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Nick Gillam avatar image

AC Coupled ESS minimum battery size

Hello

We are installing a AC Coupled 3 Phase ESS (Grid Connected) system with 15kW 3P Fronius connected on Output of 3 x 5kVa MultiPlus II. Were planning on installing approx 30kWh of BYD lithium, however i noticed on the Victron AC Coupling & Factor 1.0 rule page there is also a minimum battery size required. (in this instance it is 48kWh)

Can anyone explain this?

30kWh of BYD will deliver 30kW of power & accept up to 20kW of charge.
If the PV inverter was on the Input of the Multi the minimum battery size 3 x 2.5kWh modules acording to the Victron/BYD guide.

Regards

Nick


ESSBYDAC PV Coupling
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3 Answers
BYD_service avatar image

Thank you for 'summoning' me. For grid connected systems don't mind the minimum configuration. Only in the case of backup make sure that the battery surge power can support the systems potential surge power.

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JohnC avatar image

Yeh, guidelines are guidelines. if you want BYD, talk to BYD. There may be all sorts of factors that could bob up to affect a particular supplier's recommendations - and warranty cover.

@BYD_service may summon the forum's local BYD man..

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Paul B avatar image

Hi Nick< Not a expert here but I would suspect they are refering to the Lead Acid Battery cemistry there,

As the Lithium Phosphate batteries can deliver HIGH instant load current (within reason) I would suspect that this figure if lithium is used would be reduced by 2/3rds (best Guess)

so dont worry about the battery side


I do stand to be corected in relation to the above statement


just keep the max solar at or under the 1 to 1 rule

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Thanks Paul,

But the AC coupling guide still specifies lithium 100A/H @48v per 1.5kW of PV/inverting power so I'm still at a loss.

That works out to a 29kwh battery?

100ah x 48 = 4.8kwh / 1.5kw of solar x 10 for 15kw of solar =48kwh