Power Inverter Faults, what am I doing wrong?

my friend, it seems as though you are missing the battery and the charge controller.  correct me if I am wrong.  go in this order.

1. pv module
2. charge controller
3. battery
4. inverter

the inverter is not meant to take the input from the pv modules directly.  Inverters are meant to work off of batteries.  If the inverter is not destroyed, it likely will be if you continue to try to feed it 20+ volts pv direct.

if you want to learn more on your own,
check out the photovoltaics design and installation manual on our website. 

If you want help fixing what you have, please call us, I will help you, because nobody likes blown inverters.

james - Alt-E staff

yes, that is a standard system.  that is likely any pwm charge controller sized 6 amps or higher.  Try looking at a morningstar sunsaver 6.

As far as the panel, that voltage at max power seems very low for a 12v nominal module.  17 is a more typical number.  What is the make and model of module?  Or what are the full stats on the back (open circuit voltage, voltage max power, short circuit current, current at max power)?

It is not unreasonable to run things without a battery.  But, those things must be DC loads capable of handling PV direct type voltages!  things like water pumps, and electric fans are run pv direct often.  They usually have electric motors that can handle the higher and slightly variable dc voltage.

you were ablsolutely right, your inverter will not like 17 - 20 vdc!  you can run dc loads without an inverter, but with a battery directly off of a charge controller like the one I mentioned above, but they (the load) must use less than the amount of amps the controller is rated for.

feel free to ask away if any other help is needed.

- james - Alt-E staff

the theory is correct, at least, but the charge controller is not that sophisticated.  when it is sunny, it will put into the battery what it gets from the pv.  If you have a load on at the same time, it will draw from the battery to fulfil that load.  If the load takes out more than what the pv puts in on a daily basis, you are operating at a net loss; not good.  welcome to the basics of system design!  If you are using more energy than you are producing, it is not the components' fault, but the system designer's fault.  although more storage (bigger battery) can delay the inevitable, making less energy than you use will ultimately create a system that will work intermittently if at all.

james - Alt-E staff

it is important to note that some charge controllers have what is called a low voltage disconnect (LVD) which will disconnect the load before you wreck the battery by drawing it too low.  with morningstar controllers, the models containing a low voltage disconnect have "L" in the name for the sunsaver series, and the prostar series has an lvd as a standard feature. A low voltage disconnect can protect your batter from an untimely death, but will not fix bad system design.  Incidentally, most inverters (even no frills inexpensive ones) usually have a lvd on them nowadays.

Ok, so is it just me or does it seem pretty inefficient to have to charge a battery and then draw power from the battery as opposed to sucking power straight from the PV.  Or, is the charging technology so efficient that there is little loss from going from PV to Battery.

Either way, thanks for the info I think Im set to join the Solar revolution.

The way I'd like it to work is to have the inverter draw
directly from the Solar Panel when its generating electricity.  When the electricity isn't sufficient for the load then it would draw the necessary current from the batteries.

It just seems inefficent and wasteful of the battery to have to charge the battery before drawing current.

I'm not sure if I'm making sense.  I'm not saying I'd want the battery eliminated, just bypassed when appropriate.

Thanks for the help, I got my little system working!