The University of Auckland

Project #60: Versatile IPT Battery Charger



This project builds on a project run two years ago for a battery charger using IPT techniques to charge a multi-cell battery with a constant current/constant voltage method giving exact cell equality with no requirement for an independent cell management system.  The battery was a low voltage lithium ion battery (super capacitors were used for safety reasons) being one cell in a multi cell battery system.

In this new project the technique is expanded in two ways – the project can be run in two separate groups if required.  The first group extends the number of cells to be charged at any particular time and usually this would be the number required to get a cell balanced battery at 200-400V.  All the circuits in this development run at the same frequency that could be anywhere from 20 kHz to 85 kHz.  This has never been done before with this technology and for safety reasons the development will be at a lower voltage.  In a separate development with a second group, large electrolytic capacitors are used to give a battery distributed along 100m of IPT track with enough energy to be suitable for charging the battery in an ev while it is in motion along that track.  The electrolytic capacitors are spaced 1-2 m apart and as the vehicle passes over them these are discharged and the energy released is realised into the battery in the vehicle.  To get a good lifetime from the electrolytic capacitors the depth of discharge is restricted to 20% so that only 65% of the energy is used which makes recharging them a lot easier.  This system uses multiple frequencies where the track frequency differs from the charging frequency, and differs from the IPT coupling frequency … as required for different applications.


A working distributed power system/Battery Charger.









Lab allocations have not been finalised