Connecting 48v battery to High Voltage HV hybrid inverter

[1.21 Gigawatts]

Ive brought 16 x 280ah liFePO4 cells and a BMS, the trouble is i have a 3 phase supply, and all the 3 phase Hybrid inverters ive found in Australia are for High Voltage batteries, NOT 48v.

How can i connect e 48v battery to a HV hybrid inverter? Could i use a simple DC to DC boost converter to say take it upto 192v? or 400v? Where can i buy such a converter? Or is there a better way to do this?

In all likelihood the inverter will also want to talk to the battery BMS via RS485, which my BMS supports, but im wondering if the difference in voltage will confuse the inverter.

Really appreciate the guidance.
Cheers.

 

[1.21 Gigawatts]

Seems no one has experience with this?
Or have i asked this in the wrong section?

 

[walter-]

Some comments:
- the issue starts with the BMS and the inverter having to talk. RS485 is just a technical spec of communication method. What is being communicated is not defined*. So your BMS has to confirm it can talk to inverter XYZ and ideally the inverter manufacturer confirms the BMS is compatible. Without this, there is just no solution. So first you need to find that BMS compatible with the inverter. I do not know of BMS supporting high voltage batteries (didn't look very hard...).

Here in Europe I hit the same issue on 3 phase;
Options I see:
- Victron who can put 3 GX invertors in parallel to build a 3 phase system (actually: 1 is enough if you don't want the system as a 3 phase UPS).
- Solaredge has a 3 phase hybrid inverter for low voltage batteries. It is only 5kw towards the battery (but that can be enough).
Walter
* a BMS manufacterer stating they have a serial bus of some kind, but not specifying what it supports is just meaningless.... I have printer with a serial interface: so the BMS can print?

 

[abaksa]

Some additional comment:
there is a video on Youtube demonstrating threephase application with Goodwe hybrid inverter, Batrium BMS and a high-voltage DIY battery.
BMS is able to talk to inverter.

 

[walter-]

@abaksa possible to provide the reference to that video?

 

[abaksa]

@walter-
you could look up Batrium & Goodwe HV inverter setup instructions on yt

 

[Shinebox]

It’s definitely possible, but maybe not so easily as an end user/diyer. Some high voltage battery packs such as the LGchem resu are in fact 48v packs with bidirectional DC-DC converter. If you try to find such a device capable of doing what you want, you will quickly find that they’re (bidirectional DC-DC converters) not exactly readily available, and the ones that you can buy are very expensive and won’t even give you the output you’re likely after.

 

[carsten42]

The HV battery is made of several LV batteries connected in serial. The master BMS watches all slave BMS to provide charge/discharge parameters via CAN to the load or charger. Every single BMS does balancing within the pack, but how is the balancing of the packs done, or is this just missing? Couldn't this be a problem in the long run?

 

[walter-]

For info: the link to the video on a Batrium BMS to build a high voltage battery :

 

[walter-]

The HV battery is made of several LV batteries connected in serial. The master BMS watches all slave BMS to provide charge/discharge parameters via CAN to the load or charger. Every single BMS does balancing within the pack, but how is the balancing of the packs done, or is this just missing? Couldn't this be a problem in the long run?

when building such a battery, you need to be sure to have identical cells, identical packs.
In the example video using Batrium, I assume the Batrium Balancing is used; and as this solution is all integrated I assume it could ballance all cells to the same level. And thus balancing the individual batteries. But that gives maybe the question if this is not just one big battery ;-). But that is the only way to look at it anyway if you build something in series. You have to view it as one big battery where all individual cells need to be on the same level. If this is not the case there will be fast degradation as a battery is only as good as it weakest component. and not being balanced causes a weak component in your battery.

 

[houseofancients]

Ive brought 16 x 280ah liFePO4 cells and a BMS, the trouble is i have a 3 phase supply, and all the 3 phase Hybrid inverters ive found in Australia are for High Voltage batteries, NOT 48v.

How can i connect e 48v battery to a HV hybrid inverter? Could i use a simple DC to DC boost converter to say take it upto 192v? or 400v? Where can i buy such a converter? Or is there a better way to do this?

In all likelihood the inverter will also want to talk to the battery BMS via RS485, which my BMS supports, but im wondering if the difference in voltage will confuse the inverter.

Really appreciate the guidance.
Cheers.

not really, sunsynk/Deye are building 3 phase 48v inverters..
currently they have a 8 KW and 12 KW version

 

[DIYrich]

As I read the question, your problem is connecting 48v battery to 3 phase power? The only inverters you can find are for high voltage batteries?

Units like Sol-ark can be put in parallel for 3 phase. 1 or 2 can give you unbalanced 3 phase. You need 3 to give you balanced 3 phase. Walter mentioned some others that can be hooked up for 3 phase.

 

[walter-]

For reference 3 phase 48V hybrid inverters:
- https://www.sunsynk.org/3-phase-hybrid-inverter
- https://www.deyeinverter.com/product/hybrid-inverter-1/sun5-6-8-10-12ksg04lp3.html
and also SolarEdge - StorEdge has a 3 Phase hybrid Inverter (it is a relieve to read these last guys documents ;-)).

But no idea what is available in Australia.

 

[houseofancients]

As I read the question, your problem is connecting 48v battery to 3 phase power? The only inverters you can find are for high voltage batteries?

Units like Sol-ark can be put in parallel for 3 phase. 1 or 2 can give you unbalanced 3 phase. You need 3 to give you balanced 3 phase. Walter mentioned some others that can be hooked up for 3 phase.

Deye/sunsynk and sol-ark are the same devices, and they can do unbalanced loads over the phases

 

[carsten42]

when building such a battery, you need to be sure to have identical cells, identical packs.
In the example video using Batrium, I assume the Batrium Balancing is used; and as this solution is all integrated I assume it could ballance all cells to the same level. And thus balancing the individual batteries. But that gives maybe the question if this is not just one big battery ;-). But that is the only way to look at it anyway if you build something in series. You have to view it as one big battery where all individual cells need to be on the same level. If this is not the case there will be fast degradation as a battery is only as good as it weakest component. and not being balanced causes a weak component in your battery.

1) It is not possible to have perfectly balanced cells or packs which need no further balancing. Otherwise you would never need a balancer.
2) The balancing inside a pack is done by by the slave BMS. It takes energy from one cells and transfers it to another or just drains the higher cells via a resistor to the level of the lower cells. But how is this done at the pack level? According to the description, the master has only communication cables to the slave modules but to cables to transfer energy.

 

[Grakat]

Depending on your grid tied inverter there is usually a phase imbalance in domestic housing where 3 phase is being used. You will find that one of your phases is doing the lions share of the work when it comes to providing power to your house. You may be able to battery back up this phase. Best to check with more qualified/learned minds on this one.

 

[carsten42]

Another solution for HV inverters would be a bidirectional DC-DC converter. The HUAWEI LUNA2000 battery seems to use this technology.
The question now is: Where to find such a DC-DC converter.