MPPT buck converter ICs

google "solar charger lithium :microchip.com" to get more hits than you want on the subject.

You're going to be a busy bee!

Bee puns? Oh bee hive.

On the upside, the can of worms would attract birds, and then you can do the birds and the bees!

Tim

Yeah it will only do that when the solar panel output is less than the programmed charge rate. half the time solar output will be zero and the rest of the time is varies between zero and some.

Hi, Win -

Can you explain why you need MPPT for that?

Thanks

If you use a PWM-ed regular buck under the control of a uP you can integrate the panel MPPT and charge control function into one "thing", by using some strategy like say fuzzy logic and adding an extra state variable so you're working with as measurements per-timestep panel output voltage, per-timestep battery charge current draw, and battery SoC.

The off-time with the PWM driving the enable pin of the buck, if the buck's output circuit is Hi-Z and doesn't allow back-feeding in that state is a fine opportunity to switch a fixed reference voltage onto the Li-ion cell to measure cell impedance and thereby guesstimate current SoC

I would be interested in learning about this bee counter; someone i know would like one. Thanks, R. Baer

You may be more interested in Thomas Hudson's original version, which we have been using for a few years (see link in folder). My RIS-788 is more complicated and begs for machine assembly.

Win, please forgive me for such a dumb question. The instructable shows the Arduino code is written in C.

How do you take that code, transform it into something the Arduino understands, then download it to the Arduino?

I have been researching Arduino compilers, and the best I have come up with is the Arduino IDE. It requires Java, which I won't allow on my computers. The last time I tried, it wrote over the master boot record and required reinstalling Ubuntu.

Other tools seem to require programs such as Microsoft Visual Studio, which I don't have:

How do you do it?

Thanks

Perturb and observe works well. Light intensity changes rather slowly. Small errors don't matter much.

We've used PIC processors to do MPPT, solar tracking and other functions simultaneously. A solar panel is inherently current limited and if the battery is reasonably matched, you can't hurt it in a short time.

Use the PWM output to drive the switcher. Initialize the duty factor to the nominal value and let 'er run. When the processor has time, measure the current and battery voltage. Modify the duty factor in steps until current quits increasing...or the battery voltage reaches terminal voltage. You don't have to do this very often...seconds don't matter much. The processor is free to do a lot of other stuff.

Obviously, there are special cases to deal with at dusk and dawn. We used hall device high-side current sense due to other constraints. If you don't need a common ground, low-side sense might bee cheaper.

Give some thought to what happens if the processor runs amok.

Microchip has been buying companies with excellent but widely-divergent technologies. Their boost and buck converter engineers are in a different world than their solar-power engineers, who specialize in micro-processor MPPT converters aimed at the grid-tied crowd. I have a horde of 285-watt AC microconverters on my solar-panel roof, but that technology isn't relevant to my 2W battery system. I've already got good Microchip stuff in my design, but I couldn't find any useful MPPT stuff.

The guys in the next office make this one:

Thanks.

=0

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if you managed to overwrite the boot record by installing java then I'm not sure computers is for you ...

The C-code and libraries are universal. Atmel and others offer development environments that don't use Java. But the Arduino environment is extremely user friendly, for quick programming. You could dedicate a cheap eBay laptop for that.

It can be avoided, and I will since I can't find an easy quick drop-in chip solution. But that means I won't be eeking out every last drop of solar energy from my panel.

Thanks. I'll check Atmel and other manufacturers to see what they offer.

Yeah, what would you do with the excess power if you are charging constant current?

Rick C.

Atmel uses Java throughout. However, I discovered Microsoft Visual Studio is used by some of the Arduino compilers and is free. Downloading and installing takes a long time, but it has not crashed so far. It requires the .NET framework that comes with Win7. So far, so good.

I didn't realize Arduino used Java. But I strongly suggest you swallow your disapproval and setup one machine just for Arduino, without any restrictions. You'll save lots of pain and trouble in the end.