AGV/AMR LFP Battery The Untold Story of Warehouse Robotics Power
When Ben Einstein tore apart that decommissioned Kiva robot, he found two thermocouples welded beneath the batteries.
When Ben Einstein tore apart that decommissioned Kiva robot, he found two thermocouples welded beneath the batteries.
Four 12V 28Ah lead-acid batteries. Series connection. 48V. Thermocouples welded under the bracket.
That was in 2016. That robot was probably manufactured around 2005. Kiva launched its first-generation DU 1000 in 2005, and made major changes to its charging system in 2006. The one Einstein took apart might have been from before that change, or after. He didn't say.
At that time, very few AGVs used lithium iron phosphate.
Kiva's robots needed to charge for 5 minutes every hour. The robot weighed 110 kilograms, could lift 450 kilograms, and traveled at 5 kilometers per hour. Lead-acid batteries have limited charge cycles, around 1,500. Charging once a day would last just over four years. But Kiva's robots needed to charge many times a day.
Lead-acid batteries require adding water. They need ventilation. They need dedicated charging rooms. Adding water before charging causes overflow, disrupting the electrolyte balance. Adding water after charging is correct. But operators often got it backwards.
Lithium iron phosphate doesn't need water. Doesn't need ventilation. Can be charged anytime without damaging the battery. Cycle life is three to five times that of lead-acid—LFP can achieve over 3,000 cycles. Some manufacturers claim 4,000 cycles at 100% depth of discharge, 6,000 cycles at 80% depth of discharge.
Lithium iron phosphate has about one-third lower energy density than ternary lithium. But AGVs don't care about range like electric vehicles do. Warehouses have charging stations everywhere, a short run and you can charge.
Lithium iron phosphate has a higher thermal runaway temperature than ternary lithium. Lithium Werks' data says LFP can be charged to 100% SOC, while ternary lithium should only be charged to below 90% for safety. PowerTech Systems says lithium iron phosphate's temperature rise rate during thermal runaway is 1.5°C per minute, while ternary lithium is 200°C per minute. This difference is too large—might be due to different testing conditions.
"After switching, we no longer needed a charging room, no longer needed to add water, no longer needed a ventilation system."Allen Grady, Spirit AeroSystems — 2018
Spirit AeroSystems' Allen Grady switched the workshop forklifts from lead-acid to lithium in 2018. He told industry media that after switching, they no longer needed a charging room, no longer needed to add water, no longer needed a ventilation system. He didn't say whether they switched to lithium iron phosphate, ternary lithium, or something else.
French company Balyo's Baptiste Mauget chose lithium titanate. Not lithium iron phosphate. He said what he needed was cycle count, and lithium titanate has longer cycle life than lithium iron phosphate. Lithium titanate is expensive and has low energy density, but he said he didn't care about range. Wiferion's data says lithium titanate can charge at 5C, from 0 to 100% in 12 minutes. Lithium iron phosphate charges at 2C, taking 30 minutes.
He didn't say there was anything wrong with lithium iron phosphate. Just that lithium titanate was more suitable for his scenario.
Battery Chemistry Comparison
Lead-Acid
~1,500 cycles. Requires water maintenance, ventilation, dedicated charging rooms. Lower upfront cost but higher operational burden.
LFP (Lithium Iron Phosphate)
3,000-6,000 cycles. No maintenance needed. Higher thermal runaway temperature. 2C charging rate, 30 min 0-100%.
LTO (Lithium Titanate)
Longest cycle life. 5C charging rate, 12 min 0-100%. Higher cost, lower energy density. Best for high-frequency charging.
Alexander Technologies' article says that for small AGVs moving light cargo, the battery accounts for a large proportion of total robot weight, so energy density matters, and ternary lithium should be used. For large AGVs moving heavy cargo, the battery proportion is negligible, energy density doesn't matter, and lithium iron phosphate should be used. There's no specific case study of which company chose batteries based on this logic.
Boeing's AGVs use 48V 200Ah battery packs. After 3,500 cycles, capacity retention is still above 80%. There's no public information on whether this is lithium iron phosphate or another chemistry.
Mountz worked on logistics for Webvan before founding Kiva. Webvan built a 330,000 square foot warehouse in Oakland with 5 miles of conveyor belts. It went bankrupt in 2001, burning through $830 million. Mountz later said the bankruptcy was caused by excessive order fulfillment costs. He didn't mention batteries.
He went to Silicon Valley seeking investment, running up and down Sand Hill Road for a year. "Just a bunch of blank stares." Later, through Harvard Business School connections, he found Bain Capital. Bain invested and also introduced him to people at Staples.
Those robots are still running in Amazon warehouses. 520,000 units in 2022. Over 1 million units in 2024.
Amazon later released new robots. Pegasus is 10 centimeters shorter than the original Kiva, can lift 560 kilograms, has half the parts, and costs half as much. Xanthus has only one-third the parts of the original. There's no public information on what batteries these new robots use.
The Supply Chain Mystery
Green Cubes Technology, RELiON, Keheng, BSLBATT—these companies all sell lithium iron phosphate batteries for AGVs. Their websites all say Amazon, DHL, Walmart use their products. There's no official confirmation from Amazon or DHL or Walmart.
There's no public information on when Amazon switched Kiva's batteries to lithium iron phosphate. Or whether they switched at all.
Peter Wurman is a Kiva co-founder, now Executive Director at Sony AI. He said that without selling to Amazon, Kiva's robot count wouldn't have grown from 200 to 600,000 to 1 million. "We helped create a category."
He didn't mention batteries either.
The Teardown Record
The Kiva robot Einstein tore apart had thermocouples welded under the lead-acid battery bracket. He posted the photos online. Navigation system, lifting mechanism, charging port, busbars.
He only wrote one paragraph about the batteries. He didn't mention lithium iron phosphate.
The Questions That Remain
The story of AGV battery evolution is marked more by what isn't said than what is. Engineers make choices, companies scale operations, technologies evolve—but the documentation remains sparse. Einstein's teardown captured a moment in time: thermocouples welded beneath lead-acid batteries, a window into how warehouse robotics pioneers thought about power management in the early days.
Whether Amazon's million robots now run on lithium iron phosphate, the original technology choices of Kiva's founders, the specific reasoning behind each battery chemistry selection—these details live in engineering notebooks and internal memos, not public records.
