Up to the present time users have only had available one main type of battery to serve a multitude of remote power applications.
This of course is the lead acid battery.
There are two main variations to the lead acid battery depending upon its specific application -
engine start (or “cranking”) battery and the deep cycle variety (or "leisure battery") with main types in that family being the gel and AGM sealed lead acid types.
The lead acid engine start battery primarily designed to provide a short, high power burst of electrical current to crank over an engine while starting.
The other main type of lead acid battery is the deep cycle type, which is used to provide sustained power for electrical devices and equipment over a long time period.
This is the type of battery which is the best choice to power most common electrical appliances - either directly 12 volts from the battery itself, or 240 volts from an inverter connected to the battery.
However, both types of lead acid batteries have severe limitations.
Lead acid batteries are extremely heavy and while weight may not be an important factor for batteries in a stationary environment such as a fixed solar power installation, for use in a motive application such as in a caravan, having to “carry” such a heavy dead weight does not make much common sense. In addition, lead acid batteries contain many nasty chemicals such as sulphuric acid and toxic heavy metals like lead which are potentially hazardous for the environment.
Lead is a very heavy metal and for many years the search has been on to make a better battery that is also lighter in weight.
Lithium is the logical choice, since it is the lightest metal.
Lithium metal is manufactured from lithium salts, which are extracted through mining activities and Lithium ion batteries have been available for several years now and are in use in many consumer applications.
As with lead acid batteries, lithium batteries also are available in several chemistries, each having their particular good and bad points. The earliest lithium battery chemistries which became a commercial reality are still in use today, for consumer items like mobile phones, notebook computers and camcorders etc.
These are cobalt oxide lithium ion and manganese lithium ion batteries. Both have high energy densities, but have the disadvantage that in large format applications and in cases where many separate cells are used, which can become unbalanced during several charge / discharge cycles: there is the risk that they can potentially become dangerous, with a possibility of fire or explosion occurring under certain circumstances..
While these batteries are generally considered quite safe in small format applications, such as for mobile phones and the like (generally one cell only is used therefore this is why the battery voltage of a typical mobile phone battery is 3.6 -3.7 volts) there could be disastrous consequences should a large lithium battery of this chemistry catch fire.
There are several documented examples, where the more hazardous chemistry of lithium ion batteries (lithium cobalt oxide) has caught fire and an example of this in recent years which many people may be aware of is several instances where laptop computer batteries have caught on fire.
In the mid 1990’s Dr John B Goodenough and his research team from the University of Texas developed material used to make the Lithium Iron Phosphate battery (LiFePO4 for short).
Unlike the hazardous nature of the earlier chemistry lithium battery types, Liberty Batteries lithium iron phosphate batteries are extremely stable and safe to use. This safety combined with their light weight has found wide use for these batteries for military applications and now for commercial applications.
These batteries are in fact even safer than lead acid batteries and do not suffer from some of the problems which are inherent to lead acid batteries, such as thermal runaway, sulphation when left in a discharged condition and high rates of self discharge, if not used.
A great advantage of Liberty Batteries LiFePO4 batteries is their extremely long life. For a standby power application such as battery could be expected to have a life of up to 20 years.
Lead acid batteries generally have a life of only a few hundred deep charge cycles while a quality LiFePO4 battery can typically be charged in excess of 2000 times.
Though not quite as high in energy density as the earlier lithium battery types, the lithium iron phosphate battery still has a far higher energy density compared to the lead acid battery, see graph.
The benefits to the user of a Liberty LiFePO4 battery are many.
Another major factor which should be taken into consideration when replacing a lead acid battery with a Liberty LiFePO4 battery, is that due to the higher energy density and greater performance of the lithium battery, often a smaller battery can be used which will provide equivalent performance to the original lead battery.
For many applications a 60Ah lithium iron phosphate battery will provide equivalent performance to a 100Ah lead acid battery.
What many battery owners and users fail to realise about the lead acid battery is that its capacity (Ah) rating is usually specified at the 20 hour discharge rate.
At high rates of discharge the useable capacity is reduced due to “Peukert’s Effect”: thus a typical 100Ah lead acid battery when discharged in an hour or two may have an actual measured capacity of as little as 60-70Ah.
As soon as a load is placed on a lead acid battery, there is a sudden drop or “sag” in voltage. The voltage continues to decrease until the battery is completely discharged. By contrast, the discharge characteristic of a Liberty LiFePO4 battery is very different. The discharge curve is close to being linear. Even under very heavy electrical loads a LiFePO4 battery will maintain almost full power, with very little reduction in nominal voltage throughout its discharge cycle.
Another great benefit of these batteries for owners of caravans / motorhomes / mobility and marine is their inherent safety features. Since they do not produce flammable hydrogen under any circumstances, (even if overcharged) a LiFePO4 battery can be safely installed in a confined area such as in a caravan or campervan without fear of a fire or explosion. Also due to the compact design of LiFePO4 cells, a custom battery of virtually any shape or size can be manufactured which will fit into any tight space even if the space is of an unusual shape.
To sum up, an overview of the benefits of Lithium Iron Phosphate batteries is as follows-
· Safe technology, will not catch fire or explode with overcharge.
· At least half the weight of an equivalent capacity lead acid battery.
· Over 2000 deep discharge cycles life compared to typically around 300 for lead acid.
· Double the usable capacity of similar amp hour lead acid batteries.
· Virtually flat discharge curve means maximum power available until fully discharged (no "voltage sag" as with lead acid batteries).
· High discharge rate capability.
· Unlike lead acid batteries, can be left in a partially discharged state for extended periods without causing permanent damage.
· Extremely low self discharge rate (unlike lead acid which will discharge very quickly if left sitting for long periods)
· Does not suffer from "thermal runaway"
· Can be used safely in high ambient temperatures of up to 60 deg.C without any degradation in performance.
· 12.8V nominal, 8V maximum discharge, 14.6V maximum charge voltage.
· Can be connected in series for higher voltages or parallel for higher capacity.
· Absolutely maintenance free for the life of the battery.
· Can be operated in any orientation including inverted.
· Does not contain any toxic heavy metals such as lead, cadmium, nor any corrosive acids or alkalis thus making LiFePO4 batteries the most environmentally
friendly battery chemistry available today.
Due to the much higher initial cost of a Liberty LiFePO4 battery, several cheap pirated copies have now entered the market. The prospective battery purchaser should be very wary when considering purchasing one of these batteries since one reason for their lower price is that some manufacturers do not pay royalties to the patent holder and as such the cathode powder used in their manufacture is often a much lower quality and the battery can be expected to have a much shorter lifespan combined with overall poorer performance.
Liberty Batteries LifeP04 batteries, which are of first grade quality, will outlast several lead acid batteries and provide vastly superior performance to the lead based battery.
Lithium Iron Phosphate batteries will revolutionise remote power requirements for heavy users of lead acid batteries in coming years by enhancing the amount of power which can be stored in a given battery size, thus allowing users to power electrical equipment for longer.