Beginners questions.

System · March 2010

I have 4 Kyocera 135 watt panels connected to and Outback Flexmax MPPT 60 amp charge controller. Also have a 3000 watt pure sine inverter from Carmanah Go Power and 6 - 125 amphour flooded batterys. My question is, How long should the cooling fans run on this inverter. I noticed they only run when the voltage gets low around 12 volts.Seems like they run for an extended amount of time. They have been running for about an hour and still going. Is this normal? My second question is about the readings on the charge controller. These panels are rated at 8 amps each. We had a bright sunny day in southeast Texas today. This morning the battery voltage was 12 volts,day end maximum voltage output was 20 volts and maximum amp output was 28.6 amps. The controller bulk charged untill around noon and reached 14.4 volts. Started absorb for an hour and then float charge. I never see the maximum amp reading of 32 amps. Shouldn't I get a maximum amp reading during bulk charge or is the controller just saving my batterys? Do these readings mean I can add more batterys or do I need more panels first? I plan to add more to the system as I can afford to. I am a novice here and would appreciate any information.

Thanks
Bruce.

westbranch · March 2010

Re: Beginners questions.

Bruce, if you tell us the specs on the panels, the loads you are running, the starting volatage and the time to reach 12 .0 volts we can more readily help.

also need the battery V after you first apply a load.

ps 12.0 v is essentially a dead battery if you have it at that level for long

HTH
Eric

Cariboocoot · March 2010

Re: Beginners questions.

The short answer (unless I'm reading your specs wrong): too many batteries, not enough panels.

6 * 125 Amp/hrs = 750 Amp/hrs of batteries. 10% recommended charge current = 75 Amps (more than an MX 60 can handle {normally}).

4 * 135 Watts = 540 Watts (peak) of panels @ ~15 Volts charge = 36 Amps.

These batteries have probably been slowly drained to death, especially if you factor in good ol' Texas heat.

As far as the inverter fans are concerned, as the battery Voltage goes down the current goes up in order to maintain the same level of Watts output. This results in more heat, so the cooling fans come on. Which draws more power and loads the batteries further. Vicious cycle.

Broken record time: what are your loads?
You may need to replace those batteries, get the charge current up, reduce the loads, et cetera. In other words, 'rebalance' the system.

System2 · March 2010

Re: Beginners questions.

Thanks for your quick response. The panel specs are as follows.
Specifications for Kyocera KD135SX Solar Panel Max Rated Power (Pmax) 135 Watts
Voltage at Max Power (Vmpp) 17.7
Current at Max Power (Impp) 7.63 Amps
Open Circuit Voltage (Voc) 22.1
Short Circuit Current (Isc) 8.02 Amps
Length x Width x Depth (inches) 59.1 x 26.3 x 1.8
Weight of Panel (Pounds) 27.5
Connector Cable Type or Junction Box Standard Junction Box

This is a standard 12 volt panel
I understand I may need to purchase more panels, another charge controller and start another battery bank and plan to do so in the future.
The battery voltage was 12.0 volts when they started charging yesterday morning. Also there was no load on the system, I had not turned the invertor on. The voltage increased from 12.0 volts around 9:00 am to 14.4 volts at 12:30 pm. A total of 3 1/2 hours. 4 of these batterys are only 3 weeks old and the other 2 are 9 months old. I haven't put a tester on any of them. I still do not understand, with my batterys low in the 12 volts range and the charge controller on bulk charge with no load. Shouldn't I be getting maximum amp output from the panels of around 32 amps. I know they are capable of the output because I have seen previous day end readings of 44 amps from the same panels. Am I worrying to much about a few amps or should I be looking to see why its not operating as it should?

Thanks for your help.
Bruce.

RandomJoe · March 2010

Re: Beginners questions.

That maximum current level is only attainable under "ideal" conditions - 1000W/sqmtr. Odds are you aren't getting that right now! If the panels are at all off-angle from the sun, if the air is a little dirty or hazy, you name it. As we get into summer and the sun gets more directly overhead the peak power will rise (long as you keep them aimed at the sun).

I have almost the same panels (KD135GX) and almost never see the full wattage output. The more "real world" rating (labeled PTC in the specs) is 95W, and I regularly exceed that - ending up somewhere between the two numbers.

28.6A at 14V (assuming you saw that max current at around noon, as your system neared absorption voltage) is 400W, a bit over the "real world" rating of the panels. If the 28.6A was on the *input* side (from the panels) they probably did that about their Vmp point (17.7V) so were producing 506W - pretty darn close to ideal. (At that point in time you should have seen a higher current being fed into the batteries, about 506W / 14V = 36A. That's the beauty of MPPT controllers! )

Also note, you won't ever see 8A - that's the Isc (short circuit) current. That's what you'd see if you put a current meter directly across the leads. The pertinent value for actual operation is Imp (maximum power) which is a bit lower.

icarus · March 2010

Re: Beginners questions.

Just a quick note, with out (admittedly reading the entire thread) but a battery at 12.0 volts is already ~50% discharged. (assuming no loads and no charge).

http://www.batteryfaq.org/

http://www.batteryfaq.org/

Tony

System2 · March 2010

Re: Beginners questions.

Thanks for the answers, that cleared up some things. I am sure I will have more questions in the future, hope I can count on you guys.

Thanks again
Bruce.

Beginners questions.

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