270 watt panel only showing 150 watt on kid max

[mondo]

I have been testing out my kid for a few months now.  The display calculations on my kid are always, battery voltage reading x amp reading = watts reading, all on the first display screen.  Very different from the manuals example calculation of battery voltage reading x "battery current" (reading not shown) = watts reading.  I understand how to calculate the numbers but i dont understand why my kid calculates watts = battery voltage x pv current.  My kid has never shown watt numbers other than battery voltage x pv current,  numbers all shown on the first display. 

For instance, if my kid were to show, on the first display screen, 12.7 volts and 9.5 amps, then the watts reading would show 120w and not 257w like on the manual. 

Something is not right with my kid.

[mondo]

Am i comparing apples to oranges here?  Is the manuals example using 12 volt panels to a 12 volt battery?  Would the calculations differ this much because i am using 24 volt panels to a 12 volt battery?

That is the only thing i can think of...  Anyone out there have readings, from the first display screen, using 24 volt panels to a 12 volt battery bank, to share.  Or maybe, 12 volt panels to a 12 volt battery bank first display screen readings.   It would really help me wrap my head around this.

[Robin]

The watts display will be way off if you do not run PV minus to its terminal and battery minus to its terminal. The Kid is different from the Classic. You must have these conductors separated. I hope that is your only problem, otherwise contact tech support and they will be able to help you.

[mondo]

The watts display will be way off if you do not run PV minus to its terminal and battery minus to its terminal. The Kid is different from the Classic. You must have these conductors separated. I hope that is your only problem, otherwise contact tech support and they will be able to help you.

Pv and battery negative wires run to their terminals on the kid.  The pv negative wire is not joined with the battery negative wire.

[Mario]

The kid does not display PV current anywhere, the only current it display are Battery and Load,
the Current on the main Status Screen where it displays the Watts is Battery current and Output watts to the battery not the amount of watts coming in from the PV panel.

It Works like this: battery voltage displayed X Output Current to battery = Output watts to battery. I think you are confusing the currents.

gotta keep in mind that to keep the same amount of watts (minus efficiency) when you are bringing higher voltage down to a lower voltage the PV current will be lower and the battery voltage will be higher.
For example:
- 120v PV and 1 amp = 120W (into the kid.)
- 12v Battery 10 amps = 120W this is assuming no losses and 100% conversion efficiency.

You cannot take 120v and 10A = 1,200W. Not correct.

Right now in winter if you have a 250W panel you will see less power out because the panels are rated in perfect conditions and perfect sunlight to panel angle.

Please let me know if you have any more questions,

Mario Rodriguez

[Halfcrazy]

PV modules are rated at whats called STC (standard test conditions) of 1000 watts per meter squared. Now in the real world we are around 750-800 Watts per meter squared.

What this means is we can assume 75-80% of what the panel is rated for IF we have it perfectly angled and it is solar noon and the sky is crystal blue.

So a 250 watt module I would expect to see around 200 watts if all is perfect.

Ryan

[Mtn Don]

PV panels at higher elevations can produce more power than STC.  Can be more than perfect?     Less air = a boost in solar radiation hitting the PV cells. Our system at 8800 feet regularly produces more than the panels 624 watt STC rating. Bright sun, clear pollution free sky, low humidity, cool weather. There's gotta be benefits to counter all the losses; engine power down, cooling system less effective, reduced output from furnace, etc.   

altitude effects link  PV specific on page 18-20

[dgd]

The kid does not display PV current anywhere, the only current it display are Battery and Load,

It would be useful if the input current could be displayed.
I always assumed the KID probably used an internal shunt in the negative input hence the requirement not to common connect the input and output negatives.
This would provide a reasonably accurate input current measurement.

Or am I incorrect and there is only a shunt in the negative output line?
Or am I completely wrong and the shunt(s) are in the positive line(s)?

Dgd

[Highflyer]

Mario,

Can you add a PV input voltage and amperage screen to the scroll?  I know the PV voltage is there, but I would also like to see the input amperage if possible.

Also, I think the wattage number includes the wattage to the batteries and to a load if used, your thoughts. ( I am using PM divert and believe the wattage includes the wattage going to the batteries and the heater)

[mondo]

If i am confusing the currents it is because i am following the manual.  If i am wrong the manual is wrong. Forum member vt said the current displayed is pv current, so i checked andnit does say its pv current.  The example in the manual makes no sense at all and is very misleading.  One would think 257 watts from 12.7 x 9.5 from a controller is too good to be true, which it is.  My numbers never matched the manuals numbers and it confused me from the start.  It took many attempts asking on this forum, phone calls, and emails to tech support to finally be told, the manual is wrong.  I am very disappointed it took this long. 

I am also disappointed my last email was totally ignored by tech support.

[Doug]

Hi Mondo,

The Kid manual is currently being updated. If any part is confusing to anyone I would like to know about it.
I will be checking into this and seeing what can be done to make it totally clear.

Doug