I'm diving into solar power for my upcoming off-grid cabin project and ran into a puzzling issue. I have two 100 watt solar panels (they're matched) that are currently producing around 80 watts each according to my solar generator. When I hook them up in parallel, the generator shows about 120 watts going into the battery. I get that there's some loss from the cabling, but 25% seems way too much. I even tried connecting them in series, but my battery wasn't having it at all. The manual states it can handle up to 30V from solar input, so I'm confused about what went wrong. Any ideas?
3 Answers
It's also possible that you're not pulling the maximum from the panels if your battery isn't empty. As long as the battery has some charge, it will only take what it needs, which can limit what you see from your solar input. Make sure your battery is really depleted before running any tests! Plus, check the battery's state of charge before guessing at wattage.
It looks like you might be hitting a voltage issue with your series setup. Most '12V' panels actually put out around 18V, so when you connect two in series, you could end up with around 36V, which is higher than the 30V limit your battery can accept. In parallel, the 120W output could also be due to the solar generator's input capacity. If it limits output to around 8A or 10A, that could explain the wattage you're seeing. Just a heads-up, the brand of the solar generator could impact this too! Check how it identifies solar input vs. car charging and let us know the specs of your system.
Yeah, that voltage discrepancy makes a lot of sense. I measured 19V from one of my panels too! That series connection definitely would have caused an issue.
Don’t forget to consider wiring and connections! If the wires are undersized or poorly connected, you could easily lose power. What you described, a 25% loss, isn't uncommon. If you can, share the specs for your panels and battery, along with some pictures of the wiring. It might help pinpoint the issue!
I’ve got beefy 4mm² cabling for the panels, and I’m using 12 AWG for the connection to the power station. Everything looks solid, but I’ll double-check all my connections!
Got it! I'll ensure it's nice and low before testing again.