Acceptable MPPT Conversion Losses

Anyone know how much conversion losses are to be expected between PV input and battery output i.e. MPPT and DC to DC conversion losses?

I noticed on Victron Connect the available Solar power shows around 271W higher than the PV charger power shown on the dashboard. Not sure where these measurements are taken but assume it is on the PV input side vs. the output side of the MPPT RS 450/100. That is around 7% loss. Seems a bit high.

When running at lower power say 360W the loss is around 1.5%

Round trip efficiency should be in the region of 82% on a low voltage system. We are promoting high voltage systems as the round trip efficiency can increase to between 97 and 98.8%

EDIT: Sorry round trip meaning, Panels to Battery, battery back to AC loads… On a 51.2volt battery system

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Another strategy is to use PV inverters with a Victron Hybrid/DC MPPT combination.
That way, your load is fed directly from AC with no trip through the Inverter.
The price is that excess AC power that goes to charging the battery has an even more extended round trip. That only happens when you make more than you need, so the efficiency is less critical when that happens.

It is a bit of “swings and roundabouts” and something to consider in the initial design, not for an up-and-running system. I am just noting, for completeness, that there is room for an overall efficiency improvement if your load matches your PV generation during the day per design.

I don’t advocate spending money trying to squeeze an extra 100W out of things when it is far easier ( and usually cheaper) to buy another panel and get 300W more.


93% to 97% is the typical range.

97% (ie 3% loss) is a best case scenario, and what most marketing material will claim. You will see this on some PV inverters, but it also typically assumes operating at 25°C.

The MPPT RS you have has a max efficiency of 96%.

Ambient temperature, the input/output voltage ratio, and power level also affects the efficiency of all DC/DC converters (which is what an MPPT is).

You’re seeing about a 7% loss, which is not indicative of a problem.

Edit: Remember also that the measurement isn’t perfectly accurate either, that can also be a off by a few tens of watts.

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That would be very impressive if true, even for HV battery systems. I have never seen to-battery/from-battery efficiency numbers in inverter specs, probably due to it not being a legal requirement to meet a certain efficiency in the EU (I presume).

I also have not seen a 48V system that exceeds 92% from battery, the HV battery systems are a lot more efficient though.

@DSTSS , put an external fan on the MPPT so that the air is as cool as it can be around it.

I put a fan on which cools the area around the system AND my office. Makes a huge difference for the equipment and me. The 250/85 runs cool.

Without the stand fan, it becomes uncomfortable to keep my hand on the MPPT.

You can lose nothing.

Good idea, as long as I don’t put a microlight prop on the MPPT which consumes 100’s of times the MPPT conversion loss… :smiling_face: