Multiple solar panels to a common bus bar?

[RaymondR]

If you still only have two 12V nominal panels and an mppt controller you may get better performance by wiring the two panels in series.

Big difference between the requirements for domestic solar, which tends to use higher voltages from a lot of series wired panels, and boats where voltages tend to be much lower.

[Hoohaa]

Originally Posted by Mike OReilly

Assuming you're measuring in optimal conditions; clear noonish sky, no panel shading, panels oriented as much as possible toward the sun... then it does seem low, unless you're in a pretty high latitude. I've never hit my theoretical max of 400 watts on my system, but I often see over 300 watts, although the norm is more around 200. I run a Victron MPPT 100/30.

If all the more obvious problems are ruled out, are you sure both panels are producing? Sounds like the right peak amount from just one panel.

I'm looking at the app on my victron smart charger.
It shows the max watts on the day.
Im in Sydney and they are getting good unobstructed sun at times through the day.
I've tossed a towel over individual panels and saw roughly a 50 percent decline as each was covered.
I've used my tester to check the amps travelling through the wires coming out of each panel.
Oddly. For example
Panel 1 positive lead shows 10 Amps.
Panel 1 negative lead shows 5 amps
Panel 2 positive lead shows 5 amps
Panel 2 negative lead shows 10 Amps
This is an example of what I read you would have thought that both the positive leaves will it read the same and negative leads read the same what are your thoughts? Is this normal?
I did think that one of my quality Chinese panels may have been factory wired and reverse but I checked this and found that they were both wired correctly from the factory.
I will post the new figures tomorrow.

[Hoohaa]

Originally Posted by RaymondR

If you still only have two 12V nominal panels and an mppt controller you may get better performance by wiring the two panels in series.

Big difference between the requirements for domestic solar, which tends to use higher voltages from a lot of series wired panels, and boats where voltages tend to be much lower.

I suppose the real question I wanted answered is if I have a 350 watt panel and put it out in the sun is there any chance I'm going to get 350 Watts from the panel assuming or conditions are perfect?

[Hoohaa]

Yes that what was my original thought I will double check it tomorrow.

[Hoohaa]

On a side note.
For anyone that's interested I'm using Emily and Clark's bbms system 2 combine my 705 amp hour lead bank with my 150 amp hour lithium battery.
So far it's working brilliantly. So far I'm only a couple of weeks in on this.

[RaymondR]

With MPPT it comes down to watts in and watts out. However I notice with mine, which I rewired to series, after I discovered how little charging was actually taking place, that the performance was far better in the mornings, evenings and overcast days. I think the reason may be that MPPT has a higher overhead than series or PWM controllers.

[Wotname]

Originally Posted by Hoohaa

I suppose the real question I wanted answered is if I have a 350 watt panel and put it out in the sun is there any chance I'm going to get 350 Watts from the panel assuming or conditions are perfect?

Yes, maybe more even. Of course you have to have a suitable load for the panel to deliver the power into. For instance, if you only have a 200W load and fully charged batteries, all you can get from the panel is 200W. However if you have say a 400W load, then the panel will supply 350W and the battery will provide the other 50W.

If they are quality panels, the rated power is nominally derated slightly to allow for ageing and to ensure warranty considerations.

Output is also dependent panel temperature; colder is better.

What make and model are your panels?
Do you have a picture of the specification label on the back of the panel?

[Hoohaa]

I will post some pictures in the morning.
I just got back on board tonight.
Wotname.
Thanks for that answer. My main load would be recharging my lithium in the morning. I assume it will take whatever the panel's can supply.
I will monitor things when the sun comes out tomorrow.

[Mike OReilly]

Originally Posted by Wotname

Yes, maybe more even. Of course you have to have a suitable load for the panel to deliver the power into. For instance, if you only have a 200W load and fully charged batteries, all you can get from the panel is 200W. However if you have say a 400W load, then the panel will supply 350W and the battery will provide the other 50W.

This occurred to me as well. Your charge controller will only produce power sufficient for the demand. How large is your battery bank? And what is its state of charge when you are doing all your observations?

Could it be that the acceptance rate is simply maxed out? I understand lithium can take everything you throw at it, but all other battery chemistries have a limit as to how fast they can accept input amps. You might simply not need all the potential power from your 700 watt system. That is a lot of power for a 40-foot monohull.

[Mike OReilly]

Originally Posted by Hoohaa

I'm looking at the app on my victron smart charger.
It shows the max watts on the day.
Im in Sydney and they are getting good unobstructed sun at times through the day.
I've tossed a towel over individual panels and saw roughly a 50 percent decline as each was covered.
I've used my tester to check the amps travelling through the wires coming out of each panel.
Oddly. For example
Panel 1 positive lead shows 10 Amps.
Panel 1 negative lead shows 5 amps
Panel 2 positive lead shows 5 amps
Panel 2 negative lead shows 10 Amps
This is an example of what I read you would have thought that both the positive leaves will it read the same and negative leads read the same what are your thoughts? Is this normal?
I did think that one of my quality Chinese panels may have been factory wired and reverse but I checked this and found that they were both wired correctly from the factory.
I will post the new figures tomorrow.

Good to know they're all producing. Still possible one is under-producing though. Can you disconnect one panel, and then the other, to see what the MPPT sees?

This differing current measure is beyond my knowledge. Seems odd, but I've never checked my panels currents at the leads. Perhaps others better versed can answer (Wottie?).

Regarding max panel power, my belief (which I've never really investigated) is that the ratings are theoretical maxs that can only be achieved in ideal circumstances. Much like max fuel efficiency in a car, it's only possible in perfect conditions, and reality rarely provides perfection.

But I would expect you to be hitting the 3/4 mark, which is closer to 500 watts, not your reported 290. That seems too low -- unless there is something else going on.

[RaymondR]

"Regarding max panel power, my belief (which I've never really investigated) is that the ratings are theoretical maxs that can only be achieved in ideal circumstances. Much like max fuel efficiency in a car, it's only possible in perfect conditions, and reality rarely provides perfection."

Hopefully they actually rest some of their panels to establish the maximum power rating.

The MPPT is supposed to hold the output from the panels at the voltage where maximum wattage of output from them can be achieved.

It's 0700 where I am and the battery monitor is showing 39+ volt and 2+ amps from the panel and 14+ volts and 5.5 amps into the battery so I guess it sort of works.

[Pete7]

Originally Posted by Hoohaa

Oddly. For example
Panel 1 positive lead shows 10 Amps.
Panel 1 negative lead shows 5 amps
Panel 2 positive lead shows 5 amps
Panel 2 negative lead shows 10 Amps

How odd. Are these panels wired in series or parallel?

[Hoohaa]

Originally Posted by Pete7

How odd. Are these panels wired in series or parallel?

parallel.

[Hoohaa]

This is my set up.

[Wotname]

Originally Posted by Hoohaa

Update
I've installed my new twin 350 Watt panels.
Everything is working but is it normal to only get a maximum of 290 watts out of both the combined panels. Combined they are theoretically 700 watts.
I was told that this is normal but.
Any thoughts?
If this is the case then why the hell did I just spend over $400 upgrading my victron MPPT to A 100/50?

Originally Posted by Hoohaa

This is my set up.Attachment 267127Attachment 267128Attachment 267130Attachment 267129

This panel don't look like a 350W panel to me. It is also a low voltage panel (nominally 12V) - not good.
1. No power stated on specification label - red flag.
2. Only .923 sq M - big red flag
3. No current stated on specification label - red flag

Do you have any other data about the panel e.g model number or sales brochure etc?

FWIW, here is a typical spec for a proper 330W panel (just one I found at random but it is a reasonable quality panel.
Especially compare the panel area which is a good start on how much power you might expect.

https://www.phonosolar.com.au/wp-con...-330W-2020.pdf