Solis Solar Controller Upgrade

The stock Xantrex Solar Charger Controller is a standard PWM controller. It is mostly adequate for use with the 220W solar panel that comes with the Solis, but it can’t compete with more expensive controllers.

Why Upgrade? #

The Xantrex has a few shortcomings:

• With a 12v battery, they typically don’t harness power above 14-18volts. The 220 watt panel on the Solis is 29volts. This means that a large percentage of potential power is wasted. Estimates are all over the place, but generally you can expect a minimum of 15% more power going to the batteries with an MPPT controller for this setup.
• The Xantrex has no logging of data or statistics. Please refer to the Xantrex Solar Charger 30amp for information on what it can report.
• Some have experienced that Xantrex and the solar sytem in the Solis produces very little power overall. Switching to an MPPT controller resolved the issue. Replacing the Xantrex may also solve the problem, but like most things it is typically better to swap inexpesnive devices with slightly upgraded ones.

MPPT Controllers #

There are a lot of MPPT controllers and sizes of controllers available. Any web search will produces thousands of results. Here we will talk about the the Victron Electronics MPPT controllers, but there are a number of mfgs (Renogy, BlueSolar, Bluepower, etc) all have MPPT controllers that offer various features. They mostly work the same, so read reviews before deciding on which controller mfg and model line to go with.

MPPT Controller Sizing #

. The first larger number is the maximum voltage from the panel(s). The second number is the maximum amps to the batteries/charging system.

Don’t be intimidated too much by the math on deciding which size to go with. There are calculators onine for sizing and lots of resources. Just know typically there are two important numbers, panel max voltage and max charging amps.

For the first number, which is the maximum voltage of the solar panels the controller can handle. Each panel will have a Max voltage rating, add up the voltages for each panel and that are installed and that is the minimum the first number needs to be. For the stock 220w panel this is 29v. any controller with a max voltage higher than 29 will work.

For the second number the simplest way to approximate the minimum value is to divide the total number of solar panel Watts by the battery voltage. This will get you the second number or the maximum amps to the battery.

Once the maximum amps is calculated, the recommendation is typically to round up and then select the unit one level higher. While a 100/20 would work fine, there is no room for additional panels. 100/30 gives some headroom.

Swapping the units is actually very simple. It is almost plug and play with one caveat… The Victron devices don’t fit where the Xantrex currently is. Which leaves a few mods necessary. Mounting the Victron in the wall behind the Xantrex is fairly simple, the hole that is left can be coverd by either the Xantrex or a platic panel w/an MPPT controller display.

After the controller is in place and hooked up (literally 4 wires moved from Xantrex to Victron), the Victron has to be configured for the battery type. Victron has 5 defaults I beleive, AGM Spiral being the most obvious fit. Please see the House AGM Batteries for more details

Results #

The Victron MPPT controllers provide a wealth of informaiton which is virtually impossible to compare to the informaition the Xantrex provided. It is simply apples and oranges. The overall consensus is that an MPPT controller swap over the course of months or years will provide significnaly more power to charge the batteries.

More ramblings #

f you don’t have any issues with your battery running low or solar controller problems, no need to read further.

Lots of info below, but to summarize:  Swapping out the Xantex with an MPPT controller is inexpensive, fairly easy and IMHO worth it IF you don’t’ believe your solar setup is helping your battery or your battery is always low.  

Before I go further, quick rundown of MY experience:

• I’m not an expert, just a guy with a van and the internet.   All of this is MY opinion and I’m sure some of it is closer to “sort of how it works” than perfectly right
• My Solis 59px battery overall was a real pain to keep charged and monitoring it was even a bigger pain.  Four LEDs are not enough.
• Solar (with the Xantrex) never really did anything, in full sun I would see 6amps at max on the Xantrex.  It just never felt like it could keep up with the fridge and the lights.
• I installed a battery shunt to see what was going on and it confirmed that the battery charge was inconsistent and that solar wasn’t doing squat.
• I finally upgraded to a Victron SmartSolar 100/30… It fixed everything for me.  I’m not kidding, I just dont’ have to worry about the batteries anymore.  The batteries reach 100% almost daily without driving in the cloudy PNW.
  • I would upgrade the solar charger before a shunt install.  The charger is simpler to install and probably has more bang for the buck.   Obviosuly I’m in to the techie side of this stuff, so having the shunt is fun, but not a ncessesity unless I upgraded to Lithium w/o built in bluetooth (different post completely).

My argument for swapping the Xantrex for either the Blue Sky Energy SB3000i (no personal experience, but there are a couple other posts about this one) or a Victron SmartSolar 100/20 (I bought the 30, but I think the 20 is a better fit for the Solis)

• According to this FB group, there are quite a few issue with Xantrex, from installation issues to bad units being replaced several times.  Xantrex overall is well respected, so I’m not sure why this controller seems to present so many issues.
• The Xantrex is another one of those components that Winnebago essentially cut some cost with.  The unit is “fine” and provides a voltage gauge, but for just a bit more $ they probably could have put in a much better controller.
• From my observations/experience, the Solis stock solar panel peaks at 175watts of power.   I’ve seen the Solar panel produce 30volts and almost 6 amps in full sun on a cold day.   Which is in line with with what the Xantrex was indicating when it was installed.  The difference is the Xantrex is a PWM controller, not an MPPT controller.  This is a very hard topic to summarize, but here it goes.
  • A correctly sized MPPT Solar Charger is just better than a similar PWM Solar Charger.  Lots of arguments about this, but if your goal is to eke out as much power as possible from the stock Solis 220w Solar panel, an MPPT controller is the best way to do that given the panel is rated at 25volts.
  • Very, very, very simplified explanation of the difference – Solar panel outputs a max of 24.6volts and 9 amps (220watts).  The Xantrex PWM controller will harness the 9 amps but only around 14volts (126 Watts).  An MPPT controller will harness the whole 24.6volts and 9 amps which it “converts” to 13v x 17amps (221 Watts).  All of that is of course theoretical as a 220watt panel almost never produces 220watts to the controller (see experience noted above).
  • The actual power to the battery gains are much less.  Theoretically the MPPT will send almost 100% more power to the battery, but in real world it is more like 40% at max and lower depending on a million variables.  I would expect to see more consistency with the amount of power to the battery.   Don’t expect HUGE gains.
  • This is just my opinion and personal research done, I’m not an electrical engineer and I don’t know the actual technical process MPPT or PWM uses.   As always, YMMV.  I’m sure the comments will be full of corrections on this topic.

New controller info

• Either controller below is simple to hookup.  Essentially unplug four wires from Xantrex and plug them into new controller then set the type of batteries (AGM are the stock type)   Please follow all instructions included with controllers, there isn’t a lot of danger here, but the instructions are there for a reason.   This is a DIY change with one exception noted for each controller. 
• Blue Sky Energy SB3000i (like I said, I have no personal experience with this one) approx $250
  • Almost fits in the same spot as the Xantrex, it is just an inch or so too skinny and leaves a gap.   It would be simple to find something that fills this gaps and looks good.
  • Can charge a secondary set of batteries or the starter battery.  It has a secondary charge port can be a 2a tickle charge port that could be connected to the chassis batter pretty easily and coudl charge both sets of batteries when in storage.
  • Pretty simple readout and only one button I believe.  It can charge all kinds of batteries.
  • 40 volt max solar panel input, which is fine for the stock panel, but might be limiting if a second panel is added.
  • No Bluetooth/Smartphone access for history, etc.  Might be able to add something to enable this.  Not sure.
• Victron SmartSolar 100/20 approx $160 (+ optional display $90)
  • Does not fit in Xantrex cutout at all.  Seems like the plywood behind the Xantrex is the best place to mount.
    • To cover cutout there are three options:
      • Leave the Xantrex in place and just not connected to anything.  Maybe put a label on it that a Victron is installed behind it. OR
      • Cover the cutout with a piece of wood/art/etc. OR
      • Buy the MPPT controller display $90 and mount it in a piece of plastic or wood that fits the cutout.
  • Keeps a 30 day detailed history.  Lots of stats and information including Battery Max/Min voltage, Solar Panel yield, max wattage, max voltage.
  • Connects to a smartphone app with a clean and easy to understand interface
  • Has a “load” connection, but from what I’ve read this isn’t supposed to be used to charge another battery without some kind of DC-DC converter/trickel charger in place.
  • Is built like a tank.  Very solid and Victron is well respected (not that Blue Sky isn’t)
  • Interfaces with other Victron devices with a little work.
  • The limiting factor for this controller is the max charging rate of 20 amps.  If another panel was going to be added, it would have to be less than 7 amps as the controller can handle a much higher voltage, but will only put out 20amps (175watts is approx. 13amps + secondary panel of 7 amps would max the controller out).

Again, I can’t say this enough: This is strictly my opinion and personal observations, YMMV