need help sizing charge controller

[fopoku2k2]

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".

Thanks solar queen for really taking the time to school me. No wonder my batteries were not charged the whole day yesterday. I can't wait for my mppt charger controller that I purchased last night to be delivered

[Amy@altE]

What'd you get?

[fopoku2k2]

What'd you get?

Odyssey 50A MPPT Solar Charge Controller (Max PV Input 150VDC)

Cool?

[Amy@altE]

Right size, but I'm not familiar with the brand, so I can't comment on it.

[fopoku2k2]

Right size, but I'm not familiar with the brand, so I can't comment on it.

Oh OK. Anyways I like your online store. Do you ship international?

[Amy@altE]

All the time.

[Living Large]

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".

I'm like psychic or something - psychotic perhaps. The Queen has spoken.

The video Amy refers to is EXCELLLENT. While a fantastic tutorial, the narrator's voice also ensconces you and you will think you died and went to heaven. There is also the Dance of Joy once you have completed the task. It has it all. Seriously - that video really helped me figure out how to size the wiring properly and takes you through the NEC requirements step by step.

[fopoku2k2]

I'm like psychic or something - psychotic perhaps. The Queen has spoken.

The video Amy refers to is EXCELLLENT. While a fantastic tutorial, the narrator's voice also ensconces you and you will think you died and went to heaven. There is also the Dance of Joy once you have completed the task. It has it all. Seriously - that video really helped me figure out how to size the wiring properly and takes you through the NEC requirements step by step.

I couldn't have agreed more. Wink!!!

[Amy@altE]

You guys slay me! I've been trying to figure out out to turn that video into a guide with pictures that can be read so people don't have to suffer through my Massachusetts accent (although it's not as bad as if I lived in Boston itself, 45 minutes west makes big difference). I may post a draft here in a couple of weeks for feedback.

I do have a selecting your charge controller video that's going up next week. You just asked a week too soon. Sorry though, no dancing in it.

[fopoku2k2]

You guys slay me! I've been trying to figure out out to turn that video into a guide with pictures that can be read so people don't have to suffer through my Massachusetts accent (although it's not as bad as if I lived in Boston itself, 45 minutes west makes big difference). I may post a draft here in a couple of weeks for feedback.

I do have a selecting your charge controller video that's going up next week. You just asked a week too soon. Sorry though, no dancing in it.

I can't wait to watch that video. So I have been meaning to ask, is it advantageous wiring your panels in series or parallel. As i said earlier, I have plans of upgrading to a 1.5kw PV system by the end of the year and I was wondering if I would be getting more power from my panels if I wire them in series or parallel. I know there is also some cost involved in this selection. I would be grateful if you could explain both cost and power generation differences to me

Thank you

[SunEagle]

I can't wait to watch that video. So I have been meaning to ask, is it advantageous wiring your panels in series or parallel. As i said earlier, I have plans of upgrading to a 1.5kw PV system by the end of the year and I was wondering if I would be getting more power from my panels if I wire them in series or parallel. I know there is also some cost involved in this selection. I would be grateful if you could explain both cost and power generation differences to me

Thank you

Wiring panels in parallel requires larger wire size and an overcurrent protection system in a combiner box. That adds to the cost.

I feel it is less costly to get a good MPPT charger with a higher DC input voltage. That allows you to put more panels in series using smaller wires and if only two strings in parallel then overcurrent protection per string is not required.

[J.P.M.]

You guys slay me! I've been trying to figure out out to turn that video into a guide with pictures that can be read so people don't have to suffer through my Massachusetts accent (although it's not as bad as if I lived in Boston itself, 45 minutes west makes big difference). I may post a draft here in a couple of weeks for feedback.

I do have a selecting your charge controller video that's going up next week. You just asked a week too soon. Sorry though, no dancing in it.

I bet the written version would be shorter than the video if for no other reason than the long "aaaa's" would be gone, as in: "paaak your caaa at the laaambaaa yaaad" would take less time to read than listen to.

[Amy@altE]

I bet the written version would be shorter than the video if for no other reason than the long "aaaa's" would be gone, as in: "paaak your caaa at the laaambaaa yaaad" would take less time to read than listen to.

Well played my friend, well played.

[fopoku2k2]

Well played my friend, well played.

Solar Queen, Is it possible for my panels to charge the batteries whilst the batteries are being discharged??

[Amy@altE]

Yes.