New 300-watt solar panels 8.9amp 31v open

[Borneoboy]

Can I use these new high power panels with my existing setup?
All-in-one inverter /charger accepts up to 50 amps.
All 12v system. 4 panels at 300 watt each, 200 amp/hr lead acid battery, PWM charger built in to charge at 20 amps max and a little Honda generator for the evenings...
Present panels only 65 watt and 20 years old. !

 

[Supervstech]

If you have an mppt solar controller, yes. If not... then no. You would need an mppt controller.

 

[Forbisher]

All-in-one inverter /charger accepts up to 50 amps.
All 12v system. 4 panels at 300 watt each, 200 amp/hr lead acid battery, PWM charger built in to charge at 20 amps max and a little Honda generator for the evenings...
Present panels only 65 watt and 20 years old. !

What is the brand and model of All In One??
How many 65 watt panels?

 

[Borneoboy]

If you have an mppt solar controller, yes. If not... then no. You would need an mppt controller.

But I read somewhere you need at least 160volts to run an MPPT... is that not correct?
I would have just 120v with 4 panels.

 

[Borneoboy]

What is the brand and model of All In One??
How many 65 watt panels?

Made in China.
2 65 watt old panels

 

[Borneoboy]

If you have an mppt solar controller, yes. If not... then no. You would need an mppt controller.

Can you also explain why?

 

[Borneoboy]

Can you also explain why?

Can I somehow add an MPPT controller before the "all-in-one" if it is essential?

 

[Forbisher]

Can I somehow add an MPPT controller before the "all-in-one" if it is essential?

No

 

[Borneoboy]

Alternatively can I just use less panels (1 or 2) until upgrading to MPPT ?

 

[Hedges]

But I read somewhere you need at least 160volts to run an MPPT... is that not correct?
I would have just 120v with 4 panels.

That is not correct. Many of the MPPT chargers have an absolute max PV input voltage of about 140V to 150V.
The PV panel label (or data sheet if label doesn't have all the specs) will give Voc, open circuit voltage at one standard sun and 25 degrees C.
Also, temperature coefficient of Voc in either V or % per degree C. Something like -0.4%/degree C.
In my location I assume -15 degrees C as a record cold temperature, so -40 degrees relative to ambient 25C, and max Voc is +16% compared to label Voc.

That's the maximum. There will also be a minimum Vmp. If your string of panels has its Vmp drop below MPPT voltage range of the inverter on a hot day then you'll get less than full power. That's panel temperature not air temperature, maybe about 65 degrees C unless you are in a hot location.

"300-watt solar panels 8.9amp 31v open"

Label shows 31 Voc? How about 8.9 A ... is that 8.9 A "Isc" or 8.9 A "Imp"?
If Isc, then 31 Voc x 8.9 Isc = 276, which is less than 300. And "Watts" doesn't come from product of open circuit voltage and short circuit current.
Even if Vmp and Imp, 276 is still less than 300.

Those figures don't seem to match a 300W panel. Got a picture of the label, or link to data sheet?

 

[Borneoboy]

That is not correct. Many of the MPPT chargers have an absolute max PV input voltage of about 140V to 150V.
The PV panel label (or data sheet if label doesn't have all the specs) will give Voc, open circuit voltage at one standard sun and 25 degrees C.
Also, temperature coefficient of Voc in either V or % per degree C. Something like -0.4%/degree C.
In my location I assume -15 degrees C as a record cold temperature, so -40 degrees relative to ambient 25C, and max Voc is +16% compared to label Voc.

That's the maximum. There will also be a minimum Vmp. If your string of panels has its Vmp drop below MPPT voltage range of the inverter on a hot day then you'll get less than full power. That's panel temperature not air temperature, maybe about 65 degrees C unless you are in a hot location.

"300-watt solar panels 8.9amp 31v open"

Label shows 31 Voc? How about 8.9 A ... is that 8.9 A "Isc" or 8.9 A "Imp"?
If Isc, then 31 Voc x 8.9 Isc = 276, which is less than 300. And "Watts" doesn't come from product of open circuit voltage and short circuit current.
Even if Vmp and Imp, 276 is still less than 300.

Those figures don't seem to match a 300W panel. Got a picture of the label, or link to data sheet?

This is from the charger/inverter manual.
Seems to me to support panels up to 40vdc.

 

[Borneoboy]

Will get a snapshot of the panel data as well later.

 

[Borneoboy]

Will get a snapshot of the panel data as well later.

This is great having "someone" to talk to about solar! Have been totally isolated otherwise, apart from following nearly all of Will's YouTube videos for the past year?

 

[Borneoboy]

 

[Hedges]

Looks like that works for panels up to 40Voc cold.

Outback MX60 and MX80 offer 750W and 1000W into 12V with wider voltage range, up to 145 or 150V.
You could connect series strings, smaller wire. There are probably several other brands with wide input voltage range.

http://www.outbackpower.com/downloads/documents/charge_controllers/flexmax_6080/specsheet.pdf

Be sure to check out the other DIY Solar threads on charge controllers and panels.
I've been playing around with some expensive equipment, and others have found low-cost ones.
As for panels, a bunch of us have bought from SanTan Solar, large economical panels in the 250W to 350W range. Catch is they need to go by truck, so best deal if you can use a pallet load.

OK, that label Vmp x Imp = 290W.
Voc = 38.3? Temperature coefficient not given, but assuming -0.4%/degree then at -15C the Voc could rise to 44.4V, 10% higher than inverter 40Voc spec.

 

[RCinFLA]

At cold temps it is quite likely for that poly panel's Voc will exceed 40 vdc with a Voc at 25 deg C of 38.3 vdc,.

Mono cells temp coef is very predicable -0.33%/degC (-2.1 mV/degC ) but poly's can be all over the map depending on a given manufacturer. Poly panels temp coef range from as great as -160 mV per deg C all the way down close to mono cell at -2.1 mV/deg C. -80 mV/degC would be about +2v at freezing temp which puts it just over 40 vdc for Voc.

 

[Borneoboy]

At cold temps it is quite likely for that poly panel's Voc will exceed 40 vdc with a Voc at 25 deg C of 38.3 vdc,.

Mono cells temp coef is very predicable -0.33%/degC (-2.1 mV/degC ) but poly's can be all over the map depending on a given manufacturer. Poly panels temp coef range from as great as -160 mV per deg C all the way down close to mono cell at -2.1 mV/deg C. -80 mV/degC would be about +2v at freezing temp which puts it just over 40 vdc for Voc.

Thanks for the advice.
Here it never goes below 70 degrees, even at night. Daytime often 100, so overheating more of a problem possibly. Lead acid batteries don't last long either - two or three years max.

 

[Hedges]

Can you also explain why? [MPPT required]

PWM just throws an electronic "switch" to short the PV+ to battery+, then opens it, then shorts it.
Most current you'll get is something approaching Isc.
Transistors will burn watts as they swing the large voltage range from about 14V at the battery to about 31V at the PV panel, so probably the PWM charge controller won't handle as many watts as it could with lower voltage PV. So far down the VI curve of PV, it will produce much less power. The rest is burned up in the PV panel.
It's kind of like working the clutch in and out to regulate speed.

MPPT uses an inductor as kind of a one-winding transformer. Pulsing a transistor like the PWM, it draws a fairly steady current from PV at one voltage & current, puts out a fairly steady lower voltage and higher current into the battery. It can take in 120V @ 4A and put out 14V @ 34A.
Kind of like gear reduction, or CVT.

 

[Borneoboy]

PWM just throws an electronic "switch" to short the PV+ to battery+, then opens it, then shorts it.
Most current you'll get is something approaching Isc.
Transistors will burn watts as they swing the large voltage range from about 14V at the battery to about 31V at the PV panel, so probably the PWM charge controller won't handle as many watts as it could with lower voltage PV. So far down the VI curve of PV, it will produce much less power. The rest is burned up in the PV panel.
It's kind of like working the clutch in and out to regulate speed.

MPPT uses an inductor as kind of a one-winding transformer. Pulsing a transistor like the PWM, it draws a fairly steady current from PV at one voltage & current, puts out a fairly steady lower voltage and higher current into the battery. It can take in 120V @ 4A and put out 14V @ 34A.
Kind of like gear reduction, or CVT.

Superb explanation ! I almost understand the whole process!
Up to now they have just been Capital Letters (acronyms) !
Thanks.

 

[Borneoboy]

Superb explanation ! I almost understand the whole process!
Up to now they have just been Capital Letters (acronyms) !
Thanks.

Mind you the MPPT controllers are relatively expensive - we've been using a $30 PWM for years!
I must move up soon, probably to a 3 or 5 Kw all-in-one which all seem to use MPPT (built-in).