what charge controller do I need for a 250watt panel

[fopoku2k2]

Not high enough for a 24 volt battery, as you need 36 volts minimum. Your only option is to wire the panels in series to obtain 60 volts, and use a MPPT controller. If you were to use a PWM controller you maximum charge current is 8 amps and at 24 volts is 192 watts out of 500 watts. Use a MPPT and you get up to 21 amps of charge current.

Wow. 192 watts out of 500 watts. OMG!!!

I'm guessing even in series since my current would be small I would be using smaller batteries to bring down my arising cost.

How did you get the 36 volts minimum for a 24 volt battery?

[Sunking]

My Vmp is 30.3

Not high enough for a 24 volt battery, as you need 36 volts minimum. Your only option is to wire the panels in series to obtain 60 volts, and use a MPPT controller. If you were to use a PWM controller you maximum charge current is 8 amps and at 24 volts is 192 watts out of 500 watts. Use a MPPT and you get up to 21 amps of charge current.

[fopoku2k2]

What's the Vmp?




While a MPPT controller may be important for you, Sunkings talk of doom and gloom on PWM has some hype in it. Sure if you take 16.5 amps and multiply it by 24v it looks like you've got a lot of loss. But the thing is your battery banks voltage should be significantly higher than 24v by the time your panels are putting out anything close to it's 500w.

My Vmp is 30.3

[Sunking]

While a MPPT controller may be important for you, Sunkings talk of doom and gloom on PWM has some hype in it. Sure if you take 16.5 amps and multiply it by 24v it looks like you've got a lot of loss. But the thing is your battery banks voltage should be significantly higher than 24v by the time your panels are putting out anything close to it's 500w.

Wrong, not if the batteries are discharged enough to demand full power, they are not above nominal voltage. The voltage rise is determined by Ri plus OCV. 16 amps into .001 ohms is only .016 volts. Take that Bucho. Your math needs a lot of work.

[Bucho]

I can confirm that 37.7 is the Voc.

What's the Vmp?

To get my full rated power of 500W what would you suggest?

While a MPPT controller may be important for you, Sunkings talk of doom and gloom on PWM has some hype in it. Sure if you take 16.5 amps and multiply it by 24v it looks like you've got a lot of loss. But the thing is your battery banks voltage should be significantly higher than 24v by the time your panels are putting out anything close to it's 500w.

[fopoku2k2]

Your math needs some work. 4 x 12 in series is 48 volts.

Sorry. I meant to say they are connected in a way to get 24 volts since my inverter is 24 volts. I didn't conect the batteries myself :-p

[Sunking]

I can confirm that 37.7 is the Voc. I have four 12 volts 100AH batteries connected in series, so a total of 200AH at 24 volts.

To get my full rated power of 500W what would you suggest?

Your math needs some work. 4 x 12 in series is 48 volts.

[LETitROLL]

I have four 12 volts 100AH batteries connected in series, so a total of 200AH at 24 volts.

Four 12v @ 100ah in series would be 48v 100ah.

Only way to get your full rated power from panels is to get a MPPT controller, although your panels in parallel to your current PWM controller are about as good as you can get with PWM, potentially yielding around 400+ watts to a 24v battery (during optimum conditions). If you need every ounce of power and are going to do any real work/loads get a MPPT controller, if you are playing/experimenting around the PWM is fine.

[fopoku2k2]

First thing if you buy another PWM controller forces you to wire the panels in parallel and when you are done turns your 500 watt panels into 400 watt panels. PWM Controller Input Current = Output current. Wire your panels in parallel with PWM and you only have 16.5 amps at most.

Get you at least a 20 amp MPPT charge controller, wire the panels in series, and you will have 20 amps of charge current or 500 watts of charge power.

If I connect the panels in series meaning my total voltage would now be 75.4. So if I'm right I per your suggestion I would need a 20amp mppt controller with an input voltage of 75.4 + ?

[fopoku2k2]

As long as the 37.7 is the Voc it won't hurt the controller, the other thing you must check out is the size (AH) rating of your battery bank, and make sure you are not in a range that will grossly under or over charge the batteries, causing swift damage to them. With the PWM controller you will not get your rated power (500W) clear through to your batteries, but they work okay otherwise.

I can confirm that 37.7 is the Voc. I have four 12 volts 100AH batteries connected in series, so a total of 200AH at 24 volts.

To get my full rated power of 500W what would you suggest?

[Sunking]

First thing if you buy another PWM controller forces you to wire the panels in parallel and when you are done turns your 500 watt panels into 400 watt panels. PWM Controller Input Current = Output current. Wire your panels in parallel with PWM and you only have 16.5 amps at most.

Get you at least a 20 amp MPPT charge controller, wire the panels in series, and you will have 20 amps of charge current or 500 watts of charge power.

[LETitROLL]

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

As long as the 37.7 is the Voc it won't hurt the controller, the other thing you must check out is the size (AH) rating of your battery bank, and make sure you are not in a range that will grossly under or over charge the batteries, causing swift damage to them. With the PWM controller you will not get your rated power (500W) clear through to your batteries, but they work okay otherwise.

[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