As a user, one does not really need to know what the letters given to the various lithium battery technologies mean, apart form their relative dangers, writes Tony Brooks.
But they refer to the chemicals inside them as well as indicate they are constructed. Unless you are a design engineer I can think of no reason why a consumer should concern themselves with the construction of such cells because you buy them ready made, but I will explain the letters in a bit more detail.
What is important is that you only ever use good quality chargers or charging systems designed for the particular battery chemistry, and that the cells in the batteries are from known and reputable suppliers. People ignoring these two things are the main causes of the lithium battery fires we see in media.
LTO: Lithium Titanite
Consumers are exceptionally unlikely to come across these because they are very expensive and do not hold as much electricity (lower energy density) as other types, but they will charge very rapidly and are less affected by heat, so can operate over a larger temperature range. They may be used in electric ferries and large battery storage farms.
LiFePo4 or LFP: Lithium Iron Phosphate
The type usually used in our boats and in some of the more recent electric cars. These are arguable the most tolerant of abuse of the remaining types but still need a level of automatic protection against high and low temperatures and over and under charging.
They are less energy dense than other types, but still far more dense than Lead acid batteries. The types you buy as 'drop in' (vendors term) are equipped with an internal or external Battery Management System (BMS) to protect them. This and the fact they do not produce vast amounts of oxygen when they catch fire means they are far less likely to burn fiercely and at high temperatures that other types, so are the safest type that consumers are likely to come across.
However, the BMS will terminate charging when certain currents, voltages and temperatures are exceeded and if it happens when the alternator is charging it has the potential to wreck the alternator. This in turn lead to a more complex charging system than those most boaters are used to. Any charge source like solar or mains charger will ideally need lithium or user settings
NMC: Lithium Manganese Cobalt Oxide
We are now looking at types that totally rely upon their BMS and charger to prevent thermal runaway or physical damage causing serious fires. They are more energy dense than LFP or LTP and are used in things like power tools, e-bikes, e-scooters and many electric vehicles. They are safe enough as long as you buy reputable batteries and chargers with the correct BMS, and quality batteries who’s construction minimises the chances of an internal short circuit. It is the BMS/charger that you may find prevents your power tools working or charging in very cold or hot weather—especially if stored in a narrowboat.
LCO: Lithium Cobalt Oxide
These are very good at delivering a low current over long periods, but bad at providing high currents, so you find them in things like laptops, phones, tablets and cameras. They also do not have a very high cyclic (charge-discharge) life compared with other types. Again, they tend to be thermally unstable compared to LFP, so rely on the BMS to keep them operating safely. The comments about the correct type and quality of the battery and charger are equally applicable to LCO technology.
LMO: Lithium Manganese Oxide
These have better thermal stability than LCO and can deliver higher powers, and charge faster, but are still dangerous if abused. You will find them in portable power tools, some electric vehicles and medical equipment, so not as applicable to boat use. They also have an even lower cyclic life and in some cases it will be worse than high quality lead acid batteries.
A wide range of technologies
I hope that you gather from this that the term lithium battery covers a wide range of technologies so lumping them all in as one is not very bright. Things that happen with one technology will not be as likely to happen with another. Just because e-scooter or electric car batteries have caught fire, usually from abuse or poor quality, does not mean that the batteries on a boat are just as dangerous or prone to catching fire or exploding. To do so indicates that one does not have much of a grasp of the technologies.
One last point concerning lead acid batteries, if they develop internal short circuits, often caused by being at the end of their useful life, or subjected to an excessive charging voltage they will produce hydrogen that can explode and blow the case apart, spraying acid everywhere. They can also produce hydrogen sulphide that is a colourless gas that smells of rotten eggs. If you do not react to this it causes you to go 'nose blind, but it is also a lethal gas, so Lead acid technology is not as safe as we tend to think it is when comparing it to lithium batteries.