AC vs DC Coupling

[user 35531]

Hi,

I'm trying to understand really what is best for me. I'm looking into Solar PV + Battery storage and I want to make the most out of all my kit all year round.

I understand that DC Coupling is much more efficient. i.e. the Solar Edge kit is all DC coupled where the battery is charged directory the from the panels and then only converted to AC then it is used by the house. However with this setup, I can't take power from my battery and feed it back into the grid, or charge the battery from the grid. So in winder months when solar generation is lower, I can't charge my battery during the evening when rates are lower, and during the winter I can't charge my battery and dump excess charge into the grid when export tariffs are at their most affluent.

What are peoples thoughts on this. I'm pretty technical and was planning setting up a nodding donkey type system where i'd track the export tariff prices and dump power at the best time, and charge my battery during the night when its substantially cheaper to do so.

Thanks!

 

[johnb2713]

Hi,

I'm trying to understand really what is best for me. I'm looking into Solar PV + Battery storage and I want to make the most out of all my kit all year round.

I understand that DC Coupling is much more efficient. i.e. the Solar Edge kit is all DC coupled where the battery is charged directory the from the panels and then only converted to AC then it is used by the house. However with this setup, I can't take power from my battery and feed it back into the grid, or charge the battery from the grid. So in winder months when solar generation is lower, I can't charge my battery during the evening when rates are lower, and during the winter I can't charge my battery and dump excess charge into the grid when export tariffs are at their most affluent.

What are peoples thoughts on this. I'm pretty technical and was planning setting up a nodding donkey type system where i'd track the export tariff prices and dump power at the best time, and charge my battery during the night when its substantially cheaper to do so.

Thanks!

If you get a hybrid solar inverter that will allow both charging from the grid and charging from the solar PV.

A DC coupled battery is connected to the solar PV inverter and the inverter has a charge controller installed, it isnt 'directly connected to the panels' the voltage would be too high and you'd fry the batteries. Your right in saying it's more efficient, it's not a massive amount but it's there to be counted.

An AC coupled battery has an advantage, it can be located away from the inverter in a garage for example. Its likely that the battery will have a reasonable amount of inverter power which will help in your system.

 

[xanld]

Ok, so what's the disadvantage of an AC coupled battery?

Is it just efficiency?

Am I right that li-ion batteries are always DC, so does that mean an AC coupled battery involves its own rectifier/inverter to charge/discharge with AC? And presumably this is inefficient and expensive?

 

[xanld]

Ok possibly lots of answers here: https://electricianforum.co.uk/threads/dc-vs-ac-batteries-pros-and-cons.55011/


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