Eight Things You Wanted To Know About Lithium Batteries But Were Too Afraid To Ask
Lithium revolutionised the world of batteries, but do they suit the 4WD market?
Surely, I’m not alone when it comes to overlanders having issues with their 12-volt systems. From memory, I’ve had to purchase more than six batteries over the past four years. With the expense averaging out to over $250 per battery, it was unsustainable. I even swore never to buy a particular brand ever again (four of the batteries where that brand), but unfortunately, when the last deep cycle battery perished on the Binns Track, it was all I could get in Kununurra.
On my return home, I began researching lithium as an option for powering my auxiliary items (fridge, inverter, camp lights, air compressor etc). It seemed that the more I read, the more confused I became, there were so many different brands that all sounded different and prices from ridiculously cheap to frighteningly expensive. I then met the team from AMPTRON in Western Australia and suddenly had all my questions answered, this is what I learnt.
1. What does LiFePO4 mean?
There are several types of lithium-ion batteries. The main difference between them is their cathode chemistry. LiFePO4 stands for Lithium Iron Phosphate which is the chemistry of the cathode of this type of Lithium battery, and it is these cathodes that help in making Lithium batteries cheaper and safer than they once were, being low cost, low toxicity, well-defined performance and long-term stability. LiFePO4 is also highly resilient during oxygen loss which is what caused exothermic reactions, and fires, in other Lithium cells. This is the main type of Lithium-ion battery used in the 4WD and RV market.
2. Why are lithium batteries so light?
Lithium is one of the lightest elements, with hydrogen and helium the only two that are lighter, and they are gases. LiFePO4 batteries made up of lithium ions and carbon, making them extremely lightweight, whereas a wet cell battery is full of lead alloy or fibreglass plates and sulfuric acid.
3. What is a BMS?
The BMS is the internal Battery Management System that protects and manages the Lithium battery cells. It limits the peak voltage of each cell during charging and preventing the cell voltage from dropping too low on discharge. It also monitors the temperature, charge and discharge rates of the battery, preventing extremes during charging and discharging. This means your LiFePO4 Lithium battery is unlikely to become unstable or unsafe, thanks to these protective measures. Even if punctured, a LiFePO4 battery won’t catch fire.
4. Can I use a lithium battery as my starter battery?
LiFePO4 batteries are sensitive to heat, so placing them in your engine bay may cause the battery to operate under excessively hot conditions which could significantly decrease the battery life. Also, most LiFePO4 Lithium batteries are designed as deep cycle batteries to deliver steady power for a long period, therefore the peak current these batteries are designed to deliver is insufficient for a cranking battery. Further, the charge profile of many modern alternators is not ideal to maintain LiFePO4 batteries. I’ve been advised AMPTRON are in the process of developing a Lithium battery with high heat tolerance and sufficient CCA abilities that can operate within the engine bay and can also be used as a deep cycle battery.
5. Can I use any type of charger on a lithium battery?
The method used to charge a Lithium battery is based on a CV/CC (constant voltage/constant current) charge algorithm. LiFePO4 batteries usually require a slightly higher voltage to fully recharge compared to Lead Acid batteries, but there is no float or trickle charge stage since that is detrimental to the battery life.
Many lead-acid chargers have an equalization mode, which supplies a deliberate over-voltage charge for a short period to combat sulphation and acid stratification. Applying an equalization charge to a lithium battery may damage the cells.
The other function that lead-acid chargers have is a “return to bulk” voltage. Once the charger is in float, it will maintain the battery at a pre-set voltage. When the battery discharges under load, the voltage will reduce. Once the voltage reaches the “return to bulk” voltage, the charger will start a new charge cycle and start re-charging the battery. The problem is Lithium batteries maintain a higher voltage than lead-acid batteries while discharging, and by the time it reaches the “return to bulk” voltage the Lithium battery is already very low.
You can use a lead-acid charger on a Lithium battery, however, you mustn’t allow an “equalisation” stage. A lead-acid charger that can be set to charge no higher than 14.6v (usually the AGM setting is the best option) can be used for regular charging and then must be disconnected after the battery is fully charged. Do not leave the lead-acid charger connected to maintain or store the battery.
Ultimately, using a battery charger with a specific Lithium charge algorithm is the best option for maximum performance and lifespan of any lithium battery. One thing you’ll notice is the speed at which a LiFePO4 battery recharges, up half the time compared to a lead-acid battery.
6. Are all lithium batteries equal?
The simple answer is no, and this is why. Many lithium LiFePO4 battery manufacturers use smaller and cheaper cylindrical cells that deliver reduced discharge capacity and short life expectancy. The tabs on these smaller cells are often welded together which is susceptible to forming micro-cracks that diminish the performance and lifespan of the battery.
Manufacturers, like AMPTRON, use high-quality prismatic cell design with high discharge ratings and exceptional life cycle performance. Connecting cells by bolting them together via threaded terminals provide a stronger and vibration resistant battery.
It’s these differences in construction that also create so a range in the pricing of lithium batteries.
7. When does a lithium battery stop providing power?
Under load, a LiFePO4 battery discharges while maintaining a high voltage until it reaches about 95% Depth of Discharge. The internal BMS will cut the power supply once the battery voltage drops below its low voltage cut-off, which for a 12V battery will typically be near 10V.
8. What is the cost comparison between LiFePO4 and Lead Acid batteries?
While the initial layout cost for a lithium battery is at least twice that of a deep cycle lead-acid battery the expected life span of the lithium battery is more than four times longer than that of a lead-acid battery. A lithium battery will also provide as much as twice the usable energy of a deep cycle lead-acid battery of the same rated capacity because you can use a greater Depth of Discharge (DoD). For a quality LiFePO4 battery, you’ll realise more than 2000 cycles at regular 100% DoD and up to 5000 cycles at less than 80% DoD, compared to an AGM battery may be having a life of 400 to 800 cycles at 50% DoD. You can expect to buy at least three lead-acid batteries to one AMPTRON LiFePO4 battery that has a typical lifespan of 7-15 years.
Who is AMPTRON?
AMPTRON® is an Australian owned and operated company supplying high-performance energy storage, generation and monitoring solutions used in Recreational, Marine, Commercial, Industrial and Mining applications such as Lithium batteries, chargers, power monitors, solar panels and portable power packs including off-grid installations. Its founders have deep roots in the Electrical Manufacturing and Industrial Automation industries, but also share a love of the outdoors and like to “get out there”. AMPTRON is focussed on providing quality products and solutions at competitive prices combined with great customer service. AMPTRON have supplied me with a lithium battery to use in my 4WD.
For more information visit the team at AMPTRON