Lithium Smart Battery Manual

If, for a specific reason, the initial charge procedure needs to be performed without a BMS, this is the procedure for it. This procedure is for charging a single battery only. Please note that this is not something we recommend because this process is risky. This procedure must only be conducted under constant supervision. A constant VictronConnect session must be open to monitor the cell voltages at all times. Cell voltages can rise very quickly as they approach full charge, so the person supervising may need to intervene immediately to prevent a dangerous cell over-voltage scenario. A cell should never exceed 4V.

Initial charge without using a BMS

Charge procedure:

Introduction and when to use this procedure:

After a battery has been discharged too deeply with terminal voltages below 8V or 16V for 12V or 24V batteries respectively, a special slow charge procedure is required to recover the battery. This procedure is detailed in chapter Battery very low terminal voltage. Read that chapter carefully. After such an excessively deep discharge, it can happen that the microcontroller does not power up correctly. This chapter explains how to fix that by power cycling the microcontroller. Before opening the battery, first follow the instructions below carefully to make sure that it's actually necessary to perform this procedure at all.

Note that batteries will never be discharged to that level when installed and operated correctly. Make sure to understand why it happened, and amend the installation and/or the operation of the system accordingly.  

Please be advised that the information in this chapter is intended to help installers or technically competent people to recover a battery from an excessively deep discharge state on site, where shipping the battery for repair would be impractical. If you are uncomfortable with conducting this procedure yourself, contact a Victron service or repair centre who will be happy to do it for you. Again, note that once cell voltages go below 2V damage has already set in. At best, the battery capacity will be noticeably reduced; in the worst case, the battery will need to be replaced.

How to recognise a stuck microcontroller:

First, make sure the system is within operational parameters:

Now, verify that the BMS still signals loads and chargers to disconnect. This table details how to do that for all available BMS's

Lastly, check that the battery is not visible in the VictronConnect device list. If the battery shows, the microcontroller is running normally and a power cycling is not required.

Micro-controller reset procedure:

1		Tools needed: Nylon or rubber hammer Scraper, chisel or flat screwdriver Insulated torque socket wrench M10 (electrical tape can be used to insulate the socket and part of the wrench) Electrical tape
2		Remove the battery terminal wiring. Remove the terminal hex nuts.
3		Carefully loosen or break open the lid. This can be done with a scraper, flat screwdriver or chisel. When it creaks, it comes loose. Then continue a bit further until the lid is completely loose.
4		Remove the top cover.
5		Insulate the negative busbar terminal located next to the positive battery terminal. Do this by covering the busbar with electrical tape. See the red tape in the image on the left. Notice The electrical tape is a precaution to prevent a possible short circuit between the positive battery terminal and the negative busbar.
6		Loosen and remove the bolt that holds the positive circuit board wire cable lug.
7		Leave the positive circuit board cable lug disconnected for a few seconds.
8		Reinstall the positive circuit board cable lug and the bolt. Fasten the bolt to 10Nm torque. Remove the electrical tape.
9		Put the cover back on the battery. Reinstall the terminal hex nuts. Reinstall the battery terminal wiring.
10		Check if the BMS is now allowing loads and chargers to connect to the battery. Check to see if the battery appears in the device list of the VictronConnect app*. If the BMS allows loads and chargers, the procedure was successful. * Note that if the battery does not appear in the device list, this can be because Bluetooth has been disabled. See the VictronConnect issues chapter for more information.

Why is cell balancing needed

Though carefully selected during the production process, the cells in the battery are not 100% identical. Therefore, when cycled, some cells will be charged or discharged earlier than the other cells. These differences will increase over time if the cells are not regularly balanced.

When fully charged, the current through a lithium cell is almost zero. Lagging cells will not be charged further unless they receive "help" with this from cell-balancing electronics.

How does cell balancing work

The battery has built-in "active" and "passive" cell balancing. This ensures that all cells will be balanced. Each cell voltage is monitored, and if required, energy will be moved from the cell(s) with the highest voltage to the cells with a lower voltage. This process will continue until all cell voltages are within 0.01V of each other.

When does cell balancing take place

"Active" cell balancing begins when the first cell reaches 3.3V or less for severely unbalanced batteries.

"Passive" cell balancing starts when the cell voltages are 3.50V. This can happen only during the absorption charge stage, as during this stage, the charge voltage (14.2V or 28.4V) is high enough to for the cell voltages to also be sufficiently high to allow smaller cell differences to be corrected.

The cell balancing process is nearing completion when all cells have reached a voltage of 3.55V and the charge current has dropped below 1.5A. Balancing is complete when the charge current has dropped even further.

How to ensure that the battery remains balanced

A 2-hour fixed absorption period is recommended for lithium batteries so that there is enough time for cell balancing to take place. It is important to regularly fully charge the battery. This so the battery spends enough time in the absorption stage. A full charge once a month should be sufficient. However, there are some applications where the cells will become unbalanced quicker than usual. This is the case when the system is used more intensively or if the battery bank consists of multiple batteries in series. To ensure a well-balanced battery, a weekly full charge is required for:

It is not possible to speed up the cell-balancing process

Please note that a higher charge voltage will not speed up the cell balancing process. The cells are charged by current and not by voltage. Feeding current into a cell will cause the voltage to increase over time, but this is a fixed process. Applying more voltage will not speed this process up. In addition to this, the balancing speed is determined by the maximum current rating (1.8A) of the active and the passive balancing circuits.

How to monitor cell balancing status

Use the VictronConnect app to monitor the balance status of the battery. The app will indicate 4 balancing stages, being:

Unknown Balancing Balanced Imbalance

Cell balancing information. From left to right: unknown, balancing, balanced and imbalance.