WirelessCharger 3.0

Whenever the "Start of charge" conditions are met, WirelessCharger 3.0 starts delivering the current target as set within the chosen mode of operation. The MPU output current ramps up very quickly and runs through the battery, which sets the charging voltage (a low state of charge leads to a smaller internal resistance and to a smaller voltage). The charging voltage is a constant feedback for the charging process which will let the current reach its target as long as the set voltage threshold is not reached. 

• Constant Current phase (CC): When the battery is discharged, the MPU delivers the target current and the charging voltage is set by the battery internal resistance. When the battery is being charged, its internal resistance increases, hence increasing gradually the measured charging voltage. 
• Voltage Threshold: It is the pivot point from which it is important to reduce the charging current, so as to limit the charging voltage and in order not to go beyond the battery datasheet voltage limit. The voltage threshold in many cases is approximately the voltage reached at 80% SoC. 
• Constant Voltage phase (CV): When the battery is charged at more than 80%, the charging voltage is about to go beyond the voltage threshold, then WirelessCharger 3.0 behaves like a voltage regulator and reduces the MPU current output, just as needed, to keep the charging voltage below the voltage threshold. As the charging process keeps on going, the battery internal resistance keeps on rising, therefore WirelessCharger 3.0 keeps on reducing the charging current, until a stop condition is met. Charging during CV phase is slower.

The safest recommended settings are those exchanged directly between a Battery Management System (BMS) and the MPU in the frame of a BMS-only mode of operation: the battery permanently tells the charger what it needs, via a CAN communication. Other settings are possible, by using other modes of operation. It is important to refer to the battery manufacturer datasheet and to follow the recommended values for the charging current and the charging voltage: this will preserve the battery life cycle number and will avoid any hazardous situation:

• Charging current setting must always be below the maximum charging current value stated in the battery datasheet. 
• Voltage threshold setting should always be below the maximum voltage value stated in the battery datasheet. 
• Overvoltage setting should preferably be below the maximum voltage value stated in the battery datasheet, and at a value strictly above the Voltage threshold setting.

WirelessCharger 3.0 is based on charging stations compatible with all MPUs, whatever the types of batteries, the types of vehicles, or the selected mode of operation. The same charging station can charge a Li-ion battery right after it has charged a lead acid battery on a different type of vehicle in the same plant. 

Only the total number of vehicles and their need for recharge should be considered for an evaluation of the needed number of charging stations. 

There are applications requiring one charging station for each vehicle. Other applications can cope with one charging station for four vehicles. On average, there are two to three vehicles for each charging station.

The Battery Management System (BMS) is a specific piece of hardware in all Li-ion batteries. It does not exist in Lead Acid batteries. It aims at, among other things, balancing and protecting the battery cells and, in most cases, at communicating with the charger so as to get the proper charging current at all SoC levels, avoiding any battery hazard and maximizing the battery life cycle number.The communication of a BMS and a charger is defined by a protocol which goes up to the definition of specific bytes in a set order (e.g.: current, then voltage, then SoC, then temperature, etc ) 

A battery with a CAN 2.0B port might or might not be compatible with WirelessCharger3.0. CAN 2.0B port: it all depends on the data definition (the data matrix) which should match the ones embedded in the charger. If needed, the BMS data matrix could be updated (please refer to battery supplier) to match one of the protocol options provided with WirelessCharger 3.0. Alternatively, the BMS can speak to the PLC/VCU via CAN 2.0B so that the PLC/VCU instructs the MPU via Ethernet in PLC-only Mode. 

The many options of protocols and the many modes of operations available with WirelessCharger 3.0 grants you the maximum range of options for a suitable charging solution of your own. Should your needs vary from the ones implemented, please do consult us for additional options.

Full charging: The charging process is performed with little time constraints. It goes through the entire CC and CV charging phases, in order to reach close to 100% SoC at the end of the charging process. 

Opportunity charging or "In-Process" charging: Additional charging stations are available to perform charging during a rather short period of time, at quite a high current, when a vehicle is idling in between two tasks to perform. The benefits are real with a fast starting charger like WirelessCharger 3.0, and it is usually preferred for batteries which are not charged to more than 80% SoC. 

Intermediate charging: The charging process is set to keep the battery partially charged, as only a fraction of the battery capacity is intended to be used (small Depth of Discharge, or DoD). Charging a battery at less than 80% SoC could significantly improve its life cycle number, but will require more frequent charging sequences, all in CC phase with a shorter charging time (compared to the longer charging of the CV phase). 

The final choice of the charging sequence(s) depends on many factors related to the application needs and the hardware involved. It is specific to each application type and each vehicle design, but it is mostly a system software management topic.

There is no magnetic field around a stationary pad as along as it is not facing a mobile pad: this is impossible. Indeed, a condition for WirelessCharger 3.0 to start its operation is the establishment of a communication between the mobile electronics (MPU) and the charging station (IPS), which can be performed only if there is a close proximity of two pads with a proper alignment. This is a specific safety design of WirelessCharger 3.0, which is independent from any radio system and therefore not subject to any radio interference while in operation. 

There is a magnetic field around the pads when power is being transferred. As our designers are well aware of this, they worked out a field strength which does not exceed the legal limits and recommendations as given i.e. by the ICNIRP (International Commission for Non-Ionizing Radiation) in 2010. 

The ICNIRP recommendation is  recognized worldwide and the basis for most national legislation and standards. The fields are not to be compared with radio waves as occurring in radio communication or with mobile phones: these are electro-magnetic waves designed to be sent out to bridge large distances. It must also be noticed that magnetic fields, as used in WirelessCharger 3.0 as means for power transfer, are linked to their source, so they are always limited to the very proximity of the pads.

Most types of batteries can be used with WirelessCharger 3.0 (Lead Acid, Li-ion NMC, Li-ion LFP, etc). Batteries with or without communication port can be used as well. Accumulators can of course be used, as this should be the suitable name to use as we speak of rechargeable energy storage solutions, but generally speaking the word "battery" is being used in the industry. So let’s keep speaking of "batteries" instead of “accumulators”. 

A few battery manufacturers restrict the charging possibilities by imposing a communication byte to be activated (via CAN), hence reducing the modes of operation options to BMS-only Mode or BMS&PLC Mode.