Panel upgrading??'s

shockman · February 2013

I will try to keep this brief for my 2 finger typing. I am upgrading my system and now have a classic 150, small wind mill (160w) and at present am using 6 old panels (55w) and 2 new 125w er's. (12v system). I am getting upwards of 30amps of charge at present. I will eventually want to use 4 L16's approx. 760 a/hr total. I will also one day, when my old inv. packs it in, move to 24v system. I am going to remove the 6 old panels and put them on shop with old pmw controller and use them for chargeing boat,car, rv batts etc. My goal is to have about 1000w of panel and hopeing that is enough to properly charge the bank? My question is what panels to buy?? I would like to keep new 12v 125w x 2, if possible. Do I add 12 or 24v panels? what is the story on GT panels? I read that they are the cheapest per watt?? don't think they are as available locally, 12 and 24 are! I can use gen. to charge when ness.
Marc

Cariboocoot · February 2013

Re: Panel upgrading??'s

Okay first thing: 760 Amp hours @ 24 Volts is going to need about 2400 Watts of panel to properly charge. Your Classic 150 will handle up to 80 Amps @ 24 Volts so it will work with this.

It will also work with any sort of panels you can get over 35 Vmp out of, including two 30 Vmp panels placed in series. This means you can make use of the "odd Voltage" GT panels without difficulty. These invariably are the cheapest per Watt.

Not trying to incorporate the old panels to the new system is very sensible in my opinion. Even the 125 Watt ones. It's much easier to configure the array all new with matching panels, that way there are no surprises or disappointments.

Photowhit · February 2013

Re: Panel upgrading??'s

shockman wrote: »

...I will eventually want to use 4 L16's approx. 760 a/hr total. ...

Please note that 4-l16's will be between 350 and 430 amphours at 24 volts, or likely the 760 amphours at 12 volts. 1000 watts would not be out of line for this size battery bank, but as 'Coot said, it is likely easier to buy matching panels now.

You say 12 and 24v panels are available locally, be sure what is being called 24 volt panels, are infact 24volt panels. to properly charge a 24v system 24 volt nominal panels should have a vmp of around 35 volts. If you can get panels of 35v (VMP) then you could match up and use your existing panels, but it appears they are becoming a thing of the past and most panels are in the 26-31v (VMP) so you might not be able to match them up in the future if and when you want to expand your system.

shockman · February 2013

Re: Panel upgrading??'s

Cariboocoot wrote: »

Okay first thing: 760 Amp hours @ 24 Volts is going to need about 2400 Watts of panel to properly charge. Your Classic 150 will handle up to 80 Amps @ 24 Volts so it will work with this.

Wow 2400 watts!! It this the same amount required for 12v?? Maybe I'm using to much batt?? In load analysis I think 600a/hr is plenty, just didn't know how to get there with L16's??

It will also work with any sort of panels you can get over 35 Vmp out of, including two 30 Vmp panels placed in series. This means you can make use of the "odd Voltage" GT panels without difficulty. These invariably are the cheapest per Watt.

Do you know that GT panels are accessable here in our part of the world??

Not trying to incorporate the old panels to the new system is very sensible in my opinion. Even the 125 Watt ones. It's much easier to configure the array all new with matching panels, that way there are no surprises or disappointments.

What are the specs on GT panels? "odd Voltage"????

shockman · February 2013

Re: Panel upgrading??'s

Read between the lines, multi-quote didn't work so well for me! hehehe

Cariboocoot · February 2013

Re: Panel upgrading??'s

Normally a true 24 Volt panel will have a Vmp of 35. As such it can charge a 24 Volt system using a PWM type controller without any problem; there's enough Voltage available from the panel to bring the batteries up to full charging Voltage (which may be 30 or so) even after losses in wiring.

Some "24 Volt" panels are actually designed for Grid-Tie systems and have Vmp's of 26 or 30 or some other number that is less than what would supply that charging Voltage. Being used on a GT system they don't need to be at "ideal for battery" Voltage because there is (usually) no battery. Instead they are put together in strings to supply the right Voltage for running a grid-tie inverter. For instance twelve 30 Vmp panels gives a 360 Volt array, which is a typical operating Voltage for a GTI.

Yeah, the multi-quote often comes down to a lot of hand editing.

BB. · February 2013

Re: Panel upgrading??'s

Note that 660 AH does not tell us enough--At what voltage? x12/24/48/etc. -- Each 2x the stored energy as the one before.

I like to match the battery bank to the loads... A larger battery bank needs a larger solar array--even if the loads are small. So--over sized battery banks can cost you a lot of extra money.

So, what is your your current load? Are you looking to add more loads, or just "upgrade" to 24 volts to address wiring and battery issues because of the current 12 volt system?

-Bill

Cariboocoot · February 2013

Re: Panel upgrading??'s

shockman wrote: »

Wow 2400 watts!! It this the same amount required for 12v??

No, because you're looking at 76 Amps charge current @ 24 Volts vs. 76 Amps charge current @ 24 Volts. The doubling of the Voltage doubles the power (Watts). So 760 Amp hours @ 12 Volts is half the stored power of the same Amp hours @ 24 and requires half as much array to replenish it.

Maybe I'm using to much batt?? In load analysis I think 600a/hr is plenty, just didn't know how to get there with L16's??

Possibly. Not know what your actual power requirements are it's hard to say. Ideally you only want to discharge 25%; this is usually the best balance between battery usage and battery lifespan. Sometimes deeper is better. At any rate the power formula is constant: at 50% depth of discharge 600 Amp hours @ 12 Volts is (300 * 12) 3600 Watt hours of power.

L16's are another matter. That's a case size and they come in different capacities within that designation. 320 Amp hours, for example. So four of those would be two parallel strings of two in series giving 640 Amp hours @ 12 Volts. They are pickier about recharging than GC2 style batteries.

Do you know that GT panels are accessable here in our part of the world??

You can get them anywhere you want to pay the shipping for them.

This can get quite expensive as they tend to be large, heavy, and fragile. Check for local panel sources and see what you can find. The same goes for batteries as they are hard to ship also.

What are the specs on GT panels? "odd Voltage"????

Take a look at our host's panel section here: http://www.solar-electric.com/hiposopa.html
The ones over 200 Watts tend to be GT panels and have the odd (for battery systems) Vmps. They can be used with an MPPT controller, providing they are arranged so that the array Vmp is higher than what is needed for charging the batteries.

shockman · February 2013

Re: Panel upgrading??'s

Okay may have to help me a little here. At one time I calculated about 3500 w/hr a day. In winter we are here usually only on weekends, except this week we've been here for a stretch of 9 days. The only power consumption is 2 lights at one time varing from squirrly bulbs to floresent lights and sat. TV for 6hrs. In summertime we can be here fairly steady but may only use lights for a couple of hours but also try to run a small (6cu/ft) freezer. I beleive I also allowed about an hour of electric coffe pot when I arrived at 3500w??? Does this # seem reasonable?
I think I'm getting a handle on this 24vs12v THING. but whats confussing me is where are all the advantages if I need 2x the batts for storage? Do I need half the storage for same load??

shockman · February 2013

Re: Panel upgrading??'s

"L16's are another matter. That's a case size and they come in different capacities within that designation. 320 Amp hours, for example. So four of those would be two parallel strings of two in series giving 640 Amp hours @ 12 Volts. They are pickier about recharging than GC2 style batteries."

So a little more on L16's?? The ones available to me are either 380a/hr or 420 at a bit of a premium for the 420 so I figured the 380's. But what does pickier mean? making sure of enough amps for charging? Should I use GC's or is the extra parralel/series strings more of a downside??

Photowhit · February 2013

Re: Panel upgrading??'s

shockman wrote: »

...I think I'm getting a handle on this 24vs12v THING. but whats confussing me is where are all the advantages if I need 2x the batts for storage? Do I need half the storage for same load??....

Did you read my post?

I don't think you've got it yet...

Think of Amps as the flow of the river and volts as how wide the river is, with out both you don't know how much water is going past.

For a battery you can think of the battery banks capacity as AmpHours x Volts, so if you have a 12 volt battery bank made of 2 strings of 2 - 350 amphour batteries for a 12v 700Amphour battery bank you have a total capacity of 12x700 or 8400 Watthours. With a 24v string of 4 - 350 amphour batteries you have a 24v 350amphour battery bank and the same 8400 Watthours.

niel · February 2013

Re: Panel upgrading??'s

"...the flow of the river..."

might use the depth of the river as a better example in addition to the width. the flow would pretty much be there regardless as it is not a variable, but a constant due to gravity acting on it to go to lower altitudes.

shockman · February 2013

Re: Panel upgrading??'s

Photowhit wrote: »

Did you read my post?

I don't think you've got it yet...

Think of Amps as the flow of the river and volts as how wide the river is, with out both you don't know how much water is going past.

For a battery you can think of the battery banks capacity as AmpHours x Volts, so if you have a 12 volt battery bank made of 2 strings of 2 - 350 amphour batteries for a 12v 700Amphour battery bank you have a total capacity of 12x700 or 8400 Watthours. With a 24v string of 4 - 350 amphour batteries you have a 24v 350amphour battery bank and the same 8400 Watthours.

Okay I've never seen it related to watt/hrs, I was hung-up on amp/hrs figuring 350 vrs 700!! But a trusty calculator proves watt/hrs. So now you can explaine the chargeing side, is a watt a watt a watt, regardles of voltage?? barring line losses. Do I need the same wattage to charge both senarios??

BB. · February 2013

Re: Panel upgrading??'s

Just to be clear--It is not Watts/Hour...

It is Watts (a rate) like Miles Per Hour or Gallons Per Hour

And Watt*Hours (an amount) like Miles driven or Gallons pumped.

Similar with Amps--A rate. And Amp*Hours being an amount.

Power (rate) = Watts
Energy (used) = Watts*Hours

The differnce between Watts and Amps is that Watts already includes the Voltage Term:

Watts = Volts * Amps
Watt*Hours = Volts * Amps * Hour
Amp*Hours = Amps * Hour

For our point of view (designing solar RE systems), there is no Watt/Hours or Amp/Hours == Most of the time people mean Watts and Amps or Watt*Hours and Amp*Hours--But sometimes it is not clear from the context.

So "Watt" and "Watt*Hour" is a "complete" unit. Amps and Amp*Hours is not a "complete unit" and we need the Voltage to work out energy.

But, Amps and Amp*Hours certainly have their uses...

For a Lead Acid Battery bank, Watt*Hour wise, they tend to run around 80-90% energy efficient.

But from an Amp and Amp*Hour point of view, Lead Acid Batteries are almost 100% efficient... I.e. Amp*Hours out = Amp*Hours in.

The difference is the Voltage... Lead Acid batteries output their power at ~12.2 volts and recharge around 14.5 volts Volts:

12.2 / 14.5 = ~84% energy efficiency

-Bill

Photowhit · February 2013

Re: Panel upgrading??'s

Well actually it is watt hours since the battery amp hour rating is based on a discharge rate...but it is just too confusing for someone already confused to get into. I had amphours and the transition I thought would be easier to understand. The poor guy is already confused...

(yes I should have written Amps for the battery as well)

Photowhit · February 2013

Re: Panel upgrading??'s

shockman wrote: »

Okay I've never seen it related to watt/hrs, I was hung-up on amp/hrs figuring 350 vrs 700!! But a trusty calculator proves watt/hrs. So now you can explaine the chargeing side, is a watt a watt a watt, regardles of voltage?? barring line losses. Do I need the same wattage to charge both senarios??

Yes pretty much, it tends to be easier at higher voltage, since it requires thinner wire since you have less amps traveling for the same wattage. This becomes more important the farther your array is from your battery bank, or if you use higher wattage draws on a low voltage system the wire gauge between the battery bank and inverter may be required to be very large.

Panel upgrading??'s

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