# Adding a Tesla Powerwall Battery System

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Good Day,

I'm pretty new to using PVsol and as such trying to work out to add a Tesla Powerwall system, I need to add multiple Tesla Powerwall batteries though in order to get my desired kWh storage capacity but can't figure out how to add the required number of battery inverters as looks like there is only one battery inverter unless I'm doing something wrong? I also get the error message that the maximum charging capacity is insufficient but I am assuming this is due to the fact I don't have enough battery inverters.

Thanks

Regards

Damon

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Hi Damon,

thank you for your question! Indeed, you cannot enter the number of battery systems right now, this feature will be available in the next version. What you could do for now is to copy the battery system in the database and adjust the power and capacity values accordingly. If you want to go with three Tesla Powerwall systems, you would have to triple the charging power values and the battery capacity, for example.

The message that the maximum charging power is insufficient refers to the boost charging mode (U0-charging), which depends on the SOC thresholds of the charging strategy setup and the capacity of your battery.

For example, the Tesla Powerwall 2.0 AC from the database has a start SOC of 80% and an end SOC of 100% for the boost mode, which has to finish in 2 hours.

The C10 battery capacity is 270 Ah, the batteries run on 50.1 V, so the rated energy would be 270 Ah * 50.1 V = 13.5 kWh. So the power electronics have to charge 20% of 13.5 kWh in 2 hours, which equals to 2.7 kWh in 2 hours. If the charging would run with constant power, one would need 1.35 kW to accomplish that. But the U0 charging modes run with constant voltage while the current decreases exponentially, and because P=U*I, the charging power also decreases exponentially. This is done because batteries need to be charged very carefully when they are nearly full in order to avoid over charging.

But this also means that the initial power that is necessary for U0-charging is much higher than 1.35 kW. To calculate the necessary power you'll need to solve the integral of the exponential power curve. In this case the initial power would be around 3.1 kW (where of course the charging voltage is higher than the 50.1 V nominal voltage).

Kind regards,

Martin

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Thanks Martin, I got it!

Regards

Damon

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