4 - 435 watt sunpower panels.

BruceVanLife

New Member
I have a question for Will and the group.

I have an RV with 4 of the famous Sunpower commercial 435-watt panels on the roof.
These will eventually feed my 48v system this spring.

I have 3 large 12 v engine batteries that I am using temporarily as my house batteries too.

I am only using 1 panel currently to feed my Victron 150 / 35 controller 12-48v solar controller.

The 4 panels are connected currently into a midnite solar combiner box w each panel having its breaker combined with the controller.

Question.
With winter months coming up, is there a way to be able to access the other panels automatically without having to flip breakers on and off manually? when cloudy, foggy on the coast here in CA.
Without going over the 500-watt threshold on my 12 v system (from what I read this is the max input I can have for this current setup)

Like today it's cloudy. One panel is only bringing in 200 watts. It would be nice if 2 other panels could come up automatically but still stay under the 500/watt total to the controller

If not I will keep it. using the manual breaker method until I get my 48v battery setup after winter
 

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BruceVanLife

New Member
I don't have a top view of the panels, but they look just like my ambulance 🚑 did in San Diego
 

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FilterGuy

What, me worry?
but still stay under the 500/watt total to the controller
The limit is on what the controller will output. On the input there is a voltage limit.... but there is no power limit.

As long as you don't exceed the 150V limit of the Victron Smartsolar 150/35, you can put as many panels as you want on it. The controller will use all the power it can up to the 35A charge current limit and then just not use any more. This is called over-paneling and most MPPT controllers support it. The Victron MPPT controllers specifically state this in the documentation. (I would say ALL MPPT controllers support this, but as soon as I did someone will find one that doesn't)

What will happen with an over-paneled MPPT controller is that on sunny days it will quickly rise to the limit and stay there longer. This gives you more effective hours of production. On cloudy days, it may never reach the limit, but there will be much more production.

If you have the panels I am thinking of, they have a Voc of something like 85V. That means you can't put 2 in series on the 150/35, but you can put as many in parallel as you want without concern about burning out the controller.

Note: I would not worry for a moment about over-paneling a quality MPPT controller like Victron or Midnight. However, when over-paneling a controller, the amount of time the controller spends at it's design limit goes up. If they are not designed well, this could lead to an early failure. Therefore, I would be a little bit cautious about significant amount of over-paneling on low-end controllers even if they claim it is supported.

Warning: PWM controllers are very different. Do not over-panel them.
 

FilterGuy

What, me worry?
BTW: On a portable rig like yours it is often hard to avoid shade issues where you end up parking. As such, it is best to plan on having shading issues and build the system to minimize the impact.

The best way to minimize the impact is to have more than one controller...the extreme being one per panel.... but that gets very expensive.
The other way to minimize the impact of shade is to have Bypass and Blocking diodes. The panels probably already have one or more bypass diodes, but you should check. If the combiner box does not have a blocking diode per input string, it would be good to add them.

 

BruceVanLife

New Member
Somewhere I read there was a 500 watt max @ 12 v. And 2000 watt @ 48 v max under this controller
I will grad the pdf and read it over again.
 

FilterGuy

What, me worry?
See if I am reading this correct.

Nominal PV power
35A

35A 12V: 500W / 24V: 1000W / 36V: 1500W / 48V: 2000W

Those are the limits of what the controller will produce. They are not limits on the wattage of the input.

The link you provided is for the data sheet. This is the manual from the Victron site:


Page 56 has this:
1632598348891.png
 

fafrd

Solar Addict
See if I am reading this correct.

Nominal PV power
35A

35A 12V: 500W / 24V: 1000W / 36V: 1500W / 48V: 2000W

I didn’t read the manual, but most modern MPPTs will increase string voyage to ‘throttle-back’ PV power to desired levels (to stay under the charge limit and/or to taper-off charge current once the battery moves out of bulk/boost into float).

There may be some limit as to how high or with what granularity the MPPT can control the string voltage, and so better MPPT manuals will often specify a maximum PV array power (often 133% to 150% of max output power rating).

The situation you’ll be facing when your PV array is providing more input power than the maximum output owner rating of your MPPT is no different than the situation you’d have if PV power was within that maximum output rating but your battery was close to full…
 

camelCase

Solar Enthusiast

According to the specs, the max input current limit for the 150/35 is rated at 40 amps. Your panels probably put out about 6.5 amps ISC (verify this), and if so, you can use all 4 in parallel as that's less than 30 amps.
 

BruceVanLife

New Member
Those are the limits of what the controller will produce. They are not limits on the wattage of the input.

The link you provided is for the data sheet. This is the manual from the Victron site:


Page 56 has this:
View attachment 66287
Ohhh thanks

I will flip them all on.

Glad I bought a good controller.

Cannot wait to get my 48v system setup.
Thanks for the reply. I am not good at reading the fine print. 🤓
 

fafrd

Solar Addict

According to the specs, the max input current limit for the 150/35 is rated at 40 amps. Your panels probably put out about 6.5 amps ISC (verify this), and if so, you can use all 4 in parallel as that's less than 30 amps.
This is correct, but as I just stated, irrelevant.

MPPTs can handle oversized arrays and most everyone attaches an array that will max out the MPPT during the peak part of a clear, bright day.

MPPT SCCs are designed to throttle-back PV input power by increasing string voltage above Vmp (even driving string voltage all the way to Voc once the battery is 100% full and no more charge current is needed).

There is an upper limit to PV over sizing and most MPPTs that specify a maximum PV rating require no more than 133% or 150% of SCC maximum output power rating.

But there is absolutely no reason to design for Isc of you PV array to be lower than the maximum input current rating of your MPPT (except to be 100% certain that you are never, ever, wasting available solar power when you can use it).
 

McCarthy

Solar Addict
Same applies for all chargers, DC to DC from an alternator, AC to DC from shore power. They don't care about the max energy available, they are limited by what they can transform and output.
 

Sirtate

New Member
It's kinda like the difference between a hairdryer and your phone charger.
Too much voltage will fry them both, but as long as the outlet is providing the correct (safe) voltage, you can plug them both into the same outlet.

The phone charger will only pull the amperage needed to charge the phone, even though the outlet can provide the 15amps for the hairdryer.

the MPPT charger will only pull the watts it requires for its maximum charging output from the panels, even though there may be many 'extra' watts available.
 
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