More Solar for "Us"

[MrWizard]

Ok, I went off.the deep end?
Bought 3 used 37watt uni-solar panels and a blue sky 2000e controller for the hefty price of $400,
They were being listed as 75w panels, they are not

The tested open circuit voltage was 21+, short circuit amps 2.9
I tested each panel multiple times tilted into the sun and laying flat on the ground , got the same readings each way, that was the deciding factor, they appear to put out full power while laying flat, I will try to mount them tomorrow before it gets hot, right now 104°F
I will use the existing wiring until I buy & install the new wire

[Salvo]

Setpoint has everything to do with the MPPT efficiency. First off, the controller doesn't know the voltage of the battery. It calculates the most efficient power point by using the voltage at the output of the controller, not battery voltage. There is no battery sense line.

There are a few bad things happening with a high setpoint.

1. The higher the setpoint, the smaller the difference between controller input and output voltage. You've now eliminated the advantage of MPPT. MPPT wants to see a large voltage difference between input and output.

2. The higher the converter output voltage the lower the charging current.

3. Gassing increases. Battery overcharging.

BTW Jim, you better read the Blue Sky manual before giving false information.

Sal

bigfootford wrote:
Mppt is a function/feature that a controller does and has nothing to do with the setpoint.

If a controller has the setpoint feature then when the setpoint voltage is met which is the output of the controller to the battery then the controller will revert to the absorb voltage which is lower than setpoint. The Absorb voltage is usually low enough to stop gassing.

Jim

[MrWizard]

my turnigy power meter is a "clone" of the "watts up" power meters he has on the side of his yellow box

I love the way they track the power and give you the watts, watt's hrs, amps, amphrs

[bigfootford]

Here's a couple of utube videos to watch.

It does take a couple of times watching his videos about Mppt v/s Pwm to see how it works...

Part 2 is the better presentation but watch both.

MPPT vs PWM part 1

MPPT vs PWM part 2


Jim

[bigfootford]

Mppt is a function/feature that a controller does and has nothing to do with the setpoint.

If a controller has the setpoint feature then when the setpoint voltage is met which is the output of the controller to the battery then the controller will revert to the absorb voltage which is lower than setpoint. The Absorb voltage is usually low enough to stop gassing.

Most of the good controllers with Mppt have set points that are adjustable with a manual adjustment or by software that runs on a computer.

Mppt is used to enable the controller to take advantage of the panel voltage being greater than the battery voltage. Most controllers with Mppt need the panel voltage to be <>2 volts or higher than the battery to make Mppt work....The greater the difference between the panel voltage and the battery the greater the Mppt boost will be. There is a point where the difference/panel voltage will be too high and then you will have a loss of efficiency.

When the panel voltage is not over that 2vdc point then most of the controller's with Mppt will act like a regular Solar charger...

Jim

[LScamper]

Salvo,

Don't know how to ask this question but here goes.

Does a MPPT controller try to give maximum power out at any converter output voltage, that is if the output (battery voltage plus voltage drops) is 11 volts will the controller try to match the maximum power of the panel to the 11 volt load. And if the output voltage goes up to 13 volts will the controller track this and try to match the maximum power of the panel to the 13 volt load? If it does how does the set point play into this other than to shut of charge? I must not understand what a MPPT controller does.

[mena661]

Salvo wrote:
Didn't we cover that topic already?

Do you understand the differences between a converter and charge controller charge algorithm?

Do you believe these batteries can accept 14.4V or 14.8V all day long, each day?

Why not ask Trojan if it's OK to apply 14.8V for 24/7 duration?

Blue Sky applies the setpoint voltage to the batteries for as long as it has solar power.

Ahhhh NOW you answer it!!! No one's talking about leaving batteries at this voltage all day. I even stated in an earlier post about damage at this voltage if you had a manual charger. No one here has a manual charger so no damage from 14.6V can occur.

[MrWizard]

the batteries are not seeing 14.6

the batteries see 13.75 in this particular instance

perhaps if the sun was higher and peak rate longer time with no loads so the amps would taper before the voltage from the panels tapers, it would teach 14.6 at the batteries
But Not now, not under MY USE conditions and winter time solar conditions

as for mppt I adjusted that after I adjusted the set point and I adjusted that according to the blue sky instructions while watching both the little led indicator and the amps output reading, in fact the instructions specify this should be adjusted once the system is installed and all wiring is in place, it does not need to be readjusted unless you change something in the system like panels, wire, or setpoint, if every solar install was the same, if solar was a one size fits all ? these adjustments would not be provided and instructions on how to use them included,

Maybe when summer arrives and the sun is higher the output higher and the solar charge day longer I will need to change these settings, I will keep an eye on the batteries, but baring any symptoms of excess gassing, I'm leaving things the way they are
:B

[Salvo]

I you're interested in getting max current out of your solar controller then a lower setpoint is better.

Let's say you got 150W of solar output power.

The output current is dependent on the setpoint voltage.

Icharge = Pout / Vsetpoint

If your setpoint is 14.8V, current is 10.1A
If your setpoint is 14.0V, current is 10.7A

I haven't verified this with measurements, but that's how a MPPT controller should work.

Sal

MrWizard wrote:

14.64v controller output measured with my fluke meter

[Salvo]

This is turning real stupid.

I gather you didn't comprehend the question again. It was not solar related.

BFL13 wrote:

Please explain how Mr Wiz is going to get solar 24/7

[MrWizard]

1:40pm

14.64v controller output measured with my fluke meter

controller & Turnigy power meter both read output amps 10.40a

13.75v measured at battery with fluke meter

clear sky full sun panels flat roof
there is No evidence the solar is capable of "gassing" the batteries before next summer

I'm going to need more sun and more "generated power" than what it can produce under current conditions

[BFL13]

Salvo wrote:


Why not ask Trojan if it's OK to apply 14.8V for 24/7 duration?

.

Please explain how Mr Wiz is going to get solar 24/7

Not only that but he discharges the batteries again overnight.

[Salvo]

Didn't we cover that topic already?

Do you understand the differences between a converter and charge controller charge algorithm?

Do you believe these batteries can accept 14.4V or 14.8V all day long, each day?

Why not ask Trojan if it's OK to apply 14.8V for 24/7 duration?

Blue Sky applies the setpoint voltage to the batteries for as long as it has solar power.

[pianotuna]

Hi Salvo,

Why not call it what it is--gassing, not boiling.

-30-

[mena661]

Salvo wrote:
By definition, 14.6V is above the boiling voltage.

Do you see any advantage having a 14.6V setpoint?

Why does Trojan, Surrette, Universal, Lifeline, and etc. tell us to set our controllers to anywhere from 14.4V to 14.8V??? If this only destroys batteries, why is this recommended?

[Salvo]

You state:

"Let's say we have 20 amps @ 14.6 volts going into 200 pounds of lead. That's about 300 watts. That works out to about 1000 BTU's, if 100% of the energy going in is waste heat. That may raise the temperature 5 F internal to the battery. But of course, even worst case that doesn't happen--as Mr. Wiz's current is too low."

Almost all the energy goes into boiling the battery. Very little goes to heat. Your paragraph doesn't have any relevance.

As far as current quantity, the controller outputs current to keep the battery at 14.6V. It doesn't really matter the magnitude of that current. What ever it is, it's enough to keep the battery above the boiling point. By definition, 14.6V is above the boiling voltage.

Do you see any advantage having a 14.6V setpoint?

Sal

pianotuna wrote:


That was my point--it isn't boiling it is electrolysis. If my battery bank is at 102 C I don't want to be anywhere near by.

Since you say current doesn't matter, I'd love to see an 875 amp-hour battery gas at 14.6 volts and 1 amp.