From PV charge batteries first , then power load

[Brownian]

I want a system that uses solarPV o recharge batteries first , without powering the load. Then when fully charged, switch the PV power ( now excess ) to power load directly. Load in this case is an mppt grid-tie micro inverter

(Later I want to add timed discharge of the pack, during peak utility rates , to the inverter)

Any ideas

 

[Brownian]

Perhaps this was the wrong forum... noobie mistake

 

[Craig]

I would use a relay or solenoid controlled by raspberry pi or some other microcontroller that lets the battery load side be used only at certain times of day providing batteries are above a certain voltage. There is another thread where someone does similar to power a pond pump.

 

[gnubie]

This is something I am pondering myself. I already have a linux SBC snooping the serial output of my Victron controller so going that bit further isn't that hard. The only thing I'm wrestling with is switching the PV input in the long term. Mechanical switching will work but how many cycles can be gotten from a relay set designed to cope with say 10 amps at 100VDC is a good question. The other option is FET switching but then I have to think about not blowing up the FETs with static charges on the panels. I'm sure I'll get there eventually...

 

[Craig]

This is something I am pondering myself. I already have a linux SBC snooping the serial output of my Victron controller so going that bit further isn't that hard. The only thing I'm wrestling with is switching the PV input in the long term. Mechanical switching will work but how many cycles can be gotten from a relay set designed to cope with say 10 amps at 100VDC is a good question. The other option is FET switching but then I have to think about not blowing up the FETs with static charges on the panels. I'm sure I'll get there eventually...

Wouldn't a 100 amp SSR work?

 

[Craig]

Also are you looking at something like an A-B switch? I was thinking if just turning the battery output on and off. Looking forward to others ideas.

 

[gnubie]

It'd handle the solar no problems but static charges between the panels / roof and the equipment could easily fry it. TBH I'm not even sure if there is the potential (haha) for static to accumulate. The roof is neutral bonded.

 

[gnubie]

If I ever get around to it the plan will be to connect the PV to a MPPT controller for water heating. Now that I've thought about it it may even be practical to command the Victron to turn off it's MPPT activities / charger and then turn the HW controller on so there is no need to switch the PV at all. I'll have to look into that

 

[efficientPV]

It is easier than that. When battery charging lessens, the panel voltage goes up over power point voltage. Then just send any extra power to heater. Even though your batteries aren't fully charged, there is lots of power to send to a heater. Only in certain charge cycles is all solar panel power sent to the battery. Pretty simple, TL494, FET and capacitor bank. $25 will do it.

 

[gnubie]

I'll have to look into that

I remembered to do something for once and it is possible to command the Victron to turn its charger off using hex protocol on the serial port.