need help sizing charge controller

[fopoku2k2]

Quick question. I just bought two 250 watt solar panels rated at 8.27 amps & 37.7 volts each. Can I connect them in parallel to my existing pwn charge controller rated at 42 volts maximum solar input voltage and 30 amps rated load and charge current.

My system consist of 24 volt batteries

Thank you

[Mike90250]

Connect in parallel with a PWM controller, you are throwing away 250w or so, of power that a MPPT would harvest. If you are fine with that (and many people seem to be) than all is good if your batteries get full nearly every day.

If you have trouble keeping batteries charged, you need more panels, or a MPPT controller (not a cheap chi-com PWM with a MPPT sticker on it)

Midnight, Rogue, Tracer, Morningstar all make some good, verified MPPT controllers

[SunEagle]

Quick question. I just bought two 250 watt solar panels rated at 8.27 amps & 37.7 volts each. Can I connect them in parallel to my existing pwn charge controller rated at 42 volts maximum solar input voltage and 30 amps rated load and charge current.

My system consist of 24 volt batteries

Thank you

Besides the tip that Mike gave you on getting an MPPT type charger you will need to provide the Ah rating of those batteries and how you have them wired together. Then the proper charge controller can be determined.

[Sunking]

Why would you use a PWM controller with 500 watt of panels? Just as well throw one panel away.
If you buys a PWM charger all you need 15 amp model running a 12/24 volt battery. For MPPT depends on what battery voltage you intend to run.

40 amps @ 12 volts
20 amps @ 24 volt
10 amps @ 48 volts.

[fopoku2k2]

Besides the tip that Mike gave you on getting an MPPT type charger you will need to provide the Ah rating of those batteries and how you have them wired together. Then the proper charge controller can be determined.

I have four 100ah connected in a way (I didn't do the connection) to produce 24 volts since my inverter is 24 volts. What mppt charger would you recommend?

[fopoku2k2]

Connect in parallel with a PWM controller, you are throwing away 250w or so, of power that a MPPT would harvest. If you are fine with that (and many people seem to be) than all is good if your batteries get full nearly every day.

If you have trouble keeping batteries charged, you need more panels, or a MPPT controller (not a cheap chi-com PWM with a MPPT sticker on it)

Midnight, Rogue, Tracer, Morningstar all make some good, verified MPPT controllers

Do you think with such a setup my batteries would get full nearly everyday?

[fopoku2k2]

Why would you use a PWM controller with 500 watt of panels? Just as well throw one panel away.
If you buys a PWM charger all you need 15 amp model running a 12/24 volt battery. For MPPT depends on what battery voltage you intend to run.

40 amps @ 12 volts
20 amps @ 24 volt
10 amps @ 48 volts.

I'm using a pwm charge controller because that was what was connected to my old system. Can you help me size and select the right mppt charger controller?

[SunEagle]

I have four 100ah connected in a way (I didn't do the connection) to produce 24 volts since my inverter is 24 volts. What mppt charger would you recommend?

I am assuming each battery is 12volt 100Ah. So for a 24volt system you would have 2 of those batteries wired in series and two sets in parallel. That would give you a 24volt 200Ah battery system.

As Sunking suggested, with 500 watts of panels you will need an MPPT CC rated a minimum of 20 Amps for a 24 volt battery system.

[Sunking]

I'm using a pwm charge controller because that was what was connected to my old system. Can you help me size and select the right mppt charger controller?

I already did that.

[Living Large]

I already did that.

Close - he would like a selection also. Amy often gives advice on specific models - maybe she will stop by.

[Sunking]

Close - he would like a selection also. Amy often gives advice on specific models - maybe she will stop by.

I can do that, but geez the user needs to do some home work. Midnite Solar, Morningstar, Outback and Bluesky are the ones to look at.

[Living Large]

I can do that, but geez the user needs to do some home work. Midnite Solar, Morningstar, Outback and Bluesky are the ones to look at.

That should be enough to point him in the right direction.

[Mike90250]

Do you think with such a setup my batteries would get full nearly everyday?

all depends on how deep you discharge them.

[fopoku2k2]

I can do that, but geez the user needs to do some home work. Midnite Solar, Morningstar, Outback and Bluesky are the ones to look at.

I know I'm a newbie in this solar business. I think that's why forums like these was created for gurus like yourself to educate us. Thanks for all your advice.

Finally, if it's not too much of a bother can you help me size the electrical cable from my panels to the charge controller. I have plans of upgrading to 1kw in future

[Amy@altE]

Hi there, taking a couple days vacation to do yard work, now that Spring is FINALLY here in New England!

37.7Voc says they are 20V nominal panels. If wired in parallel, they will not have enough voltage to properly charge your 24V battery bank in the summer when they are hot, regardless of if you use MPPT or PWM. For best performance, wire them in series, creating a nominal 40V array, and use an MPPT charge controller to drop it down to the 24V. 40V in / 24V out = 1.66 drop in voltage, which means 1.66 increase in current. So the output current of the MPPT is 8.27A x 1.66 increase = 13.7A output. Times 1.25 for NEC requirement means at least an 18A charge controller. Round up to 20A. You say you plan to increase to 1000W, which means adding a second parallel string of 2 in series, so I'd plan ahead and get a 40A charge controller that can handle 4 of the panels. Morningstar TS-MPPT-45 45A charge controller comes to mind.

As for sizing the wire, I did a video on it, it requires a lot of different calculations, so is tough to describe in the forum. Go to YouTube and search for "Wiring your solar electric system".