Frequently Asked Questions

How is AGV battery charging done?

There are two ways to do AGV battery charging:

• Battery Swap-Out — The AGV’s battery is removed from the vehicle and swapped with a freshly charged battery. Most AGVs have rollers in the battery compartment to facilitate the battery exchange. Typically, the battery is rolled on to a battery cart. This cart then moves transversely across the face of a row of battery charges, each equipped with a battery stand. The used battery is exchanged with the fresh battery, which is then replaced in the vehicle. Batteries in vehicles can also be exchanged using an overhead hoist. Battery swap-out can also be performed by an automated battery change system.
• Automatic Battery Charge — Each AGV utilizes a single maintenance-free battery that normally stays in the AGV. The AGV has an automatic charge shoe mechanism that allows the AGV to make contact with a copper contact plate in the floor. This contact plate is wired through the floor to an automatic charger mounted on a column or wall nearby. When the AGV stops over the contact plate and its charge mechanism contacts the plate, the charger automatically turns on. The AGV remains on charge until needed for a load transport task. When it departs, the charger automatically turns off.

There are a number of considerations with respect to the type of battery charging to employ in a given system application. For example, in using automatic battery charging, there must be sufficient AGV idle time to allow the battery recharging to keep up with the battery usage. In an AGV train system there is normally time to charge the AGVs battery while the AGV train is waiting at a station for trailers to be loaded or unloaded. However, in an AGV unit load carrier system, the AGVs are normally kept moving a greater percentage of the time. This limits the time for battery recharging. Unit load carrier AGVs usually pick and drop loads automatically, so there is usually not much idle time at load transfer stations. In these situations additional AGVs would be required to provide sufficient idle time for the whole AGV fleet to allow automatic charging to work. Often this is accomplished by managing the charging process and scheduling AGVs to recharge as needed.

Typical automatic recharge time required can be estimated by determining the expected actual AGV moving time. A good rule of thumb is to plan on a 1:1 relationship between actual running time and required charging time. Therefore, if an AGV is expected to physically be moving for three hours per shift, it should be expected that there needs to be about three hours of automatic charging needed.