Understanding Battery Technologies: Cutting Through the Hype

When it comes to batteries in real-world applications, there’s a lot of information out there—and not all of it is helpful. At Element 82, we believe in presenting honest, practical advice based on how batteries perform in actual use cases, not just on spec sheets or internet chatter. This article unpacks the realities of charging and discharging batteries, explores different battery technologies, and debunks some common myths floating around online.

Rated Capacity vs. Usable Energy

Every battery is marketed with a certain capacity, often stated in amp-hours (Ah) or kilowatt-hours (kWh). But what does this actually mean in practice? For most battery types, including lithium and AGM, the full stated capacity isn't always usable.

Lithium Batteries: Even though they're often promoted as allowing 100% depth of discharge (DoD), in practice, the usable range is closer to 80%. The Battery Management System (BMS) limits the top and bottom end of the charge range to protect the cells, meaning you typically get about 70-80% of the rated capacity in real-world cycling.
AGM Batteries: These also don’t deliver full capacity unless discharged completely, which isn’t advised due to drastically reduced cycle life. Typically, AGM batteries are best cycled between 50% and 80% DoD to preserve lifespan. This info may be right for a motorhome with light weekend use once a month as you'll still enjoy many years of weekend use. But if you lived off-grid anyone with 10 years of experience living that way will tell you that only discharging to 70% state of charge (30% discharged) will give you over 2500 cycles or almost 7 years of usable life cycles and if you don't discharge daily that will further extend your batteries expected life years.

Charging Considerations: Rate, Temperature, and Compatibility

A battery is only as good as its charging regime. Overcharging, undercharging, or using an incompatible charger can all result in poor performance or outright failure.

Lithium: Fast charging is possible and often promoted, but comes with the trade-off of increased heat and potential wear on the cells. Charging in temperatures below 0°C is a big no-go, as lithium cells can be permanently damaged. A good BMS will prevent charging below freezing, but in cold climates, you may need a battery with an integrated heater or external heating mat.
AGM: Slower to recharge and less efficient, but far more forgiving. AGMs can handle a range of charge voltages and don’t require temperature control to the same extent. However, temperature compensation is still recommended to avoid undercharging in cold weather or overcharging in hot weather.

Notably, the CTEK MXS 5.0 charger does not truly offer temperature compensation despite what many forums claim. It derates based on internal temperature to protect itself, not to optimise charging voltage based on ambient temperature. For accurate temp compensation, use a charger with a dedicated external sensor.

Environmental Impacts

Solar Panel Orientation: In colder, southern climates like New Zealand’s South Island, the sun sits lower in the sky during winter. This means solar panels should be mounted at steeper angles to capture more sunlight and produce usable energy when it's needed most.
Battery Performance: Cold weather severely impacts lithium batteries more than AGM as Lithium should never be charged below zero degrees C, Lead Acid shouldn't be charged below minus 20 degrees C as the battery will freeze (due to its water content). Heat management is also critical for both chemistries (lead acid charging generates thermal activity) to avoid reduced performance or BMS lock outs due to sub-optimal charging or discharging temperatures.

Application vs. Internet Hype

Online forums and marketing material often highlight the best-case scenarios: 100% DoD, ultra-fast charging, or thousands of cycles. But these claims rarely hold up under real-world conditions.

Overstated Claims: Internet sources often ignore critical limitations like BMS protections, charge rate limitations due to heat, or warranty clauses that only allow one full cycle per day.
System Compatibility: Swapping from AGM to lithium isn’t just a plug-and-play upgrade. It may require a new charging system, BMS integration, and possibly safety standards approval and considerations.

Why AGM Still Has a Place

Despite the lithium hype, AGM batteries remain relevant in many systems. They are robust, simple, and require minimal active management. For legacy systems or where reliability outweighs peak performance, AGM is still a smart choice.

Conclusion: Choosing the Right Battery For Your Needs

There's no one-size-fits-all battery. Your choice should depend on your application, budget, climate, and performance expectations. Lithium offers impressive specs but demands precise management and often additional infrastructure. AGM remains a steady, dependable option.

At Element 82, we help customers find the right solution, not just the trendiest one. Whether you're powering an RV, marine vessel, off-grid home, or industrial site, we focus on performance that works in the real world—not just on paper.

Need Help With Battery Selection? Reach out to us at Element82.co.nz for advice tailored to your setup, climate, and energy goals.