The Essential LiFePO4 Battery Guide
Posted on January 02 2020
The Essential LiFePO4 Battery Guide
If you are on the hunt for batteries for your motorhome, boat, caravan or home solar system, it can be hard to decide which type will best suit it. Taking budget into consideration, you may be tempted to cut corners and buy cheaper batteries that may work in the short-term but require more frequent replacement, therefore costing more cumulatively in the long-term.
There are also environmental factors you might want to take into account. Some batteries produce harmful by-products that, when disposed of, have a detrimental impact on the ecosystem. This is amplified with the lower cost lead-acid batteries with short life cycles compared to the best lithium batteries that may last up to 8 x longer life.
What if we told you that opting for a LiFePO4 battery addresses performance, budget and environmental considerations? In this guide, we will be giving you the lowdown on everything you need to know when it comes to the world of lithium iron phosphate batteries - including everything from the differences between LiFePo4 and Lithium-Ion batteries, how they work, and what they are used for.
The first section will cover some frequently asked questions when it comes to the world of LiFePO4. Then we’ll move onto some key characteristics of it, its applications and finally, how to properly care for it.
We hope this guide gives you the know-how you need when it comes to figuring out what type of battery to buy for your motorhome boat, off-grid appliances and golf carts.
So without further ado, let’s get straight to it.
What is a LiFePO4 battery?
LiFePO4 batteries are comprised of lithium iron phosphate and are also referred to as LFP. They are a rechargeable battery and a lithium-ion variant.
If you want to get into the nitty-gritty details when it comes to its chemistry, it is comprised of lithium iron for their cathode material, which is where the current flows into, and carbon as the anode, where the current leaves.
The difference between lithium-ion and lithium iron phosphate
With both containing lithium, how different can they be?
There are, however, some key differences between the two. Firstly, lithium-ion batteries have a higher energy density - meaning they can hold more power. Lithium-ion is said to hold between 150-200 watts per kg, whilst lithium iron phosphate holds around 90-120.
The former is best suited for appliances that need a small ultra-lightweight energy storage - the likes of portable devices laptop and phone batteries are where you can usually find li-ion. The higher energy density of lithium-ion also makes them less stable during extreme charge and discharge.
LFP, on the other hand, is best for heavier duty appliances with high rates of charge and discharge and where ultimate safety is critical, the small reduction in energy density is less important in boat caravan and motorhome use as LFP is so much lighter than the old lead-acid technology they replace.
Are LiFePO4 batteries dangerous?
This is a question that gets asked a lot, along with “will my lithium iron phosphate battery explode?”
To answer the question, when compared with li-ion batteries, lithium iron phosphate batteries are considerably safer. Since the li-ion battery can hold more energy, combined with the lower thermal runaway of the chemistry involved makes them more likely to be unstable if overcharged or excessively loaded.
LiFePO4, on the other hand, has a lower energy density and is best for heavy-duty usage, such as running inverters or in Electric propulsion systems. They also don’t contain any toxic heavy metals or produce any dangerous by-products.
Different lithium chemistries have different thermal runaway temperatures, and having a higher temperature tolerance means higher stability and safety. Have a look at a comparison between different kinds of lithium batteries and their temperatures below:
So, providing you are looking after your batteries properly, LiFePO4 is unlikely to cause any harm. The safety improvement LFP offers over other types of lithium-ion chemistries is a major factor in why LFP is the battery of choice for energy storage in homes and habitable environments.
How does a LiFePO4 battery work?
According to Battery University, ions moving from the anode and cathode are what allows batteries to work. This constant movement should, in theory, keep your batteries going forever. However, when the number of cycles (charges) that you put your battery through and the rates of charge and discharge are considered, the battery begins to age - which happens to all batteries.
Lithium iron phosphate batteries are completely different to lead-acid or AGM batteries where the chemistry prefers being at a partial state of charge rather than fully charged. This makes them far more suitable for deep cycle leisure and solar storage use than traditional batteries.
You can extend the life of your LiFePO4 batteries with the right care and a little understanding (which is what we’re here for!)
How long do LifePO4 batteries last for?
Lithium-ion variants typically last longer than their lead-acid and absorbed glass mat (AGM) counterparts. With the right care and maintenance, which you can read more about in the next section, you can expect to see LiFePo4 batteries lasting for decades.
The cycles that your battery will serve depends on what it is being used for - check with your supplier or the manufacturer to find out the exact amount. You can expect top of the range models to give you over 3000 - 6000 cycles in their lifetime before their storage starts to decline significantly past 80% of original capacity.
One cycle is one discharge and recharge. If you do this once per day, this means that 2000 cycles will last you 5.4 years! This is the typical warranty period of a quality provider.
LiFePO4 Batteries can provide around 3000-6000 cycles if the voltage range of operation is reduced by 0.2V per cell.
Let’s compare this to lead batteries. LiFePO4 overwhelmingly outperform in terms of longevity, with lead-acid varieties typically providing around just 200-300 cycles. The reason for their relatively short cycles is due to how its electrodes and active materials change with use.
As with all batteries, this will depend on how well you look after them. Lead acid batteries can be damaged much more quickly if poorly maintained and left partially charged for any long period of time.
How do you charge LiFePO4 Batteries?
If you are wondering how to charge a LiFePO4 battery whilst keeping it in tip-top condition, one rule of thumb to follow when it comes to all Li-ion batteries is partially charging and partially discharging them. When it comes to batteries, you can look at their lifespan in terms of depth of discharge (DoD).
Taking a look at the graph above, we can see that partial discharging leads to a longer amount of cycles that a LiFePO4 battery can give.
This basically means that you should not allow the battery to be drained completely, and ideally, you should not charge it to full capacity. Undergoing a full charge and leaving the battery fully charged when not in use will speed up the deterioration and ageing process of the battery.
You will also need a charger specifically made for the battery type you are looking to charge. Likewise, a LiFePO4 battery charger will also only charge lithium-iron batteries as it is set to a specific cell voltage.
This is due to how lithium-Ion batteries charge at different voltages to lithium iron phosphate batteries.
What does the battery management system do?
The battery management system (BMS) of your LiFePO4 (should it come with one) is essentially the caretaker and protector of your battery system.
A BMS monitors:
- your battery’s temperature
- limits your battery from over and under-voltage
- protects you from overcurrent and short circuit
- and finally, it works to prevent cell imbalance through managing cells charge voltages.
It’s best to opt for a battery system that boasts a BMS to keep you safe whilst utilising your appliances. The BMS protects the cells from damage, switching off the battery before damage or danger occurs.
All our LiFePO4 batteries come with a battery management system (BMS) to protect the battery. HD Series looks after this silently, while the Novel Series also informs you all about your battery’s vitals, recording and advising you of any warning events during usage.
What are LiFePO4 batteries used for?
LFP batteries are suitable for a wide range of applications. In particular, they are great for deep cycle leisure use that needs energy over a long period of time, especially when charged occasionally such as in off-grid and solar applications. They are very suited to working at all states of partial charge permanently.
Some common applications include:
- As batteries for solar systems for the home
- For off-grid living
Can you use LiFePO4 in cars?
They typically aren’t suitable as a starter battery for conventional cars. This is because they require high cranking amps to get the engine going and constant alternator charging will shorten the life of the battery (unless a suitable additional management system is used as is typically found in boats and motorhomes.)
Emergency vehicles and rescue trucks with additional equipment benefit greatly especially when running mains inverters from an auxiliary battery bank.
What sets this emerging technology apart from other batteries? In this section, we will discuss some distinct features that make LiFePO4 what they are.
LFP’s high thermal runaway temperature and optimum energy density make them the safest and most popular lithium-Ion battery system. Polinovel’s integrated BMS removes the installation worry of incorrect connection and wiring failure of separate BMS systems. Finally, lithium iron phosphate produces no explosive gasses during charge or discharge, unlike lead-acid systems.
Compared to AGM and lead-acid batteries, lithium-ion batteries not only charge faster with a full recharge typically taking just 2.5 hours in a 100Ah battery at the recommended charge rates, but also offer the possibility of occasional fast charging from empty to full capacity in 1 hour. (up to 1C charge rates are possible, with a slight reduction in overall battery life)
When it comes to the efficiency of lead batteries versus lithium iron, the choice is clear. Lead acid batteries typically store around 70-80% of the energy provided in a whole charge cycle. However, when operating in the top 20% state of charge and in hotter climates, this can drop to below 60% of the charge energy provided being stored during the absorption phase.
This leads to slow charge, wasted solar energy and longer engine run times when alternator charging, wasting fuel and increasing pollution of fumes and noise.
On the other hand, lithium iron phosphate batteries store more than 95-97% of charge energy supplied and have no absorption phase leading to ultra-efficient use of the available energy and amazingly fast recharge times.
Lithium Iron Phosphate batteries last up to 15 times longer than cheap flooded lead-acid FLA batteries. With the correct setup and 50% depth of discharge, more than 6000 cycles are achieved. For most people, the investment in lithium will last the life of the vehicle they are fitted to!
In leisure battery form, they are up to 60% lighter than equivalent lead-acid batteries - making them a lightweight option. Their ultra-compact size allows you to increase capacity and maximise space. Bulky leisure batteries can, therefore, be a thing of the past! This is vital in camper vans and RVs where controlling vehicle weight is a common problem.
DID YOU KNOW: A 300Ah Lithium battery weighs about 27 KG, but provides the SAME USABLE ENERGY as a 480Ah flooded lead-acid system that would weigh around 120 KG!!!
Performance - Lead-acid batteries capacity is typically measured over 20 hours of usage drain time at low discharge rates. eg a 100Ah Battery is one that can supply 5 Amps of current for 20 hours. With lead acid technology any high usage greatly reduces the available capacity.
This is due to the Peukert Effect. This describes how as the discharge rates increase, the lead acid chemistry does not ‘keep up’ with the demand and the available energy is much less than the quoted capacity.
For example, a 100Amp load on a typical 100Ah lead-acid battery will only be available for under 30 minutes before the voltage drops below 10.5V. providing around 45Ah of the quoted 100Ah capacity.
Lithium Iron Phosphate batteries are not affected at all by the Peukerts Effect regardless of the rate of discharge. It is this that makes lithium-ion especially suited to high drain applications over longer time periods, such as EV propulsion and high drain inverters. A 100Ah LFP battery always provides 100Ah of power. if taken at 5 Amps or 100 Amps. While doing this the voltage remains remarkably stable.
Environmental impact and sustainability
We can all do our bit to reduce our carbon footprint and dispose of waste products safely as to not damage our ecosystem. Yet another fantastic characteristic of LiFePO4 batteries is that it contains non-toxic and biodegradable materials. Iron and phosphate do not produce toxic gases when operating.
They also do not contain any heavy metal materials, such as cobalt or lead-acid batteries that can cause contamination if they come into contact with nature upon disposal.
How to care for your LiFePO4 battery
Here are some essential maintenance tips that will help you to increase the longevity of your battery, whilst ensuring optimal performance for years to come:
Watch the temperature - ensure that the battery is being charged and stored in optimal temperature conditions, as lithium-ion batteries life cycles are reduced in extremely hot or cold environments. think of battery storage as having a similar approach to the way you store food - your food can last longer and won’t go off if you store it properly!
Partial charging is key - when it comes to charging, ensure that you only partially charge and discharge your battery. 100% charging and discharging speeds up the rate that your battery breaks down in the case of LiFePO4 batteries specifically. According to research from the Battery University, partial discharge and recharging limits the stress on the battery and prolongs its life.
Correct charge voltage - follow the recommended charge voltage for your safety and maximum battery life.
Final Thoughts - An Emerging Battery Technology
On your quest for leisure batteries for your motorhomes, boats, caravans and solar storage or golf carts, you will have probably come across several types of batteries; from the most commonly found wet, lead-acid, AGM and gelled varieties to the cutting edge lithium batteries, there is a whole host for you to choose from.
Whilst lead-acid batteries are cheaper, they are increasingly becoming a less effective option for appliances. due to the lower performance and higher lifetime cost. Their running costs are also significantly higher, as they provide fewer cycles and lower efficiency and need to be replaced more often.
This is where LiFePO4 comes in. Lithium iron phosphate batteries are by far the most cutting edge and versatile variety, and they deliver on various fronts: budget, performance and sustainability.
Above all, they are fast becoming a more environmentally friendlier option. The climate crisis may be one of the biggest challenges of our generation, so opting for LiFePO4 batteries can help you to do your bit for our planet.