Symptoms & Identification
The machine is completely dead. The charger is plugged in, but instead of a solid red or green light indicating a charging state, you see it alternating between red and green. This confirms the charger sees the battery pack but refuses to initiate a charge cycle due to low voltage.
- Symptom: Charger flashes alternating red and green lights.
- Symptom: Machine is unresponsive (no drive, no lift).
- Symptom: Battery hydrometer "eye" may show black (discharged) or clear/white (low electrolyte).
Tools Required
- Digital Multimeter
- Insulated Wrench Set (for battery terminals)
- Battery Terminal Cleaning Brush
- Battery Hydrometer or Refractometer
- Electrical Contact Cleaner
Safety Warning
Disconnect the main negative battery terminal before testing or cleaning connections. A wrench slipping between the positive post and the frame can cause a dangerous arc flash. Chock the wheels and ensure the machine is on a level surface.
The Technical Guide (Step-by-Step)
-
Visual Inspection. Before grabbing any tools, pop the battery cover. Look for obvious problems. Is there fuzzy, white, or green corrosion caked on the terminals? Is there a puddle of acid from a cracked battery case? Are the main power plug pins burnt or bent? These simple checks find the problem half the time.
-
Check Total Pack Voltage. Set your multimeter to DC Volts. Place the red probe on the main positive terminal of the entire battery pack and the black probe on the main negative terminal. A 24V system must read above 24.0V. A 48V system must read above 48.0V. If it's low, the charger will lock you out with the red-green flash.
-
Isolate the Bad Battery. Now, test each battery individually. A single bad battery will drag the whole pack down. Measure across the posts of each battery. A healthy 12V battery should read 12.4V to 12.7V. If you find one reading 10.5V while the others are at 12.5V, you've found the culprit. That one battery is your entire problem.
-
Verify Charger Input Power. If the batteries check out, make sure the charger itself has power. Set your multimeter to AC Volts and test the wall outlet. You need a stable 110V to 120V AC. A bad extension cord or a tripped breaker can mimic a charger fault.
-
Test Charger DC Output. Disconnect the charger from the machine. With the charger plugged into the wall, carefully test its DC output terminals at the main connector. You should see a "float" voltage slightly above the pack's nominal voltage (e.g., 26-28V for a 24V system). If you get 0V, the charger has an internal failure and is junk.
-
Check Continuity. If the batteries are good and the charger has output, the connection between them is bad. Unplug everything. Set your meter to continuity (the setting that beeps). Test the main charging cables from the connector pin to the battery terminal. You should get a solid beep. If not, the cable has an internal break.
The Part You Need
The most common parts needed to fix this fault are a single replacement battery or a new onboard charger. Less often, you'll need a new battery cable or main power connector. Waiting 6-8 weeks for a part from the dealer is a non-starter when a machine is down.
China Lift Supply stocks OEM-compatible LGMG chargers, batteries, and cables in the US to avoid that dealer lead time.
Can't wait 6 weeks for this part? We have it on the shelf in Kansas. Check the price and availability here: LGMG compatible parts
