# question

## PV power to the battery/consamption from the battery

Hello guys!

I have three-phase ve bus system with two PV chargers.

I think I have some problem with in/out power calculation on VRM portal.

If I take one-day data from VRM its look like the PV to battery power more than the battery to consumption power. So how it's happening? If I take from battery less then I use where the excess power is going?

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Daniël Boekel (Victron Energy Staff) answered ·

Hi @Alperin

A number of reasons:

-battery efficiency (charge / discharge, peukert, etc) + charger / inverter efficiency

-it can be that you use some of the energy the day after the charging has happened (and / or the other way round)

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I have a similar Problem with the efficency of the battery. I want to share two examples with you and hope for an explanation.

Example A: DC coupled PV; 2xPylontech US5000; 3Phase MP2 setup

• PV -> Battery: 4.6kW
• Battery -> Consumption: 3.6kW
• More than 20% lost

Example B: MP2 + 1xPytes 5,12kWh Battery; AC-Coupled (small system)

• PV-> Battery: 3,8kWh
• Battery -> Consumption: 3,0kWh
• More than 20% lost

Is there sth I do not understand or have wrong configured? :)

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·

Sounds about normal for pylontec. They are not as efficient as they make out.

The reabsorption cycle also affects efficiency.

Further comment lower voltage batteries tend to be a bit more inefficient.

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Alexandra ♦ ·