I need help. My system seems to drain way to fast.

[MilehighMike]

@MilehighMike , I have a similar system. 640 watts of PV and 560Ah of LiFePO4. My system rarely goes below 80% state of charge. I've been running the absorption refrigerator off of 120vac instead of propane because I have so much capacity. I tend to switch to propane at night, but could probably make it through the night with the refrigerator on AC.

As stated by many in this thread, your batteries simply are not getting charged properly.

I use a Victron SmartSolar MPPT 100/50 solar charge controller, Victron shunt and a Victron Multiplus 12/3000.

I'm adding two additional 400 watt panels. What size victron should I get? Thanks

 

[Rocketman]

I'm adding two additional 400 watt panels. What size victron should I get? Thanks

For 800w of solar on a 12v battery the Victron mppt you want is the Mppt 100/50 or the 150/60.

The 100/50 is cheaper and will do just as good of a job. The 150/60 would allow 48v battery (in the future if you wanted- probably not… and it can handle 150v of input from the panels vs 100v of input

What is the Voc on your new panels? With the 400w panels and a 100/50 you may have to put them in parallel - with the 150/60 you could put them in series or parallel- but will not know until you post the Voc.

Remember you will need awg 6ga (or bigger) to go from the mppt to the battery.

 

[HRTKD]

I'm adding two additional 400 watt panels. What size victron should I get? Thanks

Every time I need to know what solar charge controller to use with a different set of solar panels I go straight to the Victron MPPT Calculator.

If you're mixing panels of different specs, you may want to consider replacing the existing panels so that they're all the same. While you can mix panels of different specs, it's not optimal.

 

[Rednecktek]

I'm addind two additional 400 watt panels next week. What size SCC would you recomend? Thanks again.

Rule of thumb is 10a of SCC per 100w of panels, so I'd look for a 40a SCC to connect to those.

 

[MilehighMike]

Rule of thumb is 10a of SCC per 100w of panels, so I'd look for a 40a SCC to connect to those.

For 800w of solar on a 12v battery the Victron mppt you want is the Mppt 100/50 or the 150/60.

The 100/50 is cheaper and will do just as good of a job. The 150/60 would allow 48v battery (in the future if you wanted- probably not… and it can handle 150v of input from the panels vs 100v of input

What is the Voc on your new panels? With the 400w panels and a 100/50 you may have to put them in parallel - with the 150/60 you could put them in series or parallel- but will not know until you post the Voc.

Remember you will need awg 6ga (or bigger) to go from the mppt to the battery.

I don't know what Voc means & I pick the new panels on Monday so I can see then.

 

[MilehighMike]

What kind of wires and size are you using to connect battery to inverter? 12volt on 3000 watts is close to 220 amps.

They are full copper & about as thick as my thumb.

 

[Rednecktek]

I don't know what Voc means & I pick the new panels on Monday so I can see then.

VoC is Voltage Open Circuit and describes how many volts a panel will produce at 25c in clear sun. When panels are cold they produce more voltage so when your controller says "150v PVMax" that means that the sum total of your solar panels CANNOT exceed 150v. It's always good practice to plan in some overhead for cold weather.

So, if your panels say they have 40 VoC and your controller can take 100v max PV input then you can only put 2 in series for 80v. If you tried to connect 3 in series you'd release the magic orange smoke and be buying a new controller.

The 3 big numbers to look for on a panel's data sticker are:

VoC - Voltage Open Circuit - How many volts are produced at 25c in clear sun.

Vmp - Voltage the panel shoukd produce when the controller is working the panels and drawing load.

Isc - How many amps of current the panel should produce in perfect conditions at 25.

Voc is used to calculate how many panels to a string you can go.
Vmp and Isc are used to calculate performance and wire size between the strings and the controller.

 

[MilehighMike]

VoC is Voltage Open Circuit and describes how many volts a panel will produce at 25c in clear sun. When panels are cold they produce more voltage so when your controller says "150v PVMax" that means that the sum total of your solar panels CANNOT exceed 150v. It's always good practice to plan in some overhead for cold weather.

So, if your panels say they have 40 VoC and your controller can take 100v max PV input then you can only put 2 in series for 80v. If you tried to connect 3 in series you'd release the magic orange smoke and be buying a new controller.

The 3 big numbers to look for on a panel's data sticker are:

VoC - Voltage Open Circuit - How many volts are produced at 25c in clear sun.

Vmp - Voltage the panel shoukd produce when the controller is working the panels and drawing load.

Isc - How many amps of current the panel should produce in perfect conditions at 25.

Voc is used to calculate how many panels to a string you can go.
Vmp and Isc are used to calculate performance and wire size between the strings and the controller.

 

[MilehighMike]

VoC is Voltage Open Circuit and describes how many volts a panel will produce at 25c in clear sun. When panels are cold they produce more voltage so when your controller says "150v PVMax" that means that the sum total of your solar panels CANNOT exceed 150v. It's always good practice to plan in some overhead for cold weather.

So, if your panels say they have 40 VoC and your controller can take 100v max PV input then you can only put 2 in series for 80v. If you tried to connect 3 in series you'd release the magic orange smoke and be buying a new controller.

The 3 big numbers to look for on a panel's data sticker are:

VoC - Voltage Open Circuit - How many volts are produced at 25c in clear sun.

Vmp - Voltage the panel shoukd produce when the controller is working the panels and drawing load.

Isc - How many amps of current the panel should produce in perfect conditions at 25.

Voc is used to calculate how many panels to a string you can go.
Vmp and Isc are used to calculate performance and wire size between the strings and the controller.

So this charger should work? I am thinking maybe I don't need two of the 400 watts & could get by fine with just one combined with my 325s?

 

[MilehighMike]

Every time I need to know what solar charge controller to use with a different set of solar panels I go straight to the Victron MPPT Calculator.

If you're mixing panels of different specs, you may want to consider replacing the existing panels so that they're all the same. While you can mix panels of different specs, it's not optimal.

My Rv is only 25' & the roof space was very limited. I'm not sure the newer ones would fit in their place. But I have ample room on my 16' trailer I pull.

 

[Rocketman]

Those two 395w panels will work great with the Victron mppt 100/50.

You can go either series or parallel-

Good Luck

 

[HRTKD]

My Rv is only 25' & the roof space was very limited. I'm not sure the newer ones would fit in their place. But I have ample room on my 16' trailer I pull.

My RV trailer was shorter than that and I had to "make do" with only 640 watts on the roof. To get more watts I put a couple more solar panels on the ground.

I have a new trailer on order. If I had kept the old one, I was going to take off the roof cap for the absorption refrigerator (for clearance) and put another panel over the refrigerator vent. The TV antenna was likely going to suffer the same fate. Either remove it altogether or just put a panel over the top of it. I've never used the antenna.