Eric Pedersen's posts

Hello Gabriel,
You raise a great question regarding which type of charge controller to use for your system.  It's a tough call, but like most situations we encounter in PV, the answer is “it depends.”

An MPPT charge controller should do a better job of sending more power to your battery bank than a PWM controller would, but the lower Vmp of the thin film modules does decrease the gain when compared to typical crystalline modules.  That said, you should still see an improvement over a PWM controller. 

If the solar array is relatively large compared to the storage capacity of the battery bank, then my opinion would be that a PWM controller would be fine since the array would be capable of charging up the battery bank without the "extra" power that an MPPT controller would supply.  If the array is sized so that you need every last watt hour of production to keep the batteries charged, then an MPPT controller starts to make a bit more sense. 

Something else you could consider would be to use an MPPT controller and wire the PV array at 24V.  This would give the controller a bit more voltage to work with, and would also help with voltage drop in the wire runs.  Most MPPT controllers will allow you to come in at a higher nominal array voltage to charge a lower battery bank voltage.

One last option, depending on the PV module you are using, would be to just add another PV module to the array.  This may not always be an option, and it may be much more expensive than the cost of an MPPT controller, but with the cost of PV coming down so much recently, some modules actually cost less than the more expensive MPPT controllers and will definitely increase your production.  This may not work for your situation, but it may be worth considering if the scenario would allow it.

Regardless of how you configure the system, the question remains, is the small gain you would receive worth the higher cost of an MPPT controller?  When you consider the life span of the array and the charge controller, then that small daily gain can really add up.  If your array is having a tough time keeping up with the loads upon the battery bank, then anything you can do to increase production is going to be useful.  Ultimately, the decision is yours, but hopefully some of this was helpful!


Eric Pedersen
altE Staff
eric @ altestore.com

Hello John,
How you wire the PV modules will depend on the type of charge controller that you are using.  Just because the charge controller manual says that it can handle up to 44.2V doesn't mean that it is able to step that voltage down to the 14-15 volts that a 12V battery bank would want to see for proper charging. 

It is likely that the charge controller is capable of charging a 24V battery bank with a 24V nominal PV array.  That would explain the maximum input voltage of 44.2V. 

There are more sophisticated charge controllers that are capable of stepping down a higher PV array voltage to a lower battery bank voltage.  This type of controller is called an MPPT controller, and while they are more expensive than other types, they actually do provide a gain in charging current over their less-sophisticated counterparts. 

If you had this type of charge controller, then you could potentially wire up the 2 Kyocera KD135SX-UPU modules in series.  This would help with voltage drop along the wire run, as you mentioned.  I would only consider this method if you were CERTAIN that the charge controller is an MPPT controller, and the PV array input did not exceed the maximum power input of the controller.

To echo the other comment from Tom, what charge controller do you have?

Eric Pedersen
AltE Staff
877-878-4060 x141
eric @ altestore.com

Hello Jerry,

The short answer to your question is "No".  Unfortunately, at this time there is not an inexpensive charge controller that can step down solar array voltage to a lower battery bank voltage, while maximizing the energy harvest from the array.  A more sophisticated charge controller is simply going to cost more than one that has less capability.

That said, given the size of the system you are considering, perhaps a different combination of PV module and charge controller would be a more economical solution.  Using cost as the guideline, a more powerful single solar module that operates at a nominal voltage of 12V, coupled with a PWM type charge controller may cost less and still get the job done. 

There are several PV module and charge controller options that could work, but if you really prefer to use the Kaneka 60W PV modules to charge a 12V battery bank, an MPPT controller will be required.

If we can be of any help identifying other options, please me know.


Eric Pedersen
AltE Staff

877-878-4060 x141
eric @ altestore.com
"Making Renewable Do-able"
http://www.altEstore.com/

Hello Shaman,

Thomas has it right in that "all things being equal", 1 solar module is easier to install and wire up correctly than 2.  That said, don't rely solely on wattage of the PV modules in question as your criteria for the equality of the modules. 

Just because the output way be the same in terms of watts, that does not mean that the two options would work equally as well.  They may operate at different voltages, even if the output in wattage is the same.  This effects the other components in a system, or may not allow one option to be used with other equipment.

Be sure to consider all of the specifications of the solar modules you are considering, not just the raw output. 

I hope that helps!

Eric Pedersen
AltE(R) Staff

Making Renewable Do-able™
www.altEstore.com
T: 877.878.4060 x141 or +1.978.562.5858 x141
eric @ altEstore.com

Hello John,

Thanks for the feedback on the Evergreen B modules that you installed, particularly the specifics on the small spacing problems.  I'm also glad to hear that their performance is in line with the A modules.  I appreciate your comments, please let us know if there are any updates!


Eric Pedersen
AltE Staff
877-878-4060 x141
eric @ altEstore.com

So I have noticed a posting or two here on the forums about B-Grade PV modules and wanted to make a couple of comments and see if anyone had any experience with them that they wanted to share.

So what are B Modules?  In general, manufacturers of solar panels will sometimes inadvertently build PV modules that have small cosmetic defects or blemishes that can affect the appearance of the solar module.  Typically, these discolorations will have very little to no effect on a module's performance.  Because B modules do not have a completely uniform appearance, they can usually be purchased at a lower price than their "A" module counterparts. 

Most manufacturers offer their full warranty on the B-grade modules so one can be confident that it will perform within its expected output range.  Be sure to to check this out before purchasing, to make sure that no special exemptions exist.

"B" modules can be hard to come by because most manufacturers do not plan to make PV modules with small imperfections.  They can represent a great value since their performance should be on par with A-grade modules. 

I'm eager to hear any comments either way from people who currently have B modules in use out in the field.  Have there been any issues or failures?  Are they working along with A modules with no appreciable difference in performance?  Thanks for any input!


Eric Pedersen
AltE Staff
877-878-4060 x141
eric @ altEstore.com

Hello Tim,

The Whisper 500 wind turbine may not be the right answer for you if your goal is to connect to the grid.  Like a lot of wind turbines, this one is made to send the power it produces to a battery bank, not directly to the utility grid.  Even the 220V "wild" AC version needs to be used in conjunction with a battery bank because its output is not consistently in the narrow range that the utility grid needs for code compliant connectivity.

This leads directly to your second question about what else would be needed to connect the wind turbine to the grid.  In addition to the turbine and controller, tower and battery bank, you would need a grid-tied with battery back up inverter, appropriately sized AC and DC disconnects, suitable wiring, and a lightning arrestor wouldn't hurt either.  That should cover most of the primary and secondary components.

There is another option from the same manufacturer, Southwest Wind Power.  It is called the Skystream 3.7, and that wind turbine is made to connect directly to the utility grid, through the included inverter that carefully manages the turbine's output.  You can learn more about it by clicking on the link below:

http://www.windenergy.com/products/products.htm

I hope that helps!

Eric Pedersen
AltE Staff
877-878-4060 x141
eric @ altEstore.com

At this time, there is not a charge controller on the market that is designed to handle such high DC voltage.  Unfortunately, you would have to change the design of the PV system to be able to incorporate batteries and a Grid-tied with battery back up inverter if you want to make use of the PV system when the utility power goes out.


Best of Luck,

Eric Pedersen
AltE Staff
877-878-4060 x141
eric @ altEstore.com