Using half a panel?

[solarfather]

I'm thinking of getting some cheap 250W panels and will be using some in smaller systems (setups that would have used 100W, but the 250W will cost me 1/3 the price of new 100W panels). If I block off half of the panel will all the specs be halved so as to not overload my system?

eg. Is this a reasonable approximation? And how would best to block off the panel?
Open circuit voltage (VOC): 37.6 V -----> ~18V?
Max power voltage (VMP): 30.3 V ------> 15V?
Short circuit current (ISC): 8.85 A -------> 4.42A?

 

[gnubie]

Technically if you can work out how the bypass diodes vs cells is arranged you could probably do it but there's bound to be a better way. The voltages would be reduced in this attempt, the current would remain at 8.85 amps.

Are the existing 100W panels ~18v etc? How are they configured, 2 in series? Perhaps parallel the 250W panel with that series string. If you could post more detail of how things are currently set up and how you are trying to set them up with the 250W panels some better advice can be given.

 

[JoseAgustinV]

I'm thinking of getting some cheap 250W panels and will be using some in smaller systems (setups that would have used 100W, but the 250W will cost me 1/3 the price of new 100W panels). If I block off half of the panel will all the specs be halved so as to not overload my system?

eg. Is this a reasonable approximation? And how would best to block off the panel?
Open circuit voltage (VOC): 37.6 V -----> ~18V?
Max power voltage (VMP): 30.3 V ------> 15V?
Short circuit current (ISC): 8.85 A -------> 4.42A?

How much amps is you SSC? You should check if they can handle the 250W panel, can you provide the specs of your solar panels and SSC?

 

[solarfather]

Technically if you can work out how the bypass diodes vs cells is arranged you could probably do it but there's bound to be a better way. The voltages would be reduced in this attempt, the current would remain at 8.85 amps.

Are the existing 100W panels ~18v etc? How are they configured, 2 in series? Perhaps parallel the 250W panel with that series string. If you could post more detail of how things are currently set up and how you are trying to set them up with the 250W panels some better advice can be given.

Thanks for the quick response. I don't have any of the 100W application systems yet, I'm just seeing if I can massively overbuy on the 250W (since shipping is the major cost here for these panels) the 250W panels and still use them in other smaller applications. So any advice on how to flexibly use these is appreciated, thanks!

 

[solarfather]

How much amps is you SSC? You should check if they can handle the 250W panel, can you provide the specs of your solar panels and SSC?

Thanks, I am thinking of the Santan 250W panels https://store.santansolar.com/product/santan-solar-t-series-250w/

I don't have a specific system yet, but am seeing if I overbuy the number of panels (already have a use for them in 250W configuration) how flexible in repurposing I can be with them in lower spec configs (yet to be determined).

 

[JoseAgustinV]

You should be able to use almost every SSC with these solar panels, you don't need to get less voltage. If you have a small SSC you could just add solar panels in parallel to avoid increasing the VOC but it depends on which SSC you will be using.

Currently, I have a small 12v system with a 40A SSC, I have 2 100w solar panels in series connected to it but I could just replace those with one of your 250W solar panels. Just as an example, my SSC has a Vdc range of 15-80V, so 30VMP from your panels is ok, and Max VOC on it is 102V, It will be safe enough to get 1 or even 2 of the panels in parallel for my system, I will not use them in series for my system just to be safe with voltage the ranges.

The only reason I have 100W panels instead of those 250W panels its because I will spend a lot more money on shipping, but I would love just to have 2 of these.

 

[solarfather]

You should be able to use almost every SSC with these solar panels, you don't need to get less voltage. If you have a small SSC you could just add solar panels in parallel to avoid increasing the VOC but it depends on which SSC you will be using.

Currently, I have a small 12v system with a 40A SSC, I have 2 100w solar panels in series connected to it but I could just replace those with one of your 250W solar panels. Just as an example, my SSC has a Vdc range of 15-80V, so 30VMP from your panels is ok, and Max VOC on it is 102V, It will be safe enough to get 1 or even 2 of the panels in parallel for my system, I will not use them in series for my system just to be safe with voltage the ranges.

The only reason I have 100W panels instead of those 250W panels its because I will spend a lot more money on shipping, but I would love just to have 2 of these.

Yes, shipping is expensive, but seems to be flat rate, so I am thinking just getting a few extra for various projects, thanks.

One thing it doesn't appear I can charge without blocking may be this portable pack: https://www.amazon.com/Rockpals-Por...9KFEAEW1TYX&psc=1&refRID=J8CW3J5EC9KFEAEW1TYX

Specs:

SPECS

Capacity	280WH/75000mAH, 300W, 600W Peak
AC Output (pure sine wave)	AC110V±10%, 60Hz±1Hz
Solar Input Charging	18V, 60W-100W

 

[JoseAgustinV]

Yes, shipping is expensive, but seems to be flat rate, so I am thinking just getting a few extra for various projects, thanks.

One thing it doesn't appear I can charge without blocking may be this portable pack: https://www.amazon.com/Rockpals-Por...9KFEAEW1TYX&psc=1&refRID=J8CW3J5EC9KFEAEW1TYX

Specs:

SPECS

Capacity	280WH/75000mAH, 300W, 600W Peak
AC Output (pure sine wave)	AC110V±10%, 60Hz±1Hz
Solar Input Charging	18V, 60W-100W

This can handle only up to 100w on solar panels, and the battery is very small also.

Im not familiar with those solar generators, i prefer having a separated battery bank, im currently using a MPP solar 12V, it is an All in one system it has a 800w inverter and a 40A SSC, you should consider it, very simple to install.

 

[solarfather]

This can handle only up to 100w on solar panels, and the battery is very small also.

Im not familiar with those solar generators, i prefer having a separated battery bank, im currently using a MPP solar 12V, it is an All in one system it has a 800w inverter and a 40A SSC, you should consider it, very simple to install.

Thanks, yes I have that exact same 800W MPP solar box as well! Since you have it as well, how would you recommend using these Santan panels with it? Specs again: ( https://store.santansolar.com/product/santan-solar-t-series-250w/)

Side note it seems the 1000W MPP solar box is more easily available for info on the web, was the 800W replaced with that model?

 

[solarfather]

This can handle only up to 100w on solar panels, and the battery is very small also.

Im not familiar with those solar generators, i prefer having a separated battery bank, im currently using a MPP solar 12V, it is an All in one system it has a 800w inverter and a 40A SSC, you should consider it, very simple to install.

Also, I have seen people running the 800W MPP Solar system without a battery, and using the AC bypass, any updates on the safety and reliability of that? I know its probably not really designed for use without a battery, but it seems to work for people? Actually scratch that, I've seen people using MPP Solar boxes without a battery, well at least disconnecting the battery and showing it works, but I don't know if it was the 800W or a different version, def wasn't the green hybrid ones though.

 

[JoseAgustinV]

Thanks, yes I have that exact same 800W MPP solar box as well! Since you have it as well, how would you recommend using these Santan panels with it? Specs again: ( https://store.santansolar.com/product/santan-solar-t-series-250w/)

Side note it seems the 1000W MPP solar box is more easily available for info on the web, was the 800W replaced with that model?

Yeah, i think they replaced the 800w model with a 1000w model.

You can add up to 2 of these panels to your mpp solar unit, add them in parallel to be safe with the voltage ranges, dont wire them in series.

 

[JoseAgustinV]

Also, I have seen people running the 800W MPP Solar system without a battery, and using the AC bypass, any updates on the safety and reliability of that? I know its probably not really designed for use without a battery, but it seems to work for people? Actually scratch that, I've seen people using MPP Solar boxes without a battery, well at least disconnecting the battery and showing it works, but I don't know if it was the 800W or a different version, def wasn't the green hybrid ones though.

I dont know if it can be used without a battery, but even if it can be used in bypass mode its useless, imagine an UPS wihout a battery, your appliances will turn off when you have no grid connection or when the voltage of the grid is too high or too low.

Ive heard of some 'special' mpp units that will work with solar but without batteries, but i think the is only some specific unit that can do it, this one can't.

 

[solarfather]

I dont know if it can be used without a battery, but even if it can be used in bypass mode its useless, imagine an UPS wihout a battery, your appliances will turn off when you have no grid connection or when the voltage of the grid is too high or too low.

Admittedly I haven't setup my MPP Solar yet, but from what I saw, it should auto switch over to AC power when there is not enough Solar Input to run whatever you have hooked up, I've seen a video where that works where there is no battery attached. Isn't that how yours works when your battery doesn't have enough power and you are hooked up to AC?

 

[JoseAgustinV]

You

Admittedly I haven't set up my MPP Solar yet, but from what I saw, it should auto switch over to AC power when there is not enough Solar Input to run whatever you have hooked up, I've seen a video where that works where there is no battery attached. Isn't that how yours works when your battery doesn't have enough power and you are hooked up to AC?

Yes, you can configure it to auto-switch to the grid when the battery is in a certain voltage, or even using the battery only when there is no grid available. You can't use solar input to run your appliances without a battery, so having this without a battery is useless.

 

[solarfather]

You

Yes, you can configure it to auto-switch to the grid when the battery is in a certain voltage, or even using the battery only when there is no grid available. You can't use solar input to run your appliances without a battery, so having this without a battery is useless.

Ah maybe not the 800w version. At least the 5048mg version is the one that doesn't need a battery.