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Rebuilding my Solar Power System after 3 years Storage
eidolon:
When time eases up I'll do a long series on the discrete water heater board which is really cheap. I'll let this be the depository for the build.
MadScientist267:
That's essentially the classic "pseudo mppt" design. Drift however is almost a moot point, as none of these circuits actually "track" actual power. The PV drifts more than the components in the control ever will.
Anything that "OR's" the input and output voltages and pulls the PWM of the converter back when output voltage is hit or when input voltage falls below threshold accomplishes the base functionality... Much better than direct connection or a simple converter... But not as well as a true tracking scheme that hunts for the sweet spot periodically.
As for the TL431 implementation, yep sometimes you gotta get crafty hehe... That said, yes, a TL431 and an opto work well in tandem on this, and the isolation allows for super simplicity on literally any converter topology (no jumping thru hoops, just have the transistor side tug on the Vfb pin all but directly). The most stable version of it I've messed with involved a TL431 on either side into a relatively low impedance divider to set up the Vfb.
Either way, always interesting to see another version of this circuit... They're very useful where the cost (or parasitic nature) of a true MPPT can't be justified.
eidolon:
It is not quite like that. A lot od MPPT is just crap and doesn't really operate at the true power point. As there is a bypass diode about every 10V on a panel and I've seen controllers sync to lower voltages and stay there in a shading situation even after it passes. One of my MPPT controllers has a micro monitoring the panel voltage and when it drops low for a period of time it disconnects the panel to reset it. Immediately higher wattage and voltage. MPPT is solar for muggles so they can connect any panel to any battery and not know anything. When heating water, voltage is everything. Constant voltage ends up just as good as power point at a lower voltage. Constant voltage can track.
WooferHound:
Building and installing my two Lithium Power Banks.
//www.youtube.com/watch?v=_gkMMkdAkII
WooferHound:
I'm still having trouble getting my new Lithium Battery Bank to take a full charge. When Full it should read close to 21 volts, the highest I have seen it is 19.5 volts (3.9v per cell) which is only 25% according to the BatteryGO monitor.
For the last 2 weeks I have left the 6 Solar Panels in Series Pairs. On a Sunny day with heavy haze the total Panel output was measured open circuit 42 volts at 2.5 amps. The battery bank should be around 20 amphours. Right now the panels are connected directly to the battery bank, bypassing the charge protections. Haven't messed around with the Buck / Boost converters again for charging. Have been looking at some small MPPT controllers.
I have fully converted the system to work at any voltage between 12 & 22 using Buck converters to control the voltage or current for every individual load.
My Audio Amplifier is the only item that is running straight off the battery, it will work up to 25vdc. I made it from an Amp Module and is a really beefy little thing at 15 watts per channel. Added a green indicator light to it while I was inside it to check it's voltage capability. It sounds louder and cleaner than ever running at the higher voltage.
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