Charge Controller Q's - MorningStar Sunsaver MPPT

Toyman

Hi there,

New to solar, but have been studying for a while and finally about to purchase a small scale system for my cabin (off-grid). One of things I have been trying to decide on is a decent charge controller. The supplier I have been dealing with has been using mostly BZ products due to their lower cost. They claim they haven't had many issues since using them predominantly for the last couple years. I know from searching this site that there are many out there that would beg to differ greatly on this.
For that reason I have been looking to use another controller, but the only other one he has readily available in my price range is the Morningstar Sunsaver MPPT 15 amp controller. I am planning on using two 125watt (250 watts total) panels in series to the controller. The max rating for each panel is 7.14amps @ 12volts. The specs for the Morningstar read 200watts max input @ 12volts and 400watts max @ 24volts. If I am reading this right then should I be alright with this controller if my panels are tied together in series??

Any and all help and advice appreciated!

Thanks!

BB.

Re: Charge Controller Q's - MorningStar Sunsaver MPPT

You have a perfect fit... Add that a Remote Battery Temperature Sensor is pretty much mandatory for this controller as it tends to estimate a bit high on temperature (and highly recommended for all controllers with the option).

One question is... Do you have plans to add any more panels to this system (should you consider a larger controller)?

If you choose a 24 volt battery bank--that will allow you to add more panels later--and reduce the wiring size for you battery bank (2x the voltage, 1/2 the current).

If your system remains small and does not need to output much power--12 volt battery bank will be OK (especially if you have 12 VDC loads to power). Note that it is very difficult to send 12 VDC very far (12 volt nominal - 10.5 volt cutoff--leaves you with 1.5 volts for wiring drop and such).

I am guessing your panel's Vmp is ~17.5 volts--just right for 12 volt battery charging or placing two in series for 24 volt charging too.

-Bill

Solar Guppy

Re: Charge Controller Q's - MorningStar Sunsaver MPPT

Yes, the Sunsaver Mppt would be fine, its limited to a maximum output of 15 amps and your panel in series would be a good fit. Panels rarely get rated output and if they do the Sunsaver will safely limit the output current regardless of the input available.

Regardless of what brand you choose, stay away from the BZ, its criminal that they are still sold

Toyman

Re: Charge Controller Q's - MorningStar Sunsaver MPPT

Thanks for the quick replies folks!

No plans to expand anytime in the near/distant future. Only upgrade I can foresee would be to replace the 12V deep cycle 100amp/hr batteries I currently have with some higher quality/ higher output 6V batteries.
I would like to keep it 12V as I do run some 12V electronics straight off the batteries. I did read it correctly that the MorningStar could convert 24V pv input into 12V charging output to batteries right?
I'm planning on using a TrippLite 2000w inverter/charger, so with my 2 back-up generators that I currently rely on 95% of the time I will be able to keep my batterie's up if required.
Another Q: What is an acceptable wire gauge to use to run approx. 50ft with the panels tied together (24v) to the controller, and can solid wire be used or only stranded (I've been told both, but I seem to think otherwise)??

Thanks!

BB.

Re: Charge Controller Q's - MorningStar Sunsaver MPPT

The controller will efficiently down convert anything from ~17-75 VDC (PDF Spec. Sheet).

Your nominal current is 7.14 amps at ~35 volts. Minimum wire rating would need to be 7.14 amps * 1.25 (NEC derating) = 8.9 amps. Round up to 15 amp / 14 awg minimum gauge.

Of course, you have the voltage drop issue.... You could lay out the wire with 12 volts drop at 7 amps--but you would lose almost 1/2 the power in heating the wiring. Normally, aim for 3% maximum loss--most people tend towards 2-1% loss...

You can use this calculator for voltage drop... Pick "Adverse" temperature, pick 14 AWG, 50 foot distance (not wire run) and 7.14 amps==Get 2.6 volt drop

• 35 volts * 3% = 1.05 volt drop
• 35 volts * 2% = 0.70 volt drop
• 35 volts * 1% = 0.35 volt drop

1. 14 AWG => 2.6 volt drop
2. 12 AWG => 1,7 volt drop
3. 10 AWG => 1.0 volt drop
4. 8 AWG => 0.7 volt drop
5. 6 AWG => 0.4 volt drop
6. 4 AWG => 0.3 volt drop

10 AWG would be fine... 8-6 AWG will work well. Your choice

Use either solid or stranded wire (for building wiring). Don't bother with very finely stranded wire (like welding cable)--unless you need the flexible cable because the system moves around (like on a cart). Welding cable is a pain to terminate properly (the fine strands are difficult to crimp / clamp with standard hardware).

Stranded wire will not transmit the power any better than solid wire (skin effect only affects AC / switching DC -- which these MPPT do switch--but only when less than 100% panel current is needed--so losses from surface resistance should not matter).

-Bill

Kamala

Re: Charge Controller Q's - MorningStar Sunsaver MPPT

I'm very happy with my SunSaver MPPT. As B.B. points out, it's input voltage can be anything from 17V to 75V. My 3 panels are in series and I have seen upwards of 50V going into the controller. With this higher voltage, 10AWG works fine.

I also have the PC RS-232 interface. While certainly not essential, it does allow you to see what the system is doing in real time. I got it mainly to access the custom setpoint feature of the controller. I only had to adjust the setpoints by a couple of 10s of millivolts to match my AGM batteries.

K

niel

Re: Charge Controller Q's - MorningStar Sunsaver MPPT

the sunsaver will work, but if the mppt action is greater than about 5% of the stc rating you will not recoup the extra power above that due to the controller's 15a current output limitation. 90% of the time i'm sure it will be below that point. also if you expand on the pv system any then you will need another controller and more wire. if you can live with lower mppt gains and no expansion this will work fine.

RWB

Re: Charge Controller Q's - MorningStar Sunsaver MPPT

The Sunsaver MPPT is a very very nice Solar Charge Controller and it it totally customizable to make it do just about anything you could want it to do if you have the Computer Data Cable for it. You can monitor exactly what the system is doing in real time and actually record that data and look at it later in a graph format like these pictures from today where I was testing 2 of our 110w 21% Efficient Foldable Panels.

You could always add an Extra Sunsaver MPPT later for a total of 30Amps of charging input. If you need more than 30Amps then buy a Tristar MPPT 45A Charge controller. The cost for both of them is about the same.

Toyman

Re: Charge Controller Q's - MorningStar Sunsaver MPPT

Thanks for the good input!

Another thing I was wondering was if I would be better going with the remote display for the Controller or the Inverter/charger? Both are about the same cost and other than the remote on/off control for the inverter they seem to do/show about the same info. Is that correct?

Thanks.

icarus

Re: Charge Controller Q's - MorningStar Sunsaver MPPT

IMHO the biggest mistake newbies make is undersizing systems. As such, controllers are expensive to up size when you realize that your needs are bit more than your figured. I am a perfect case in point, went from 63 watts of panel and a 15 amp Sunsaver, then to a 25 amp Bluesky, and now with ~450 watts of panels, the loads have grow, the panel capacity has grown, the batteries have grown and I am using a Rogue MPPT controller which I love. The Rogue is competitive with the Bluesky and maybe a bit cheaper than the Morningstar. That said, for what I have spent on all my controllers over the years I could have bought a MX 60 or two!

Do remember, systems tend to grow.

Take a look at the Rogue. Marc is a member here and a number of folks are happy with his controller and customer service (and the price) but by all means, avoid the BZ!

Kamala

Re: Charge Controller Q's - MorningStar Sunsaver MPPT

Toyman wrote: »

... if I would be better going with the remote display for the Controller or the Inverter/charger? Both are about the same cost and other than the remote on/off control for the inverter they seem to do/show about the same info. Is that correct?

The controller remote will control/display info re: controller and the charger/inverter remote will control/display info re: inverter/charger. Both may display info re: the battery bank. I you just want to monitor the battery bank, you might consider a battery monitor (with shunt) such as the TriMetric,