Hello,

I have an IVT MPPT solar charger which comes with a logging unit capturing a few charging process parameters in (semi) real-time to a SDCARD.

After going through a few weeks of data I'm left with a question about efficiency of solar chargers and in specific the MPPT variant.

A snapshot from the SDCARD log - captured during noon in southern Europe

Panel output 156 Watt 32,70 Volt @ 4,8 Amp
Battery input 137 Watt 26,9 Volt @ 5,1 Amp

Now the voltage drop over the IVT charger is 5.8 volt at let's say 5 Amps.

Does that mean the IVT consumes about 29 Watts in the process?
It seems rather high to me, making me doubt the logging function
or my reasoning.

What can be expected from a solar charger in terms of efficiency?

My solar system is 24 volt based and is built into a truck. The components:

- 2 Siemens Solar Panels : 12V / 120 Watts in series
- IVT MPPT charger
- 24V @ 230 Ah AGM battery bank

Joined board after following MPPT related info on the web. Good info here btw.

Cheers!
Arno

Hello Arno, welcome to the forum.

As you can see from your results, the current going to the batteries is higher than the current coming out of your panels, so your MPPT is working.

The unit isn't consuming 29watts, we need to compare I/O power, not voltage.

On the input we have 32.7V * 4.8A = 157W.
On the output we have 26.9V * 5.1A = 138W.

Difference (or power loss) is actually: 157 - 138 = 19 Watts.
You cant compare the voltage drop, because you MPPT drops the voltage to boost the current. Thats its job.

We can calculate your system efficiency like this: (Pout/Pin)x100
Therefore, (138W/157W)x100 = 88%

Although 88% is average (in MPPT standards), we can see that it is still more effective than panels alone without a MPPT because your charge current is higher than your panel output current. So your system is still working, and the MPPT doing its job.

Hope this helps,
Tony.

Thx for your answer Tony.

19 Watts sounds more acceptable when 157 Watt is being captured.

Consequently, the voltage drop would be 19 / 5 Amps = 3.8 Volt, reducing actual input voltage from 32.7 (minus 3.8) to 28.9 Volt. Although the measured voltage values are higher, i can understand it's due to the characteristics of the DC-DC conversion process.

Also measurement values are samples with inaccuracies in value as well as in timing. The IVT samples 4 values (input / output for V + A) for 1 measurement. These are probably not exactly synchronized in time. (parallel versus serial/sequenced samples)

Still the 19 Watts (iso 29 watts) has to sink in for a while - it seems quite a bit to me. Think I'll measure voltages using a Fluke Scopemeter 123 in trend setting just to have a 2nd opinion.

What would be the benchmark for a highly efficient MPPT controller?

Cheers!
Arno

LaptopNomad wrote:What would be the benchmark for a highly efficient MPPT controller?

IMO, a good MPPT should have a conversion efficiency over 94%.

Wrote a bit about the 20 Amp IVT MPPT solar battery charger.

http://www.laptop-junction.com/toast/content/mppt-solar-power-battery-charging

It's produced by Innovative VersorgungsTechnik GMBH in Hirschau Germany. The IVT replaced a STECA PR2020 – a classic PWM multi-stage solar battery charger. So far i see higher amps with the IVT i've never seen with the STECA. Both are the cheaper brands sold on the European market.

I like the SDCARD slot - At the first try it caused trouble with older SDCARDS. It seems it's incompatible with older flash memories. A recent LEXAR 2Gb SDCARD works. Unfortunately measurement accuracy is not mentioned in the manual. To me that seems very "un-german" to forget.

Cheers!
Arno