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Connecting 36 cell solar panels to a 60 cell system


Tariq
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I have two 60 cell 270 watt panels in series at present, have been given two 160 watt 36 cell panels, what would be the best way to connect them to the  270 watt panels to get the best utilization

thanks 

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6 hours ago, Tariq said:

I have two 60 cell 270 watt panels in series at present, have been given two 160 watt 36 cell panels, what would be the best way to connect them to the  270 watt panels to get the best utilization, could I connect all four panels in series

thanks 

 

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11 hours ago, Tariq said:

have been given two 160 watt 36 cell panels, what would be the best way to connect them to the  270 watt panels to get the best utilization

You didn't say what the battery voltage of your setup is. If it is 48V, then two 36-cell modules in series won't be enough to charge a 48V bank. If you have a 24V bank, then you can add an extra MPPT. An extra 320W at 24V, you could use a small 15A MPPT for that. Cheap cheap.

There is one other way. If the 36-cell modules have the same Imp (current at max power), ie they make similar current to the 60-cell modules, you could string them up in series without loss of power (they will pass the same amount of current, no bottleneck). But again, this is just not going to divide nicely into your existing 2 x series setup. If you just tack them onto the end, you extend your current setup with 120 series cells to 120 + 72 = 192 cells. This will make up to 135V on a cold morning, but your peak power will be around 100V. If the MPPT can handle it (and again, the current capability of the module must match the other modules), then that might be an idea.

To give you an example, I presently have two kinds of modules on my roof. I have 335W Canadian Solar modules, 72 cell modules, and they push around 9A (but at >36V). Then I have a bunch of older Tenesol modules, 150W each, 36 cells, and they too push around 8.5A (but at a lower 18V or so). If I put one of the 72-cell module sin series with one of the 36-cell modules, I'll end up with one 108-cell string, which will make around 54V at max power, and push 8.5A (the lower of the two), so I turned my two modules into one 460W module. My loss is therefore 460/(335+150) = 0.95, ie this little shenanigan lost me 5% of the total power.

Would I do this? No... probably not.

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7 hours ago, plonkster said:

There is one other way. If the 36-cell modules have the same Imp (current at max power), ie they make similar current to the 60-cell modules, you could string them up in series without loss of power (they will pass the same amount of current, no bottleneck). But again, this is just not going to divide nicely into your existing 2 x series setup. If you just tack them onto the end, you extend your current setup with 120 series cells to 120 + 72 = 192 cells. This will make up to 135V on a cold morning, but your peak power will be around 100V. If the MPPT can handle it (and again, the current capability of the module must match the other modules), then that might be an idea.

That seems quite likely the case - the cells are just about the same wattage 4.44W vs 4.5W, so it just depends on wiring.

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