Mismatched panels can be put together in the same string, but there are some rules to follow to keep the system safe and efficient.
In a series string, you need your panels to be the same technology, similar output, and a similar open circuit Voltage. The limiting factor with series panels is the current – if you have a low current, high voltage panel in series with a high Voltage, low current panel, it will limit your output current and potentially overheat the low current panel.
For parallel strings, your panels must be the same technology, your parallel strings must be as close as possible to the same open circuit Voltage (5% out is considered the safe limit), the tilt angle must be within 5%. This is if they are ‘paralleled’ on the roof, without a breaker in between or power conditioning equipment such as micro – inverters.
If you have multiple parallel strings going through breakers, they still need to be the same technology and within 5% Voc, but they may be facing different directions / at different angles.
Are these 12V panels?
In industry, panels that are under 25V open circuit are commonly referred to as ‘12 Volt panels’, which leads people to think that if they have a 12V battery, they need a ‘12 V panel’ (which is actually 24V). Not the case.
There are two basic types of solar controllers – There’s a whole other tech talk on them but it boils down to:
PWM: Can halve the Voltage coming from the solar panel (so can bring 24V down to 12V). Not very efficient, not very good for your batteries in the long run as they tend to let through high frequency Voltage ‘spikes’.
MPPT: Can handle much higher Voltages (Most ‘12V’ MPPT’s take between 45 and 100V max. input). More efficient. Often comes with 3 – stage charging, takes excellent care of your batteries.
This means – With an MPPT, any panel you like can be a 12V panel. Generally speaking, getting a secondhand commercial grade house panel and an MPPT controller is going to cost about the same amount of money as a brand new 12V panel with a PWM (there are good 12V panels and there are also extremely bad ones), and will take better care of your batteries.
What’s the difference between monocrystalline and polycrystalline panels?
Record–breaking efficiency belongs to the monocrystalline panels, but generally speaking a 200W monocrystalline will be the same size as a 200W polycrystalline. Monocrystalline panels generally do better in the heat, polycrystalline panels genrally do a bit better in diffuse light conditions (i.e. partial shade)
What’s the best flexible panel
There are three main types of solar panel cell. Monocrystalline, polycrystalline, and amorphous.
Monocrystalline and polycrystalline are made from silicon wafers. Whilst a few brands like Sunpower have made more flexible cells, all mono-and-polycrystalline cells are brittle. A mono or a poly flexible panel is simply not going to last very long. You’ll get longer if they are framed or if they are mounted well, but you will be lucky to get 5 years from a good one and they often don’t last 2.
Amorphous flexible panels exist. Amorphous solar cells are very flexible and durable, and amorphous flexible panels are very expensive.
