Adding new panels

RoySalisbury · March 2014

I'm looking to add some more panels before the summer to offset the summer load of A/C equipment. I figure that 2 more of my current panels is all I can squeeze into my current Outback Charge controller (FM60). However, it looks like the panels that I wanted to get are no longer available (Kyocera 215/220). So, I may need to start looking at other panels, but they don't put out the same amp and VoC. I was told that I should not mix the panels if they are off by much (VoC).

So, I guess what I really need to do is think about a new charge controller... or more accurately a second one. Can anyone shed some light on hooking up multiple charge controllers? They would be configured to charge the same battery bank (24v). Would I just get another Outback FM60 (or FM80), plug it into my outback hub? Can I then put new panels of a larger size on this one?

Any help is appreciated.

Roy

Cariboocoot · March 2014

Re: Adding new panels

Actually it's Vmp and Imp that matter when mixing panels. But you've found out the gist of the problem: the panels of today don't match the panels of yesterday and probably won't match the panels of tomorrow. Welcome to the wonderful world of technology evolution.

There's no problem with putting multiple charge controllers on one battery bank, especially not in the manner you propose: another FM controller connected to the HUB. It should work just fine. The only thing better is MidNite's "Follow Me" function where one acts as the "master controller" and tells the others what to do.

You can put any panels on the new controller so long as the array Vmp is high enough for the system (in this case above 35 Volts). One thing you want to check is that the combine current of the two controllers does not exceed the maximum for your battery bank. Otherwise, all is good.

mike95490 · March 2014

Re: Adding new panels

Charge controllers can be paralleled into a battery bank. If they are the same brand, the same gear can control them both.
If they are different brands, you still simply parallel wire them into the battery bank. But you need to verify the voltage set points, so they "play well with others" and one does not do all the work because it's voltage meter is a little tweaked.
and if you are adding a 2nd array, you may want to consider skewing their aim, 20 degrees to spread your harvest over more of the day, instead of all bunched up at noon. Depending on local conditions.

RoySalisbury · March 2014

Re: Adding new panels

Cariboocoot wrote: »

You can put any panels on the new controller so long as the array Vmp is high enough for the system (in this case above 35 Volts). One thing you want to check is that the combine current of the two controllers does not exceed the maximum for your battery bank. Otherwise, all is good.

OK.. Max battery current is not something I thought about. Right now it is 4 x 420amp 6V trojans. I had 8 of them, but one of cells in one battery died and had to take the bank down to half (where it should have been anyway).

I believe even with the single battery string I am still good. I'll probable get the FM80 and 2 (or possibly 3) new Kyocera 250's.

Roy

RoySalisbury · March 2014

Re: Adding new panels

mike95490 wrote: »

and if you are adding a 2nd array, you may want to consider skewing their aim, 20 degrees to spread your harvest over more of the day, instead of all bunched up at noon. Depending on local conditions.

Hmm... Not a bad idea. I'll have enough power generation, but spreading it out across the day a bit better might be a good idea.

Roy

Cariboocoot · March 2014

Re: Adding new panels

Roy;

Those Trojans will take 84 Amps without worry providing it isn't sustained. I don't know how big your existing array is but 750 Watts more should add about 24 Amps. If the existing FM60 is "maxed out" you'd be right at that 84 Amps.

I don't see a problem.

RoySalisbury · March 2014

Re: Adding new panels

That is what I thought. This time of year I get about 43 amp at max output for the existing CC and panels. I have the generator cycle once a week that will hit it with 80 amp max for about an hour (3am).

Now I just need to figure out where I am going to mount the new panels.

Roy

vtmaps · March 2014

Re: Adding new panels

Cariboocoot wrote: »

Those Trojans will take 84 Amps without worry providing it isn't sustained. I don't know how big your existing array is but 750 Watts more should add about 24 Amps. If the existing FM60 is "maxed out" you'd be right at that 84 Amps.

And if you add a few more panels to the new controller, you might have problems. There are two solutions that come to mind:

1) As Mike mentioned, aim the new array towards the west. By the time its producing its maximum power the batteries will be in absorb. Once the batteries are in absorb, they will not accept too much current, no matter how much they are offered. Since you want the extra power for A/C, it would be good to have more power late in the day. By the way, some folks have had success putting an east and a west array on the same controller. Both arrays are not producing their maximums at the same time. Do a search for 'virtual trackers' or 'virtual tracking'.

2) If you have Outback's Flexnet DC battery monitor, you can program the controllers to not exceed whatever battery current that you choose. It's called 'Global Amps'.

--vtMaps

catamount · March 2014

Re: Adding new panels

Cariboocoot wrote: »

..But you've found out the gist of the problem: the panels of today don't match the panels of yesterday and probably won't match the panels of tomorrow. Welcome to the wonderful world of technology evolution..

Is there anything wrong a 36V panel paralleled with a group of (2) 18V panels wired in series? Not saying the OP should do this, but I've been wondering. If it is possible, how close do they have to be in voltage?

Cariboocoot · March 2014

Re: Adding new panels

catamount wrote: »

Is there anything wrong a 36V panel paralleled with a group of (2) 18V panels wired in series? Not saying the OP should do this, but I've been wondering. If it is possible, how close do they have to be in voltage?

If the Vmp's of the strings match you can parallel them.
The only caveat here is that sometimes the make up is so different there can be back-feeding problems if the low Voltage panels are shaded.

But that doesn't arise when you're talking about 17-18 Volt panels paired with a 35-36 Volt one.

Cariboocoot · March 2014

Re: Adding new panels

vtmaps wrote: »

And if you add a few more panels to the new controller, you might have problems. There are two solutions that come to mind:

1) As Mike mentioned, aim the new array towards the west. By the time its producing its maximum power the batteries will be in absorb. Once the batteries are in absorb, they will not accept too much current, no matter how much they are offered. Since you want the extra power for A/C, it would be good to have more power late in the day. By the way, some folks have had success putting an east and a west array on the same controller. Both arrays are not producing their maximums at the same time. Do a search for 'virtual trackers' or 'virtual tracking'.

2) If you have Outback's Flexnet DC battery monitor, you can program the controllers to not exceed whatever battery current that you choose. It's called 'Global Amps'.

--vtMaps

This would definitely be a problem if you used two controllers each capable of >10% charge rate and had no significant loads detracting from the actual current going to the batteries.

Usually batteries are charged enough in the early hours that by the time the arrays are capable of full power the batteries don't need it and don't take it. vtMaps experience with the AC charger and array coupled is a different scenario because the AC charger is always capable of full output power. And usually the AC charger is not used if the array is capable of doing the job.

RoySalisbury · March 2014

Re: Adding new panels

vtmaps wrote: »

2) If you have Outback's Flexnet DC battery monitor, you can program the controllers to not exceed whatever battery current that you choose. It's called 'Global Amps'.

I have an Outback Flexnet. I was not aware of this setting, but I will look into it. There has been once or twice that both the generator and the charge controller were outputting power, and it exceeded 100 amps. But at that time I had all my batteries hooked up, so could have taken the load. But I will defiantly need it now that I only have the one bank.

Roy

vtmaps · March 2014

Re: Adding new panels

RoySalisbury wrote: »

I have an Outback Flexnet. I was not aware of this setting, but I will look into it.

I posted an excerpt from the manual here:

http://forum.solar-electric.com/showthread.php?p=152925#post152925

--vtMaps

Vic · April 2014

Re: Adding new panels

RoySalisbury wrote: »

I'm looking to add some more panels before the summer to offset the summer load of A/C equipment. I figure that 2 more of my current panels is all I can squeeze into my current Outback Charge controller (FM60). However, it looks like the panels that I wanted to get are no longer available (Kyocera 215/220). So, I may need to start looking at other panels, but they don't put out the same amp and VoC. I was told that I should not mix the panels if they are off by much (VoC).
Roy

Roy,

It APPEARS that Wind-Sun MAY again have these PVs. Have not tried to order any, but, the No Stock indication for this product is now gone. FWIW ... you may have gone a different direction:
http://www.solar-electric.com/kyocera-kd220gx-lfbs-220-watt-polycrystalline-solar-panel.html

FWIW, Vic

Adding new panels

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