Two controllers, Two Panels, One Battery

[DLTooley]

I’m doing the final tweaks on my new 280ah Luyuang build, adding a second panel on a second controller.  

It was working fine yesterday when the vehicle was parked under the carport and only the smaller panel was receiving sun.  Today I moved out into the open and only the larger panel is charging.  

I have two Victron 75/15s, one running a 100 watt 12v panel, the other a 385w 24v panel.  The 12v is in float while the 24v is still in bulk.  As this is supposed to work, the only thing I can think of is that the MPPT’s aren’t playing well together due the differences in input voltages.  

As an aside the 385w controller is substantially over paneled, the 24v input is below 15a, but the 12v output is capped at that same 15a.  

I can also test adding the second controller to that same single panel, likely with a similar peak output, but a lesser cloudy day output.  But that’s not my first choice, seems even more likely to have issues, and is a bit of a wiring kludge.

 

[jonyjoe303]

The 385 watt panel/controller is probably raising the battery voltage high enough that the 100 watt panel/controller think its full and thereby going into float.
On the 385 watt panel I would get a larger controller, I have a 60 amp makeskyblue mppt (about 130 dollars) on my 365 watt panel. When the sun is overhead I can get up to 27 amps out of the panel. When I was using an ecoworthy 20 amp mppt on the 365 watt I maxed out at about 23 amps. Its probably not a good idea to run such a large panel on a 15 amp controller longterm. On 385 watts you can be hitting 28 to 29 amps of power on a sunny day, almost double the rated output of the victron 75/15.

 

[DLTooley]

The 385 watt panel/controller is probably raising the battery voltage high enough that the 100 watt panel/controller think its full and thereby going into float.
On the 385 watt panel I would get a larger controller, I have a 60 amp makeskyblue mppt (about 130 dollars) on my 365 watt panel. When the sun is overhead I can get up to 27 amps out of the panel. When I was using an ecoworthy 20 amp mppt on the 365 watt I maxed out at about 23 amps. Its probably not a good idea to run such a large panel on a 15 amp controller longterm. On 385 watts you can be hitting 28 to 29 amps of power on a sunny day, almost double the rated output of the victron 75/15.

My battery was pretty close to full, the higher voltage makes a lot of sense.  I’ll test that out over the weekend.  

Hopefully I’m ok short term with the Victron, I’d presume I’m not the only one to make that input/output mistake.  

Thanks very much.