Help with array configuration

solarsquirral · February 2016

Hi guys thanks in advance for any pointers. I have 17 she'll sp75. 75 watt panels And a trace c60 controller. How would you recommend the configuration of array strings. I was thinking two strings of 8 and but the controller says max 55vdc. So with a open circuit voltage of 21.7 does that mean I can only have two panels on a string? Another question was breaker size and fuses. Thanks

solarsquirral · February 2016

Specs for panels are. Rated current 4.4/ short c 4.8. 15 amp series fuse

Raj174 · February 2016

Hi solarsquirral,
What is the battery voltage

solarsquirral · February 2016

12 volt.

Vic · February 2016

HI solarsquirral,

The C-60 is a PWM controller. For the best efficiency, the PV Vmp voltage needs to be just a bit above battery voltage.

SO, strings of eight will result in far too high of an input voltage to the CC, and it would FRY.

You would probably want "strings" of one PV, ie, all in parallel, and there is a limit in the output current that the CC can handle.

This is the Data Sheet for those PVs, I believe
http://www.physics.arizona.edu/~cronin/Solar/TEP module spec sheets/shell installation.pdf

More Later, Vic

solarsquirral · February 2016

So are you saying I should have 17 single strings

Raj174 · February 2016

If the battery were 24 volt you could run 8 strings of 2 panels. You could also do that with an MPPT change controller. However with a PWM controller and 12 volt battery the only way to go without wasting power is wiring the panels in parallel. A lot of wiring I know. An MPPT controller would help that but for that much amperage your looking at several hundred dollars. I believe 6 to 8 amp breaker or fuse should do for parallel connections

solarsquirral · February 2016

How many to a string in parallel ?

Raj174 · February 2016

1 to a string, so no strings. Their amps add up and the voltage stays the same. So 60\4.4= 13 panels max

solarsquirral · February 2016

13 panels max in parallel or 13 panels max for controller

Raj174 · February 2016

13 panels max for controller, however read the controller manual, It might be able to shave off the over current. I have not encountered that many panels in parallel and am not 100% sure the controller can't dissipate the extra amps above it's designated amount. The reason more panels would be better is better production in morning, evening and cloudy days, i. e. lower light conditions.

One other thing, the array output needs to match the battery bank capacity

Raj174 · February 2016

For example, if the controller is outputting 60 amps then a lead acid battery bank would need to be no smaller than 500AH.
If it's an AGM bank then something around 300 to 350AH.

solarsquirral · February 2016

Thanks for the info. The bank is made of four 6v 550ah Wired in series parallel. The cc can Handel 85 amps intermediatly I'm trying to set it up so I get a solid 60 amps flowing during absorb charge.

Raj174 · February 2016

That's great, sounds like that will do the job, good luck

vtmaps · February 2016

solarsquirral said:

The bank is made of four 6v 550ah Wired in series parallel.

You could configure those batteries to be 24 volts. Then you could have 2 panels to a string, and you would have a more efficient and more stable system. Maybe.

The reason for the 'maybe' is that your panels have a Voc of 21.7 and two in series would have Voc of 43.4. That may be too close to the controller max input voltage of 55. When the panels are cold, before the sun warms them up, they will have a Voc that could get up above 55 volts (depending on your climate).

--vtMaps

Help with array configuration

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