anyone know a way to slightly reduce the voltage of solar panels?

[texasjames]

I have 2 solar panels, they are 275 watts, 38 VOC and VMP 31
what I NEED (for a specific solar generator) is:
watts: 550
VMP > 36
VOC < 60

if I connect them in series, my volts reading is about 64
so I assume that covers the requirement "VMP > 36"
but violates "VOC < 60"

is there any way I can make them work? maybe a way to slightly lower the volts to just under 60?

 

[timselectric]

Wire them in parallel.

 

[timselectric]

Wire them in parallel.

Never mind, that won't work either.
You don't have the right panels for your charge controller.

 

[texasjames]

parallel won't meet the requirement of MV P >36
I figure the only way is if I can reduce the combined 64 volts to get it under 60.
so....somehow lower the volts by 5

 

[timselectric]

Open the junction box on a panel and bypass one string.

 

[Madco]

5V/100W zener diode in series will get it in range when operating but will still run afoul of the Voc limit when not at the MPP. The diode will dissipate around just under 100w and will run hot even with a good heatsink. You'll need to match panels with the controller-one or the other will need to be replaced.

 

[texasjames]

Open the junction box on a panel and bypass one string.

interesting. I might try that.

 

[wme]

Point it the wrong way, add a couple of HD diodes in series

 

[Quattrohead]

The two panels in parallel may still work ok, definitely give it a try at least.

 

[mikefitz]

The designers of the Lion Energy Satari decided the solar input range should be 36 Vmp to 60 Voc volts, published in the specification.
They will sell you some of their own panels , a 100 watt, specification 35 Vmp, again from the specification.
In theory the unit should not work with their own panels!

You have the wrong panels or the wrong 'Power Station'.

It's possible you have damaged the unit by using the panels in series.

Two Renogy 200 watt panels in series should be suitable.

200 Watt 12 Volt Monocrystalline Solar Panel

The Renogy 200 Watt 12 Volt Monocrystalline Solar Panel is one of the main components for any solar power (PV) system. Whether you plan to use the solar panel for seaside travels to the beach or your cabin in the mountains, this panel can be a great start or addition to any Renogy off-grid system!

eu.renogy.com

 

[Pappion]

Power a small incandescent light bulb with it. It won't be Open circuit any more. Maybe a night light will do. Verify with a meter.

 

[Pappion]

Point it the wrong way, add a couple of HD diodes in series

Won't work. The diodes will have junction leakage resulting in VOC.

 

[Pappion]

Point it the wrong way, add a couple of HD diodes in series

Should work for a while and shorten the lifespan.

 

[ncsolarelectric]

It will probably work with them in parallel, it just won't deliver full power because the voltage is low and the current is limited. I would try it before adding diodes that dissipate power as heat. The controller should protect itself from overcurrent, but it can't protect itself from overvoltage.

 

[fafrd]

I have 2 solar panels, they are 275 watts, 38 VOC and VMP 31
what I NEED (for a specific solar generator) is:
watts: 550
VMP > 36
VOC < 60

if I connect them in series, my volts reading is about 64
so I assume that covers the requirement "VMP > 36"
but violates "VOC < 60"

is there any way I can make them work? maybe a way to slightly lower the volts to just under 60?

In theory, you could try wiring your two panels in parallel and boosting string voltage to 36V (or higher) using a DCDC boost converter such as one of these: https://www.amazon.com/dp/B08NF556Z...=1&sp_csd=d2lkZ2V0TmFtZT1zcF9waG9uZV9kZXRhaWw

Your 2 275W panels are rarely going to be putting out more than 17.75A @ 31V, we’ll below the input overcurrent limit of 35A and boosted to 36VDC @ a maximum of 97% efficiency, that 550W of inout power will result in no more than 533.5W of output power meaning 14.82A @ 36V, we’ll belo the 20A upper limit and lightly above the ‘please enhance heat dissipation when current is over 15A)’ limit .

If you boost voltage to 40V or 50V you can reduce output current down to 13.34A or 10.67A but likely at the cost of decreased efficiency.

I’ve got a panel with Vmp of ~40V that I’m currently using to charge a 24V LiFePO4 battery and I’m mulling switching to 48V and thinking about using one of these to boost voltage to 60V so I can charge the higher-voltage battery…

 

[fafrd]

It will probably work with them in parallel, it just won't deliver full power [b{because the voltage is low[/b] and the current is limited. I would try it before adding diodes that dissipate power as heat. The controller should protect itself from overcurrent, but it can't protect itself from overvoltage.

I think you meant because the voltage is high, not low.

In parallel, the ideal string voltage is Vmp = 31V but the SCC won’t allow string voltage to drop under 36V.

So the panels will be driven at a higher voltage than Vmp pushing current and power down below where it could have been.

As a very crude swag, we can assume linear current reduction between Imp = Pmp/Vmp = 17.74A @ Vmp = 31V and 0A at Voc = 38V.

36V is 71.4% of the way from Vmp to Voc meaning current could be driven down by as much as 71.4% to only 5.07A.

5.07A x 36V = 182.5W, a 67% reduction in power.

It’ll work and it won’t damage anything, but you’d be throwing away 2/3 of your potential power…

 

[DIYrich]

2 panels in series is 62v when producing. You will need a high wattage resistor to bring it under 60v. Hopefully it can also bring down voc under 60v too.

 

[texasjames]

It will probably work with them in parallel, it just won't deliver full power because the voltage is low and the current is limited. I would try it before adding diodes that dissipate power as heat. The controller should protect itself from overcurrent, but it can't protect itself from overvoltage.

the reason it doesn't work in parallel is because the unit's threshold of 36 mvp is never reached

 

[Quattrohead]

VMP = voltage at max power, does not mean it won't work.
Try it.

 

[fafrd]

the reason it doesn't work in parallel is because the unit's threshold of 36 mvp is never reached

No, it operates just fine at a voltage of 36V, it’s just going to be piss-poor efficiency.

If no current is flowing at Vmp / 31 volts then string voltage will increase towards Voc. That increase continues until current starts to flow of Voc is reached (which is the maximum voltage that can be reached with no current flowing).

As the string voltage increases from Vmp towards Voc is must reach 36V on the way and at that point the SCX starts charging at whatever current the string will give it (which, as I posted earlier is a little as 33% of the power that could be produced at a string voltage of Vmp).