I recently installed 2 140 w panels and a 15 a controller. what I dont understand is that on a day of no clouds, sun at its most direct point I only get 7.8 a from the controller to the battery bank. I expected in the area of 12 a . I wired panel 1 pos to panel 2 pos,
panel 1 neg to panel 2 neg (parallel). am I doing something wrong? my location is north east Indiana. the panels are mounted flat on the roof.
The full rating is only during perfect - absolutely perfect - conditions.
Here's some things that might be working against you:
1) They are best when angled directly towards the sun - a little angle goes a long way. Flat mounted panels will not get full rating (unless your bus is angled - not recommended :) ).
2) Humidity, dust, smoke and other atmospheric conditions can affect output.
3) Heat decreases output.. so hot days, means less power.
4) Even a touch of shadow on the panel can severely diminish their output. Check for anything that might be casting a shadow - trees, overhangs, roof airs, antennas, etc.
- Cherie
Quote from: pd4104252 on August 30, 2012, 04:57:34 AMI recently installed 2 140 w panels and a 15 a controller. what I dont understand is that on a day of no clouds, sun at its most direct point I only get 7.8 a from the controller (snip)
What's the voltage for that 7.8 Amp?
rule of thumb is 30% loss with flat panels, that checks with chart to me.
If your panels have only 33 cells in series, their voltage when hot will fall too low to get full output current. Using 36 cells will get you high enough voltage to use the full output current, but you will probably get best power with an MPPT controller because the controller will match the voltage of the cells to the voltage of the battery being charged.
For what it's worth.
Tom Caffrey
The amperage to the batts is also dependent on the state of the batts. As the state of charge (percentage) goes up, the less amperage the controller allows to pass through.
Ed
state of charge along with panels being flat on the roof might be the answers,
i never let my batteries go below 12.2V so maybe i won,t see over 7.8A.
Someone asked about the voltage, I will try to get to the bus around noon when the sun is at its highest and check the viltage from the panels along with the voltage from the controller. Maybe i should add one more panel. my controller is good for 15A and seeing that i'm net retired yet i don't forsee getting south far enough to damage my controller due to too much amperage.
1. keep your panels clean - i have 20A of panels on my roof but will only get 12A if they are covered in dust
2. what charge conteroller are you using -
3. your charge controller will "throttle" the delivered power according to the charge state of the batteries
-bulk - all available power
-float - programmed volt/amp
-absorb - programmed volt/amp