mppt vs pwm

Those "RJ Specials" are of course not MPPT as claimed. No buck converter. But they do a decent job as regular Series PWM.

pianotuna wrote:
I agree 24 or 48 volts would be the route to follow for the battery bank.

Method 3 on the smart gauge site for the wiring. I.E. equal length cables from all jars to a buss. correctly interconnecting multiple twelve volt batteries

With 24 batteries that works out to six "strings" of four jars, assuming each jar is 12 volts. Voltage at the buss is 48.

I'm still trying to find a good price on better controller, but am trying out cheap ones while I wait for a deal.

http://www.ebay.com/itm/10A-20A-30A-12V-24V-Auto-Switch-MPPT-Solar-Panel-Regulator-Charge-Controller-LN-/231464958089?pt=LH_DefaultDomain_0&var=&hash=item7b91b49fa8

You shouldn't have any more questions after reading that thesis.

That thesis is way more interesting than mine was on analog multipliers.

jrnymn7 wrote:


Cloud Effect

Ductape wrote:

JiminDenver wrote:
That is because you are only applying a dollar symbol and not looking for the best tool for the job. The only time dollars should be a consideration is if you look at it and either would fill the need. That's when you look at the advantages and cost of each.

Exactly. If you are looking for maximum performance from a limited roof space for instance!

That can lead to having a number of smaller 12v panels instead of a few bigger 24v panels. But it does not tell you whether to put the 12s as 24 and use MPPT or leave them as 12 and use either PWM or MPPT.

JiminDenver wrote:
That is because you are only applying a dollar symbol and not looking for the best tool for the job. The only time dollars should be a consideration is if you look at it and either would fill the need. That's when you look at the advantages and cost of each.

Exactly. If you are looking for maximum performance from a limited roof space for instance!

What mppt can't do is raise voltage higher than what is coming in from the panels. But if the panels are 30 volts and the batteries are nominally 12 volts that is hardly an issue.

BFL13 wrote:

brulaz wrote:

BFL13 wrote:

...
I almost understood that part just above, where the buck converter tries to balance the power at its input with the power being used at its output. It has to find a voltage at the input that will get the power down to what is being used at the output.
...

Suspect that it is the buck converter as directed by the microprocessor that is doing this. Not the buck converter by itself.

Well my little buck converter gizmo by itself was hopeless. It got saturated and all that. Then I was told here it needed a bunch of other circuits stuck on so it would behave properly.

Not surprised. It needs some intelligence as how to set its duty cycle. Salvo's diagram probably sums it up pretty good. Battery and Panel sensors feed the microprocessor (dual microprocessors in the Rogue3048!) that in turn controls the Buck converter's duty cycle.

Or something like that. Pretty awesome little black box ...

O.K., I was under the impression, low irradiance resulted in much lower panel voltage. But I just looked at a graph that shows it is Isc that suffers considerably with low irradiance.

Page 10 of the actual study;

Cloud Effect

So, is it fair to say the mppt controller, in the rainy day test, would have found most of its Input Power (watts) in the form of voltage, as the curve would be a low and long one? (low amps/near full Voc)

brulaz wrote:

BFL13 wrote:

...
I almost understood that part just above, where the buck converter tries to balance the power at its input with the power being used at its output. It has to find a voltage at the input that will get the power down to what is being used at the output.
...

Suspect that it is the buck converter as directed by the microprocessor that is doing this. Not the buck converter by itself.

Well my little buck converter gizmo by itself was hopeless. It got saturated and all that. Then I was told here it needed a bunch of other circuits stuck on so it would behave properly.

BFL13 wrote:

...
I almost understood that part just above, where the buck converter tries to balance the power at its input with the power being used at its output. It has to find a voltage at the input that will get the power down to what is being used at the output.
...

Suspect that it is the buck converter as directed by the microprocessor that is doing this. Not the buck converter by itself.