A reference project for a battery bank on a sailing yacht using the 4x WB-LFP200AH cells for the board battery and the BMS123 Smart. The battery pack is charged from the on-board AC/DC charger (35 Amp) and the generator (up to 80 Amp).
Question: How should new cells 3.2V 40AH, 60AH, 90AH, 100 AH, etc. be formed before first usage?
Answer: The new 3.2V LFP cells delivered from the warehouse are partially charged. However before the first use, it is essential to charge each cell to full capacity. The initial charging should be done with the charging current set to less than 1C (typically 0.5C), till the voltage level of 4.0 V is reached.
There is no other need for LFP 3.2V cells to be formatted or otherwise specially prepared for the use. After the first charge to full, the cell is ready to be used for use.
The above charging rule is also applied to the initial charge after the cell has been unused or stored for a long time. If not used more than 1 month, it is recommended to make again an initial charge to full....more >>
Question: Can I charge the 12V LFP battery using a conventional auto-moto charger 12V?
Answer: With most of “cheap” car battery chargers you **cannot** charge the 12V LFP battery. Cheap chargers often end charging at 14V. As a result the LFP batteries are not charged sufficiently. In order to charge to full you need to reach above 16V.
If you have an “advanced” manageable charger, it can be used provided you can set the charge level to at least 16V.
Simply said: you can charge with any kind of charger if you make sure that the battery voltage reaches at least 16V, but does not exceed the maximum limit of 17V.
Question: What are the experiences of balancing 12V batteries, when, for example, four pieces of 12V/40Ah in the series?...more >>
You must charge before the first use!
We remind all users of the LFP cells and LP batteries that the cells and batteries MUST be charged to full voltage level BEFORE assembling into a pack and before starting to be used.
For the 3.2V cells, the full charge voltage level is 4.00V and the charging is described here. For the 12V LP batteries the full charge voltage level is 16.00V. More details about the use of 12V batteries is here....more >>
Why is the BMS needed for a LFP battery pack consisting of many cells?
Answer: The Battery Management System (BMS) allows you to monitor the battery pack operation. Since the battery consists of a serial string of many cells, you need to monitor each cell to prevent from deep discharge or over charge. The BMS will give you information about the cell voltage levels and can issue warnings if there is a problem with any of the cells.
The BMS with balancing option will balance the cells (usually during charging) to make sure all cells have the same capacity (=voltage) levels.
The BMS also allows data logging so that you can see the history of the operation of the each cell in the battery. This way you can detect if there is any problem with one or more cells in the battery pack.
Charging individual cells using the regulated (laboratory) power supply
Many of the laboratory power supplies allow charging of the individual cells. Using such a regulated power supply is a suitable method for performing the initial charging or for the balancing of a single cell in a battery pack (by means of charging to a fixed voltage level).
There are usually 3 steps to follow: 1) set the target voltage (open voltage) – without the connection of the battery (3.65 at the picture), 2) start charging and set the current to be used (3.0 A at the picture), 3) when the charger reaches the target voltage – it usually starts to reduce the charging current until a low value. (3.66 V reached at 0.04A). It is a time to stop charging and disconnecting the charger.
Check these FAQ published on our blog to understand the initial battery charging
We remind all users of the LFP cells and LP batteries that the cells and batteries MUST be charged to full voltage level BEFORE assembling into a pack and before starting to be used. source
The new 3.2V LFP cells delivered from the warehouse are partially charged. However before the first use, it is essential to charge each cell to full capacity. source...more >>
I want to make the initial charge of all the LiFePO4 cells to the same maximal voltage level of 4.0V. How can I do that?
EDIT: This article gives the example of 4.00V charge level. The same information is to applied for charging to other voltage levels: e.g. 3.65V, 3.70V, 3.80V, 3.90V. Different voltage levels may be applied for initial charging based on the manufacturer specification.
ANSWER: The best way it to find a power supply or a charger that will charge to the 4.0V directly. Another solution is to charge using the laboratory power supply or the regulated power supply that allows to set the final (maximal) voltage limit. We suggest to check with the local electronic components suppliers for these products....more >>
Initial charge voltage levels
Question: I wish to equip my workshop with the proper tools. Can you offer me following chargers: one model with cut off voltage at 3.65V, one model with cut off voltage at 3.80V and one model with cut off voltage at 4.00V?
Answer: There is no need to have so many different chargers. The typical chargers that are sold by GWL charge to 3.65V (for single cell). Please see some additional comments....more >>
FAQ: “Sudden” battery discharge
I have bought a several of LFP cells and made the pack with them to replace the lead-acid battery in my houseboat. The LFP battery was working great and it gives much more capacity than the lead acid. However after several weeks of usage, I came back after the weekend and I found out that the battery is completely discharged. Why this happen?
Please note that unlike the lead acid batteries, the LFP batteries will be completely damaged if you discharge them bellow the minimal voltage (usually >2.5V per cell, or bellow 10V for 12V battery). This may happen if you have some equipment that takes the power from the battery continually. Maybe you simply forget some light or some equipment „on“, and after few days the battery is deeply discharged and damaged forever....more >>