The single cells charges: 3.6V 5 Amp and 3.6V 18 Amp
Proper charging of the LiFePO4 cells is a must. The single cell chargers allow charging of single LFP cells directly. GWL offers two models: 3.6V/5Amp (POW4V5A) and 3.6V/18Amp (POW4V20A2). These chargers should be used to make the initial charging of the LFP cells. They can also be used for individual cell balancing inside the battery pack. Every person working with LiFePO4 technology should have these chargers at hand to charge the cells properly.
Initial charging - with 3.6V chargers
The cells must be charged one-by-one before the assembly of the battery pack. You can use the 3.6V chargers (POW4Vxxx) product to charge the cells.
Charging with up to 16 Amp – check your AC socket quality first!
For 16 Amp charging currents we recommend to connect the open end of the charging cable directly to an electrical distribution board. It is also recommended to use CEE Caravan plug or the 3-phase 16/32A 400V 5pin plug.
In case of using common Schuko 16A home plug there is higher risk of melting the connector while operating with more than 10A continuously. Only high quality rubber connectors should be used! Check the socket quality - especially the springs (which hold the contact) for aging!
FAQ: Battery Overcharged – What to do?
In case of failure to charge properly, the overcharge will result in damage of the internal cell structure. In base of mild overcharge, there is some chance to recover the function of the cell.
If overcharge happens, follow these guide lines:
1) Remove the charger and stop charging immediately.
2) Discharge the cell slowly with reasonable currents (bellow 0.1C, bellow 10A for 100Ah cell). The discharge should last until the voltage drops to normal level (e.g. 3.2V for LFP cells)
3) While discharging, open the safety valve to allow the internal pressure to release. (Not all cells have the safety valve designed to be opened. Please contact us for specific instructions.)
4) If the cells are swollen, we suggest to follow the instruction to press the cells back to their original size (see details here).
After the cells have been restored, we suggest to make some testing cycles to see the performance of the cell. (E.g. 5 to 10 cycles). For cells that were overcharged by mistake, we strongly suggest to avoid repeated charging them to full voltage. Charging to 80% ~ 90% level of nominal capacity is a good way to avoid further degradation of the cells that were already overcharged.
Customer reference: high speed chargers for initial charging
The customer reference of the customized high-speed charging (up to 5V/100Amp) to make the inital charge of the LFP cells.
The picture shows high capacity cells being charged and balanced during the intial charging.
The operation of the battery pack and its capacity
The battery should never be discharged too low. It should also never bee overcharged. You should always stay within the safe limit of the operation. See the suggestion of the capacity indication by the BMS123 software settings.
Connecting the ELCON (TC Charger) to a BMS
The diagram shows how to connect the BMS to the ELCON/TC charger using the analog ENABLE signal wiring.
Check our offer of TC-Charger products here.
Universal 12V Charger 6A (4 cells, 1 batt)
The inteligent 6 mode automatic charger for lead-acid and LiFePO4 batteries (12V or 4S cells).
- For charging to full voltage (for LiFePO4 cells) you need to choose the SNOW mode.
- For charging with 6 Amp (full current) you must select the “Truck/Van" mode.
Check the product here.
LFP cells will bloat if overcharged
The photo shows the results of an unattended charging from a regulated charger that had a failure. The cells were kept charging up to 4.8V per cell.
The result is obvious: due to the overcharge the cells start swelling and the housing expands.
On the other hand, this accident proved that LiFePO4 cells are a quite safe battery technology. In this hazardous situation, there was no significant temperature increase, no gas leak, no explosion, no fire. (With lithium polymer cells - so called „lipoly“ cells - such kind of over charge would result in an uncontrolled fire.)
The lesson taken from this accident:
- Never left batteries charged unattended.
- Always install multiple protections to have a backup protection in case of failure of the primary device.
- Operate batteries in places where there is a proper fire safety (not on a wooden table in a closed room).
- Even professionals can make a mistake or meet with a failure that can lead to an accident.
Can the automotive 12V battery charger be used for LiFePO4?
Some chargers can be used, some cannot. There are two things that need to be considered:
1) Full charge voltage. The LiFePO4 batteries need to be charged at least to 14.6V. However, some automotive 12V battery chargers charge only to 13.8V or even less. This is not sufficient. Only chargers with higher charge voltage may be used. Note: some chargers support higher voltage by manual selection of something like „a boost mode“.
2) Trickle charge not supported. The LiFePO4 batteries will be damaged when left on charge with the trickle mode charging. Most automotive 12V battery chargers have the trickle mode as a default setting. With LiFePO4 batteries, the charging must be stopped and the charger needs to be disconnected after the charge cycle is finished. If the charge disconnect after full charge, it may be used for LiFePO4. It is a must to avoid the trickling charge mode.
FAQ: Charger performance loss due to a poor connection of the clamps
Question: We have a charger with the specification of 20Amp current. However the current of the charger is sometimes lower. Why is this so?
Answer: For high current charge and discharge, the resistance of the connections is significantly important. If the connection is not good it will cause overheating and the energy loss. For example, some of the chargers have clamps to connect to the battery. If the clamps on the battery terminals are not positioned properly there maybe a loose connection that will cause energy losses. As a result, with the increased resistance, the current of the charger may be reduced.
Solution tips: check the cabling of the charger, check the tightness of the clamps, remove any dirt from the terminals, do not connect the clamps to iron screws, connect to copper or aluminum terminals directly. For best performance use properly soldered hooks rather than the clamps.
Check also this article on voltage drop
FAQ: Changing the Charger Voltage Levels
Question: I have purchased a battery pack and a charger from your company some time ago. Now I decide to add few more cells to increase the voltage of the battery pack. How can I increase the charging voltage of the charger? Can I change the program of the charging curves (ideally in 1 V increments) to work with the higher voltage pack?
Answer: The charges sold by GWL are not user adjustable. The voltage level settings are fixed at the manufacturing point and there is no direct way to change the settings afterwards. We also do not offer any “update” of the chargers to work at higher voltage.
Warning: both the battery manufacturers and the charger producers strongly recommend using only chargers that have the voltage level fixed according to the battery pack. When using a charger for higher voltage on a lower voltage battery pack, the pack can be easily overcharged and damaged. It is not worthy to make the risk to charge a battery pack with an unmatched charger.
Conclusion: the voltage of the charge must match the voltage of the battery pack.
See also: FAQ: Charger max voltage adjustment
FAQ: Charging modes for the MPPT Tracer series
Question: Which battery type setting should be used for the LiFePO4 cells/batteries with the MPPT Tracer Solar Charge controllers?
Answer: The voltage levels are shown at the table. Changing the battery type will change the maximal voltage level between 14.2V, 14.6V and 14.8V. All of these levels are pretty OK for the LiFePO4 cells.
Note: check the details on the LiFePO4 battery charging levels (14.4V vs 16V) and study details why to avoid keeping the battery at full charge voltage level.
Additional note: please keep in mind that the voltage levels for the MPPT chargers (Tracer series) are at 25*C nominal. With the temperature decreasing, the voltage levels will increase as indicated in the manual: -30mV/*C. This means that for temperature 15*C (of the MPPT temperature sensor) the voltage levels will increase by +0.3V
Summary: for cold temperatures (15*C and less) you may wish to have the setting for GEL and/or SEALED battery to stay bellow the safe charge voltage of 14.6V per battery.
QUESTION: Are the lithium cells charged before shipping to the customer?
ANSWER: No. The cells are not charged. They are shipped in the same condition as received from the factory. The cells are shipped with 50% and less energy left in them. The cells must be charged to full and balanced (equilibrated) by the customer before the installation of the battery pack.
For safety reasons it is forbidden to transport the batteries that are fully charged. In case of an accident the fully charged cells would release all energy and could cause serious damage. The less energy is left in the cells during transportation, the safer the transportation is.
During the manufacturing process, the initial charge is made at the factory. Following this initialization charge, the introductory charge and discharge cycles may be performed at the factory to verify the cells specification, capacity and internal resistance. After these test cycles the battery is usually left at 50% capacity, ready for the shipping.
This capacity is sufficient for the 12 to 15 months of the storage. Since the self-discharge rate is bellow 3%, the cell will not discharge by itself, and it stays in a perfect condition all the time. (Additionally if the cells should have some internal problem, the cell would get self-discharged to empty condition during the period of storage)
If the cells are to be stored for one year or more, we recommend to make the full balancing charging before the storage of the cells. The charging should be repeated once in 12 to 15 months.
Prior to installation of the battery pack, the cells must be individually charged to the full voltage level as specified by the manufacturer. This will make the battery pack consistent and fully balanced (equilibrated).
See also the cell charging FAQ.