Faster is better. The early bird gets the worm. The tortoise and the ha—wait a second. We all know who won that race. Speed isn’t everything, especially when it comes to charging your fleet of AMRs. In fact, there’s plenty you sacrifice when opportunity charging is your go-to AMR battery charging solution.
Opportunity charging allows your robots to intermittently charge their batteries via contacts on your warehouse floor, then return to begin a new mission. While the idea sounds like a winner in theory, it’s important to understand the various opportunity costs of opportunity charging. Let’s take a closer look.
Limited Battery Power and Productivity
It’s easy enough to overlook, but a major sacrifice of opportunity charging is the tradeoff of power and productivity in favor of a quicker charge time. AMRs that engage in opportunity charging are only getting a power boost, charging their batteries to 80-85 percent state of charge (SOC). This means each robot has multiple charge breaks each shift. These breaks might seem short (up to 45 minutes each), but they lead to reduced throughput because the battery is built into the robot, taking it out of commission—unless you expand your fleet to accommodate for the lost labor.
But more goes into the battery power problem than meets the eye. Consider exactly what you’re tasking each robot to do. AMRs that use opportunity charging might be picking and packing orders to ship, but they also power and bear the weight of their payload, including the items they’re tasked to move and attachments that help with those tasks. End effectors, sensors, cameras and other attachments use up battery energy just to operate, while the weight of the picked orders (like a tote of beauty supplies or grocery items) also uses energy. The harder your machines work, the more they’ll require charging!
Compromised Battery Life
Consider this: every time your cell phone drops below 50 percent, you charge it. That strategy works for a bit, but soon enough, that phone is terrible at holding a charge! The same mentality applies to opportunity charging in AMRs.
Frequent charging of robot batteries reduces their life. So, it’s completely normal and expected for opportunity-charged batteries to only last three years, as opposed to the 5-year life of autonomously-charged batteries. After all, the robots are used for multiple shifts each day, constantly supercharged, and their batteries are only equalized (charged to 100 percent SOC) on weekends or low-volume days.
Additionally, the batteries used in AMR opportunity charging applications are smaller, compared to those used in autonomous applications. Smaller is better, right? That’s no guarantee. You could potentially start off with a battery that’s powerful, but that power quickly dries up, with no backup to rely on.
Higher Operating Temperature
In opportunity charging, robot operating temperature has to be monitored. That’s because the batteries in these machines generally run hotter than their autonomously-charged counterparts. The rise in temperature comes from a stronger, quicker charge, but also a lack of cooldown time between charging and return to work. An opportunity-charged robot tops itself off to 80 percent SOC and zips back to the warehouse floor for its next mission.
Think of it like working your full-time job and only napping each night for just long enough to recoup a portion of your energy. Similarly, opportunity-charged batteries must work harder because they gradually get hotter throughout the work week. Major cooldowns really only happen on low-volume days, when the robot has the chance to take a break.
Learn Why Autonomous Charging Always Wins
If your facility runs multiple shifts each day, opportunity charging might work in your favor. But keep in mind the obvious opportunity costs of opportunity charging, too. From lost productivity and battery power to payload problems, opportunity charging has its flaws.
So what’s the better approach? Using robots with large and powerful batteries that run longer and can be hot-swapped in seconds when you DO need to recharge. IAM Robotics trusts autonomous charging solutions for our suite of products, giving you the power to do more. Read our post for a side-by-side view of opportunity and autonomous charging.
Already in the market for a new material handling solution? Ask us about Bolt™, the new AMR from IAM Robotics.