Quick sanity check

[RoySalisbury]

I have 6 ea 320w panels (49.5v voc/8.6a isc) and 6 ea 205w panels (33.2 voc/8.36 isc). In the past I have used separate CC's for each string, but due to some re-wiring and re-location I need to try and minimize the cable runs.

So was thinking I would put all 12 in series. I know I will loose some wattage, but I think it will be minimal and worth the loss compared to the cost.

Volts = (49.5*6)+(33.2*6) = 496.2v (CC can handle 500v)
Amp = Lowest isc in string = 8.36a

Again, I know there will be some potential power loss, but its better then leaving all the 205w panels offline (~ 1kw/h).

Roy

 

[timselectric]

So was thinking I would put all 12 in series. I know I will loose some wattage, but I think it will be minimal and worth the loss compared to the cost.

They will all output as 205w panels.

Volts = (49.5*6)+(33.2*6) = 496.2v (CC can handle 500v)

Too close. Not worth the risk.

Again, I know there will be some potential power loss, but its better then leaving all the 205w panels offline (~ 1kw/h).

One less for safety.

 

[RoySalisbury]

They will all output as 205w panels.

Hmm ... I thought that in series that you add up all the VOLTS and use the lowest AMPS. In parallel you add al the AMPS and use the lowest VOLTS.

 

[RoySalisbury]

Too close. Not worth the risk.

I could always leave one of the 205w panels out so I was not so close to the 500v max of my CC. I'd still gain the other 5 (or really 4 with power loss).

 

[Bluedog225]

Volts times 1.2 should not exceed max allowed voltage. Strict limit.

That‘s the quick rule of thumb I remember.

The midnite solar calculator made my head hurt.

 

[RoySalisbury]

Volts times 1.2 should not exceed max allowed voltage. Strict limit.

That‘s the quick rule of thumb I remember.

The midnite solar calculator made my head hurt.

Depends on if your talking nominal or open circuit. The nominal voltage for the 330's is 40.1 .. Open circuit is 49.5 ... I always calculate with open circuit (VoC) so that I am within limits and don't have to deal with other factors. Its not good for calculating actual usable output, but it makes sure I am in safe limits.

 

[John Frum]

Are you overlooking the temperature coefficient?

 

[Bluedog225]

I thought it was voc times 1.2. But others will be certain.

 

[RoySalisbury]

Are you overlooking the temperature coefficient?

I'm not looking at going to the moon here .. just getting a few hundred extra watts vs having to run a new line and separate CC.

 

[John Frum]

I'm not looking at going to the moon here .. just getting a few hundred extra watts vs having to run a new line and separate CC.

I'm not sure you answered my question.
Your panels.
Your charge controller.
Your magic smoke.

 

[timselectric]

We are just trying to help you not destroy your SCC.
1.2 x VOC.

 

[LydMekk]

And do NOT measure this against the MAX of your PV input.
Consider the max of your MPPT charger, which is way lower than 500V....more like 425V.
So stick to strings combined STC VOC under 400V. That will be 8 panels times 49.5Volts per panel.

If you do, there will be less drama and no noxious smoke...which is a good thing.