A safe lithium battery pack for electric pushback tractors. In the article on our in-house developed planetary gearbox, we explained what makes the drive train for pushbacks so efficient that pushback operators can do 20 – 25 pushes on one battery charge. But this efficient drive train is not enough without a quality battery pack. The battery pack of the pushback conversion kit consists of a lithium battery chemistry. But why do we choose lithium and not the already well-known and trusted lead acid?
In the GSE market, electric equipment has been used for a long time, such as for belt loaders or for stairs. There, lead-acid batteries are generally used. Lead-acid batteries are relatively cheap, easy to install and widely available. Only, the advantages of lead-acid packs do not outweigh the disadvantages of a lithium pack to electrify pushback tractors. Why? Because lead-acid packs have the characteristic that relatively little current can be extracted in a long time compared to most lithium packs. Given that the powertrain for pushbacks requires relatively high power, comparing to the powertrain of a staircase or belt loader, a lead-acid pack is not sufficient. Finally, a pushback tractor still needs to push 92 tonnes of kilograms.
If a deep traction lead-acid pack is used anyway, it would mean, the battery life would be 500 cycles. With 10 to 15 pushes in 1 day, if properly maintained, the lead-acid battery would be written off within 2 years.
But why do we state this? Simply, we have already made the mistake for the end user. Our first prototype electric powertrain for pushback tractors used a lead-acid battery pack. Test data showed that the battery degraded, or in other words, the effective capacity of the battery decreased. Furthermore, we saw that in very high ambient temperatures (>45 degrees Celsius), battery degradation accelerated. Above 45 degrees does sound like exceptionally hot, but on a platform with black asphalt in southern European areas, it certainly isn’t!
Therefore, together with Aviaco GSE, we have developed a lithium package with an average lifespan of 7 – 9 years, where maintenance is not required. Compared to lead acid, this can lead to an equipment operational cost savings of between 30% and 50%.
By using lithium, the total package can operate in high ambient temperatures, such as with our customers in southern Europe. In addition, the battery pack can be heated, so it also functions well in areas with very low ambient temperatures (<0 degrees Celsius). And last mentioned but one of the most important points, the battery chemistry used is LiFeYPO4. This chemistry has the property of being highly resistant to overheating compared to other lithium chemistries, making this battery chemistry considered safe.
Furthermore, lithium packs enable us to use airport charging infrastructure smarter and more effectively. Why? We will discuss that another time.
