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Expanding 440W System on Keystone Camper

Seanzinator

New Member
Joined
Oct 3, 2024
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3
Location
Wyoming
I recently purchased a new Keystone RV and it came from the factory with SolarFlex Discovery 440i package which includes (2) 220 watt solar panels, Victron SmartSolar MPPT 100/30 charge controller, and 2000 watt power inverter.

I typically boondock the majority of the time and would like the solar to maintain indefinitely. The solar doesn't seem to keep up with all my loads, mainly a 10 cu.ft. 12 volt DC refrigerator. I noticed that the panels are rated for 5.78A at 33.2V. Why would Keystone install 33V panels on a 12V system? Is it more efficient to have higher voltage and let the MPPT convert to higher current? I am seeing the PV current peak around 8-9 amps and the MPPT charge the batteries at about 15 amps.

I am looking at expanding the solar and am interested in input on these options:

Option 1: Adding two additional panels with similar specs in parallel. I'm guessing I would want to match the rated voltage as close as possible to my existing panels (33V)? Seeing around 15 amps of charge current right now, this would probably max out the Victron SmartSolar 100/30. Depending on the current, I might have to upgrade to Victron 100/50.

Option 2: Adding two panels with a second Victron 100/30. There would be two separate PV systems with their own Victron 100/30. This would provide redundancy in case one fails or maybe one set of panels is shaded? I'm not sure how the system behaves if half of it is in the shade. I like the idea of the redundancy but as far as monitoring with the Victron app, I think it would be easier to monitor one controller instead of two. Also, it wouldn't be as critical to match the panels to my existing panel specs. Would I still want 33V panels or a standard 18V panel?
 
Do not look to the panels volts or amps.
Watts are watts and mppt make the amps and the volts you need.

Reason that higher volts on the solarpanels is that the wire can be smaller.
Other reason a mppt have to start with 5 volts difrence vs the battery volts.
So how higher the volts go to the mppt how faster it start .

I do not know if you panels are in series or parallel.
But you mppt output will be around 30a on 14.2 volts.
In optimal conditions.
In bad conditions it will do about 18a on 14.2volts.

So what do your mppt output for now ?
Use Victron app if your mppt is a smartsolar model

For the rest i will use a victron battery sensors and connect that on the battery and than to the victron mppt.
Its make that the Victron can work more optimal for charging
If you have a victron shunt and that is connect with the mppt .
Than you do need that sensors set from Victron.

For the shunt or sensor you need to setup a victron ve-smart network setup from out the mppt Bluetooth.
And set the victron shunt or Victron battery sensor to that network

With the same victron ve smart network you can set 2 mppt in pair mode .
Means both will work like one unit .
And you can see both in you bluetooth app .
You only need on smart or battery sensor from Victron to work with both mppt
I you have more than 2x battery you still only need one battery smart sensor .
You stick that one on the busbar ware both battery are connected parallel.
 
Why would Keystone install 33V panels on a 12V system?
The panel voltage has to be higher than the battery voltage for the MPPT controller to start working. Regard the MPPT solar controller as a power converter, so the panel volts can be anywhere in the specified Input range of the controller. For the Victron 100/30 , that's Vbatt+5, up to 100 volts. Maximum efficiency is around 1.5 to 2 times battery volts, but there is little difference for higher voltages. Note as the panels, heat up the voltage falls, so typically you may loose 10 to 15 % of specified voltage. The panels are currently in parallel, max power volts 33, open circuit volts 40.
solar doesn't seem to keep up
With flat panels and loss due to temperature, expect around 70% of rated power from the panels. I suspect your panels are flexible type which tend to produce less power than rigid types. Also the efficiency of the system will depend on battery, lead performs much worse that lithium, in getting the best from solar charging.
If the inverter is always in standby it may have a significant Idle current.
I would have expected seeing yield in the low 20s amps with good solar conditions from 440 watts of panels..
Option 1: Adding two additional panels with similar specs in parallel.
It's possible, the 100/30 limits the maximum output current to 30 amps, 'overpanel' is an accepted technique but you losse out around midday. If you update to a 100/50, the additional panels added in parallel should have similar Vmas power +/- a volt.
Option 2: Adding two panels with a second Victron 100/30.
This option is perhaps the better, as it does not limit you to using similar panels to those installed . You can use panels in series, in parallel or a combination of series and parallel.
Panels are specified by two voltages, V max power, and Voc ( open circuit volts). When considering the maximum input voltage of the controller, its Voc that's important.
Questions,
are the existing panels flexible types?
Is there anything on the roof causing partial shade?
Is the inverter always on line?
What battery type and capacity?
 
are the existing panels flexible types?
No, there are two rigid 220W panels in parallel.

20240831_163301644_iOS.jpg

Is there anything on the roof causing partial shade?
No, they are mounted to the roof and unobstructed. With the Victron trends, I have only seen about 15 charging amps. I thought it should be higher as well. I did some troubleshooting by disconnecting each panel and verified that they are each contributing about half power.


20240910_221631000_iOS.png

Is the inverter always on line?

No, actually there is an error code on the inverter and it has not be producing AC power. For the time, I have the disconnect shut off. Working on getting warranty support and/or possibly replacing it all together with a Victron Mulitplus or something else more reliable.

What battery type and capacity?

I am currently running two 6V GC2 220ah lead acid batteries. Potentially looking to upgrade to lithium next season. I estimated my daily usage to be about 1,500 Wh per day. It seems like the two 6V would keep up for about 2-3 days but the solar would not. I'm thinking about 200-300ah of lithium should suffice as long as I can expand the solar.
 
I think you can double the PV on the roof and keep the Victron solar charge controller. If you're overpaneled (more PV watts than the nominal watts of the solar charge controller) that's OK. Just don't ever go over the PV Input Max Voltage amount the solar charge controller is rated for. In your case, 100 volts is the max.

If you're seeing 33 volts on the PV side of the solar charge controller then the panels are likely wired in parallel. If you add two more identical panels then I would wire the two existing panels in series, the two new panels in series and then put those two strings in parallel. You'll have about 66 volts and around 30 amps. You're not maxing out the solar charge controller, but if you want more margin, the 100/50 is a good choice.

Since you're in Wyoming, you have to take into account the cold temps when sizing the solar charge controller (volts). The Victron MPPT Calculator can tell you how close the PV volts will get in the winter to the Max PV Input Volts of the solar charge controller.
 
If you add two more identical panels then I would wire the two existing panels in series, the two new panels in series and then put those two strings in parallel.
Is there any advantages/disadvantages wiring 2S2P vs 4 parallel other than reducing current and wire size?
Is one configuration better than the other for partial shade?
 
Is there any advantages/disadvantages wiring 2S2P vs 4 parallel other than reducing current and wire size?
Is one configuration better than the other for partial shade?
Parallel if one panel in the shade have only a problem on that panel
The rest will not have a problem.

Series if one go down it can than other volts go down.

New panels have more bypass against volts drop from a panel in shade if the panels are in series.

Really the big probleem is more if you panels have to be in series that its the same output to sent to the gridd.
If you go to a battery than really your volts are all ready higher than you battery setup.
So if there is volt drop it really do not have impact.
 
Is there any advantages/disadvantages wiring 2S2P vs 4 parallel other than reducing current and wire size?
Is one configuration better than the other for partial shade?

From my experience, if one panel is shaded (trees, etc) then they're all shaded. So I don't arrange for that type of shade. The shade I do configure for is the rooftop A/C unit. The panels on the left side are in series, the panels on the right side are in series and then I parallel those two strings.

2s2p means you don't have to buy fuses. 3+ panels in parallel and you have to use fuses.
 

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