DC Power connectors - Anderson Type 50A and 120A
Check our new offer of the DC power connectors. We offer the popular “Anderson” type 50A and 120A connectors with several different voltage marking:
How does the CBM work if the charging current is higher than the balancing current?
The balancing current of the CBU module is about 1.7A. If the charging current is higher than the balancing current, the voltage will continue to increase gradually. If the charging current is lower than the balancing current, the voltage will decrease slowly.
The diagram shows that the balancing of the CBU starts at 3.67V and the voltage is reduced to 3.64V and does not keep increasing as fast as without the balancing. However the charging current is 2A while the balancing current is 1.7A so the voltage starts increasing slowly again. This is a proper way the CBM operate when the balancing the cells.
FAQ: How to connect the small cylindrical cells together?
Answer: First never try to solder the contact to these cells. You are sure to damage the cell by over heating. Any temperature above 70*C is damaging to the cells! Without professional soldering equipment it is not possible to make the connection.
We suggest using the round-cell battery holders. The holders for big „D“ size cells can fit some of the cell. The contacts for the holders for the lithium cells can be purchased form a local electronics shop (check the German Conrad as an example).
See the photos of some possible solutions.
Q: I am using a new laboratory Power Supply (PS). This PS is able to charge to a max. of 30 Volts and a current of max. 10 Amp. What I do is setup the PS to 4 Volts and 3 Amp. At the end of the charging, the PS automatically reduces the current to 0.01 Amp.
This is 100% correct. For large capacity cells (40AH and more) you can even charge with the full power (of 10A current), there is no need to reduce the current to 3 Amp.
During the final stage of the charging, when the cells is “full” it does not absorb any more energy and the current will decrease to a very small value. The charging can be stopped when the current is 1% or less of the nominal capacity (1% of 40AH cell is 0.4A).
The voltage of 4V should not be kept at the cell terminals after the current has already dropped; the power source needs to be disconnected. After the charging is finished and the PS is disconnected, the voltage of the cell will drop back to some 3.40V ~ 3.20V after some period of time.
Q: Please explain how you can charge a cell to 4.00V volt. And why some people suggest charging to 3.65 Volt.
We recommend to reach 4.0V for the initial charge. The 3.65V is a usual charging level for the regular operation of the cells. This means after you make the initial charge to 4.00V you continue to use the cells and charge to 3.65V (or 3.80V or some similar level) for the regular operation. Simply said charging to a lower level will extend the cell’s total life span (in number of cycles).
Q: What is the maximal allowable voltage difference between the cells, to see it was fully balanced?
There is not any difference to measured. All cells must be charged to the same level (e.g. 4.0V or 3.8V or 3.65V) after they reach this voltage level and stop absorbing the current (the 1% limit), they are fully charged.
After the charge voltage disconnection, the cells drop the voltage back to the nominal level 3.2V. Each cell may go its own way (speed), but after starting to be under load, they should match the voltage approximately again.
For large quantity of cells, you may wish to charge many cells at the same time using high current chargers.
See an example here:
http://gwl-power.tumblr.com/post/3297893710/the-charging-12-pcs-of-20ah-cells-the-initial
You can also charge single cells with a charger that allows charging the single cells with 3.65V
http://www.ev-power.eu/Chargers-6V-to-36V/Charger-3-6V-6A-for-LiFePO4-cells-1-cell.html
Internal Resistance of the Winston Battery Cells
Study the official document with the information about the internal resistance of the LiFeYPO4 cells produced by the Winston Battery.
Check the explanation of what the internal resistance is together with a demonstration test.
Such connection is not recommended and may not work properly. There are several reasons.
The danger of deep discharge of the battery after the charging is finished. Most chargers have some minimal consumption when connected to the battery. If the charger is left connected for a long period of time, the charger may discharge and deplete the battery completely.
Need to reconnect to resume function. Most chargers need to reconnect to resume the charging function. If the charger is connected permanently it will not resume charging unless the terminals are disconnected for some time and connected again.
The danger of an accident. The charger’s electronic may not be designed to be permanently connected to the battery if not charging any longer. After some time some components may overheat or become defective. In any case, we always recommend having proper fusing and disconnection option for any cabling connected to batteries. This allows disconnecting the batteries in case of an accidental short circuit connection or malfunction.
An idea: to allow repeated charging of batteries without the need for manual reconnection, the hint may be to use some timer device that will connect the batteries to the charger to allow the charging. However again we give the warning, that any battery charging must be properly monitored by a human operator.
Question: My mistake I discharged my battery pack very low voltage and the cells are misbalanced. I think the RT-BMS system does not work properly. What shall I do?
Deep discharge: please avoid the deep discharge of the battery pack at any case. You need to monitor the battery pack continually to protect against such deep discharge. You should stop using the pack when the voltage gets too low. You should disconnect the pack from the load in case the pack will be left unattended for a longer period of time. You should never operate the equipment with no supervision.
RT-BMS operation: the RT-BMS system CBU modules measuring input is powered from the cell voltage. If the voltage of the cell drops too low, the CBU unit does not work properly. See the BMS instruction document, page 2: „Operating voltage of the measured cell min 1.8V. max 5.0 V“. In fact the BMS units (CBU modules) may not work reliably under 2.0V! The CBU will stop working with 1.8V and less. The BMS cannot report correct values for these under-voltage cells.
Restoration of the battery pack: you need to charge the cells one by one slowly, to restore the capacity and to get the battery pack balanced again. Check the instruction about:
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
The cells must be charged individually to full voltage level (typically 4.0V) before assembling the battery pack. This way the cells will be fully charged and balanced before the first use of the battery pack and there will be no need to balance the cells using the BMS with balancing. source
Using 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). source
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. source
Battery Charging Guidelines as published by Sinopoly
The charging diagrams (in PDF file) show the steps of the charging process for the best state-of-art charging process.
The CellLog8s has a bug in the firmware. I’ve contacted the OEM via a radio-controlled model forum and he provided me with an updated firmware (v2.08). The problem with the original firmware was that the alarm output from the cell / pack alarms did not trigger reliably when beyond the set points.
The CellLog8s also has a hardware bug in it that causes a cell load imbalance when used with more than 6 cells. As delivered from the factory, it draws power from only cells 1-6 for the CPU and display. So cells 7 and 8 would gradually go out of balance with cells 1-6. The makers posted a picture of a hardware modification (adding a wire jumper) that cures this so that all 8 cells are drained equally. Unfortunately, it then does not work with 2 cells only after the mod (but I’m always going to be monitoring 8 cells so that’s ok). They also posted an optional modification to replace one SMD resistor to reduce power consumption when using more than 6 cells. I’ve made both of these modifications.
http://www.rcgroups.com/forums/showpost.php?p=13452879&postcount=143
I’m using the CellLog8s alarm output with some external relay logic to provide an ENABLE/DISABLE input to the AC inverter load. All AC inverters are designed for lead acid batteries and their Low Voltage Disconnect (LVD) settings are too low for lithium batteries (21V on a 24V battery inverter). So I use the CellLog8s to send a DISABLE signal to the inverter when the pack Voltage reaches either 24.0V or any one cell in the pack reaches 3.00V. That guarantees that the battery isn’t discharged by more than 90% in normal use. The system then has to be manually reset by pressing a button on the relay logic controller, which provides an ENABLE signal to the inverter. This allows the normal remote control for the inverter to send a START command. The reset button cannot work until the CellLog8s alarm condition is cleared (by recharging the battery) so even if you try to force the load to restart, it cannot until the battery has been recharged enough.
FAQ: What is the charging voltage of the 12V battery? 16V or 14.4V?
Question: Some web pages and the GWL blog says that the final voltage of the charge for 12 LP battery is 16V. But some other pages and some charger specifications give information about charging to 14.4 ~ 14.6V. What is the difference?
Answer: The maximal charge voltage for the LiFePO4 technology is 4.00 per cells (16.00V per battery). This is the recommended charge voltage for the initial charging to balance all the cells to the same full level. Check the explanation here.
However for the long term use it may be better not to charger to full, but to charge to a lower voltage to get the maximal life-span. For example charging to 3.65V per cell is considered to be around 85% charge. It works very well for 1000, 2000, 3000 and more cycles. That is why some of the chargers (example the TC-Charger models) charge only to 3.65 V per cell (14.6V per battery). See the additional information at this post.
FAQ: How should the PCM battery be protected against improper use?
Even though the PCM battery does contain the PCM board (Protective Circuit Module), the purpose of the PCM board is not to be used instead of the proper battery protection. The battery with the PCM needs to be protected as any other lithium battery.
Proper fusing – it is necessary to protect the battery against accidental over discharge by a proper fusing. Using a proper fuse protects not only the battery but also it protects the equipment, as the fusing does not allow too high currents to pass through the device in case of a failure. You should always install a proper fuse to protect the battery. (For example for a 12V/100W equipment you should install a 10AMP fuse. For the 12V batteries it is easy to use the 12V fuses manufactured by the automotive suppliers.)
Deep discharge protection - As indicated in the specification file, the deep discharge voltage for the 12V PCM battery is set to 10V. You need to install battery-monitoring equipment to disconnect the load from the battery if the voltage drops to the 10V level. You should not rely on the PCM board only. The PCM board is only a last instance serving as a additional (backup) protection in case of the failure of the main protection against deep discharge. (See also here)
Over charge protection - The maximal voltage for the PCM battery is given as 14.6V. To protect the battery against overcharge, you should install a over charge protection that will disconnect the charging source from the battery when the maximal voltage is over-reached.
Over heating protection - The PCM module inside the battery can be over heated during high current discharge/charge or during the balancing of the cells. The battery should not be operated in unventilated enclosures that do not allow for the release of the heat. If the battery is mounted in an enclosure, proper ventilation must be insured.
Fire protection - no matter what kind of equipment you may be using, you always need to consider the fire protection. The batteries should be never used in places where some flammable gases may cause explosion. When using the battery, the battery should not be placed close to flammable substances, like paper, plastics, wood or other materials. Any kind of battery should be installed in fire proof cabinets to protect from fire in a case of a battery failure or an accident. We strongly recommend to install fire alarms at any place where batteries are charged and discharged. Please remember the fire is a good servant but a very bad master!
FAQ: Can a battery be charged when being discharged?
Answer: If the charging current is higher than the discharge current, it is possible to charge the battery when being under load. When charging the charging current will be first consumed by the load and only the current in extra will be used to charge the battery: Example: the discharge current is 4 Amps, the charging current is 5 Amps. The effective charging for the battery will be the difference: 1 Amp.
Wind Power Energy Output and Force Calculation
What is the energy output a wind turbine can generate? What is the force the mast (pole; holder) of the wind turbine must withstand during strong winds? Check our interactive XLS to see the answer.
FAQ: CAN Bus equipment operation
Question: I have a BMS with CAN option. I have a battery charger with CAN connector, I also have a dash board (display unit) with CAN option. How can I make these components work together over the CAN bus?
Answer: In most cases you need a master CAN bus unit to make the equipment work together. Most of the CAN bus equipment is only either sending data (Read Only mode) or receiving commands (Write Only mode). This equipment has no additional logic to make decisions of operation for other equipment or to control it. The logic of the operation must be set by the master CAN bus unit.
Example: BMS system is sending data (about the status of the battery pack). A ventilator with CAN input is only receiving data (turn on/off and the rotation speed). The BMS itself cannot manage the ventilator. There must be the CAN BUS master unit to process the data from the BMS over CAN and to decide if the temperature is over the limit and when the ventilator is to begin the operation. Then the CAN bus master unit i will send data to the ventilator over the CAN bus.
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