If you haven't seen https://www.youtube.com/c/OffGridGarageAustralia/featured he has done lots of real testing on this. His conclusion for him with his victron charge controller was to set absorption voltage of 3.45 per cell for 1hr, tail current of 0.5% and 3.35V for float.


Charging lf280k

https://dokuwiki.pejaime.com/doku.php?id=burim:jk-bms

====== connection ======

https://mr-manuel.github.io/venus-os_dbus-serialbattery_docs/general/install/


===== Voltage profile for 16×EVE LF280K (51.2 V) on Victron / Venus OS =====

^ **Parameter** ^ **Everyday value (long cell life)** ^ **Weekly / monthly “top‑balance”** ^
| **Bulk = Absorption voltage** | **55.2 V** (3.45 V / cell) | up to **56.8 V** (3.55 V / cell) for 1–2 h once every 1–4 weeks to let the BMS finish balancing |
| **Float voltage** | **54.0 – 54.4 V** (3.375 – 3.40 V / cell) | same as Bulk if you prefer a “no‑float” strategy |
| **Re‑bulk / Restart** | 53 V | n/a |
| **Tail‑current (Charged‑current)** | 4 % C ≈ 11 – 14 A for one 280 Ah string | same |
| **Absorption time** | 30 min for a single 280 Ah string (add ~10 min per additional 100 Ah) | 1 – 2 h (only during the top‑balance) |
| **Maximum charge current** | 0.2 – 0.3 C → 56 – 84 A per 280 Ah string (respect BMS CCL) |  |
| **Low‑voltage shut‑down** | 46 – 48 V (2.88 – 3.00 V / cell) | 40 V hard‑stop (BMS) |
| **Dynamic cut‑off** | 47 V (helps avoid nuisance trips under high surge) |  |
| **Sustain voltage (ESS)** | 50 – 51 V |  |
| **Equalization** | Disabled (LiFePO₄ does **not** need it) |  |

==== Where to put the numbers in Venus OS ====

- **Settings ➜ DVCC**
  * **Enable DVCC**
  * **Limit managed battery charge voltage** → *55.2 V* (or 54 V if you want to be ultra‑conservative).  
    If your BMS already broadcasts a Charge‑Voltage‑Limit (CVL), set the DVCC ceiling slightly above that so the BMS remains in control.

- **Inverter/Charger parameters (VE‑Configure → Charger tab)**
  * *Bulk = Absorption* = **55.2 V**  
  * *Float* = **54.0 – 54.4 V**  
  * *Absorption time* = **30 min**  
  * *Re‑bulk* = **53 V**  
  * *Tail current* = **4 %**  
  * *Charge current limit* = BMS CCL or ≤ 0.3 C

- **ESS assistant (if used)**
  * *Dynamic cut‑off* = **47 V**  
  * *Sustain* = **50 – 51 V**  
  * *Minimum SoC* = reserve of your choice (typically 10 – 20 %)

==== Why these numbers? ====

  * **Cell longevity** – Cycling between ≈ 3.0 V and 3.45 V per cell dramatically extends life while losing almost no usable capacity.
  * **Balancing opportunity** – Briefly holding 3.45 – 3.55 V lets the passive balancers in most BMSs keep the cells level.
  * **Failsafe** – If CAN communication is lost, these manual set‑points protect the pack while still allowing useful operation.

> **Tip:** After entering the values, watch *Battery ➜ Charge voltage* in Remote Console.  
> If it never exceeds 55.2 V during normal solar charging, you are treating the LF280Ks very gently.

Enjoy those monster 280 Ah cells!


===== LiFePO₄ Charging – Full Conversation =====

Below is the entire exchange (user questions and assistant replies) rendered in DokuWiki markup so you can paste it straight into your wiki.

----

=== 1. User Question (2025‑05‑14) ===  
While fully charging a LiFePO₄ battery like the **EVE LF280K** daily isn't inherently harmful, it's not the optimal practice for maximizing lifespan. For best performance and longevity, it's recommended to keep the charge level between 20 % and 90 % most of the time, with occasional full charges (to 100 %) for cell balancing.

**Q:** *How often to fully charge to 100 %?*

----

=== 1. Assistant Answer — How often to top‑balance ===  

^ Your use pattern ^ BMS type ^ Suggested “top‑up” to 100 % ^ Why ^
| **Daily cycling** (solar self‑consumption, EV, etc.) | *Passive* balancer ≤ 100 mA | **Every 25–40 cycles** (≈ 4–6 weeks) | Passive shunts need hours at the very top to bleed a few Ah and allow the slowest cell to catch up. |
|  | *Active* balancer ≥ 0.5–1 A | **Every 2–3 months** (or when ΔV > 10 mV at 80 % SOC) | Active balancers move energy continually, so cells seldom drift far. |
| **Lightly‑used backup pack** (few cycles / year) | Any | **Twice a year** | Self‑discharge, not cycling, is the main imbalance driver here. |
| **Brand‑new pack or after firmware changes** | Any | **One deliberate full charge** | Gives the BMS an accurate SOC reference and starts all cells in sync. |

*Assumes healthy EVE LF280K cells at 15 – 30 °C. Tighten the interval if your pack runs hotter; loosen it in cool climates.*

**Why not top‑balance every day?**

  * Calendar aging studies show that holding LiFePO₄ at high SOC accelerates capacity fade; 90 %‑SOC storage loses capacity about 1.7 × faster than 10 %‑SOC storage under identical temperature.  
  * Community data: packs limited to ≈ 3.37 V / cell and topped up monthly record cell‑voltage deltas under 5 mV.  
  * Users with strong active balancers still stay under 5 mV even when they only top up every three to six months.

**Signs you should run a full charge earlier**

  * Cell‑delta > 30 mV at the bottom of discharge or > 15 mV at ~80 % SOC.  
  * Sudden SOC errors of ≥ 10 %.  
  * High‑voltage trips before the expected amp‑hours have been returned.

**Bottom line:** For a pack cycled every day, a **monthly** top‑balance is a good compromise. With amp‑level active balancers you can stretch to **quarterly**; standby packs only need a **semi‑annual** top‑up.

----

=== 2. User Question (2025‑05‑14) ===  
*How to limit in Victron Venus OS so that it charges only to 90 %?*

----

=== 2. Assistant Answer — Limiting charge to ≈ 90 % on Victron Venus OS ===  

Venus OS (v3.50+) cannot enforce a “Max SOC” directly—only voltage & current. Therefore you have two mainstream approaches:

^ Method ^ What you cap ^ Works with ^ Effort ^ Notes ^
| **A. Lower the charge‑voltage ceiling** | Cell voltage (≈ 3.35‑3.40 V / cell) | Any Victron charger, MPPT, Multi/Quattro | Very easy | Gives ~88‑92 % SOC. |
| **B. Scripted SOC control via MQTT/Modbus/dbus** | Real‑time SOC | GX device running Venus OS | Medium | Stops exactly at 90 % and restarts at e.g. 80 %. |

----  
==== Option A — Set a lower charge‑voltage ====  

  - **Update firmware** on the GX and all chargers so DVCC governs every device.  
  - **Settings → DVCC** → tick **“Limit managed battery charge voltage”** and enter the voltage that equates to ~90 % SOC:

    ^ System voltage ^ Set‑point for ≈ 90 % SOC ^  
    | 12 V (4 S) | **13.5 V** |  
    | 24 V (8 S) | **27.0 V** |  
    | 48 V (16 S) | **54.0 V** |

    *Figures assume 25 °C and taper current < 0.1 C.*

  - In every charger: set **Absorption = Float** voltage, **Absorption time = 1‑5 min**, **Float =** same voltage.  
  - Verify that charging now ends at ≈ 88‑92 % SOC.  
  - Once a month raise the limit to 55.2‑56 V (3.45 V / cell) for 30‑60 min to let the BMS balance.

----  
==== Option B — Exact 90 % with a script ====  

  1. Enable **MQTT** on Venus ( *Settings → Services → MQTT → On* ).  
  2. On a Pi, Home‑Assistant, or the GX itself install **Node‑RED** (or use Python).  
  3. Flow logic:

    ```text
    • Subscribe: N/<portalID>/battery/+/Soc
    • If SOC ≥ 90 %
        → publish 0 V to /Settings/SystemSetup/MaxChargeVoltage  (turns charging off)
    • If SOC ≤ 80 %
        → publish normal CVL (e.g. 54.0 V) to same path (re‑enables charging)
    ```

    `/Settings/SystemSetup/MaxChargeVoltage` is what the GUI toggles when you tick “Limit managed charge voltage,” so changing it over MQTT takes immediate effect.

  4. Keep the charger’s own voltage limits at your normal balancing value (≈ 56 V); the script decides when to apply them.

----  
==== Practical tips ====  

  * **Don’t starve the balancer** — Schedule a monthly full charge with passive shunts; active balancers can wait 2‑3 months.  
  * **Temperature matters** — High SOC + high T accelerates aging; if cabinet > 35 °C, aim for 80‑85 % instead.  
  * **Tail‑current** — With the lower CVL, taper ends earlier; reduce tail‑current cut‑off so absorption finishes cleanly.  
  * **Firmware < v3.10?** Early Venus couldn’t throttle Multis—upgrade if yours still charges to the old voltage.

----  
=== Bottom line ===  
Until Victron offers a built‑in “Max SOC” slider, the simplest routine is:

  *Enable DVCC → set charge‑voltage limit to ~54 V (48 V system) → very short absorption → raise it once a month for balancing.*

This automatically keeps your EVE LF280K pack in the 20 – 90 % sweet‑spot for long life.