More Solar Panels

[peternap]

The truck driver just called. I have two more 185 watt panels coming from Sun Electric.
The last two from them are kicking butt.

This gives me a little over 1K on the primary bank which isn't all that large so I'll have a lot of wasted energy.
Unless someone (Windpower, Don, Etc) can think of a reason not to, I think I'll wire the dump circuit in with the panels charging charging bank 2.

Bank 2's charge controller doesn't have a dump circuit but if it looks like I have excess there, I can always replace it with another Xantrex.

Any thoughts??

[MountainDon]

I'm not familiar with the nature of the dump. Is it a regulated voltage or does it wander along with sun intensity.

[peternap]

I'm not familiar with the nature of the dump. Is it a regulated voltage or does it wander along with sun intensity.

All the dump does is bypass the charge circuits in the controller after the batteries are fully charged.

What comes out is what the panels are supplying.

I've hooked it to various things, a hot water heater, the pump for my well, outdoor lighting, etc. I just hate wasting power.

[MountainDon]

If it's unregulated then you'd need to regulate it if using to charge the other bank. Then there's the question of how the two will interact as full charge there approaches.


I used to worry about what to do with the excess PV power when the batteries are full. Then I noticed the sun was being "wasted" as it fell on the ground beside the PV modules. I figured I couldn't do anything about that unless I spent more money.  I stopped worrying.    

[peternap]

If it's unregulated then you'd need to regulate it if using to charge the other bank. Then there's the question of how the two will interact as full charge there approaches.


I used to worry about what to do with the excess PV power when the batteries are full. Then I noticed the sun was being "wasted" as it fell on the ground beside the PV modules. I figured I couldn't do anything about that unless I spent more money.  I stopped worrying.   

I'm not sure why it needs to be regulated Don...regulated to what?
It goes in just as another panel would and then goes into the second charge controller in parallel with the second banks panels.
Am I missing something?

The Charge controller for bank 2 would control the charge for that bank.

[NM_Shooter]

No worries on having no-load on the PV panel.  It will sit there forever and ever without harm.  It will still degrade, being in the sun, but it will not harm the panel to have it in the sun with no load or a light load.  No need to dump, unless you have something you want to keep warm somewhere :-)

They are not like a wind generator.  If you spin that fast enough without a load, the voltage goes up with the increase in velocity.  This voltage can get high enough to start causing dielectric breakdown and the doggone thing can burn up. 

PV panels have a measured and specified maximum open circuit voltage, and a maximum short circuit current.  Unless you are stacking a bunch of them in series, and your charge controller is not rated to accept the highest voltage at low load, you got nothin' to worry about. 

[MountainDon]

I was thinking the dump was going direct to the batteries.    Depends what the PV module mix is feeding into the second bank. If they are close, not a big deal. Of course I'm talking about ideal situations.... can't help myself on that. 

[peternap]

No worries on having no-load on the PV panel.  It will sit there forever and ever without harm.  It will still degrade, being in the sun, but it will not harm the panel to have it in the sun with no load or a light load.  No need to dump, unless you have something you want to keep warm somewhere :-)

They are not like a wind generator.  If you spin that fast enough without a load, the voltage goes up with the increase in velocity.  This voltage can get high enough to start causing dielectric breakdown and the doggone thing can burn up. 

PV panels have a measured and specified maximum open circuit voltage, and a maximum short circuit current.  Unless you are stacking a bunch of them in series, and your charge controller is not rated to accept the highest voltage at low load, you got nothin' to worry about.

I'm not worried about no load NM....I'm just trying to use up all the power I can.
Bank B does not have as much wattage to it as bank A. Bank A should be able to go from discharged to fully charged in a few hours now but bank B will still take two days to go from 11.5 volts to full charge.

I'm thinking that with the addition of the dump power I could go from discharged to full charge on B..in a couple of hours.
But then again, I've never done it.

[peternap]

 
All the panels are rated at 12 Volts Don (21volts max with a couple a tad hotter) and wired parallel to the charge controller. For the A bank that's 4 (soon to be 6) 185 watt panels and a few 45 watt ones. That's on bank A.

Bank B, C and D are 45 watt panels and E is just wind and hydro.

It seems silly at first glance and it would horrify the power snobs but doing it that way allows me to control the usage better and never really run short of power. If I do, I just reallocate a bank at the board. Since I use very little AC, I can handle it with several small inverters.

[peternap]

After spending an hour on the phone with Xantrex tech people, we decided it not only would work but was a good idea considering the mix of batteries I have.

They did say not to try it on the wind system because after the batteries were charged, the power would have nowhere to go. I'm not sure he's right on that because the wind system has it's own controller with it's own diversion control going to a 12 volt pump.

[NM_Shooter]

They did say not to try it on the wind system because after the batteries were charged, the power would have nowhere to go. I'm not sure he's right on that because the wind system has it's own controller with it's own diversion control going to a 12 volt pump.

Is your pump always running?  The only problem would be if the pump turns off. 

[peternap]

It is always running as long as it has power. It trickle feeds a holding tank.

[Windpower]

Interesting problem

I think I would opt for another pump for the dump

It is what I am planning at the farm for an irrigation water tank

[peternap]

Interesting problem

I think I would opt for another pump for the dump

It is what I am planning at the farm for an irrigation water tank

I tried daisy chaining the solar banks this weekend and it worked. It speed-ed up recharging on the less powerful arrays considerably.

[glenn kangiser]

My thoughts would be that the pump will only burn so much power.. excess will be excess.

The regulator you are dumping to needs to have enough capacity to handle the combined power of all panels but I assume you thought of that.

[peternap]

My thoughts would be that the pump will only burn so much power.. excess will be excess.

The regulator you are dumping to needs to have enough capacity to handle the combined power of all panels but I assume you thought of that.

We'll talking apples to oranges Glenn. The pump is on the wind generator and has been set up that way for a couple of years. I'm ot changing that.

I have multiple 12 volt solar arrays on multiple battery banks.
The main array is a lot larger than the others and one of the others is downright anemic.

I set the charge controllers for the solar arrays for diversion and use the dump to add to the charging capacity of the next smaller array/bank.

When that one is fully charged the dump from that one which includes the diversion from the first one feeds the next one. I don't have a diversion on the last one so the buck stops there but with solar, it doesn't matter if there's a load or not....at least it doesn't appear to.

I did have to make some measurements because in theory this should far exceed the 60 amp rating of the charge controllers, but it didn't over the weekend. I put fuses inline in case it does.

[glenn kangiser]

Ok - I have it now.