you get double power, put a leaf on one and the power drops entirely for this line to half. Panels are multiple solar cells in series and parallel to build resilience and the correct current and voltage. One weak link in the chain and the whole line contributes nothing to the whole system.
If you have another battery with BMS or better yet MPPT then this changes it, one panel to one battery is a great, efficient and resilient system.
muddbone46@reddit (OP)
Yeah, I’m really impressed by the Mega 2 but was even more impressed with their customer support. I had a pre-sale question about the unit. Before I even made my purchase, I received an email response the same day and a call the next day to make sure I understood their answer. It’s my understanding that Oupes donates units to people with medical needs for backup power needs. Anyway, what would be the results of running those two panel sets in parallel instead of in series?
IGetNakedAtParties@reddit
So I corrected my mistake, apologies for that I was talking about in parallel. If you connect them in series this may work as the MPPT can tolerate higher voltages. Here the voltage is combined, 20+18=38V but the currant is limited by the weaker panel. This causes a little heating and can damage cells if they're mismatched by a lot, which is why they typically don't get connected in series.
IGetNakedAtParties@reddit
Jesus I've messed up series and parallel in my last comment! Let me correct it.
Least-Welcome@reddit
here's a solid site to compare portable power stations, for anyone interested: https://wattsreview.com/Products
Maleficent_Mix_8739@reddit
Differing wattages are fine it’s differing voltages that can cause issues.
muddbone46@reddit (OP)
Ok. So different wattages in series or parallel?
Maleficent_Mix_8739@reddit
Always parallel. If you run series your voltages will stack. Solar panels use the same rules as batteries when wiring.
PristineSKS@reddit
Excuse me I believe you may be mistaken. Whether you wire an array in parallel or series depends on the limiting factor (lowest max, current or voltage) on the panels in the array and cannot be determined without knowing the array specs.
Maleficent_Mix_8739@reddit
Since so many companies are using standardized connectors, you might look for a combiner cable set. Harbor freight had them a couple of years ago.
PristineSKS@reddit
https://footprinthero.com/solar-panel-series-and-parallel-calculator
Exciting_Turn_9559@reddit
Not much of a deal if it doesn't work with what you have. Even less so if it wrecks what you have.
Ryan_e3p@reddit
There's more to wattage that needs to be calculated; voltage is another thing. Then, there is how you hook them up (serial vs parallel), and the tolerances of your charge controller to ensure you don't need exceed the max amps, watts, and voltage.
Once you start mixing panels with different specs, you are potentially going to have inefficiencies start to rear their head. As an example, depending on how you hook up those panels, you could only end up producing the lowest voltage across all the panels, which is inefficient since it sort of "ignores" the voltage of anything past that, which results in less than peak performance.
You're diving into some "in the weeds" DIY that even I would be hesitant to jump into without doing some serious research and having my calculations double and triple checked before I hook anything up.