Solar Panels in Series with MPPT Controller

Jax0913

Great thoughts! @Trailpixie we have many of those troubleshooting steps, but I will definitely go back through the list and make sure all are correct. I was thinking there might be an issue somewhere, so your info is helpful. I will also check the settings on my controller and make sure they are right for my system like @ChanW suggested, I might have screwed that up. Thanks everyone I appreciate all the good ideas and knowledge! 

Jax0913

So looking at everything today, the panels seem to be working great. In full sun, fully charged in no time. Checked my solar controller to make sure it is showing the same settings as Bluetooth seems to be perfect. Went into the settings on the charge controller to make sure it was set to 24v like @ChanW suggested, when I set it to 24volts, save and exit, the display still shows 12v 

Tundra57

@Sharon_is_SAM I do- three of them. :-). So now we have beaten the connection method and controller to death---

What panels do you guys reccomend? Rentergy seem popular. I would want suitcase type for easy setup and 200w to supplement my roof 200W.

Sharon_is_SAM

@Tundra57, I think that Renogy suitcases are well made and a good buy.  I think it is easier to manage the 100 watt suitcase, rather than a single 200 watt.  Easier to store, too.

Tundra57

@Sharon_is_SAM. I already have the Nucamp fitted solar on my 400 tab. Any idea if adding more panels is possible? Did not look up the Vicron spec yet.

Sharon_is_SAM

Check this out.
https://tab-rv.vanillacommunity.com/discussion/comment/120289#Comment_120289

Cbusguy

@Tundra57 The factory installed a victron 75/10 solar controller in my 320.   which means 75 volts max and 10 amps max.    With your roof top solar and additional panels you are very likely to exceed 10 amps.    

Tundra57

Thanks I see I would have to replace the controller for a larger capacity Vicron unit to add just panels. I was just thinking that if I had two controllers both reading the battery and deciding on charge rate they might not be in agreement which might not get me max output. I think I'll check with Vicron. Do we know who manufactured the solar panels on the current tab 400 2019? Maxbe it doesn't matter, but if they are all in parallel I assume they would best be the same.

Sharon_is_SAM

Here is a discussion regarding adding a portable suitcase and a separate controller.  If you stick to one controller, I think you would need to run your portable panels in parallel to the installed, flexible panels.

https://tab-rv.vanillacommunity.com/discussion/7283/attaching-suitcase-solar-to-t-b-400/p1

Quote from AM Solar:

“Multiple Charge Controllers – If your desired solar array has a charging current that exceeds the current rating of your preferred charge controller, you can use multiple charge controllers. These charge controllers would be connected in parallel to each other across the battery bank.  The Blue Sky IPN-ProRemote can monitor up to eight charge controllers in a single system.”

MarkAl

Just found this thread, great discussion.  As I see it:
For series: Pro
- Arrays should be outputting similar currents.
- One MPPT controller needed (assuming the controller can take the higher max voltage).
- Because Power loss = I^2 * wire Resistance, halving the current reduces the power loss by a fourth, more power available to charge the batteries - voltage is irrelevent for loss, only determines what the total current will be. Why cars went from 6 to 12 volts long ago and houses have 240 volts in Europe (and even in this country but it's split in half and delivered at 120 for safety).
- Lower cost wire for same resistance (or power loss).

For parallel: Pro
- Arrays of different outputs or shaded locations (one on trailer, one in the sun), this maybe significant. Though each array will need a controller to isolate the other's different voltage. This brings up a voltage drop issue and the controller could require a separate voltage sense wire from the battery to compensate and maximize the battery charge.  If this isn't done one controller may be shutting down the lower producer anyways.
- If your arrays have a normal battery charge controller included this maybe a better way to go? I haven't thought this through however - my head was starting to hurt.

The complexity of different situations may be why different setups are better than others.

The problem is dealt with on large arrays that get partial shade by having multiple controllers for small numbers of cells to reduce the problem of series limited by low currents but that is well beyond the problem of having 2 or 3 arrays connected to a common battery.

Sorry, the subtle issues with this are probably beyond the space this is taking

Tundra57

I did buy two 100watt solar suitcases. Each suitcase has a diode array so that a higher output solar cell doesnt force current around the others. I already have a Victron controller with the factory solar. I added another Victron just for the suitcases. I fitted a solar connector to my tab wired to the controller solar panel input. I then run the suitcases in parallel and plug them into the tab connector. On a sunny day, first i turned on everything 12v. Then looked at the factory solar output to the battery, it was around 10Amps. Then i pulled the solar panel fuse and connected the external suitcases and got around 12Amps.

Finally i put the factory solar fuse back in and ran both. I got around 22Amps.

So this tells me with seperate controllers the factory and exterbal panels coexist well.

BTW, both controllers are MMPT Victron with bluetooth monitoring.

(Edited spelling for search purposes.)