Under the hood: Morningstar SunSaver MPPT.

Buckin' Bronco

This is the Morningstar Sunsaver MPPT charge controller, capable of pumping 15 amps into a 12 or 24 volt battery system from an up to 75V input. It’s fairly simple, though the 6P6C jack can be used for Morningstar’s Modbus system or Remote Meter to add more control, programming, and monitoring capabilities. The unit is driven by a Microchip PIC18???* microcontroller.

A typical MPPT controller consists of a switching buck or buck-boost converter with the input connected to the solar panel array, and the output connected to the battery system. A microcontroller monitors the solar array voltage and current (and multiplies them to calculate the power) periodically, and adjusts the switching of the converter appropriately to keep the input side voltage at the solar array’s maximum power point, Vmp.

Inside the Morningstar Sunsaver MPPT, there is… a switching buck converter with a micro… etc. Here you go:

* The conformal coating stuck to the top of the chip made it difficult to read. Like the flavor of PIC matters? XD

Control/Logic Board

No fans or other active cooling are needed. The inductor is thermally coupled to the back of the housing, which is a tall metal fin attached to the heatsink/base. The switching transistors are, undoubtedly, potted somewhere in there. The potted construction is also used on the SunSaver PWM controllers.

Simple, elegant, but here’s the big question: WHY does it cost $250?! Rest assured, I’m scouring the market for some *good* low cost MPPT controllers. This is just a very good and not quite as low cost controller!

Xantrex XW-MPPT-60-150: Squeezing 60 amps through a toothpick

It doesn’t smell too great in my office right now…. some Xantrex XW-MPPT-60-150 charge controllers just came back that are completely, totally burned up. SCORCHED. OWNED. PWNED. TEHPWNZRIATED.

All images are clickable for full resolution, as always (4000×3000 px)

First off, here’s why I think these blew up. Note the four small pins on the back of each contact of the large screw terminals. Each of them is probably 18 gauge… if even. It’s hard to judge since they’re square pins.

Up to 60 amps of current will flow through these little four-legged pieces of Chinese scrapmetal when the controller is running full tilt.

FYI, National Electrical Code requirements would call for AT LEAST 6 AWG assuming the conductors are copper — which they are not, they’re tin plated steel.

Aaaaaaand now, the results.

Burnt components and pieces of plastic fall out of the controller whenever it’s handled, and it’s left a wretched smell to permate my workspace. The copper PCB traces are still there and didn’t fuse, but the solder has melted away on them from the heating, and several components in the vicinity desoldered and fell right out of the controller.


Topside. The top of the terminal block and delaminated PCB

Under the hood: The Outback FM80

Warning: Engineering porn ahead. All images are clickable to view in full resolution.

The Outback Power FM80 solar charge controller is a high performance MPPT controller which converts a solar array’s output (up to 150VDC, 64 amps) down to charge a 12, 24, 36, 48, or 60 volt DC battery string using a high efficiency switching buck converter and an extremely flexible microprocessor control system. It is field programmable from the front panel and can be linked to other system components using Outback’s communication buss and the MATE controllers for system logging and remote control.

It is extremely well built, and solid as a rock.

More photos below…

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gimme gimme shock treatment

(Special thanks to The Ramones)

An engineer came into the office today who will remain nameless mainly because I forgot his name. He told me of hijinks at the Dayton Hamvention in which he rigged a portapotty’s seat with conductive tape, a dc flourescent lamp driver, and a small solar panel on top of the ‘loo. When sunlight hit the panel, the seat became… Well, the least pleasant portapotty seat ever.

Now that’s … Special.

Heart Transverter

Well, this is new. Years ago, Heart Interface Corporation made a really nice line of renewable energy and vehicle ac inverters and inverter charger units. At some point, the company became Trace Engineering, which was then bought out by Xantrex, who promptly worked hard to make most of the better products and engineering go away in favor of nasty Chinese rubbish. 😛

Well, Heart Akerson is still around today in Costa Rica, and his new company, Heart Transverter, has a pretty fun product going.

Basically, it’s one green 2KW box of switching converters, software defined and highly programmable, with two dc input/output busses, one +50VDC output, one ac input, and one ac output… and it does… anything you want it to, including serving as a grid tie inverter, pv controller, charge control ….

A companion unit can be used for sophisticated load monitoring and control of six circuits.

It is designed and manufactured in Costa Rica, which is pretty amazing in itself.

The brains of the system are on a small remote control unit about the size of a sandwich, with a usb interface for programming.

Believe me, I’m most curious and intrigued. I didn’t get to see it running today, sadly. I’d love to see this in action.

I should add that the Heart Transverter logo is pretty cool. Yeah, I have a little obsession with how neat the old Heart Interface logo was 😛

ASC Charge Controllers

ASC Charge Controller
ASC Charge Controller

Over here at Sun Electronics, we sell a lot of Specialty Concepts ASC charge controllers. They’re very simple, reliable units employing shunt regulation to halt battery charging once the battery is full.

By “shunt regulation”, this means they basically short out the input from the solar panel.

They’re very simple. There’s nothing to adjust, nothing to do but just hook it up and go. A small red LED on the top indicates that the solar power input is present and the batteries are charging (it goes out when the batteries are full and the controller is shorting out the output). The entire unit is “potted” in an epoxy filling and  very moisture resistant – great for marine applications and severe humidity exposure.

Here’s one controller where you REALLY need to make sure that you’ve sized it correctly. Make sure that the total short circuit amperage (Isc) on your solar panels is lower than the controller’s rating… or you WILL blow the poor thing sky-high. Other than that, it’s pretty much set it and forget it. The switching is very slow, and the controllers are unlikely to generate any RFI. They’re very popular with our customers.

Click the block diagram to view it full size. This is what’s inside the unit. Please be sure you hook up the battery leads with the correct polarity, otherwise the controller just… ceases to be. The few damaged ones I’ve ever seen wound up failing with the battery terminals shorted. If proper fuses are used*, this would just blow the fuse between the controller and battery, preventing any damage or overcharge.

The AUX relay shown in the block diagram is provided on units with a low voltage warning/disconnect.

* Please properly fuse your system or I will throw things at you.

The AIMS Power 3000 Watt Inverter/Charger

I’ve been having fun with this AIMS Power PWRIC300012W while pretending to be productive here at the office for the last couple of days.

Franklin from IndoorGenerator sent this unit over for me to play with, and I’ve found it to be very good. The unit combines a 3000 watt modified sine wave power inverter, automatic transfer switch, and 30 amp smart charger all in one nice, compact, lightweight package.

Yesterday I beat the holy splunge out of it with various test loads including a portable air conditioner and large 1/3 horsepower AC motor, and ran it at 2.8KW output for the better part of an hour. It barely even got warm to the touch.

From my testing, I found that the inverter only has two weaknesses to it.

First, like any high frequency switching type inverter, it can sometimes run out of power and turn off suddenly while trying to start loads with a large inrush current. This includes large halogen/incandescent lights, large motors, and compressors. If you’re starting such a beast off a switching inverter, it should be the first thing to be turned on, and any other loads should be removed before attempting to restart the large motor/light.

Charger board - J1 and mysterious green LED near center

Second, the transfer switch isn’t instantaneous. The power goes off for about a second during the transfer from battery to AC or AC to battery.

A very useful little LED meter is present on the end of the unit next to the outlets. By pressing the button next to it you can select whether to view the battery voltage, DC input amperage, or AC output wattage in Kw. While AC power is present and the unit is charging the batteries, the output Kw and DC amperage both show as zero. I would have liked to have a DC current measurement visible during charge like the Xantrex TR series provides, but I’m not gonna complain much about it.

When the inverter goes into overload, the LED display on the end shows “E01″. I also managed to get the inverter to glitch a couple of times – weird things happened like the battery voltage reading coming back as ” 0.4″, or the inverter shut down and showed “Err”. Both of these problems went away as soon as I replaced a 1 AWG battery cable in the test setup which was becoming stinky hot! Oops. Too much voltage drop!

As the inverter begins to get near maximum power output, the peak to peak voltage begins to fall a bit. The unit compensates by shortening the 0-volt pauses on each cycle to maintain 120Vrms through manipulation of the duty cycle. Lights will not change brightness, but some AC induction motors may become weak as the wave approaches being a 120V peak to peak square wave. I noticed this only after applying around 2.7KW of load. The Daewoo portable air conditioner I was running did not show any problems with this, but a large industrial fan (of doom) began to slow down a little.

The charger is rated at 30 amps output. I clocked it at 33-34. It is, interestingly, built on its own board inside the top of the unit. This is a lot different than the charge system in the Xantrex Freedom series units I’m used to refurbishing, on which the same (massive) transformer and transistors are used to convert and regulate the current for charging. The internal 3-stage charger works fine on flooded cell batteries, but the absorption voltage got too high for a gel battery. I measured 14.82VDC. This may be in range for AGM batteries, however — check your battery manufacturer’s recommendations!

Today, I popped the top off and started looking around inside.

The build quality is very nice. It appears that the lower board is in charge of converting 12VDC to 170VDC. The board at upper right contains the AC transfer circuitry, a current sense transformer, and an H-bridge to chop the 170VDC into modified sine wave. The board at upper left is the charger.

The charger board has a jumper (JP1) located on it. Removing JP1 and turning on the charger activates equalize mode (about 15.3VDC). The small green LED located near JP1 comes on when the charger is in absorption or equalize mode. Unfortunately, significant disassembly of the unit is needed to access JP1, and activating any function of the unit while it’s open like this will expose lethal voltages to the user… so let’s just say that until a switch is brought out to the end panel of the unit, this feature is not Ready For Prime Time. AIMS didn’t even know the jumper was there! I only figured this out as I tried toggling the jumper to see if it was there to reduce the voltages for use with gel batteries.

The cooling fans at the end of the unit run whenever the charger is active, and otherwise… very rarely. It barely gets warm at all while in invert. All of the transistors that have any significant amount of current across them are heatsinked to the extruded, finned alumimum chassis. This is a design borrowed from high power car audio amplifiers, which have to put up with being wedged in all sorts of weird ways into hot car trunks with little air circulation.

My final verdict: If you’re looking for a good low-cost, lightweight modified sine wave inverter/charger, this is probably just what you’re looking for. If you’re running any large motor loads, however, be prepared to go over and reset the inverter when they fail to start.

H-bridge and AC transfer board

If the cost and weight aren’t that much of an issue, I’d step up the Xantrex Freedom or Xantrex TR series; they cope with starting large motor loads by just throwing everything they’ve got at it, current limited only by the inductance of the transformer. The motor makes hilarious sounds and the inverter output voltage dips during the ordeal, but it’ll start the motor, whereas a lightweight switchmode inverter like this will just go “Noooo! OVERLOAD! Now you get to come over here and reset me! HA HA!” Plus, the Freedom and TR have a much stronger charger.

Hey guys stop reversing the polarity on your Xantrex Freedom units :P


Or, “Now presenting, the all new for 2011 International Rectifier PwndFET Transistors”

I suspect this happens when someone reverses the battery leads on a Xantrex Freedom series inverter. The IRF1010E HEXFETs are blown to bits! On the power board for a 1000 or 1500 watt unit (they both appear to be the exact same board), there are ten on each side.

The symptoms are usually an inverter which goes through the right motions of going into charge and invert, but no output is seen. Sometimes, the unit even makes the right sort of sound as if it were going into charge/invert. Inspection of the FET board will reveal… this.

The other devices on the board appear unaffected. Coming soon: an experiment to see what happens when the IRF1010E’s are replaced! Does this lead to a perfectly working board… or just an object which remains a paperweight? Stay tuned…

The IndoorGenerator…

The designer of the IndoorGenerator power units just dropped by here at Sun a few minutes ago. Their products are really interesting, especially for those of us down here in the Hurricane Belt.

Their product is, in a sense, like a giant UPS. Sealed maintenance-free lead-acid batteries are paired to a power inverter/charger unit in a nice cabinet. It’s also possible to get a unit from them which features a solar charge controller, and an outdoor rack to pair a couple of nice big solar panels to the system for off-grid operation!

Now, you see where I said “nice cabinet”? I mean it. Go look at their page for the PowerCubes – they look like a piece of fine furniture. You could use one as a nice end table or coffee table.

They also make some less aesthetically fancy but very functional UPS systems for commercial and office use. He was talking about using Outback Power inverter/charger units inside some of his systems, and those would be awesome for such use – they produce very clean power and transfer back and forth perfectly.

For those of you urban cliff dwellers, they also have a very nice looking balcony unit that unintrusively sits out there and can be wired to solar panels.

He’s going to bring over one of their standard series units in a couple of weeks for us to play with. I look forward to putting it through its paces and brewing a pot of coffee or two…

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