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In the first edition of my solar learning series I shared 5 Facts You’ll Want To Know About Solar. As my research has continued, I’ve come across some myths, truths and facts about solar that are worth sharing.
The myth of more batteries
One myth people have come to believe is that by adding more batteries to their setup they’ll get more power. The reality however is that they should probably be adding more solar first. From my research I learnt that this meant that you need to get more power to fill your battery which made sense enough on its own but it really came to life with this analogy.
If I want more wine, I don’t buy more wine racks. Particularly when the racks I have are only half full (I’m an optimist). If I want more wine, I buy more wine. And then, when my wine orders start showing up faster than I can (responsibly) drink them, and I’ve started overflowing to the linen closet, that’s when I invest in more wine racks.
If you’re not quite following, replace ‘wine’ with solar panels and ‘wine racks’ with batteries and hopefully you’re there. Rule of thumb, if your wine rack (battery) isn’t full by lunch time (on a typical sunny day), than you probably need more wine (solar panels).
To top it off, you need a good solar regulator that’s been set up correctly. This will ensure that there’s no risk of your battery overcharging or your solar regulator being damaged.
The truth of output
Confusingly, the industry uses twin scales when it comes to measuring the output of solar panels. The first, Standard Operating Conditions (SOC) is used for development and selling and this is usually the most prominent in the advertising. The reality of SOC output is achievable only atop a high tropical mountain around noon on a freezing cold day. The other scale, Nominal Operating Cell Temperature (NOCT) indicates typical usage and will be the more likely output but you’ll generally only find this in the technical data or on the panel itself, not on the ad.
I came across some maths that explained volts to watts and something else about amps but to crux of it is this, the SOC scale that is advertised to you is overselling the output by about 25% i.e. if it says you’re getting output of 100 watts, it’s more like 75 watts.
In another unfortunate turn of events for us trusting solar newbies, regulators with Maximum Power Point Tracking (MPPT) don’t ‘provide’ up to 30% more power despite the claims. An MPPT solar regulator doesn’t actually provide more power at all. What it does is recover some power that would be otherwise lost, similar to how a car’s torque converter optimises engine power. No I don’t know what that means but I couldn’t come up with another wine analogy.
Also that ‘30% more power’ is mainly for an hour or so after sunrise and before sunset or during light cloud coverage, basically when battery voltage is very low. And that ‘up to’ should probably be capitalised.
So all of that is to say that MPPT works, but in reality it’s more like 10-15% ‘extra power’. It’s a function built into most high-quality solar regulators and included with some portable solar panels. So while it might not be on the list of must-haves when making your purchase decision, if you’re getting quality you’ll likely end up with the benefits of MPPT anyway and I’m not going to say no to extras!
The facts about watts, volts and amps
OK so I avoided the maths on this one in the last section but now it’s time to wise up and understand watt it all means. It’s really very basic actually…
Watts(power) = Volts x Amps
Solar power is like a rainwater system
A basic way to understand solar power is to liken a solar setup to a rainwater system. The roof of a house that gathers the water is the solar panel, and the water tank is the battery. The greater the size of the roof, or the more watts a solar panel has, the more water that can be gathered. The water tank is pressurised and connected to a hose, with the water pressure representing voltage and the flow of water (or the water flowing) in the pipe attached to the tank representing amps.
So let’s break it down:
Watts – The amount of power the solar panel is capable of producing. Back to the rainwater system analogy though, little or no rain = little or no water. So littler or no sun = little or no power.
Volts – The pressure of electricity being produced – think about the water pressure in your shower.
Amps – The actual amount of electricity flowing through the solar panel and cables. This flow varies depending the amount of sun, the battery size and if it’s full or empty.
Well there you have it. You might need more solar panels, not more batteries. You’re probably getting less watts than you think. And solar power is like a rainwater system.
Tune in next time when I take a deep dive into regulators!