SIMPLE EFFECTIVE LITHIUM ION (LFP) BATTERY MANAGEMENT!
Lithium Ion batteries require cell balancing during charging and protection from over-charge and over-discharge. This seemingly simple function is of utmost importance in mission critical environments. It is also one of the most difficult functions to achieve with absolute safety and reliability.
The EV Power Battery Balancing System has been developed specifically for large format Lithium Iron Phosphate (LFP, LIFEPO4) batteries such as Thunder Sky and Sky Energy (CALB) cells. It can also work with other LFP battery brands with minimal modification.
This system has been in continuous development for several years and has evolved to the point where we can claim it to be one of the most reliable and effective battery management systems available.
For pricing please check the webstore
The EV Power system consists of two main parts:
1) Cell Modules - one per cell, act as standalone shunt regulator balancers and link together to provide cell level voltage monitoring.
2) Battery Control Unit - one per battery pack, monitors the signal line to the cell modules and takes action to prevent charging or discharging if the heartbeat signal is broken.
All lithium Ion batteries require a battery management system (BMS). There is no way around this. There are numerous examples of catastrophic failures where no BMS has been used.
After several years of field testing we have established that at a minimum a BMS must have the following basic functions:
1) Balance the cells during charge to level the state of charge of all cells in the pack.
2) Protect each cell in the battery from going outside its safe voltage range.
The EV Power system is known as a distributed BMS. That is, the functionality is distributed across the battery, not centrally located.
EV Power BMS Features:
- Modular - one small balancing module bolts directly to each cell.
- Simple - A one wire interface is all that is required. No wiring birds nest.
- Scalable - Battery balancing from one cell up to any number.
- Fail Safe - the unique EV Power one wire current loop safety interlock system prevents any cell from going over/under voltage.
- Hermetically sealed - plastic encased cell modules resist dust and moisture
- Flexible - the master control unit can work with almost any charger.
- Reliable Analogue - analog electronic cell modules, no computers in high EMI environment. We have systems working for 5+ years already.
- Standalone - The EV Power BMS can be powered from the battery it protects. Most other BMSs require external 12V input for their power, adding more complication and unreliability.
- Safe Installation -Isolated signal wire connections.
- Easy Cell Status indication - LED indicators on each cell.
- Cost Effective - low cost per cell for large format Lithium Ion batteries. That said, we place quality before cost.
- Developed, patented, refined and manufactured in Australia since 2007. We innovate...
Low profile means no space is required above the actual cell bolts for the cell balancing modules. Please compare with other systems using PCBs attached to the cells.
Plastic encapulated circuitry protects cell balancing modules against dust and water. We believe in quality products!
Low quiescent current draw. Our new V8 cell module at 3.3V consumes just 2mA. At this rate it takes 10+ years to drain a 180Ah cell. Of course it will never overdischarge any cell because it switches off at 2.5V.
Try this with MiniBMS !!
There is a lot of hype about battery management systems for Lithium Ion batteries. Should a BMS have cell by cell voltage monitoring and reporting to a central display unit? Should cell temperatures be recorded and reported? Should the BMS be able to bypass large charge currents? What about active balancing and a CAN bus interface?
The answer is, NO. These functions are not essential.
Sophisticated BMS’s may provide an impressive list of functions but are prone by their very complexity to problems both in installation and usage.
SIMPLICITY = RELIABILITY.
SIMPLICITY = LOW COST
SIMPLICITY = EASY TO UNDERSTAND
The EV Power BMS is the simplest system in the world that will actually provide balancing and fail safe voltage protection of large format LiFePO4 batteries
Extra monitoring functions can be easily layered on top of a simple BMS. A simple BMS should form the core of any large format LFP battery.
Modern LiFePO4 cells are very safe and manufactured to close tolerances. With a BMS they will not explode or catch fire. They should be highly reliable and operate with the minimum of intervention from the BMS. It is there as the last line of defence.
The EV Power system designed for LiFePO4 cells of 40Ah and larger performs the basic functions simply and well. It does not rely on digital microcontrollers on each cell but to date has proven itself to be fail-safe and highly reliable. This has been proven in many road going electric vehicles which are demanding applications for a BMS.
Our cell modules are epoxy encapsulated against moisture and dust. This IS important because it is moisture and dust that will cause electrical problems in other systems down the track. Also important is that it does not rely on any connectors which can wriggle loose and fail. The EV Power BMS is a genuine one wire system where all the connections are soldered. It can monitor any number of cells in up to four banks and has provision for temperature monitoring also.
As well as high quality with gold plated terminal connectors it is reasonably priced. This is all you need in a BMS.
Q: ... what do think about Bottom Balancing LPF 100A/Hr Lithium Ion batteries? Your thoughts would be appreciated.
A: Bottom balancing would counteract what the BMS cell modules try to do as they will keep trying to balance at the top voltage. There is an idealogical point of view that if you bottom balance the battery pack it will never go out of balance and you won’t need a BMS. This is not based on evidence or on science and simply does not work in my experience. Judging by the number of people coming to us for a BMS for previously purchased cells it would appear that quite a number of customers agree.
Q: Why do I need a Battery Management system?
A: Lithium Ion batteries are made up of two or more cells connected in series. Each cell has a slightly different capacity due to manufacturing tolerances and environmental conditions. After several charge/discharge cycles the cells begin to go out of balance and so a balancing system is required to keep the cells all at the same state of charge. The BMS also prevents overcharge and overdischarge of any cell in the battery which is essential when using Lithium Ion batteries.
Q. Why does the EV2 master unit use the battery pack for its power. Why not 12V input so it can run off the vehicle auxiliary 12V supply.
A. It can be modified to run from any voltage 12V - 350VDC. However first and foremost it is most important that the cell module signal loop must be isolated from the master unit power input otherwise a signal wire accidentally contacting a battery terminal can make the 12V auxiliary system live at potentially fatal voltages. Some imitation BMS systems do not do this, dangerous!
Q: Why does the EV Power system use solder connections for the signal loop rather than removable terminals.
A: For complete reliability. The cell modules are there for the life of the battery so there is no reason to use removable lugs.
Q: What digital outputs does the BMS provide?
A: Most of our BCUs now support RS232 output of one record of status information per second.
Q. What charger should I use?
A: Almost any switchmode SLA charger with the correct peak voltage is suitable. However there may occasionally be problems with cell balancing due to the incorrect charge curve. Our dedicated LFP chargers are recommended.
Q: Will the BMS work if the batteries are in different locations around the car?
A: Yes... However, it is advisable to keep all the cells in one physical location if at all possible. Cable resistances, temperature and moisture differences in different locations of the car can result in unforseen problems and shortened battery life. This has nothing to do with the BMS, it is about design and common sense. Also placing batteries in car crumple zones SIGNIFICANTLY COMPROMISES SAFETY in the event of an accident. Remember that batteries are the fuel tanks of an EV and due consideration should be given to locating them, even at the expense of load space. It is also important to maintain weight distribution between the front and rear axles of a car.