The Core Tradeoff
Every GPU purchasing decision between lead acid and lithium comes down to one question: how often will you use it? The two chemistries serve the same function — delivering a high-current burst to start an aircraft engine — but their cost curves cross at a specific usage threshold. Below that threshold, lead acid wins on economics. Above it, lithium wins, often dramatically.
The rest of this guide quantifies that crossover point and the factors that influence it for your specific operation.
Weight Comparison
This is the most immediately obvious difference and the one that matters most for portable operations. Lithium iron phosphate (LiFePO4) cells have a significantly higher energy density than sealed lead-acid, which translates directly to weight savings.
For a maintenance shop where the GPU sits on a cart next to the aircraft, weight is a convenience factor. For a helicopter operator who carries the GPU onboard, or a line service technician who moves GPUs between aircraft dozens of times per day, a 40-pound weight reduction translates to measurable reduction in physical strain and time per aircraft turn.
Start Pac reports their lithium units weigh 42% less than their lead-acid equivalents. StartStick, which only offers lithium, achieves starting capability in a 10–20 lb package — a weight class that lead-acid chemistry cannot physically reach at useful starting amperages.
Cycle Life
Cycle life is the single largest factor in total cost of ownership and the primary reason lithium eventually wins at higher usage rates.
A "cycle" in this context means one discharge-and-recharge event at the depth of discharge specified by the manufacturer. Aircraft engine starts are typically shallow discharges — the GPU delivers a high-current burst for 10–30 seconds, then recharges. This means real-world cycle counts are often higher than rated, as shallow cycles cause less degradation than deep cycles in both chemistries.
At one start per day (365 cycles per year), a lead-acid pack will need replacement in roughly 12–18 months. A lithium pack performing the same duty cycle will last 5–10 years before capacity degrades below useful levels. Over a 5-year period, you will buy three to four lead-acid packs versus one lithium pack.
Cold-Weather Performance
This is the one area where lead acid has a qualified advantage — and it is more nuanced than the marketing materials suggest.
Lead-acid batteries lose capacity in cold weather but can still deliver current at temperatures down to approximately -30°C, though at significantly reduced output. LiFePO4 cells deliver reduced capacity below 0°C, with more severe degradation below -20°C. At very low temperatures, the internal resistance of lithium cells increases enough to limit peak starting current.
However, the practical distinction is narrower than the specifications imply. At -20°C, both chemistries are delivering substantially reduced performance. The operational question is not "which chemistry works better at -25°C?" but rather "at what temperature does my operation require heated storage or pre-conditioning regardless of battery type?" For most operations, that threshold is somewhere between -15°C and -20°C.
For operations routinely below -20°C — northern Canada, Scandinavia, Alaska — heated storage enclosures are recommended for both chemistries. The weight savings of lithium often fund the heated enclosure within the first year.
Charge Time
Faster charging directly impacts operations in high-volume environments. An FBO processing 20 starts per day cannot afford a 12-hour recharge between uses — either the operation stocks multiple lead-acid packs or it switches to lithium. Start Pac's Quick Change system addresses this differently by allowing sub-60-second battery module swaps, but the replacement modules themselves still need to be charged.
5-Year Total Cost of Ownership Model
The following model compares a representative 28V lead-acid start pack against a lithium equivalent over a 5-year period at three different usage levels. Pricing is based on publicly available retail data from manufacturers and distributors as of early 2026.
Our Recommendation
The Decision Framework
Choose lead acid if: You start your aircraft fewer than 100 times per year, budget is constrained upfront, and weight is not a critical factor. Private owners with single-aircraft hangars fall here.
Choose lithium if: You average more than 100 starts per year, weight matters to your operation, or you need faster recharge cycles. FBOs, MROs, flight schools, helicopter operators, and military operations should default to lithium — the 5-year cost savings fund the premium and then some.
Need help matching a specific GPU to your aircraft? See our GPU Sizing Guide or browse aircraft-specific recommendations. For a full comparison of manufacturers, see Best Aircraft GPU 2026.
Frequently Asked Questions
Is a lithium aircraft GPU worth the extra cost?
For operations averaging more than 100 starts per year, lithium's longer cycle life and lower weight typically result in a lower 5-year total cost of ownership despite the 2–3x higher upfront price. For private owners with fewer than 50 annual starts, lead acid remains more cost-effective.
How much lighter is a lithium GPU than lead acid?
Lithium iron phosphate start packs weigh approximately 40–50% less than lead acid equivalents with the same starting capacity. A unit that weighs 80 lbs in lead acid typically weighs 40–48 lbs in lithium.
Do lithium GPUs work in cold weather?
LiFePO4 cells deliver reduced capacity below 0°C, with significant degradation below -20°C. Lead acid handles cold somewhat better at moderate sub-zero temperatures but also loses capacity. For operations routinely below -20°C, heated storage or pre-conditioning is recommended regardless of chemistry.
How long does a lithium aircraft GPU last?
Lithium iron phosphate cells are rated for 2,000–5,000 charge cycles depending on depth of discharge, compared to 300–500 cycles for sealed lead acid. In practical terms, a lithium GPU used daily for engine starts should last 8–12 years before capacity drops below useful levels.