Heating of batteries using reactive power
View Patent ↗A circuit and method are provided for allowing self-heating of a battery used to power an AC motor by way of connection to a DC to AC inverter circuit. The inverter is selectively controlled to generate a heating mode AC current at the DC side connection to the battery, wherein the heating mode AC current is formed substantially of only a reactive AC current component and substantially no DC current component. In accordance with another aspect, the heating mode AC current is generated to fill the idle time in the operation of the battery.
1. Apparatus for heating a battery used for providing electrical power to a vehicle, the apparatus comprising:
an inverter circuit electrically connected to an electric motor and the battery for generating an AC output based on a DC output from the battery; and
a controller arranged to selectively control the inverter circuit to generate a heating mode AC current at the connection to the battery, the heating mode current comprising a reactive AC electric current component and substantially no DC electrical current component, wherein when received by the battery, the heating mode AC current will cause the battery to internally self-heat.
2. The apparatus of claim 1 wherein the controller is arranged to cause the inverter circuit to generate the heating mode AC current during an idle time in the operation of the battery.
3. The apparatus of claim 1 wherein the battery comprises a series connection of a plurality of battery cells, wherein the inverter circuit is connected to the plurality of battery cells without a center tap.
4. The apparatus of claim 1 wherein the inverter circuit comprises a capacitor connected across the connection to the battery, the apparatus further comprising a switch arrangement connected in series with capacitor, the switch arrangement being controlled to be open when the inverter is generating the heating mode AC current to prevent the capacitor from being shorted by the heating mode AC current.
5. A circuit for powering an electric motor comprising:
an inverter circuit electrically connected to the electric motor on an AC side of the inverter circuit, and a battery on a DC side of the inverter circuit; and
a controller arranged to selectively control the inverter circuit to generate a heating mode AC current at the DC side comprising a reactive AC electric current component and substantially no DC electrical current component, wherein when the heating mode AC current is present on the DC side, the heating mode current will cause the battery to internally self-heat.
6. The circuit of claim 5 wherein the controller is arranged to cause the inverter circuit to generate the heating mode AC current during an idle time in the operation of the battery.
7. The circuit of claim wherein the battery comprises a series connection of a plurality of battery cells, wherein the inverter circuit is connected to the plurality of battery cells without a center tap.
8. The circuit of claim 5 wherein the inverter circuit comprises a capacitor connected across the DC side, the circuit further comprising a switch arrangement connected in series with capacitor, the switch arrangement being controlled to be open when the inverter is generating the heating mode AC current to prevent the capacitor from being shorted by the heating mode AC current.
9. A method for self-heating a battery used to power an AC motor by way of connection to a DC to AC inverter circuit, the method comprising:
determining temperature conditions indicative of a need to heat the battery;
controlling operation of the DC to AC inverter circuit so as to produce a heating mode AC current at the connection to the battery, the heating mode AC current comprising substantially only a reactive AC current component and substantially no DC current component; and
supplying the heating mode AC current to the battery until a desired internal battery temperature is reached.
10. The method of claim 9 further comprising controlling the generation of the heating mode AC current so as to be timed to be supplied to the battery during an idle time in the operation of the battery.
11. The method of claim 9 wherein the battery comprises a series connection of a plurality of battery cells, and the method includes connecting the inverter circuit to the plurality of battery cells without a center tap.
12. The method of claim 9 wherein a capacitor is connected across the connection of the inverter circuit to the battery, the method further comprising protecting the capacitor from being shorted by the heating mode AC current by opening the connection to the capacitor.