Combiner box or 2nd MPPT on a 6500EX?

[shaggy745]

Hi all,

I have a 6500EX inverter. I'm currently running 8 x 210W panels in series. I know that it is good practice to only put matching or similar voltage panels in a series string.

I want to expand my system with some larger panels, and curious as to the best options. Can a combiner box be used to combine strings of different voltages and then that feeds into 1 mppt? Is it better to run a second independent cable back to the inverter and put the added panels on that as a separate string for MPPT 2? That is more copper to run for sure. I'm assuming though that the 2nd mppt on the 6500ex can be totally different voltage that the 1st?

Thanks for any advice.

 

[timselectric]

Use MPPT 2.

 

[shaggy745]

Use MPPT 2.

Could you elaborate? What makes that preferable to a combiner box? Can definitely go that route but it's more copper to run. Thanks.

 

[timselectric]

If using different voltage panels. They shouldn't be mixed together.
It's not just good practice.
It's about getting good production.
They belong on different MPPT's.

 

[Gavin Stone]

It’ll just drop to whatever the weakest link is. That’s why it’s always best practice to not mix different voltages. If you can’t fit the strings on the mppt’s in the inverters, then the next best option is a separate charge controller.

 

[SolarPowerAficionado]

With the 6500 you have 2 seperate MPPTs so you can run 2 different strings of panels to the inverter without any worry. With 8 panels at 210 watts you have 1,680 watts of solar. With the 6500 you can have up to 8kW of solar total. You just need to make sure you stay under the max voltage and amperage of the MPPT. On the 6500 it's 500VDC and 18 amps per MPPT. With a max of 18 amps per MPPT you really don't want to parallel panels..i.e. use a combiner box.