Adding additional battery storage

[bad habit]

I currently have 2 eg4 6500ex in split phase. 4 kw of panels and 20kw of battery storage 4s4p consisting of 16 redodo 12v lifepo4 batteries. My question is can I add/build another 20kw of storage and tie it in to my system if it shares the same chemistry, voltage,and ah?? Will the different bms between the 2 banks be an issue? Seems to me like they would operate separately but redodo says no different bms protocol. I really wanted to add a server rack or another 20kw of chins idk can't seem to get a solid answer except buy only our batteries any help would be appreciated.

 

[sunshine_eggo]

I currently have 2 eg4 6500ex in split phase. 4 kw of panels and 20kw of battery storage 4s4p consisting of 16 redodo 12v lifepo4 batteries. My question is can I add/build another 20kw of storage and tie it in to my system if it shares the same

chemistry,

Yes

voltage

Yes

and ah??

This doesn't matter much. Different capacity, cell choice and configuration all influence how current is shared.

Will the different bms between the 2 banks be an issue?

Not necessarily unless you're shooting for inverter communication.

Seems to me like they would operate separately but redodo says no different bms protocol. I really wanted to add a server rack or another 20kw of chins idk can't seem to get a solid answer except buy only our batteries any help would be appreciated.

If you're trying to get communication between two different battery types, that's not likely to happen unless the two systems use identical BMS and protocol.

If you want ONE of the 20kWh banks communicating with the inverter, and you want to simply parallel a "dumb" 20kWh bank to it, that's fine. Since the drain on the communicating bank will be half of what it was, the reported SoC will be approximately correct.

 

[bad habit]

Yes



Yes



This doesn't matter much. Different capacity, cell choice and configuration all influence how current is shared.



Not necessarily unless you're shooting for inverter communication.



If you're trying to get communication between two different battery types, that's not likely to happen unless the two systems use identical BMS and protocol.

If you want ONE of the 20kWh banks communicating with the inverter, and you want to simply parallel a "dumb" 20kWh bank to it, that's fine. Since the drain on the communicating bank will be half of what it was, the reported SoC will be approximately correct.

Thanks for the wisdom I figured as much but needed someone with more experience than me with lipo4 chemistry to clarify. Don't need any communication (closed loop) but would I need another victron smart shunt on the other 20kw bank? Like I have now to read soc. Watchpower app isn't very accurate at all with the eg4 6500ex

 

[sunshine_eggo]

Thanks for the wisdom I figured as much but needed someone with more experience than me with lipo4 chemistry to clarify. Don't need any communication (closed loop) but would I need another victron smart shunt on the other 20kw bank? Like I have now to read soc. Watchpower app isn't very accurate at all with the eg4 6500ex

You don't need one. Simply connect the 2nd bank in parallel with the first. Use the primary negative of one bank as the main (-) with the shunt installed between battery and inverter(s). Use the primary positive of the other bank as the main (+). Depicted below.

 

[GXMnow]

When you do go to add the additional battery, try to get the batteries as close to the same state of charge before connecting them together. Some of the server rack style batteries do have a charge current limiting system, but I would not put all my trust in that. At least with LFP cells, if they are both between 40% and 75% SoC the voltages should be close enough that the current between the two won't be too crazy. My system is using Li NMC cells, and my BMS units do not have any current limiting other than just turning off. So I needed to get the battery voltages to within 0.05 volts, and even then, I saw over 50 amps from the higher state battery, going into the lower one. I spent another 3 hours with a 10 amp buck converter to pull energy from the higher battery and put it into the lower one. Then when I connected the batteries, the current between them was down to just 15 amps, I was fine with that. After a few cycles in parallel, the batteries will balance out nicely and share the current based on their true capacity. My newer battery cabinet has about 8% more capacity than the older set, so it shows about 8% more current while both charging and discharging. That is totally expected, and it naturally keeps both banks at the same percentage state of charge. Each battery cabinet actually has 2 strings, and I use my clamp amp meter once in a while to check each string. The two strings in each cabinet are always within 1 amp of each other, but both strings in the new cabinet are always showing that 8% more current than the two in the old cabinet.

 

[DaveZ Solar]

I'm adding 2 additional eg4 life P04 bat's on top of a 6 pack server rack. I'll need to change the master battery position for communication cable connections. Does anyone know if I can just change the DIP switches for the new master position (moving to bottom from top to allow additional upward expansion) or is it best to keep the existing master as the master and physically change its position to the bottom of rack? All is working great and don't want to mess with success!

 

[GXMnow]

The physical position of where the master is does not really matter.
You could just set the two new battery modules to the next higher addresses and it will work fine.

The only issue would be the address order not matching the actual position order. If that really matters to you, yes, you could change all of the dip switch settings and assign the bottom battery as the master. Just make sure all of the BMS units are running the same firmware for them to talk and work together. If the new batteries have a different BMS, you might not be able to add them into the communication string. I do not see any need to physically move the batteries around. They should all talk fine and any of the BMS units can act as the master.

 

[DaveZ Solar]

The physical position of where the master is does not really matter.
You could just set the two new battery modules to the next higher addresses and it will work fine.

The only issue would be the address order not matching the actual position order. If that really matters to you, yes, you could change all of the dip switch settings and assign the bottom battery as the master. Just make sure all of the BMS units are running the same firmware for them to talk and work together. If the new batteries have a different BMS, you might not be able to add them into the communication string. I do not see any need to physically move the batteries around. They should all talk fine and any of the BMS units can act as the master.

Thanks for your help, as far as firmware they are all the same EG4 48V Life P04 batteries. Purchase dates are about 6 months apart. Do you suppose they could have different firmware levels? If so how do you do the updates? I've had to do updates to the 6500EX's but not the batteries. Thanks again!

 

[GXMnow]

Do you suppose they could have different firmware levels? If so how do you do the updates?

That would be a question for the vendor. Some equipment get's new firmware fairly often, while other gear might not get an update for years if it is stable. If your batteries are a model with a screen, it should show be able to show you the firmware version.

Sine they are all EG4 batteries, I would hope they can all talk together, even if the firmware is on a different step. Do you have the software on a computer to directly monitor the batteries? That would show you all the parameters and let you see each module.

 

[DaveZ Solar]

Thanks again for the input, I don't have the LL batteries and have no method of monitoring them. I am going to contact SS this week to inquire on details placing the new batteries in service. I finally had time to finish building the rack extension to house them this weekend. I may actually get them into service in the next week or so. Once again..Thank You!