Migrating from flooded lead acid to LiFePo4 - battery recommendations and considerations

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Tom Ranson asked Feb 6, '23

Migrating from flooded lead acid to LiFePo4 - battery recommendations and considerations

Hi all,

I currently have 8x Leoch DT126 240Ah (C20) flooded lead acid batteries in a 4s2p for 24V 480Ah being used in an ESS system. Let's just say that I am very underwhelmed with how they are performing, and I wish I had purchased LiFePo4 batteries in the first place.

I am now evaluating migrating to LiFePo4. I require around 200Ah of usable capacity at 24V, similar to my current 480Ah at 50% DoD.

I want to be as economical as possible, without making the same mistake again.

What would you recommend I purchase, and what considerations do I need to make with moving to LiFePo4? I am totally new to lithium batteries in solar systems, so please explain it like I'm five.

I believe I can install something like 2x 200Ah in a 2s configuration, and potentially expand this to a 2s2p if I need more.

I have in my current system:

8x Leoch DT126 240Ah FLA batteries (4s2p) for 24V 480Ah

2x MPPT 100/30

1x SmartShunt 500A

1x Multiplus ii 24V 70A/3kVA

1x Cerbo Gx

Some prominent questions:

1. Do I need to be looking for LiFePo4 batteries with an integrated BMS? Or can I use non-BMS batteries? Pros and cons?

2. How to link BMS batteries to the Cerbo Gx?

3. Recommendations for particular battery makes and models?

Many thanks in advance and please let me know if you require further information.

Lithium Battery

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2 |3000

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Tom Ranson commented · Feb 07, 2023 at 10:39 AM

Do I need batteries which can communicate with the Cerbo? Or can I just use any generic LiFePo4 battery with an integrated BMS as a straight drop-in replacement for my current lead acid?

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Answer 1 · 2023-02-06T20:36:02Z

snoobler answered · Feb 06, 2023 at 08:36 PM

1 LFP batteries MUST have a BMS that monitors and protects cells. That must either be a built-in BMS to a "canned" battery or through a separate device. Period. Use a LFP battery without any BMS of any kind, and you'll destroy it.

2) You'll need a battery capable of communicating with the GX via BMS-Can or VE.Can.

3) Nope.

5

2 |3000

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Tom Ranson commented · Feb 07, 2023 at 10:37 AM

@snoobler many thanks for the advice.

Do I *need* a battery that can communicate with the Gx? Is this strictly necessary when using lithium? Or can I just use a generic LiFePo4 battery with integrated BMS as a straight drop-in replacement for my existing lead acid?

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kevgermany ♦♦ Tom Ranson commented · Feb 07, 2023 at 11:08 AM

No, you can put the necessary settings in the Victron setup and leave the BMS disconnected from the Cerbo. With some batteries that pretend to be Pylontechs this is essential.

But you lose all the info that would normally come from the batteries, so a shunt to measure battery voltage, SOC etc. is needed.

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Tom Ranson kevgermany ♦♦ commented · Feb 08, 2023 at 12:25 PM

Ok understood. So as I already have a SmartShunt in the system it would seem that I can go down the route of installing more economical batteries which don't have a Victron-integrated BMS.

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snoobler Tom Ranson commented · Feb 09, 2023 at 02:15 PM

LFP batteries are required to ship at 30% or lower SoC due to hazmat regulations. If you use 12V LFP to make 24V, make sure that you charge the batteries you plan to use in a 2S string to full in parallel at 14.4V and hold for two hours.

New batteries are rarely at identical states of charge and will often trigger over-voltage BMS protection if wired in series without pre-charging in parallel.

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Tom Ranson snoobler commented · Feb 10, 2023 at 04:34 PM

All noted, thank you very much.

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