A salesman told me an MPPT charger triples solar panel output?

[Onemoreproject]

I am increasing solar output on my boat and am looking at purchasing one REC365NP2-Black N-PEAK 2 Black Series 365 Watt Monocrystalline Solar Module. The voltage is 34.3 and the Amperage output is 10.63. When I asked how many amps per hour can this panel generate, he told me 30 amps. Tripling the solar output has not been my experience with the 2, 110w Solarland Panles that I currently own. They are connected to a Morningstar MPPT 45 controller. Each of their outputs is rated at 6.3A and their voltage is 17.3. The most I have seen going into my batteries on the battery monitor is 12A. This was confirmed by my fluke Multimeter.

The salesman also said that the output from one large, higher voltage panel produces more current than 2 low voltage, smaller panels. He said the MPPT controller converts the solar into more useable power but that is not my real world experience. It doesn’t seem like a good idea to replace 2 panels with a combined higher output with one panel with a lower output. Can someone please confirm or refute what’s the salesman is telling me?
Thanks for sharing your knowledge and experience.

[markxengineerin]

It sounds like you might be confused by the way to use watts, amps, volts, etc to understand system performance.
https://www.rapidtables.com/calc/ele...alculator.html should help with that.

It's easiest to compare watts being produced by the panel(s), going through the controller, and into your batteries, and ignore all the other numbers. The new single 365 watt panel will most likely produce more than your 2*110=220 watt total existing panels. I would not try to compare amps, amps per hour, volts, or any other metric, that just confuses things. Use watts.

The MPPT controller question seems irrelevant- but the salesman was not lying, they are slightly better than the alternative.

In your new system, make sure to use big enough wires and good connections on them- this is a common reason why DIY installations don't perform up to what should be possible, based on the component datasheets. I would expect more like 17-18 amps from your current system (measured at a 12.5V battery), and you report only 12. This could be due to bad wiring choices. If you are measuring current at the panels (upstream of the controller) rather than the battery (downstream of the controller), and they're at 17.3 volts, then that's about right. 17.3 volts * 12 amps is = 207watts, within reason for 220 watts of panels.

[Pete7]

MPPTs won't triple the output, but a 365w panel will of course generate more power than your existing 2 x 110w panels. Expect to see about 25A going into the batteries on a really good day with the panel facing the sun.

The MPPT will use the higher voltage and adjust it down to create the maximum current it can, just not triple. Just picking up on what Mark has said, you will need different sized wire from the MPPT to the batteries compared to the wire from the new panel to the MPPT because the current will be higher and the voltage lower. There is a risk of greater resistance reducing the MPPT output which would be a shame for the sake of a couple of metres of new wire.

You will need another MPPT if you want to also use the existing panels to charge the batteries in addition to using the Tristar 45 and that would be worth doing if you can arrange it. Nearly 600w ought to give enough power to use an electric kettle and induction hob or heat water etc during the summer, say from April to October.

Pete

[fourlyons]

An mppt controller will produce more usable output than the alternative, a pwm controller, but not 3x.
It's possible you have never seen more than 12 amps with your present setup because their state of charge was never low enough. As charge goes up, the amps the battery will accept goes down and volts must go up, something the mppt controller can do.

[noelex 77]

The salesman is exaggerating a little, but not unreasonably so.

The MPPT controller when attached to the 365w panel indicated will almost triple the current produced by the solar panel (for a 12v system), as the solar panel voltage is almost three times the battery voltage. 3x would require a deeply discharged battery, or one subject to a heavy load. I doubt whether you will experience 3x in practice even occasionally. Most of the time you will see the output current will be around 2.5x the input current.

In terms of the output, 30A could just be briefly achieved in exceptionally good conditions with a deeply discharged battery, but anything more than 25A would be doing very well for this sized panel and it would still require excellent conditions.

The 365w panel would be a significant improvement from your current set up. As Mark has already indicated, concentrating on the total wattage of the solar will provide the best guide. Increasing to 365w from your current 220w should produce around 65-70% more total energy than your present set up, all other things being equal.

[smac999]

the mppt has a small improvment over pwm. however with a 34v panel you must use a mppt. (unless you battery bank is 30v) pwm must use same voltage panels as battery. (few volts higher)


a panel making 10a at 30v will make ~23a at 13v after going through the mppt. the wattage (amps x volts) remains the same...

[Onemoreproject]

Originally Posted by Pete7

MPPTs won't triple the output, but a 365w panel will of course generate more power than your existing 2 x 110w panels. Expect to see about 25A going into the batteries on a really good day with the panel facing the sun.

The MPPT will use the higher voltage and adjust it down to create the maximum current it can, just not triple. Just picking up on what Mark has said, you will need different sized wire from the MPPT to the batteries compared to the wire from the new panel to the MPPT because the current will be higher and the voltage lower. There is a risk of greater resistance reducing the MPPT output which would be a shame for the sake of a couple of metres of new wire.

You will need another MPPT if you want to also use the existing panels to charge the batteries in addition to using the Tristar 45 and that would be worth doing if you can arrange it. Nearly 600w ought to give enough power to use an electric kettle and induction hob or heat water etc during the summer, say from April to October.

Pete

Thank you for all the great information. The wire I have connected to my panels now is either eight or 6 AWG So I think I’ll be OK With what I am using.

[wholybee]

There are some conflicting comments, so to clarify them.
Understand the difference between power (Watts), current (Amps) and charge (Amp hour). Confusing these terms leads to incorrect understanding.

As markxengineerin says, you should be comparing Watts of the panel, not Amps or Voltage. An MPPT will not appreciably increase the power delivered from a panel. It is more efficient, and you might be able to measure that, but other than measuring it you probably won't notice your batteries charging any faster.

The "triple the output" statement isn't true, but probably comes from the observation that with a panel that outputs a voltage much higher than the required charging voltage, the MPPT controller will reduce the voltage, and the amperage will increase. In the case of a 30V panel charging a 12V battery, the current will increase about 2.5x. However, the wattage(and that what matters) delivered to the battery will not change. A 350W panel will deliver about 350W regardless. Two 110W panels will produce about 220W total.

[PaulCrawhorn]

Ah per day into your battery is the useful measure.

If the Ah input is greater than Ah consumed, nothing more will be captured.

With panels at voltages suited for PWM, MPPT only adds another 10-15% at most.

But for high voltage panels MPPT is required.

Getting an appropriately sized Victron MPPT per panel is so cheap, even considering PWM is a bit silly

[Onemoreproject]

Thanks again for your responses. In addition to replacing the panels I bought a Victron MPPT to replace my Morningstar 45. The bottom line is that all this cruising sailor cares about is increasing the amps that flow into the battery bank to keep the lights on and the beer cold. With the two 110 watt, 17.3v panels, the most I ever saw was 12 to 14 amps max on my battery monitor coming from the panels with 0 load. 12 amps is approximately double the 6.3 current output on the back of each panel. That is why i thought that the output from the new 365 watt panel would only be 10.3 amps. But it seems that the new panel is going to produce more. I didn’t mention that I also have a new 108 watt Solibian panel to mount on the dodger. So I am going to have the potential of 468 watts of solar to keep my new 440ah AGM Lifeline battery bank happy. I want to do more sailing and less motoring this winter in the Sea of Cortez, so more energy has to come from the sun.

[wholybee]

The max theoretical Amperage you can expect is simple:
110W / 13V ~ 8A
220W / 13V ~ 17A
365W / 13V ~ 28A
You don't need the current and voltage numbers on the back of the panel for that.

[StuM]

Originally Posted by Onemoreproject

Thanks again for your responses. In addition to replacing the panels I bought a Victron MPPT to replace my Morningstar 45. The bottom line is that all this cruising sailor cares about is increasing the amps that flow into the battery bank to keep the lights on and the beer cold.

The cruising sailor should be concerned with putting as many amps as the batteries can absorb during the day when there are other loads such as chartplotter, radio, fridge/freezer, autopilot(?)....running so that when the sun goes down, he has full batteries to supply his overnight needs.

[StuM]

Originally Posted by noelex 77

In terms of the output, 30A could just be briefly achieved in exceptionally good conditions with a deeply discharged battery, but anything more than 25A would be doing very well for this sized panel and it would still require excellent conditions.

That's neglecting house loads. If you've got a 10 A draw from devices on board, 30 A comprising 20 A into the battery and 10 A to the loads would not be unexpected. Fire up an induction plate, a microwave or kettle at lunchtime and you'll be able to draw all 30 A with no problem (and you'll also need some out of the batteries as well )

[noelex 77]

Originally Posted by StuM

That's neglecting house loads. If you've got a 10 A draw from devices on board, 30 A comprising 20 A into the battery and 10 A to the loads would not be unexpected. Fire up an induction plate, a microwave or kettle at lunchtime and you'll be able to draw all 30 A with no problem (and you'll also need some out of the batteries as well )

It is dependent on battery voltage. If the panel is outputting its theoretical 365w and there are no losses in the system, the battery voltage would have to be below 12.2v while charging to achieve a 30A output. In practice there will be losses in the system from factors such as voltage drop in the wiring, inefficiencies in the voltage conversion etc. To balance this out, most panels can produce over their panel rating in exceptional conditions.

It is a good point that low battery voltages can be seen with high discharge currents, but as there is 30A coming into the battery offsetting the draw, it would have to a very high and sustained load to force a well charged healthy battery voltage below 12.2v when it has been receiving a high solar input for some time. In practice, I think the only possibility for a genuine 30A would be with a heavily discharged battery, together with a high load ensuring the fundamental voltage is on the low side. Even then a genuine 30A will be very rare.

[PippaB]

Originally Posted by Onemoreproject

...When I asked how many amps per hour can this panel generate, he told me 30 amps....

Actually, the salesman was reasonably close in answering the basic question, "how many amps will I get into my battery?", which is close to triple (realistically more like 2.5x) what is coming from the panel. Of course, the voltage is 1/3 what is coming from the panel, so, neglecting losses the power is the same. The triple "output" comes from the OP using amps as the measure of power.

As noted, an MPPT controller is the only reasonable way to achieve power production when using a high-voltage panel to charge a lower voltage battery.