panel compatibility question

mark68 · April 2014

Re: panel compatibility question

BB. wrote: »

Vmp~30 volt panels will not (properly/efficienty) charge a 24 volt battery bank...

A 24 volt battery bank needs >~29 volts to charge--And the Vmp in hot weather can fall by 10-20% (~30 volts * 0.8 = 24 volt Vmp). While the panels can charge (morning/evening & discharge battery bank, etc.)--It does not leave much room for wiring and controller voltage drops.

With 30 volt Vmp panels, an MPPT charge controller with 2-3 30vmp panels in series for a "high voltage" array--that is a good solution.

You can still use your 12 volt/true 24 volt array (Vmp>35 volts) with a (less expensive) PWM charge controller--And move your MPPT controller to the new non-standard battery Vmp voltage array.

Move the combiner box over to the array too--And you will have plenty of room for expansion.

No correct answers--Just options that can work fine. Do a couple paper designs for your ultimate system and see what would work best for you.

-Bill

Thanks Bill. I have four 125 watt panels up now,two 140 watt panels to install. That leaves room for four more panels. I think I will just fill it out with 12 volt panels. My combiner box is on my array. My charge controller is 50 amp so I think i will just keep it on this string and then when I do my larger watt 24volt array then buy the larger controller for that. It is a good controller but lacks the amp capacity. It will work fine for this array but wont handle too many high watt/amp 24 volt panels.

Cariboocoot · April 2014

Re: panel compatibility question

The "true 24 Volt" panels are rapidly disappearing in favour of the 30 Vmp GT style. Usually they would be more than 150 Watts and less than 200 Watts, although not always. This is the only one NAWS has listed now: http://www.solar-electric.com/eoplly-ep125m-72-190w-monocrystalline-solar-panel.html

mark68 · April 2014

Re: panel compatibility question

Cariboocoot wrote: »

The "true 24 Volt" panels are rapidly disappearing in favour of the 30 Vmp GT style. Usually they would be more than 150 Watts and less than 200 Watts, although not always. This is the only one NAWS has listed now: http://www.solar-electric.com/eoplly-ep125m-72-190w-monocrystalline-solar-panel.html

Thanks for the link. That panels Vmp is within 10%{ 36.11} of the 12 volt panels {35.8} I am using and would be compatible. Going to have to think about this one.

Vic · April 2014

Re: panel compatibility question

mark68 wrote: »

I dont have a specific panel chose yet but like that I could get 250 or even 300 watt panels in 24 volt vs 150 watt is as good as I have found in 12volt ...

Hi Mark68,

Normally, we here all try to reference what the host of this great site -- wind-sun -- stocks. But, recently, there are few true 24 V PVs available on this site.

There are SOME 275 - 305 watt PVs that are true 24 V available at good prices, other places.

You might consider searching for Canadian Solar CS6X-305P PVs -- 305 STC watts, with a Vmp of 36.3 V. These are LARGE PVs @ 77" X 38.7", and 49 Lbs, but these seem to be somewhat available at about $1.00 per watt PLUS SHIPPING. Hope that wind-sun will choose to stock some of these ... have been thinking about adding some more here. These dimensions might not work for your application, but worth a look.

FWIW. Good Luck, Vic

mark68 · April 2014

Re: panel compatibility question

Thanks Vic, I like those Canadian Solar 305 watt panels. Requested a shipping quote for those. Four panel minimum order,tho that will fill out my array. Yes will do some measuring to see if these panels will fit. The wind and sun 190 watt panels are my other option,I know they will fit. I wonder why there are fewer choices for true 24 watt panels? Are most systems grid tie?

westbranch · April 2014

Re: panel compatibility question

Off grid is still very much a niche market... ie read that as small, and the GT market is huge relatively...

panel compatibility question

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