question

hdb avatar image
hdb asked

Add a second LiFePO4 battery bank - is my schematic ok?

Dear all,

For those interested: I'm going to add a second battery bank to my parents' installation.

This is the existing schematic: schematic-original.png


I would modify the system using:

15 (not 16 as mentioned initially) times a 3.2V 200AH prismatic LiFePO4 cell, so 15s configuration. (click to open)

A would use a 16s 300A Daly BMS (because I hear nothing but good things about this BMS) (click to open)


Basically I would connect the now 15s (not 16s as mentioned initially) battery in parallel with the other 15s6p pylontech batteries.


Given that each battery in the future system will be connected in parallel, and each with it's own BMS, I don't see a problem;


The schematic would become (adding my homemade battery):


schematic-modified.png.


In practice I would simply add the homemade battery to the 2 copper bars, since there is room (free holes):


free-room-on-bars.jpeg


In theory I could add the system to VRM using CAN cable between Daly BMS & Victron Venus GX, but I don't think that's really needed. But it would be nice to see the battery in the system overview so that my dad can monitor it.



Please let me know if I'm being realistic or about to make a huge mistake.

MultiPlus Quattro Inverter ChargerLithium BatteryBMSPylontechVenus GX - VGX
schematic-original.png (82.2 KiB)
schematic-modified.png (92.4 KiB)
free-room-on-bars.jpeg (109.3 KiB)
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4 Answers
seb71 avatar image
seb71 answered ·

Won't work.

Way different voltages.

Pylontech batteries are 15 cell.

Your new battery is 16 cell.

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marekp avatar image marekp commented ·

But 15 cells in that new battery would work.

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hdb avatar image
hdb answered ·

seb71 & marekp


Thanks for your replies.


I wasn't aware of the fact that the US2000 had a 15-cell (15s) configuration since most 48V systems have a 16s configuration. The datasheet doesn't mention the 15s config, but Victron indeed mentions that it is a 15s system.


So, to rephrase my question:


  • Would my setup work if I make a 15s battery with Daly (15s) BMS?
  • Is CAN communication between Venys & Daly BMS essential? I believe not.
  • Could my setup harm anything in any way? .

Thanks & Regards,

Hendrik



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seb71 avatar image seb71 commented ·

15 cells in series should work, but in theory when you put more batteries in parallel, all should be the same. And the wires should be the same.

You must use a fuse for that, too (between the new battery and the positive busbar).


I guest the cost is the reason why you don't just add more Pylontech modules. But that would be the better way in this case.

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marekp avatar image marekp commented ·

This additional battery cannot be connected to Venus GX. That communication is already taken by Pylontech.

BMS inside this new battery will control it's cells and turn the battery off if something is not correct.

You would need the way to see if that battery is still connected because Venus GX would not know it.

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hdb avatar image
hdb answered ·

seb71 & marekp


Thanks for your replies, once again.


Indeed I would opt for a homemade battery instead of extra pylontech batteries because the price is considerably lower.


I thought that there are other CAN ports available on Venus GX and therefor I could connect another battery to monitor it.




venus1.jpeg



venus2.jpeg


venus3.jpeg




venus4.jpeg




Sorry for the bad image quality.




venus1.jpeg (141.9 KiB)
venus2.jpeg (130.5 KiB)
venus3.jpeg (139.2 KiB)
venus4.jpeg (90.5 KiB)
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marekp avatar image marekp commented ·

From what I learned in my short schooling in the Victron system, GX can only control one battery.

I am still learning so I can be wrong.

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derrick thomas avatar image
derrick thomas answered ·

You can connect the Daly to the gx using this driver

https://github.com/Louisvdw/dbus-serialbattery

And then look at this virtual battery installation to aggregate the 2 batteries together and feed that information into the Venus os as one main battery

https://github.com/arrow1800/Victron-VirtualBattery

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