There are more solutions than obstacles. Nicolas Zart
Unlike today’s lithium-ion EV batteries, older nickel metal-hydride (NiMH) batteries, common in early hybrid vehicles, had different charging requirements. NiMH batteries were never designed to be regularly charged to 100%. Instead, trickle charging at lower current levels was recommended to avoid damage, and charging periods were carefully limited to prevent overheating and capacity loss.
From Lead-Acid to NiMH, to Lithium
Lithium batteries have a fixed voltage cut-off and require complex charge termination detection, such as pulse charging or measuring temperature rise. We’ve been told to use superchargers or fast-chargers are little as possible as it can lower the life-span of lithium batteries. Today, electric vehicle (EV) drivers are told to charge to 100% since lithium-ion batteries have a constant voltage limit and built-in management systems.
However, despite charging algorithms that allow batteries to reach a full 100%, experts now explain that lithium-ion cells are best preserved by avoiding frequent full charges. This is because the battery management systems restrict charging currents and voltage at the upper range to protect cell health, but the chemical stress of being fully charged still accumulates damage over time.
In other words, understanding these underlying differences is key for EV owners to maintain battery life. Unlike lead-acid and NiMH, lithium-ion technology can handle higher voltage limits during charging safely when managed well, yet it still benefits from being kept mostly between about 20% and 80% charge for daily use. Regularly topping off to 100% is better reserved only for times when the maximum driving range is needed. And yes, the same applies to your smartphones and most likely, advanced air mobility (AAM) aircraft.
Fast forward to today, with EVs becoming more popular as a clean alternative to gas-powered cars, recent studies reveal that charging to full capacity frequently can harm your battery and shorten its life.
Why Charging to 100% Can Damage Your Battery
Modern EVs use lithium-ion batteries, which are sensitive to how often and how fully they are charged. Charging a battery to very high levels causes increased chemical stress inside the cells. This stress accelerates battery wear and reduces its overall lifespan.
When the battery is nearly full, its internal resistance increases. This creates more heat, which can cause faster degradation. The same applies to very low charge levels. Keeping the battery charged between about 20% and 80% reduces this stress. This charging range is sometimes called the “sweet spot” or “golden zone” by manufacturers and experts. And this sounds exactly like we were told 25 years ago.
What the Science Says
Back in 2008, I visited the Garage of the Future at Southern Edison. The center was researching charging and discharging and had found back then EVs could drive up to 200,000 miles without noticeable battery degradation. There was no fast-charging involved. Today, more research from multiple EV charging labs shows that limiting the charge to this middle range can reduce battery degradation by up to 40% compared to batteries often charged fully or deeply discharged.
Smart Charging Features Help Maintain Battery Health
Thankfully, modern electric vehicles have built-in tools that let drivers set upper charging limits. Using these features to charge only up to 80% daily can help preserve battery life. Some manufacturers also program charging algorithms that adjust speed based on battery temperature and conditions to optimize longevity.
To raise your battery life, you should always choose to charge at lower speeds when possible. Fast charging is convenient but can generate excessive heat and accelerate wear. Use slower chargers like Level 2 for routine charging. This also means you should avoid draining your battery completely. Just charge to 100% when you need it, not all the time.
What about AAM?
As we chase after higher megawatt (MW) in the industry, we also realize that fast-charging will reduce the lifespan of these batteries, especially in very hot and populated areas where electric vertical take-off and landing (eVTOL) aircraft will be forced to hover or to adopt shallow FATOs. Today, most EV owners can charge up to about 80% daily, and 100% as needed for longer range.