diy solar

diy solar

Dyi battery to fronius hybrid inverter

Nostra

New Member
Joined
Apr 30, 2021
Messages
5
Hi, Im new in this and wonder if someone know if its possible to use a dyi battery pack to fronius hybrid inverters or is it only possible to use their recommended HVM, LG chem or Resu wall packs?
 
Hey, I am also interested in the same topic. Seems Fronius GEN24 has capability to connect to a pack and they recommend BYD, but info on what BYD pack does are very limited.
 
GT made hybrid like inverters use high Vdc battery packs (internally they connect it directly, like a PV string).
Some packs have an internal 48V and use a boost converter to make 3-800Vdc from it, some put a lot of cells in series.
Like BYD where a pack (102V) is two 48V pack in series.
So you can do the same. But do not forget you need a BMS for every 48V pack and a big one for the whole 4-6-8s 48V pack.
Or you can use a very expensive Batrium BMS.
So not impossible, but I do not recommend it. High Vdc is dangerous. Avoid it as much as you can.

MPP/Voltronic has real Hybrid where 48V battery can be connected. And not silly 3kW for protected load but 5-10-15-... 85 kW. And even can be paralleled so if one is not enough you put a 2nd next to it. And they generate power to the same phase.
 
Thanks. Not sure I understand everything since Im not experienced.
I could read this from the fronius web page that the BYD/ HVM has a nominal voltage of 51.2 V per module. These different voltages subsequently lead to different charging and discharging power. Would this allow me to use 16s to a 48V pack? If not putting it together myself, would the Gyll 48V work you think?
 
It could work but will not.
The main reason is that you need a BMS for the 48V packs like 2 x 48V or 4 x 48V (2s 96V or 4s 192V).
They are in series and you would need a very strong balancer to equalize them.
I never ever saw such a beast. There is a reason why high V packs are so expensive.

The cheap (and really cheap) solution is to buy an MPP Solar ($700) or Growatt off-grid inverter (5kW), and use your 48V pack with that.
Everything connected to this inverters has UPS power. The grid-tie inverter produces power to you and to sell.
Only one function is missing : no backfeed from battery to grid.
Like here:
575369_grid_tie_ups.jpg
 
It could work but will not.
The main reason is that you need a BMS for the 48V packs like 2 x 48V or 4 x 48V (2s 96V or 4s 192V).
They are in series and you would need a very strong balancer to equalize them.
I never ever saw such a beast. There is a reason why high V packs are so expensive.

The cheap (and really cheap) solution is to buy an MPP Solar ($700) or Growatt off-grid inverter (5kW), and use your 48V pack with that.
Everything connected to this inverters has UPS power. The grid-tie inverter produces power to you and to sell.
Only one function is missing : no backfeed from battery to grid.
Like here:
575369_grid_tie_ups.jpg
Is that possible to run the MPP without solar panels connected to it, but batteries get charged only from solar from Fronius inverter (without importing from the grid)
 
The cheap (and really cheap) solution is to buy an MPP Solar ($700) or Growatt off-grid inverter (5kW), and use your 48V pack with that.
Everything connected to this inverters has UPS power. The grid-tie inverter produces power to you and to sell.
Only one function is missing : no backfeed from battery to grid.
Like here:
This is pretty much the set up I have except my grid tied inverter powers the house directly.

My all in one off grid unit is primarily for backup power to cover us during grid outages but I plan to take the pool pump off-grid once I have added the off-grid solar array.

I can run it in UPS mode with the circuit board cutover switch set to backup position and it will operate just like the diagram above.

Is that possible to run the MPP without solar panels connected to it, but batteries get charged only from solar from Fronius inverter (without importing from the grid)
Yes. This is exactly how mine is set up now, just batteries and no solar PV input. The off grid inverter's AC input comes from a circuit that gets its power from the grid and/or the grid tied solar PV system. This keeps the batteries topped up ready for action in case of an outage.

But if you already have a decent sized grid tied solar PV system I wouldn't use the off grid inverter for regular power supply as:
i. the off grid inverter will have a power output limit, you can only pass through so much power and this may be somewhat less than what you need at times - a grid tied system can typically supply much greater current.
ii. there will be energy losses doing it this way when the grid tied inverter can just supply the energy to the home directly
 
I have a 10kw solar array with 2x5kw Fronius grid-tie inverters, I want to minimize the grid use while providing backup power for any outage, any recommended configuration to have a DIY battery bank.
Currently, I'm thinking of installing a Victron mulitiplus 2 -10kw inverter with a DIY battery bank, but the Victron inverter is quite expensive (around 5k AUD)
 
Is that possible to run the MPP without solar panels connected to it, but batteries get charged only from solar from Fronius inverter (without importing from the grid)

For the first part yes, you can use MPP inverter without solar panels.
There is even the 5048MK (for EU/AU/Africa/Asia so not US) and the LV-MK model (for US) that is a double conversion unit.
So it is an Online UPS where if you want you can connect solar panels to it too.

Batteries charged from Fronius works but it is not perfect. You have to set in the UPS inverter to only charge from 8-17.
And set the charging A lower than the Fronius produces.
If a storm comes the Fronius produced power can be lower and can charge a bit from grid.
So not as perfect as a one unit hybrid system like with the Voltronic/MPP hybrid inverter.

575369_hibrid.jpg
 
I have a 10kw solar array with 2x5kw Fronius grid-tie inverters, I want to minimize the grid use while providing backup power for any outage, any recommended configuration to have a DIY battery bank.
Currently, I'm thinking of installing a Victron mulitiplus 2 -10kw inverter with a DIY battery bank, but the Victron inverter is quite expensive (around 5k AUD)

The joke is that this is the main reason people ask about hybrid systems :D
They have a Grid-Tie but they realize that in a blackout that does not work.
The easy solution is the off-grid expansion.

Victron is a very good inverter but extremely expensive.
An 5kW MPP inverter is about $700. Can be paralleled so more working to the same phase. Up to 9 item, so 45kW on a single phase.
Also 8kW MPP inverter MAX is about $1000. Can be paralleled up to 6 item.
Growatt is like smaller MPP but more expensive ... I think they even made by the same company: Voltronic
Everyone of these can be used with user made 48V batteries (AGM or LiFePO4)
 
I have a 10kw solar array with 2x5kw Fronius grid-tie inverters, I want to minimize the grid use while providing backup power for any outage, any recommended configuration to have a DIY battery bank.
Currently, I'm thinking of installing a Victron mulitiplus 2 -10kw inverter with a DIY battery bank, but the Victron inverter is quite expensive (around 5k AUD)
Have a read of what I did in this thread:
 
Hi, I just got a Fronius Gen24 Symo 5.0 inverter. I am going to start looking into reverse engineering the communication between the battery and inverter so that we can get a DIY solution available. I'll post more about this in a build thread.

EDIT: Here's the build thread: https://diysolarforum.com/threads/dalas-solar-powered-workshop-diy-powerwall-coming.23732/

So to start with the Fronius inverter reverse engineering, is there some user on this forum that has batteries hooked up to a Fronius inverter? It would make it so much easier if we could get a log file from a working system!
 
Hi, I just got a Fronius Gen24 Symo 5.0 inverter. I am going to start looking into reverse engineering the communication between the battery and inverter so that we can get a DIY solution available. I'll post more about this in a build thread.

EDIT: Here's the build thread: https://diysolarforum.com/threads/dalas-solar-powered-workshop-diy-powerwall-coming.23732/

So to start with the Fronius inverter reverse engineering, is there some user on this forum that has batteries hooked up to a Fronius inverter? It would make it so much easier if we could get a log file from a working system!

Waiting to hear about it.
Am I correct that Froni gives only 3kW power to the protected load ?
 
Hi, I just got a Fronius Gen24 Symo 5.0 inverter. I am going to start looking into reverse engineering the communication between the battery and inverter so that we can get a DIY solution available. I'll post more about this in a build thread.

EDIT: Here's the build thread: https://diysolarforum.com/threads/dalas-solar-powered-workshop-diy-powerwall-coming.23732/

So to start with the Fronius inverter reverse engineering, is there some user on this forum that has batteries hooked up to a Fronius inverter? It would make it so much easier if we could get a log file from a working system!
Looking forward to hear about it. As I understand from my Fronius hybrid 5.0.3S is that it can give 5kW AC to the grid (240V system here in Sweden), and 3kW to a battery pack so 8KW at maximum load. We are 3 weeks from the summer soltice so we got power from 4:00 to 22:00 and my panels are not tilted.
Hi, I just got a Fronius Gen24 Symo 5.0 inverter. I am going to start looking into reverse engineering the communication between the battery and inverter so that we can get a DIY solution available. I'll post more about this in a build thread.

EDIT: Here's the build thread: https://diysolarforum.com/threads/dalas-solar-powered-workshop-diy-powerwall-coming.23732/

So to start with the Fronius inverter reverse engineering, is there some user on this forum that has batteries hooked up to a Fronius inverter? It would make it so much easier if we could get a log file from a working system!
 
Yes you are (Output data PV point = 3000VA), but AC nominal output (Pac,r) = 5000W ?

Here's the Sunspec Modbus specification, to get the discussion started on how to make a compatible DIY battery: https://sunspec.org/sunspec-modbus/

How do you want to solve the high Vdc battery and BMS problem DIY ? Did you find a 3-400Vdc BMS? Or with equalizer ?

Jep 3kVA that means mostly 2,4kW (pf 0,8)

Looking forward to hear about it. As I understand from my Fronius hybrid 5.0.3S is that it can give 5kW AC to the grid (240V system here in Sweden), and 3kW to a battery pack so 8KW at maximum load. We are 3 weeks from the summer soltice so we got power from 4:00 to 22:00 and my panels are not tilted.

I am not sure but I do not think that it gives 5+3(2,4?)kW.
Possible when there is a blackout 5kW part stops and 3kW starts.
So when not a blackout it is in bypass mode for the protected load (and can give more power than 3kW because it comes directly from grid)
 
How do you want to solve the high Vdc battery and BMS problem DIY ? Did you find a 3-400Vdc BMS? Or with equalizer ?
The battery packs I have are Nissan LEAF ones (400VDC with BMS), but if the voltage is not matching what the inverter needs it's pretty easy to re-arrange the layout. My only concern with using the LEAF pack BMS is that the shunts are so tiny that it takes forever to balance a pack. If I need to change BMS I will most likely opt for Batrium or something similar. The missing link is an arduino/raspberry linking the Battery pack to the inverter by acting as a middle-man (which we will figure out in this thread :) )
 
How do you want to solve the high Vdc battery and BMS problem DIY ? Did you find a 3-400Vdc BMS? Or with equalizer ?

Jep 3kVA that means mostly 2,4kW (pf 0,8)



I am not sure but I do not think that it gives 5+3(2,4?)kW.
Possible when there is a blackout 5kW part stops and 3kW starts.
So when not a blackout it is in bypass mode for the protected load (and can give more power than 3kW because it comes directly from grid)
Ok good to know and I dont have any battery now so 5kW is maximum. Actually get 5.2kW since the inverter is under rated I guess. Now I just need to find out what electric components are used from 20:00, thought I turned off the floor heating we have during winter months in the bathrooms.
 

Attachments

  • A8A09C1F-A402-48B5-9C5E-2318D6722060.jpeg
    A8A09C1F-A402-48B5-9C5E-2318D6722060.jpeg
    130.9 KB · Views: 7
The battery packs I have are Nissan LEAF ones (400VDC with BMS), but if the voltage is not matching what the inverter needs it's pretty easy to re-arrange the layout. My only concern with using the LEAF pack BMS is that the shunts are so tiny that it takes forever to balance a pack. If I need to change BMS I will most likely opt for Batrium or something similar. The missing link is an arduino/raspberry linking the Battery pack to the inverter by acting as a middle-man (which we will figure out in this thread :) )

Batrium is a very expensive solution. For 400V you need 125 longmon (with LFP) or ... ok I do not want to calculate the price :)
LEAF battery is NMC I think (fire danger). Better to put it outside in a shed or something.

Also I am not sure this is all you need.
The battery is connected directly to the Froni inner, like a PV string (no regulation). And the PV V can change up&down.
So you will need some boost (or buck-boost) converter to be able to set the correct V to charge the battery.
Too much V and you damage the battery. Too less and does not charge. Also you need to limit the charging A not to exceed like 0,5C (by setting the charging V lower automatically).
The discharge side will be OK without any circuits but you will need like a FET based system to change to charge or discharge.
In theory ...
 
Back
Top