LIPO Battery round trip losses

[Andy]

This may be of interest for people planning storage. From my last years figures I am experiencing an average of around 23% loss in the round trip. This a Pylontech/Quattro/VictronMPPT combo. I was often charging and discharging at max power during the summer.

[AlBargey]

This may be of interest for people planning storage. From my last years figures I am experiencing an average of around 23% loss in the round trip. This a Pylontech/Quattro/VictronMPPT combo. I was often charging and discharging at max power during the summer.

That's not good!

I get just under a 22% loss / 78% round trip efficiency with old FLA cells: Hoppecke, Quattro, Victron MPPTS's

My totals since installing a SmartShunt:





I also set up a Pylon, Multi, Victron MPPT system for a houseboat only really used for weekends, so it's not a very efficient system with the constant Multi base load, and they get 84% round trip.





I asked peoples round trip efficiencies a while ago on the Victron forum, and some people were getting closer to 90-98% with LiFePo4!

[openspaceman]

So is that what a smart shunt does, logs what goes in and what comes out? On the DC side?

[nowty]

It really depends exactly what you are measuring and whether your DC coupled or AC coupled. Some people are only measuring DC in to DC out. Some people measure DC in to AC out. And some are measuring AC in to AC out.

My old 24V Lead acid system measuring AC in to AC out was only 67.4% efficient. My latest 48V system with lithium is similar to what Andy is getting at high 70’s % on the full round trip. But even on my old system with LA the DC to DC round trip was 90.5%.




DC to AC efficiency can be very poor if just running low power background base loads most of the year.

[Krill]

I've been wondering about this for a while, most specifically the most efficient rate to discharge the batteries, and charge from the grid over night.

I figured from the curves it was in the 25% to 40% range and this is another potential benefit to having paralleled inverters. Just need to best way to make one inverter work up to 40% and then kick in the second inverter...