Problems wiring my panels

andy300z · November 2010

Hello. I have recently purchased (3) 80watt panels and when its configured in series i am getting 51v and 15amp,Which should be 51v @ 5 amps. When its configured in parrallel i am getting 17v @ 5amp which should be 17v @ 15amps. I need help i can seem to get the right voltage beased on the type of wiring configuration.I even disconnected the diode it does not help Thanks.

p.s These panels are 80w 12v panels monocrystaline.

Windsun · November 2010

Re: Problems wiring my panels

We need to have the actual model number and manufacturer.l

BB. · November 2010

Re: Problems wiring my panels

How do you know you are getting 51 volts at 15 amps instead of 51 volts at 5 amps? Are you measuring it with a meter, reading from a solar charge controller, or what?

Or are you confusing series parallel connections and making a mistake in your math?

When you place panels in series, the voltages add and the current remains the same.

When you place panels in parallel, the current adds and the voltage remains the same.

It should be impossible for your panels to output 51 volts at 15 amps:

power = volts * amps = 51 volts * 15 amps = 765 watts

You have 3x 80 watt panels and the maximum output would be 240 watts. For three 80 watt panels:

Vmp=51 volts; Imp=4.7 amps for 3 in series
Vmp=17 volts; Imp=14.1 amps for 3 in parallel

-Bill

andy300z · November 2010

Re: Problems wiring my panels

I have the 3 panels on my shed which is fed into a home made combiner box
The combiner box is made with two grounding bars. All the red wires go to one bar and all the black wires goes to the other bar.
When i measure the voltage & amps with my fluke meter on the bars i am getting
17v @ 5amps which should read 17v @ 15amps which is a parrallel wiring

When i rehook the wire in a positive negative configuration where i have the one black going to the bar and one red going to the other bar i am getting 51v @ 15 amps which should read 51v @ 5amps. which is series wiring

From the combiner box my wired are going to a breaker panel and i am getting the same results. I was on my roof for hours retesting with the same results.
I have even bought another multi tester.

info on panel its made by lotus

Electrical Data
Model LT80
Cell Material Mono Crystalline
Maximum Power 80 Watts
Cell Grade A
Nominal Voltage 12 Volts
Maximum Voltage 17.5 Volts
Open Circuit Voltage 22.1 Volts
Maximum Current 4.57 Amp
Short Circuit Current 4.94 Amp
Maximum System Voltage 600V

niel · November 2010

Re: Problems wiring my panels

current does not flow without a load so i have no idea how you indicate you have current flowing. is this using the meter as the short circuit while measuring current?
as to putting + to - i am not sure that somewhere along the line that you may have shorted panels out or not as the arrangement you have is not that clear to me.

andy300z · November 2010

Re: Problems wiring my panels

yes i am measuring the current by puting my leads on the plus & negative terminals. no load

I even retested each panel which provide 20v @ 5 amps

Andy

BB. · November 2010

Re: Problems wiring my panels

You cannot measure the current with no-load... Either the meter has to be set to Amps (10 amp full scale is typical for most meters--So I am not sure how you are measuring 15 amps).

And, you have to be careful with using a DMM in current mode... If you attach the leads to the wrong device/circuit (like a large battery bank)--you will be in for some sparks, popped fuses, and possibly damaged DMM/Equipment.

Be very careful.

Are you measuring the current with a solar charge controller?

If you have a solar charge controller, what brand/model do you have... There are two major types PWM and MPPT--and while the do the same job, they behave entirely different with series vs parallel connected solar panels.

-Bill

andy300z · November 2010

Re: Problems wiring my panels

Bill

I ran home to get lunch and i rechecked my system wiring.
I have the 3 panels wired in series which produces 51v @ 15amps

I purchased a craftman multimeter that goes up to 20amp dc so the reading is there.

When i change the wiring to parrallel i am getting 17v @ 5 amps at the breaker panel.

Is this a right way to test amperage with my 20amp dc meter or do i need a load ?

I am in the process of puchasing an outback fm80 mppt controller and i am aware
about the series & parrallel wiring option with these controllers the 51v @ 15amp is perfect enviroment for this charge controller.
I am just confused about the readings i am getting

Thanks for your time

Andy

BB. · November 2010

Re: Problems wiring my panels

Using a current meter on the panels measures the Isc-short circuit current. A perfectly valid test. Isc is just a bit higher than Imp.

What you are describing should be physically impossible.

Either you are describing the setup incorrectly, mixing up the physical writing, using the meter wrong, or have a bad meter or meter battery.

-Bill

andy300z · November 2010

Re: Problems wiring my panels

I am going to take a day off tommorrow and rip the system apart and retest ,this thing is driving me nuts.

Thanks bill for your patience and advise

I will follow up on my progress providing i dont fall off the roof . lol

Problems wiring my panels

Comments

Categories