SOFAR ME3000SP inverters.

[ALAN/ALAN D]

Gentlemen down the road has bought.

Three SOFAR ME3000SP Inverters.
Three banks of 16 Cell 304AH LifePO4 batteries.
He has a single phase supply.
His winter load can be a few K.W. At times.
How do people think the three ME3000 inverters are going to work together running at the same time. Will they get confused and work all connected at the same time.
Will it be better to just use 1 inverter and switch charged battery banks onto the inverter one at a time.
Has any one tried running three 16 Cell 304AH LifeP04 banks in parallel. With one inverter.
Is this the way forward.

[Stinsy]

The interesting part is where he get's his electric from. Does he have solar? Does he have a ToU tariff?

Here is what I'd do:
- Arrange the batteries into a single 16s3p pack with interlinks and an active balancer.
- Setup one inverter with a CT to charge the batteries during the off-peak period and target zero import/export the rest of the time.
- Use another inverter purely as a supplementary charger during off-peak. Additionally you could set this inverter to discharge at a constant rate during the peak (eg 500W or 1kW) if the house has a constant load (eg ASHP).
- Sell the 3rd inverter.

As you correctly assume, several inverters all trying to target zero import/export is unlikely to be successful. Lots of people have tried and ended up with situations such as one inverter charging at full whack while the other discharges at full whack.

Is there a reason the fellow didn't just buy a single larger inverter?

[Tinbum]

They will work together but you have to add extra CT's.

[jonc_uk]

They will work together but you have to add extra CT's.

I disagree.

I have 2x ME3000SPs with a shared CT (both CT inputs in series) and it works fine. You don't have control of which inverter is doing what amount of the load or charging, but as long as they are on the same battery bus then this is fine. I have never (in a year or so) had a push-pull between them.

The biggest problem with the proposed setup is that you have no reporting from the battery. This will mean the inverters are sensing voltage at the end of a cable with other charge/discharge current on it. This will cause problems with calculated state of charge where another inverter is pushing or pulling current from the battery (meaning over or under-reporting of state of charge).

In practice, I found that using the default battery setting (which you would be using in this case) will cause problems with multiple inverters and commented on it here: https://www.setfirelabs.com/green-energ ... hase-setup - it looks like the inverter is attempting to compensate for the internal resistance of the battery and adjusting the voltage based on inverter charge/discharge current. Obviously it has no knowledge of any other inverter, and the battery technology is wrong.

Stinsy's setup looks the safest.

[ALAN/ALAN D]

Thanks Gents.

He has got P.V. South / East / West.

Ref “ Arrange the batteries into a single 16s3p pack with interlinks and an active balancer. “

Three balance systems. One on each bank. Then connect the three banks in parallel at the 57 volt cells. ?

Or connect each cell in parallel on all three banks with one balance system. ?

[Stinsy]

Thanks Gents.

He has got P.V. South / East / West.

Ref “ Arrange the batteries into a single 16s3p pack with interlinks and an active balancer. “

Three balance systems. One on each bank. Then connect the three banks in parallel at the 57 volt cells. ?

Or connect each cell in parallel on all three banks with one balance system. ?

Just one balance system is the most economical solution. You only need thin wires paralleling up each cell to its buddies in the other strings because you’re only expecting teeny amounts of current.

[Tinbum]

They will work together but you have to add extra CT's.

The biggest problem with the proposed setup is that you have no reporting from the battery. This will mean the inverters are sensing voltage at the end of a cable with other charge/discharge current on it. This will cause problems with calculated state of charge where another inverter is pushing or pulling current from the battery (meaning over or under-reporting of state of charge).

In practice, I found that using the default battery setting (which you would be using in this case) will cause problems with multiple inverters and commented on it here:

You can use communication between the battery and inverter.

[jonc_uk]

You can use communication between the battery and inverter.

Ah yes - I had assumed this was going to be a dumb balancer on some loose cells.

If a proper BMS is communicating with the inverters, then you can put in as many inverters as you can communicate with.

[Countrypaul]

I assume he has already got a grid tied pv system
Has he got any DNO permission for greater than 3.68kW export, or has he applied for, is it G99 approval ?
Having more than 1 me3000 potetially exporting (assuming fault condition for example) might be an issue.

[Tinbum]

Thanks Gents.

He has got P.V. South / East / West.

Ref “ Arrange the batteries into a single 16s3p pack with interlinks and an active balancer. “

Three balance systems. One on each bank. Then connect the three banks in parallel at the 57 volt cells. ?

Or connect each cell in parallel on all three banks with one balance system. ?

Just one balance system is the most economical solution. You only need thin wires paralleling up each cell to its buddies in the other strings because you’re only expecting teeny amounts of current.

Stinsy and I tend to disagree on the best way of doing this. I would have a BMS on each of the 3 sets of batteries. Personally I think safety features are required and communication with the inverter. The word 'expecting' worries me.

You could have one set of batteries for each inverter or you could parallel them as one pack. Having separate packs could result in heavier or lighter use between packs.