SYSTEMS AND METHODS FOR CONTROLLED BATTERY HEATING
Systems and methods for low temperature charging a battery, which may be performed alone or in combination with heating a battery. In some aspects, the low temperature charging method involves obtaining a susceptance response of a battery, and upon a change in the susceptance response of the battery, altering a charge signal to the battery. It is understood that changes in susceptance are correlated with phase changes of a battery electrolyte—e.g., as a battery warms from a low temperature where the electrolyte is partially or completely frozen (solid) to a higher temperature where it changes to a liquid state, there is a change in susceptance. As the electrolyte changes from solid to liquid as understood from a change in the susceptance response, the charge may be increased as the electrolyte thaws.
1 . A method of low temperature battery charging comprising:
obtaining a susceptance response of a battery, and
upon a change in the susceptance response of the battery, altering a charge signal to the battery.
2 . The method of claim 1 wherein the change in the susceptance response is correlated with a phase change in an electrolyte of the battery.
3 . The method of claim 1 wherein the susceptance response is a frequency of peak susceptance.
4 . The method of claim 3 wherein the change in the susceptance response is a change in a rate of change of the frequency of peak susceptance.
5 . The method of claim 2 wherein altering the charge signal comprises increasing a charge current magnitude when the susceptance response is correlated with a phase change to a liquid in the electrolyte.
6 . The method of claim 1 further comprising:
heating the battery with an alternating current waveform.
7 . The method of claim 6 wherein the alternating current waveform is a portion of the charge signal also including a direct current portion, and further comprising:
upon a change in the susceptance response of the battery, altering the charge signal to the battery by increasing a magnitude of the direct current portion of the charge signal.
8 . The method of claim 7 further comprising discontinuing the alternating current portion of the charge signal.
9 . The method of claim 7 wherein the direct current portion of the charge signal further comprises a shaped leading edge that transitions to the direct current portion.
10 . The method of claim 9 wherein the charge signal includes repeating charge waveforms comprising the shaped leading edge, the direct current portion and a rest period.
11 . A method of low temperature battery charging comprising:
obtaining a measurement indicative of a phase change in an electrolyte of a battery; and
upon identifying the phase change in the electrolyte of the battery, altering a charge signal to the battery.
12 . The method of claim 11 wherein the measurement is a temperature measurement.
13 . The method of claim 11 wherein the measurement is of frequency of peak susceptance.
14 . The method of claim 11 wherein the phase change is a change from a solid to liquid of the electrolyte as temperature increases.
15 . The method of claim 13 wherein identifying the phase change comprises identifying a change in a rate of change of the frequency of peak susceptance as the battery is warmed.
16 . The method of claim 11 wherein altering the charge signal comprises increasing a charge current magnitude.