5 key consideration when mix and matching solar modules in a solar power system

Home » Knowledge » Renewables » 5 key consideration when mix and matching solar modules in a solar power system

It is a common question that is being asked more so in companies dealing with solar power systems. For instance, in a situation where a customer has an assortment of modules they want to install in the same solar power system. They have a stockpile on hand that they want to put to good use.

In some cases they may have an older solar power system that they want to expand upon or replace a few faulty modules that are now outmoded. The knee jerk answer seems to be ‘No way!’ Do not fret.

Typically the mixing of solar modules from different manufacturers and of dissimilar voltages, wattages and amperages is not recommended. However, if you take certain factors into careful consideration you can easily achieve this goal.

Also Read:Why Solar Power Panels are necessary for you

When mixing solar modules is important to remember that it is not the wattage of the modules that is important to consider. When connecting modules of dissimilar electrical characteristics in series, it is each module’s current that plays a heavy role in how the string is going to perform in the solar power system. The opposite is true of modules that are connected in parallel. In this case, each module’s voltage impacts on how the string will perform in the system.

However, this does not mean that we should start connecting any mix of modules together and call it a day. When their electrical characteristics are too far apart the effect on the system’s production could be tremendous. Compare the module’s data sheets. Only modules with exact amperage, or as closely similar as possible, should be wired in series connection. On the other side of the balance, that rule applies to dissimilar modules wired in parallel connection. Only in that case, the voltage of those modules must be matched as closely as possible.

Series and Parallel Connection

Say you want to connect modules in series and one module type is 8A and the rest are 8.5A. The 8.5A modules will all be dragged down to the 8A of the module that is brought into the string. This in turn will bring down the overall output of the entire string.

Now, let us say we have a 30V module that we want to bring into a 40V string where the modules are all in parallel connection. In this instance, the parallel modules are pulled down to 30V and reduce the overall output of the string.

String(s)

It is not all that cut and dry, however, there are other considerations to take into account before mixing your modules. For example, if the string(s) with dissimilar modules are connected to an MPPT channel on a charger or inverter, the MPPT control would not be able to optimize the string due to the different current or voltage.

Quantification

Another factor to consider, is that in older operating systems, that are in operation where you want to mix in a different module, you cannot rely on the data sheet for the existing module. This is because of the expected degradation of these modules over their lifespan. Therefore, despite maybe having close electrical characteristics on datasheets, in reality these specs have likely have changed and this should be quantified before paring the new modules into the strings.

Module alignment

Additionally, if you are in the situation where you are considering mixing up your modules you want to ensure that your modules are very close in their electrical characteristics. For paralleled strings, try to match the module voltages as closely as possible. In series strings, match their ampere rating as close as possible. In either case, the lower of the two values will determine the production you can expect out of the solar power system.

Micro-inverters and Optimizers

Finally, it is worth noting that the majority of mismatch production losses can be mitigated with the use of micro inverters or optimizers. These two technologies allow each module to be treated independently within the system, ensuring maximum production from each panel. Its highly recommend the use of micros or optmizers if you are considering pairing dissimilar modules into one system.

4 thoughts on “5 key consideration when mix and matching solar modules in a solar power system”

  1. I realized this is 3.5 years late, but no one seems to have replied to David’s query. Personally, I have never seen “12V panels” that really output 12V. Vmax and Vopen on most panels for 12V systems are typically 17 to 21V. I believe what the author of this article is saying is to read the specs on the label at the back of those panels. It depends on how many cells your “12V panel” has. E.g. if your 100W panel is 17V max, then it outputs 5.88A at max. On the other hand, if your 100W panel is 21V max, then it’s output 4.76A at peak.

    With 4 of these in parallel, you are talking about either 17V at 23.52A or 21V at 19.04A. From what I’ve seen, larger panels only output higher voltage (nominal 24V, 36V, 48V). Very few of them exceed 10A at peak, even 420W panels. So a 320W 12V panel that outputs 20A is uncommon.

    We are talking about voltage and amperage on the input side of the controller (output from the solar panels), not the battery side. If you have a PWM controller, then adding higher voltage is meaningless. Your 320W panel alone may output 40V at 8A, but if you put that through to a PWM controller, you would only get 13.3-14.4V at 8A charging your battery. However, if you use a MPPT controller, it would charge your 12V battery at close to 25A.

  2. Consider rewriting Its highly recommend the use of micros or optmizers if you are considering pairing dissimilar modules into one system.
    to
    It is highly recommend the use of micros or optmizers if you are considering pairing dissimilar modules into one system.

  3. This is really good to know about this topic to discuss in detail.The mix matching solar modules.
    I have read many article but the you have mentioned are very rare..Thanks for the point..
    Awaiting for the new updates form your side.

  4. I have 4 x 100 watt 12volt ~5amp panels in parallel. Making 400watts 12volt ~20amp string.

    Can I add a single 320 watt 12volt ~20amp panel in the above string someway, somehow to it.
    What size controller am I looking at?

    Thanks so much for your help
    David

Comments are closed.