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groovy avatar image
groovy asked

Grid to grid ess

Hello I have a multiplusII with polytech batteries. I have dynamic prices that are different every hour. Also I have a second grid with a normal price plan. On this second grid I have cheaper prices sometimes then the first one with dynamic prices on some hours. Now I will charge the batteries with grid 2 and discharge then during peak hours on grid 1. Is it possible to put grid2 on AC1-out and grid1 on AC1-in and feed in from grid2 to grid1 ? This will prevent the losses for charging the batteries and vice versa. I found that you can connect AC1-out to an PV inverter of generator but grid2grid is nowhere discribed . Thanks for answering.

multigrid
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3 Answers
shaneyake avatar image
shaneyake answered ·

This is not possible with a Multiplus-II.
The quattro has 2 AC inputs as so it would be possible.
You can always have a second multiplus on the second grid connection.

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Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

NO! Never connect a grid to the AC Out! That can damage or destroy the MultiPlus!

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groovy avatar image
groovy answered ·

@Matthias Lange - DE , thanks for your answer good to know that I do not have to try it.

@shaneyake , you mean the second multiplus connected to the second grid and charge the batteries with them while you discharge them with the first multiplus ?

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shaneyake avatar image shaneyake commented ·

Correct. Quattro would be able to switch between grids so you wouldn't have any of the AC->DC->AC losses for the loads but we have some grid connections where we do the AC->DC->AC and you only lose a few percent if you do it right.

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groovy avatar image groovy shaneyake commented ·
Thanks for your reply. I have a easysolarII also available. Is it not bad for the battery to do it like this ? What do you expect on losses for the AC>DC>AC conversion ? I have Pylontech us5000 batteries . I will look for the Quattro in the meantime .
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shaneyake avatar image shaneyake groovy commented ·

Depends on your plan. If it is inverter A to Inverter B then batteries aren't affected.

If it is inverter A to charge batteries to full and then discharge fully then using B it will cycle the battery. There are a few different ways to get the inverters to hold the battery at a voltage and directly power inverter B.

Conversion losses depend on load. Here is some graphs for the 48/5000. Easysolar 48/5000 has the same inverter.
https://community.victronenergy.com/questions/56351/multiplus-485000-efficiency-curve.html

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