# Mixing panels of different brands and wattages...

We've got a situation where we'd like to make an array where we combine 4 BP SX-160B panels in series and 4 Suntech STP 175-24/Ab-1 panels in series, together in parallel. The array will power a Grundfos 16 SQF-10 water pump through a CU200 controller.

Any idea if this will work alright? Will this cause problems for the controller?

What kind of performance we can expect? Our understanding is that we will get a performance somewhere in between just 8 BP's or just 8 Suntech.

Here are the specs on the panels:

BP SX-160B
Pmax=160W
Voc=43.6V
Vmp=35.0V
Isc=4.8V
Imp=4.6A

STP 175-24/Ab-1
Pmax=175W
Voc=44.2V
Vmp=35.2V
Isc=5.2V
Imp=4.95A

Re: Mixing panels of different brands and wattages...

I don't see any big issues...

The worst case results would probably be the loss of 15 watts * 4 series Sunpower panels = 60 watts (out of a ~1,280 STC watt array)--reduce Vmp to the level of the BP panels.

If you get a good deal (and/or prompt delivery) on your panels, the 60 watts is within the +/-10% that more panel manufacturers warranty anyways.

You probably would not be able to even see the difference in day to day real life operation. (for example, the BP 160 panels, rated at 160 watts STC, in real life 95F day, will produce a maximum of ~128 watts per panel, in a real system).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Posts: 1,832Registered Users, Solar Expert ✭✭✭✭
Re: Mixing panels of different brands and wattages...

The STC Vmp of the four-module BP string will be 35.0 V x 4 = 140.0 V.
The STC Vmp of the four-module ST string will be 35.2 V x 4 = 140.8 V.

Allowing for tolerances and environmental operating conditions, these values are easily close enough. The Imp’s of the two strings will just add, and you’ll end up with an array with an STC power rating of ~140 V x (4.6 A + 4.95 A) = ~1,337 W.

HTH,
Jim / crewzer
Re: Mixing panels of different brands and wattages...
crewzer wrote: »
The STC Vmp of the four-module BP string will be 35.0 V x 4 = 140.0 V.
The STC Vmp of the four-module ST string will be 35.2 V x 4 = 140.8 V.

Allowing for tolerances and environmental operating conditions, these values are easily close enough. The Imp’s of the two strings will just add, and you’ll end up with an array with an STC power rating of ~140 V x (4.6 A + 4.95 A) = ~1,337 W.

HTH,
Jim / crewzer
thanks very much jim.