โMar-14-2015 10:00 AM
โMar-18-2015 08:08 AM
CA Traveler wrote:Salvo wrote:I wanted to determine the panel and controller output capability and used the inverter, etc to draw the maximum amps from the controller. The controller kept the battery voltage at about 13.8V.
What was Vbat when charging at 43 A? Was it held down?CA Traveler wrote:
As another reference point my 3x250W flat panels on 3/3/15 in Phoenix with a clear sky produced 43A or 600W at the controller output. This was for 1.5 hours before the clouds moved in. There were several peaks of 48A. For 2X panels this would product 28A or 400W.
โMar-17-2015 10:39 PM
Salvo wrote:I wanted to determine the panel and controller output capability and used the inverter, etc to draw the maximum amps from the controller. The controller kept the battery voltage at about 13.8V.
What was Vbat when charging at 43 A? Was it held down?CA Traveler wrote:
As another reference point my 3x250W flat panels on 3/3/15 in Phoenix with a clear sky produced 43A or 600W at the controller output. This was for 1.5 hours before the clouds moved in. There were several peaks of 48A. For 2X panels this would product 28A or 400W.
โMar-17-2015 08:48 PM
โMar-17-2015 07:42 PM
Switching one panel on and off is not practical. It requires climbing the roof to connect-disconnect MC4 plugs, or running an extra wire loop all the way to the inside of trailer with a switch on it. Either scenario is complicated, and you might not even be there at that exact moment when switching is necessary.
FWIW, I wouldn't bother switching off one panel. It's too much of a hassle, and your buddy would be a slave to the limits of the controller. The controller will probably work fine. Nothing is really lost if it quits working.
โMar-17-2015 05:58 PM
โMar-17-2015 04:51 PM
tpi wrote:
He already has the controller-and he will upgrade it if he's switching off a panel too often and giving up needed power.
โMar-17-2015 11:43 AM
CA Traveler wrote:
As another reference point my 3x250W flat panels on 3/3/15 in Phoenix with a clear sky produced 43A or 600W at the controller output. This was for 1.5 hours before the clouds moved in. There were several peaks of 48A. For 2X panels this would product 28A or 400W.
A 20A controller sounds marginal.
โMar-17-2015 09:17 AM
โMar-16-2015 07:22 PM
โMar-16-2015 06:32 PM
โMar-16-2015 04:59 PM
โMar-16-2015 12:54 PM
tpi wrote:
This is the plan I'm thinking-
1. Have panels switched between panel and controller, so on June 21 midday (or similar seasonal) in clear weather one of the panels can be switched off if there is chance of exceeding controller capability. When in storage-just operate on one panel for maintenance.
2. On an as needed basis, when present in the RV maybe he can push the envelope a bit with the controller and let it limit to the 22 amps..in the event he needs the power. If something starts to smell hot, feel hot etc. he can shut off a panel. Depends on his comfort level with that.
3. Living in CA he does a lot of camping fall winter or spring where all capacity could be used. Mornings and afternoons in the summer too. Overall he should get good bang for buck on the panel installation. And he's open to another controller in the event of it being too restrictive.
โMar-16-2015 11:46 AM
Almot wrote:tpi wrote:
1. Several mentioned the controller clipping when fed above rated wattage. I'm familiar with audio amplifier clipping-and I assume controller is some kind of switching power supply. What is going on when the controller is clipping? The pulses can only be to a certain level?
2. When the batteries are fully charged what is the mechanism for the controller to back off the charging? I would assume it not shunt the excess power into heat.
1) No. With MPPT controller you can input as much amps as you want, and it will block the excess. You only need to watch out for input volts - max input voltage of the controller should not be exceeded.
2) No, MPPT controller won't shunt the excess into heat when battery is full.
When battery state is nearing Full, its resistance rises and current drops. Controller simply can't push into battery more current than it would accept. The only thing that controller "controls" at this stage, is the volts. At ~80% charge the controller enters Absorption stage where it's keeping the voltage constant and slightly elevated, 14-15V. Cheaper/simpler controllers have non-adjustable timed Absorption, usually 60 minutes. Better/more expensive controllers have adjustable timed Absorption (you can adjust the time), and also current-based absorption - the Abs stage ends when current drops to certain level (this level you can also adjust). Some other controllers change the duration of Abs stage depending on the voltage at the beginning of charging. Bluesky is not the most advanced line of MPPT, they are a "OK" line.
When Abs stage ends, controller enters the Float stage - at this stage it's keeping the battery at constant low voltage ~13.6V until the charging current drops to zero or sun goes down. Then controller shuts down.
As noted by others, we are talking here about MPPT controllers because with 24V panel you can only use MPPT. PWM controllers have the same Abs and Float stages, but they work differently when it comes to "clipping".
โMar-15-2015 09:29 PM
Almot wrote:Blue Sky gives specific warning against over driving the controller.
With MPPT controller you can input as much amps as you want, and it will block the excess.