Newbie question regarding controllers

ILFE · November 2013

Hi,

I was just reading a thread here, and something came to mind.

Can a controller be fed with 24vdc from PV panels, while supplying 12vdc to the batteries and load? Or, does everything connected to it have to be the same voltage system wide? That is the solar, batteries, and load all have to be 12vdc or 24vdc? At the moment, everything is 12vdc.

This came up, because I am considering buying three more panels and converting the PV array to 24 volts. However, all of the current circuits connected to the load side of the controller are 12 volts.

I don't know why this never crossed my mind before.

westbranch · November 2013

Re: Newbie question regarding controllers

Simply, YES if you have an MPPT controller.
See MidNIte Solar Classic and the KID models at www.midnitesolar.com, Kid due out in January 23014 or the Rogue controller

ILFE · November 2013

Re: Newbie question regarding controllers

I have a PWM controller, a MorningStar ProStar 30M. But, that was what I figured, without actually going through and wiring it up to check.

Thanks for the information.

westbranch · November 2013

Re: Newbie question regarding controllers

without MPPT you will not get/use any production over the nominal 12 v rating (+-17v ) needed to charge your battery.

ILFE · November 2013

Re: Newbie question regarding controllers

westbranch wrote: »

without MPPT you will not get/use any production over the nominal 12 v rating (+-17v ) needed to charge your battery.

I'm not sure I follow you. The meter has shown as high as 14.? volts, while charging?

Cariboocoot · November 2013

Re: Newbie question regarding controllers

What happens when you put a panel with "higher than normal" Vmp on a 12 Volt system through a PWM type controller is that you get the panel's current output, but the Voltage is "pulled down" to the battery's level.

So a panel with 30 Vmp and 7 Imp (210 Watts) acts he same as a panels with 17.5 Vmp (typical for 12 Volt panels) and 7 Imp or 122.5 Watts. The additional power possible from the higher panel Voltage is not realized.

westbranch · November 2013

Re: Newbie question regarding controllers

that 14.4 is the avg voltage for charging a (nominal) 12 v battery, the 3 (+-) other volts are used to run the CC, line loss, etc.
for example a healthy 12v battery will usually be at ~ 13.2 V after a charge cycle.
An MPPT has the ability in Bulk to convert any panel voltage above that (~17v) to amperage and send it to the battery, PWM can not do this bit of 'magic'.
does this explain?

ILFE · November 2013

Re: Newbie question regarding controllers

Forgive my ignorance here.

But, why are PWM controllers even sold today, now that MPPT controllers are on the market, and are - well, superior to them?

ILFE · November 2013

Re: Newbie question regarding controllers

westbranch wrote: »

that 14.4 is the avg voltage for charging a (nominal) 12 v battery, the 3 (+-) other volts are used to run the CC, line loss, etc.
for example a healthy 12v battery will usually be at ~ 13.2 V after a charge cycle.
An MPPT has the ability in Bulk to convert any panel voltage above that (~17v) to amperage and send it to the battery, PWM can not do this bit of 'magic'.
does this explain?

Sorry. you and I were replying at the same time.

I see what you mean. But, I still wonder why PWMs are even sold now. What purpose do they serve, if their technology is dated?

westbranch · November 2013

Re: Newbie question regarding controllers

price... that's it... well matched panels ie 12v or 24 v , don't gain much with MPPT if used on that size of battery, but you can use the MPPT's down conversion ability with much higher voltages to reduce line losses between PV and CC.

ILFE · November 2013

Re: Newbie question regarding controllers

westbranch wrote: »

price... that's it... well matched panels ie 12v or 24 v , don't gain much with MPPT if used on that size of battery, but you can use the MPPT's down conversion ability with much higher voltages to reduce line losses between PV and CC.

Are you saying the system voltage can be much higher by the panels being in series, while still providing 12v or 24v to the bank?

In this case, line loss can't be much. The cable between the panels and the controller is no more than 10 feet. But, I do see what you mean.

I was going to go with an MPPT controller when I originally set up this array. However, here, trying to find a controller - almost any controller, short notice, is like pulling hen's teeth.

We are talking really rural, here.

westbranch · November 2013

Re: Newbie question regarding controllers

ILFE wrote: »

Are you saying the system voltage can be much higher by the panels being in series, while still providing 12v or 24v to the bank?

Yes, you get a lot more options with MPPT

ILFE wrote: »

In this case, line loss can't be much. The cable between the panels and the controller is no more than 10 feet. But, I do see what you mean.

Not in your case but in mine it is > 60 feet one way so I will be series connected for 48 (nom.) volts to 24V batteries. I could also go to 72V or 96 or?? but down conversion losses are greater the more distance between the 2 voltages.

ILFE wrote: »

I was going to go with an MPPT controller when I originally set up this array. However, here, trying to find a controller - almost any controller, short notice, is like pulling hen's teeth.

We are talking really rural, here.

have you tried our sponsor? It may work out for youif drop shipped to a reputable intermediary?

ILFE · November 2013

Re: Newbie question regarding controllers

westbranch wrote: »

have you tried our sponsor? It may work out for youif drop shipped to a reputable intermediary?

Not yet. But, I did learn they will ship to Cambodia. I also have placed my first order with them.

I just realized I have not received notification of my invoice. Thanks for the reminder.

Fortunately, I can afford to wait for shipments, now that the initial array is up and running.

Thanks for the reply. Most enlightening.

BB. · November 2013

Re: Newbie question regarding controllers

More or less, PWM are not bad for less than 400 watt arrays... And over ~800 watts, MPPT are usually the batter choice.

But we have to remember the costs--PWM is 1/4th the cost o MPPT (but "high voltage" Vmp panels for GT systems are getting pretty cheap).

Your best bet is do a couple paper designs with different controllers/options and see what works best for you.

-Bill

Newbie question regarding controllers

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