New 400W kit, seems off

casperthevan

Hi Everyone!

New member here-- I'm very appreciative of the information you all have included. It has been a great help to me.

Primary issue (i think): Where are the amps?

I just installed a 400W Renogy solar kit on my van conversion over the weekend and wanted to have you all help me troubleshoot.

Right now I'm operating without any loads at all while I make sure everything is working (and before I bolt down the panels for good).

Here is what I'm working with:

• This exact solar kit including 4x100W Renogy solar panels 
• 40A Rover MPPT charge controller
• 12V 2x155ah (SLR155) AGM batteries from VMAX -- these are new, we're purchased 2 months ago and sat inside until install this past weekend.

Batteries are wired in parallel. Panels are wired in parallel with a 4 way Signstek connector.

12V system, CC set on Sealed battery and 12V system.

I'm based in Atlanta Georgia, it is winter, but I'm seeing some data coming through the Renogy Bluetooth app that seems off to me for a 400W setup.

Questions I have:

After 2 days of the Charge Controller being on, I'm pretty sure something is not quite right in my system. Let's use today as an example. Relatively sunny with a couple hours of full sun mid-day at a minimum.

Here are some of the stats I looked at this evening. 

During the most sunny part of the day (around 12:30), I checked the system and here is a snapshot from the bluetooth app that is connected to the CC:

• 21.4V from panels
• 1.44A from panels (THIS IS MY CONCERN) 
• 31W of power from panels
• 14.6V of charge voltage on battery during boost charge phase
• 2.05A of current in battery during boost charge phase

Should the A reading during the sun be about 4x5A = 20ishA (or at least some respectable amps reading due to the parallel configuration?)

Here is the full-day summary for the same day

• Total Charge Ah: 11
• Max Charge power reading for the day: 32W... of 400W
• Min Battery Volt: 12.7V this morning (this is relatively full, right? I don't trust the Renogy controller SOC % reading)
  
• Max Battery Volt: 14.7V

My core question is: It looks like the voltage off the panels is about right, as I think that normal operating voltage for the panels is around 18(maybe a few volts high, but I'm assuming thats okay). The amps are not even giving me a reading that makes sense for a single 100W panel, not to mention four.


What do you all think?

littleharbor2

 Sounds like your batteries are full and cant accept any more current, causing your array to go open circuit, hence the high
 input voltage reading.


 With an MPPT controller you need to series wire your panels, 2s2p

Wheelman55

I defer to the experts as to how you should wired your panels. 

As far as the low amp reading, it seems correct for fully charged batteries. 

I run two ARB fridges off of one 12v battery, connected to 180w folding panel with a 10 amp max output. 

In the morning on a full sun day the panels will put out 9 to 10 amps by 9:30 am here at the 29th latitude in the USA. 

The amps ramp down as the AH ramp up. By 11:30 am the batteries are full and the amp output reads 0.0. AH reads 19-20. 

Throughout the day the amps put back what’s needed to run the fridges which is approx 0.2 to 1.5 amps. AH ends up just a few AH more than what it took to get to full charge, meaning that as the day progresses the system adds back what is used during the day. 

Your system seems to be charging just fine. 

As an experiment try running some loads, like a fridge, overnight. Pick a day when you’ll have full sun if you can. 

FYI. Your panels will produce their full amps only in full sun. Any cloud or tree cover will reduce the amp output. On partly cloudy days you’ll see your amp output vary with the cloud cover.

casperthevan

littleharbor2 said:

 Sounds like your batteries are full and cant accept any more current, causing your array to go open circuit, hence the high
 input voltage reading.


 With an MPPT controller you need to series wire your panels, 2s2p

Extra question: with a MPPT controller, is it really an issue to wire panels in parallel? This is all on top of a van that will be partially shaded in a lot of situations (in a forest, for example) so I'm trying to minimize the impact of that. Can you give me a sense of the performance difference between parallel and series?

Estragon

The main advantages to using an mppt controller:
- to run higher voltage strings, minimizing voltage drop and wire size for long runs.
-can produce a bit more in cold temps
- tend to include more features and programability
- allow for the use of larger panels (tend to be cheaper $/watt

The main drawbacks are typically higher cost, higher self-consumption, and problems with partial shading of long strings.

In your application the advantages are likely not worth a lot.  Mppt do need some voltage overhead to buck to battery voltage.  There's a chance with hot panels the Vmp could be too low.

Note that even in parallel, the panels may not produce much with the sort of dappled light you'd get in a forest.  Even bare branches will matter if close enough to make distinct shadows.

Also, with 4 panels in parallel, they should really be individually fused before the 'y' connections, but not needed if 2 strings of 2 panels.

Photowhit

Something that is rarely know by people starting out, is solar panels tend to produce about 75% of their name plate in optimal conditions. During winter, with panels mounted flat on top of a van, you will  pretty much never have the  panels angled within 15 degrees of perpendicular to the sun.

You  have gotten some good advice, apply  load and see if you  don't see an immediate increase in the amps the charge controller allows through.  Charge controller basically control the system voltage by increasing or decreasing the flow of  current(amps). If the system  is allowing 1.2  amps through to maintain the set voltage, and a load is applied, the Charge controller  will allow enough amps up to the amount available, to keep  the system voltage at the prescribed level.