Nominal 24 volt 300 watt pump, SmartSolar MPPT 75/15, 3 X Suntech 175 watt grid connect panels (OC 45 volts) in parallel. Which terminals to use, or would a battery setup with daylight sensor switching be better? All suggestions gratefully received!
asked
Connecting solar DC bore pump without a battery - load or battery terminals? - or???
Hi John. You'll need batteries for the 75/15 to reference a V, else it won't know what to do.
It *should* be able to drive your pump directly from the 'Load' terminals, but 300W is heftyish, and if you strike issues you could go direct from batts. Maybe then you'd need a timer/daylight sensor/load terminal driven relay to switch it for batt protection. But let's call that a worst-case scenario.
300W outta 24V is 12.4A if the sun dies. A pair of 12V 100Ah should suffice in practice. If you only have a need for a few hours of pump/day, you could go with less. Too low and the V sag could make tuning the 75/15 a challenge in low light.
There are specialty pump systems that can supposedly work direct from pv, but I know nought of them, and cost may also be an issue.
