lithium & solar power LiFePO4
FAQ: Different capacities of new Cells, with guaranteed minimum capacity according to Cell specifications. Question: I make first initialization charging and I have already balanced cells.  After next discharging and charging some cells is discharged faster than others. I think that capacity of some cells is slightly less, so they cannot be balanced. Do I have to replace the cells?
Answer: Following the manufacturer guidelines: if one or more battery cells are faster or slower in charging, this does not mean they are defective.  The manufacturer guarantees a minimum capacity, but very often some of the cells may have more “Ah” than others, but always meet nominal capacity that is listed in the specification. Example: for 500 Ah cells, if the battery capacity is above 500 Ah, then there is no reason of complaints. Rather, it is great to have a capacity over 500 Ah.Note: The positive tolerance of  the LiFePO4 cell capacity is not a cause for complaints.

FAQ: Different capacities of new Cells, with guaranteed minimum capacity according to Cell specifications.

Question: I make first initialization charging and I have already balanced cells.  After next discharging and charging some cells is discharged faster than others. I think that capacity of some cells is slightly less, so they cannot be balanced. Do I have to replace the cells?

Answer: Following the manufacturer guidelines: if one or more battery cells are faster or slower in charging, this does not mean they are defective.

The manufacturer guarantees a minimum capacity, but very often some of the cells may have more “Ah” than others, but always meet nominal capacity that is listed in the specification.

Example: for 500 Ah cells, if the battery capacity is above 500 Ah, then there is no reason of complaints. Rather, it is great to have a capacity over 500 Ah.

Note: The positive tolerance of  the LiFePO4 cell capacity is not a cause for complaints.

Overview of support information for the LiFePO4 cell charging
Overview of FAQs related to charginghttp://gwl-power.tumblr.com/post/20369751437/   
Questions on charging LFP cellshttp://gwl-power.tumblr.com/post/22582172319/    
I want to make the initial charge of all the LiFePO4 cells to the same maximal voltage …. How can I do that?http://gwl-power.tumblr.com/post/46595246130/  
The single cells charges: 3.6V 5 Amp and 3.6V 18 Amphttp://gwl-power.tumblr.com/post/90848216126/ 

Overview of support information for the LiFePO4 cell charging

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.
http://www.ev-power.eu/Chargers-6V-to-36V/

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.

http://www.ev-power.eu/Chargers-6V-to-36V/

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.

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.

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.

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.

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.

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.
Controlling Analog Charger by BMS123
Many chargers supports communication with BMS over an analog ON/OFF dataline. This way the controlling of the charging process is enabled. The controlling is especially important during the final part of the charging process. When BMS detects high voltage at one of the cells, it is necessary to slow down the charging or stop the charging completely.
How to control a TC charger by BMS123 is included in user manual at the page 9 (http://www.ev-power.eu/docs/pdf/BMS123_Manual_v1_1.pdf) and it is very well working with our TC charger product line (http://www.ev-power.eu/Chargers-TC-1-5-kW/ or http://www.ev-power.eu/Chargers-TC-3-kW/).
Now now you can control also chargers which supports only ON/OFF function through the Wago connector (http://gwl-power.tumblr.com/post/13367362802/faq-rt-bms-connection-to-chargers-the-wiring-of). See the picture above for connection.
The complete drawing is available here: http://www.ev-power.eu/docs/web/BMS123-Analog-Charger.jpg

Controlling Analog Charger by BMS123

Many chargers supports communication with BMS over an analog ON/OFF dataline. This way the controlling of the charging process is enabled. The controlling is especially important during the final part of the charging process. When BMS detects high voltage at one of the cells, it is necessary to slow down the charging or stop the charging completely.

How to control a TC charger by BMS123 is included in user manual at the page 9 (http://www.ev-power.eu/docs/pdf/BMS123_Manual_v1_1.pdf) and it is very well working with our TC charger product line (http://www.ev-power.eu/Chargers-TC-1-5-kW/ or http://www.ev-power.eu/Chargers-TC-3-kW/).

Now now you can control also chargers which supports only ON/OFF function through the Wago connector (http://gwl-power.tumblr.com/post/13367362802/faq-rt-bms-connection-to-chargers-the-wiring-of). See the picture above for connection.

The complete drawing is available here: http://www.ev-power.eu/docs/web/BMS123-Analog-Charger.jpg

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 charger unit disconnects (stops) after reaching the full charge, it may be used with LiFePO4. It is a must to avoid the trickling charge mode.

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 charger unit disconnects (stops) after reaching the full charge, it may be used with 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: 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: 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