Off-Board versus On-Board Battery Chargers
Depending on their power requirements, LEV batteries can be charged either directly from the grid (i.e. any standard wall outlet) through a dedicated on-board charger or through the use of a low cost off-board charger.
Off-board chargers are more suitable if:
- The LEV can be easily located / moved close to the charger (even with an empty battery!) (i.e. e-bikes, folding e-scooters)
- The LEV battery does not require a complex battery management system, e.g. low cost sealed lead acid (SLA) batteries (i.e. low cost scooters, electrical wheelchairs
- Whenever charging requires very high power, because of limitations of weight/volume on the vehicle itself - as is the case for electrical forklifts
AC on-board chargers are more suitable if:
- More flexibility in charging is needed (no special infrastructure has to be installed, no need to carry additional charging equipment) (i.e. low speed EVs (quadricycles), golf carts, small electric lift trucks)
- More complex battery management systems are used, e.g. for Lithium ion batteries (i.e. high power e-scooters)
The on-board charger's performance is evaluated by its power-conversion efficiency and power quality (i.e. total harmonic distortion and power factor). As for all items installed in the vehicle, size (the smaller, the better), weight (the lighter, the better), and lifetime (the longer, the better) are critical parameters. Conventional on-board chargers usually have a two-stage structure consisting of a power factor correction (PFC) stage and a DC-DC power-conversion stage. This specific structure brings along major drawbacks such as low efficiency and circuit complexity, and a bulky intermediate DC link capacitor. Due to high current flowing through the intermediate DC link capacitor significant power loss is caused, what considerably reduces the capacitor lifetime, eventually leading to capacitor failure. As an alternative to the two-stage structure single-stage approaches are being investigated with the aim to eliminate the PFC stage and reduce the DC link capacitance.
Energy Efficiency – Critical Factor with Further Pick-up in Sales
At this moment, the battery charger market for LEVs is mostly cost driven, as the majority of LEVs sold today are low cost two- and three-wheelers. However, considering that the number of LEVs is expected to grow further, the efficiency becomes particularly important. Especially in countries with weaker power grids every percentage point of efficiency increase translates into significant energy savings. A noteworthy relief of the national power networks!
Infineon’s LEV Battery Charger Solutions
Infineon's LEV on-board and off-board battery charger solutions comprised of power MOSFETs, gate driver ICs, PWM/flyback controllers, integrated power stage ICs and microcontrollers are optimized to fit any system. In order to satisfy as many customer requirements as possible different topologies are available and meeting a variety of cost / performance optimization targets is possible.
Customers benefit from small form factors, best-in-class performance ratio (attractive pricing with competitive long term price down roadmap), easy-to-use technologies, powerful and reliable components.