Mar-21-2014 05:38 PM
Mar-23-2014 07:07 AM
AStinker- wrote:
In my case it doesn't matter which calculator I use because I don't know for sure which Voltage or Load Current from the panel specs I should be using.
Mar-23-2014 05:10 AM
Mar-23-2014 03:54 AM
Mar-23-2014 12:23 AM
Almot wrote:AStinker- wrote:
But isn't the input voltage still important somehow? If not why are we worried about voltage drop from the panels to the controller?
With MPPT the drop is important because this converts into lost amps and amp-hours.
With PWM - people more familiar with these low-tech devices 😉 will correct me if I'm wrong - the voltage drop is not important as long as it is not lower than the highest Absorption voltage that you might need, i.e. Absorption on a cold day. As noted, and I agree, that it should also not be higher than 15V on a cold day.
So 15V is your lower limit of input after voltage drop at 77F. If it's lower, the controller with temp-comp won't be able to raise it as needed on a cold day. Controller with temp-comp will be able to lower it down from 15 on a hot day.
OTH, your controller should have means to limit maximum output to 15V - maybe it already has it as factory-preset. My controller has adjustable upper voltage.
Mar-22-2014 10:57 PM
Almot wrote:westend wrote:
Most of those wire size calculators should be used with two conductors since you have both a (+) and (-) phase. Don't know if the one you used calculates like that or not.
He didn't tell which one he used. Assuming it's Southwire - most people use it - you enter "single conductor" because it's obviously not a 3-phase, but you enter a total (+) and (-) run of your wire. Very often (though more often in roof installs than in portables) the + and - leads are different length, but it is the total + and - that counts.
Mar-22-2014 08:18 PM
AStinker- wrote:
But isn't the input voltage still important somehow? If not why are we worried about voltage drop from the panels to the controller?
Mar-22-2014 07:58 PM
westend wrote:
Most of those wire size calculators should be used with two conductors since you have both a (+) and (-) phase. Don't know if the one you used calculates like that or not.
Mar-22-2014 04:59 PM
MEXICOWANDERER wrote:
A thought that comes to mind is 100' 8 gauge twin cable is heavy, bulky and a real snake to wrestle with.
Mar-22-2014 11:28 AM
Mar-22-2014 11:23 AM
AStinker- wrote:BFL13 wrote:
This calculator us useful in that
A. it counts going both ways so you don't have to wonder if you need to double the distance.
B. You can try different gauges and see what you get for voltage drop.
What it does not do is tell you what amps you will get with what voltage drop. We had a thread about all that where that got answered using watts (so of course I got confused 🙂 )
Just fill in your own numbers instead of whatever is there now
http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.061&voltage=12&pha...
In my case it revealed how with 24v panels and 12v battery, you need to do the panel to controller at 24 and the controller to battery at 12. With 12v panels you do both at 12
Ok thanks again BFL
I hope you haven't already answered this but in the calculator do I enter the Voc or Vmp of my panels?
And for Load current do I use Isc or Imp of my panels?
Mar-22-2014 11:21 AM
Mar-22-2014 10:53 AM
BFL13 wrote:
This calculator us useful in that
A. it counts going both ways so you don't have to wonder if you need to double the distance.
B. You can try different gauges and see what you get for voltage drop.
What it does not do is tell you what amps you will get with what voltage drop. We had a thread about all that where that got answered using watts (so of course I got confused 🙂 )
Just fill in your own numbers instead of whatever is there now
http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.061&voltage=12&pha...
In my case it revealed how with 24v panels and 12v battery, you need to do the panel to controller at 24 and the controller to battery at 12. With 12v panels you do both at 12
Mar-22-2014 09:53 AM
Mar-22-2014 09:36 AM
Mar-22-2014 09:30 AM
pianotuna wrote:
Hi,
Fusing is done to protect the wire. It is also done to prevent catastrophic failure. It has little to do with protecting the charge controller.
A lead acid battery is capable of doing welding--that is why you need to fuse.