Method and apparatus for ground fault detection in an electric work vehicle

1 . A method of performing a ground fault test on an aggregated battery of an electric work vehicle, the aggregated battery comprising a plurality of battery packs,

wherein the electric work vehicle comprises an isolation monitor and a circuit configured to connect the aggregated battery to the isolation monitor, wherein the circuit comprises a plurality of contactors configured to facilitate connection to the circuit and disconnection from the circuit of each of the plurality of battery packs, wherein the isolation monitor is integrated within the electric work vehicle and connected to a chassis ground of the electric work vehicle,

the method comprising:

detecting with the isolation monitor an existence of a ground fault;

notifying a user of the electric work vehicle of the existence of the ground fault;

opening the plurality of contactors;

sequencing closure of the plurality of contactors to include each of the plurality of battery packs in the circuit with the isolation monitor, and using the isolation monitor to determine that at least one battery pack of the plurality of battery packs that is included in the circuit with the isolation monitor comprises a faulty battery pack, wherein the faulty battery pack comprises a ground fault; and

disconnecting the faulty battery pack or battery packs.

2 . The method of claim 1 , wherein the method further comprises, prior to sequencing closure, determining that the ground fault is in at least one battery pack of the plurality of battery packs.

3 . The method of claim 2 , wherein determining that the ground fault is in at least one battery pack of the plurality of battery packs comprises closing the plurality of contactors to include all of the plurality of battery packs in the circuit with the isolation monitor.

4 . The method of claim 2 , wherein determining that the ground fault is in at least one battery pack of the plurality of battery packs comprises opening the plurality of contactors to include none of the plurality of battery packs in the circuit with the isolation monitor.

5 . The method of claim 2 , further comprising notifying the user of which battery pack of the plurality of battery packs is the faulty battery pack or battery packs.

6 . The method of claim 2 , wherein the battery packs of the plurality of battery packs are connected in parallel.

7 . The method of claim 2 , wherein the electric work vehicle further comprises a battery management system and a controller area network, and wherein the isolation monitor communicates with the battery management system over the controller area network.

8 . The method of claim 2 , wherein the electric work vehicle comprises a machine power electronics apparatus that comprise the isolation monitor.

9 . The method of claim 2 , wherein sequencing closure of the plurality of contactors comprises including only one of the plurality of battery packs in the circuit with the isolation monitor at a time.

10 . The method of claim 2 , wherein prior to sequencing closure of the plurality of contactors, the method further comprises sequencing closure of the plurality of contactors to include more than one of the plurality of battery packs in the circuit with the isolation monitor at a time, and using the isolation monitor to determine whether the battery packs that are included in the circuit with the isolation monitor comprise a faulty battery pack.

11 . The method of claim 2 , wherein the method further comprises, after disconnecting the faulty battery pack, determining with the isolation monitor that an additional ground fault exists in the electric work vehicle.

12 . A ground fault test apparatus for an electric work vehicle, wherein the electric work vehicle comprises:

an aggregated battery comprising a plurality of battery packs;

a battery management system;

an isolation monitor; and

a circuit configured to connect the aggregated battery to the isolation monitor,

wherein the circuit comprises a plurality of contactors configured to facilitate connection to the circuit and disconnection from the circuit of each of the plurality of battery packs;

wherein in response to the isolation monitor detecting an existence of a ground fault, the ground fault test apparatus is configured to:

notify a user of the electric work vehicle of the detection of existence of a ground fault;

use the battery management system to:

open the plurality of contactors of all of the battery packs;

close the plurality of contactors of a first subset of the plurality of battery packs to determine that the first subset excludes a faulty battery pack; and

sequence closure of the plurality of contactors to include each of the plurality of battery packs of a second subset of the plurality of battery packs in the circuit with the isolation monitor in turn, and use the isolation monitor to determine that at least one battery pack of the second subset of the plurality of battery packs that is included in the circuit with the isolation monitor comprises the faulty battery pack, wherein the faulty battery pack comprises a ground fault; and

disconnect the faulty battery pack.

13 . The ground fault test apparatus of claim 12 , wherein the electric work vehicle further comprises a battery management system and a controller area network, and wherein the isolation monitor communicates with the battery management system over the controller area network.

14 . The ground fault test apparatus of claim 12 , wherein the ground fault test apparatus is further configured to output an identification of the faulty battery pack.

15 . The ground fault test apparatus of claim 12 , wherein the ground fault test apparatus is further configured to determine whether there is an additional ground fault after disconnecting the faulty battery pack.

16 . A method of performing a ground fault test on an aggregated battery of an electric work vehicle, the aggregated battery including a plurality of battery packs, the electric work vehicle including an isolation monitor and a circuit configured to connect the aggregated battery to the isolation monitor, the circuit including a plurality of contactors configured to facilitate connection to the circuit and disconnection from the circuit of each of the plurality of battery packs, the method comprising:

detecting an existence of a ground fault with the isolation monitor;

closing the plurality of contactors to a first set of battery packs of the plurality of battery packs in the circuit with the isolation monitor;

determining with the isolation monitor that the first set of battery packs does not include a faulty battery pack;

closing the plurality of contactors to a second set of battery packs of the plurality of battery packs in the circuit with the isolation monitor;

determining with the isolation monitor that at least one battery pack of the second set of battery packs includes a faulty battery pack experiencing a ground fault;

sequentially opening and closing the plurality of contactors to each of the battery packs of the second set of battery packs, to determine that at least one battery pack of the second set of battery packs is a faulty battery pack; and

disconnecting the faulty battery pack.

17 . The method of claim 16 , further comprising outputting a notification identifying the faulty battery pack.

18 . The method of claim 16 , wherein either i) each of the first set of battery packs and the second set of battery packs includes a same number of battery packs, or ii) one of the first and second sets of battery packs includes one additional battery pack than the other of the first and second sets of battery packs.

19 . The method of claim 16 , wherein disconnecting the faulty battery pack includes opening the contactors to disconnect the faulty battery pack from the circuit.

20 . The method of claim 16 , further comprising:

after disconnecting the faulty battery pack, permitting operation of the electric work vehicle with power stored in the battery packs other than the faulty battery pack.