22.3 All-Electric Equipment: Batteries, Charging, Drives & Diagnostics

All-Electric Equipment: Batteries, Charging, Drives & Diagnostics

All-electric equipment replaces the combustion engine with stored electrical energy and electric drives, but hydraulic, thermal, mechanical, and stored-energy hazards remain. Machines may use traction motors, electric implement drives, electro-hydraulic pumps, or several coordinated motors.

Map the Powertrain

A system may contain a high-voltage battery; battery-management and cell-monitoring units; current, voltage, and temperature sensors; service disconnect; fuse; positive/negative contactors; precharge resistor/relay; DC link; inverters and motors; DC/DC converter; charge inlet/controller; and thermal circuits.

The BMS estimates state of charge from current, voltage, temperature, and learned capacity. State of health describes degradation of capacity or power. Cell imbalance is the spread among groups, not low total charge. Insulation status describes separation from chassis. Keep these quantities distinct.

At key-on, controls check low-voltage supply, emergency stops, interlocks, isolation, temperature, and communications. Precharge raises DC-link voltage before main contactors close. A resistor, contactor, inverter, interlock, communication, or 24-volt fault can prevent ready mode.

Charging

A machine may use onboard AC charging, offboard DC charging, or battery exchange. Power conductors and pilot/communication circuits coordinate connection, allowable voltage/current, battery temperature, isolation/earth conditions, and contactors.

For no-charge, determine whether charging never begins, stops, is slow, or derates hot. Check:

• supply/protection, connector condition, contamination, lock, and cable temperature;
• pilot/communication and charger faults;
• state of charge, cell temperature/spread, insulation, and BMS limits;
• pumps, valves, fans, heaters, chillers, coolant, and ambient restrictions;
• onboard-charger input/output or offboard handshake;
• software, schedules, and operator settings.

Do not force contactors or defeat locks. A full, cold, hot, imbalanced, or isolation-faulted battery may correctly request zero current.

Charging adds an external source to high-voltage isolation. Secure the external supply and account for bidirectional/auxiliary paths. Only qualified workers open high-voltage enclosures, using the same absence-of-voltage discipline described for hybrids.

Propulsion, Implements, and Regeneration

For no-propel or derate, review faults, torque commands, motor speed/current, DC voltage, temperatures, derate reason, brake/neutral/seat inputs, and mode status. After safe isolation, inspect cooling and connections. Thermal derate can result from blocked exchangers, low coolant, pump/valve faults, air, sensors, or excessive mechanical load.

Inverters create controlled multi-phase AC. Resolver/encoder faults can cause shutdown or rough torque without motor mechanical failure. Bearings, reduction gears, parking brakes, and driven pumps still need conventional diagnosis.

Regeneration converts kinetic or potential energy to electricity. It may be limited by full charge, battery temperature, traction, component heat, or faults. Foundation braking must still function; changed retarding feel is a system symptom, not proof the friction brakes failed.

Damaged Batteries

Crush, penetration, short circuit, heat, or improper charging can make lithium-ion cells vent or enter thermal runaway. Warning signs include rising temperature, unusual odour, hissing, smoke, popping, leakage, swelling, or repeated isolation faults. Do not casually open or touch the pack.

Activate the OEM/site emergency plan, isolate the area, call the required specialists, and monitor from the specified safe location. Re-ignition can occur after smoke stops. Quarantine, cooling/suppression, lifting, packaging, transport, and storage depend on chemistry, damage, charge state, and dangerous-goods rules. Never ship a damaged pack as ordinary scrap.

Recommission

After approved repair, inspect seals, vents, fasteners, connectors, supports, cooling, and interlocks. Restore in sequence while monitoring isolation, precharge, contactor feedback, cell spread, temperature, DC-link voltage, and DC/DC output.

Verify charging as applicable, propulsion both directions, implements, service/parking brakes, regeneration, thermal control, emergency stops, displays, and alarms. Confirm faults do not return and software matches the machine. Document measurements, parts, battery handling, and tests.

Separate No-Ready, No-Charge, and Reduced-Power Faults

These complaints can share warning messages but follow different enable paths. For no-ready, verify the low-voltage wake-up sequence, emergency and operator inputs, interlock loop, isolation result, precharge rise, contactor commands/feedback, and communications. For no-charge, add external supply, protective earth or isolation, connector lock, pilot communication, BMS charge permission, and charger conversion. For reduced power, focus on active derate reasons, component temperatures, battery power limits, inverter current limits, mechanical load, and cooling performance.

Trend related values rather than viewing one snapshot. A cell group that reaches the upper limit early may stop charging even when average pack voltage looks normal. A weak low-voltage battery may collapse only when pumps and contactors are commanded. A cooling pump can report commanded on while flow remains absent. Compare request, response, and physical result.

Do not replace a battery solely from one state-of-health estimate. Confirm the approved capacity or power test, temperatures, calibration state, usage history, and warranty procedure. Likewise, never clear a crash or isolation event merely to see whether the machine moves.

When towing, lifting, or recovering a disabled electric machine, account for motor-generated voltage, electric parking-brake release, gear-reduction damage, battery location, and the manufacturer's recovery points. Secure the machine and damaged energy storage before transport. Electric diagnosis ends with safe logistics as well as restored function.