Please help me select the correct electronic device to control the voltage from an 18v PV to a 12v load while automatically shutting down the power at dark. I purchased an "MPPT 10" charge controller but then learned that this item is a "fraud" and not truelly an MPPT controller. MTTP is apparently the manufacturers name. Don't know if I should use it or not. The 100w, 18v PV will only power (or recharge the battery that supplies) a 12v water pump continuoulsy during the day. What device should be used to control the power supply and automatically shut down power at night. Thanks.
Controller or Other Device Help Needed.
- Thread starter LarryJ
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If you get a 12V panel that's well matched to the power requirements of the pump, you just hook up the panel, it will run the pump. when the sun goes down, it stops.
It sounds like you bought a charge controller. That's for charging a battery from a solar panel, not driving a load.
It sounds like you bought a charge controller. That's for charging a battery from a solar panel, not driving a load.
Yeah, well I bought the panel based on recommendations of others who said panels only put out 80% on average of stated rating. The "12v" panel is mounted to my shed and ain't comming down. It delivers 22v, and I suspect it's the reason why my first pump stopped working while it was connected directly to the panel. So, as I said above, I bought a charge controller that may or may not be the correct device.
It's not. A charge controller is for charging. There are step-down transformers that can take the 18V of your panel and convert it to 12V.
Something like this with a wide input range:
I've never used one, and there may be other issues. You would need to select one with sufficient power to drive your pump.
Something like this with a wide input range:
I've never used one, and there may be other issues. You would need to select one with sufficient power to drive your pump.
OK, thanks. I'll look into it.
If I wanted to run the pump off the battery and allow the PV to charge the battery, wouldn't a charge controller be needed to do that?
I agree with @snoobler, you only need a SCC (Solar Charge Controller) if you have a battery to charge. A 12V DC pump could be driven directly from a PV panel so long as it had enough 'umph' to get over the initial surge current required to drive the pump. When a big load is connected to PV panel/cell, it's output voltage (and therefore power it can deliver) collapses, that's why driving pumps is hard for a PV panel on its own. But this can be achieved with a sufficiently big enough panel.
Do you have specs for your DC pump? You're looking for the 'stalled rotor current'. Let's say that this is 12A. You'd need to match this to the Isc (Current Short Circuit) specification of your PV panel. A typical 100W panel will generate Isc = circa 5.5A, so in this example, two 100W panels in parallel might have sufficient 'umph' to get the motor running. Once it's running it'll actually operate on a far reduced current.
Obviously, your pump will only pump when there is sufficient solar irradiance to drive it, which means that it will effectively automatically switch off at night, but you might also struggle if clouds come over. Most people add a battery to their system to overcome these challenges. If you do, that's when you need a SCC.
Make sense?
Edit: corrected typo.
Do you have specs for your DC pump? You're looking for the 'stalled rotor current'. Let's say that this is 12A. You'd need to match this to the Isc (Current Short Circuit) specification of your PV panel. A typical 100W panel will generate Isc = circa 5.5A, so in this example, two 100W panels in parallel might have sufficient 'umph' to get the motor running. Once it's running it'll actually operate on a far reduced current.
Obviously, your pump will only pump when there is sufficient solar irradiance to drive it, which means that it will effectively automatically switch off at night, but you might also struggle if clouds come over. Most people add a battery to their system to overcome these challenges. If you do, that's when you need a SCC.
Make sense?
Edit: corrected typo.
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Yes, exactly. My response crossed yours.
If you do end up adding a small battery and an SCC, try to get one with a 'load out' function, and use this to drive the pump. The 'load out' terminals will only operate when there is sufficient solar irradiance to deliver whatever spec the load-out terminals are specified for. Usually, the load-out terminals can aslo be configured e.g. Victron SCC's, so you can say turn on at x, turn off at y etc.
OK great. Now we're getting somewhere. As it turns out (and as noted in my first post) I bought an SCC, then found this review of that device which says it's a complete fake SCC.
Should I use it? Assuming this is a PWM-type SCC, then the simple answer is no. But, as I said, you only need an SCC if you're planning to add a battery. If you are planning to add a battery, then, yes, you will need an SCC. I've already linked you to a recommendation.
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