Reply To: Using capacitors instead of a battery

[lorenzop]

capacitors are interesting, but not the best choice for solar power storage due to the way they discharge and drop in voltage faster, as other posters have mentioned. what’s interesting is, as a large capacitor drains, the voltage will drop smoothly, but eventually will be low enough an inverter will power off, even though a capacitor would still have plenty of current left to deliver.

what if, you put a capacitor bank before the charge controller? you would still need a lead acid battery, but I wonder if a capacitor bank would be worth having to supplement. may also need a dump load or disconnect to prevent over charging the capacitors. the way I picture this experiment working, solar panels charge the capacitors, which feeds into an efficient MPPT charge controller, then into a smaller lead acid battery bank. the charge controller can then pull more power from the capacitors after sundown, and draw them lower than what an inverter alone could do.

taking the experiment a bit more to the crazy side, you can wire a DPDT relay to switch 2 banks of capacitors between parallel and series. put a sensor on each bank to detect when they’re both lower than 50%, then trigger the relay to switch the banks over to series which puts your MPPT charge controller back to 100% voltage. although the current will be about 25% of what you had when it was in parallel, the voltage will be boosted high enough to allow a deeper draining of the capacitors, which they’ll be more than happy to do daily.

what do you think of my idea? I’m unsure if this would help or hurt efficiency in the real world, but it is interesting and could be worth trying. any flaws I haven’t thought of?