Why do the legs move slowly or not lift at all when the battery is weak?
The torque produced by a 12V DC leg motor is directly related to the voltage reaching it. If the battery is weak the voltage collapses under load, the motor slows down, draws more current to do the same work, and the current protection and timeout check of the GRV485 stop the movement. This is not a fault but protective behaviour; the solution is first to fully charge the battery and check the connection points.
The moment an electric leg starts taking the weight of the RV, the load on the motor reaches its peak. At the same moment the battery is at the point where it is most stressed. If the battery is half empty or its internal resistance has risen, the terminal voltage drops seriously under this load.
The chain works like this:
- Voltage drops -> motor torque drops -> movement slows down or stops.
- As the motor tries to finish the job, its current draw rises.
- The rising current trips the hardware-level current protection of the GRV485.
- If the movement does not complete in the expected time, the timeout check steps in and the operation is stopped.
Order of checks:
- Fully charge the service battery, then try again.
- Look for oxidation and looseness on the battery terminals, the fuse holder and the connectors; a bad contact here behaves just like a weak battery.
- Check the negative return path; a poor chassis connection is a very frequent cause.
- If the battery is old, remember that on lead-acid/AGM deep discharges of around 80% on a regular basis roughly halve its life; a battery that has lost its capacity collapses under load even when fully charged.
If the problem persists after these steps, contact AXI technical support for a parameter check over remote support.
The full topic: How to choose levelling leg capacity