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Bjorn Embrechts avatar image
Bjorn Embrechts asked

Need a little help setting up first battery

Hi everyone,

I need some help planning some stuff...

I would like to set up (at leased) two 18S1P packs whit individual Bms's and parralel them to supply a 3f multiplus II 5000 System and monitor every cell.

I'm having trouble wrapping my head around this as this is my first large scale pack.

Do I need a BMS that talks victron, or can I just stand alone the packs and use the lynx shunt to measure the overal battery array... And tune the bulk, float, absorb settings.

I'm not sure what the pitfalls are, and hope you guys Can enlighten me sort of speek.

Projected materials:

- Daly Smart BMS (has CAN and UART, but don't think it speaks the same language)

- 36 x 280Ah lifepo4 cells devided in to two 18S packs

- Lynx shunt

- Lynx disributer


Lithium BatteryBMS
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2 Answers
Jesse avatar image
Jesse answered ·

I don't think the BMS needs to "talk victron". It simply balances the cells and disconnects the output when things are unsafe. Power off is a universal language!

Given it's an 18S2P system it would be worth considering for redundancy having two separate strings each with their own BMS, though I've also seen them simply wired together 2 parallel cells each in each link of the series.

Otherwise sounds like you're ready to go. I don't have any experience with the Lynx Shunt, looks like it's expecting a Venus device to talk to so you can control a relay using state of charge for instance? Not mandatory, properly configured the Multiplus shouldn't damage the battery but it could be hard to limit it to a 20% depth of discharge for instance.

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Bjorn Embrechts avatar image Bjorn Embrechts commented ·

Hi Jesse, thanks for your insight on the matter.
I'm pretty new to this low voltage stuff but reading tons of forums you start reading about the dangers of using 2 different BMSs in parralel, forced charge from the other pack and stuff like that, and because the charge and discharge line is the same there is no real way of separating the 2 packs... because eventually they will always be discharging on the same potential wire to the inverters.

I would not mind trying it... doesn't make sens to buy 1 BMS anyway, might as well buy 2.
I read a post somewhere about the Daly BMSs (at leased some models) do talk to Victron via the USB-UART adapter, plugged in to a Pi with VenusOS or whatever its called.

For now I am tempted to go with the set and forget approuch to the battery, just wack an overkill BMS in there, with balancing, let it do its thing, and use a Shunt to keep track of the SOC ... somehow... it will probably take some tweaking to get it right by just trying it i guess, and i can experiment with the UART to USB thing to my Cerbo...
The Shunt connects to the Cerbo to so...
That's an other thing... how does Victron react to multiple batteries reporting SOC...

(Down the rabbit hole we go)

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seb71 avatar image
seb71 answered ·

For a 48V (nominal) system, use 16 LiFePO4 cells in series, not 18.

Keep the other four cells as spares, if you already got them.

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seb71 avatar image seb71 commented ·

Also, get a SmartShunt instead of a Lynx shunt. It's cheaper and does the same thing.

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seb71 avatar image seb71 commented ·

You are also missing a GX device. So add a Cerbo GX to your list.

Charging only from the grid?

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