Tech talk: Know your batteries

FB: How good is a battery on a standard bike?

A: Standard batteries which, nowadays, are normally sealed AGM (absorbed glass mat, a special design of glass fibre mat designed to wick/absorb the battery acid/electrolyte between the battery plates), are normally very effective and far better than the previous, often leaky, regular vented lead-acid batteries of my youth, which often created nasty corrosion problems via their unavoidably necessary overflow pipes. AGM batteries contain only enough liquid to keep their very fine mat wet with sulphuric acid electrolyte, meaning that if their case is punctured, no excess liquid is normally available to leak out, making them ordinarily spill-proof. Being sealed also allows their use at odd angles; they deliver high starting currents on demand; and provide a relatively long service life with good electrical reliability – even when deep cycled or discharged. They are also maintenance-free, and are lighter than the flooded lead-acid type.

FB: What are the functions of the battery on, say, a modern sportsbike?

GH: At the end of the day, only two functions are ordinarily required: the storage of enough energy to start the bike’s internal combustion engine alongside providing sufficient lasting power between engine cycles to maintain electrical current to systems such as clock, odometer and alarms.

FB: How long do they last?

A: That depends on quite a lot of variables! For example, if a battery is well maintained, (an AGM battery here) they will typically have a lifespan of five to ten years, which can be double that of their flooded lead-acid predecessors.

FB: How can you get the best from them?

A: Using a bike regularly both keeps engine start times and battery load to a minimum and the battery remains conditioned by being charged from the bike’s own generator after each start. Should regular use of the bike not be possible – such as during winter months – then removal of the battery from the bike is a good solution. While the battery is in storage, the use of an intelligent charger is desirable as well. If the battery is to remain on the bike then the use of an intelligent charger is absolutely essential, or you’ll probably be bump starting the thing come summertime.

FB: What are the main reasons they go wrong?

A: Usually, it comes down to natural ageing and lengthy over-discharge. The former can be minimised by regular normal use and the latter minimised by ensuring any battery put on permanent winter charge has its intelligent charger reset weekly to guard against the charger unknowingly becoming inactive (i.e. as could happen as the result of a momentary mains power drop or power cut).

FB: What’s the main difference between lead-acid and lithium batteries, and how did they come about?

A: After initially gaining momentum within the radio control model market – due to the fact that the various types of cells grouped together generally under the ‘Lithium’ banner can store a huge amount of energy in a very small space when compared and still contain no potential harmful acid – the technology graduated to mobiles, tablets and laptops along with other consumer products, and now to motorcycles, too.

FB: Do they bring any other advantages?

A: As AGM batteries are so reliable and efficient, Lithium battery advantages – as with any product – can often be somewhat overstated by their makers to promote them, but as they contain no acid they are undoubtedly safer to handle than earlier flooded lead acid types. The main difference between them is weight, though. The various types of Lithium battery, when well maintained and fully functioning, ordinarily deliver a higher energy to mass ratio,

i.e. more energy than a conventional battery for the same mass/size, or the same energy capacity for a lower mass/size. Where saving weight and/or space is important – or when more energy becomes required to start an engine – such as in the event of it being internally tuned with a higher compassion ratio, for example, then it’s undeniable these modern battery types can sometimes provide the only possible starting solution within the packaging space available. They can also be beneficial in ‘total-loss’ situations where – typically smaller capacity race or competition – bikes are running without a generator, but which still need electrical power to drive things like dashboard instruments, quickshifters or exhaust power valves.

FB: Are there any drawbacks?

A: Even though the various types of Lithium battery, because of the absence of acid loss, are often described as ‘maintenance-free’, they’re certainly not ‘care-free’, and certain types can suffer permanent and even irrecoverable damage if they are ever allowed to become totally discharged (i.e. below 8v) or overcharged, as may happen if an old-fashioned transformer-type charger was attached to a Lithium battery and which attempted a charge input level of above 15 volts. For these reasons, we would always recommend that a rider buys a Lithium battery where the battery manufacturer also provides a dedicated charger (such as a Shorai, that has a specific charging port on the front of the battery), or they ensure that the charger they have has a specific Lithium charging mode.

FB: Is there a time where a lithium battery shouldn’t be used?

A: Lithium batteries are known to have their output reduced in very low temperatures, so if a bike was planned on being used in extremely cold conditions, it may be preferable to stick with a conventional battery type.

FB: Are they worth the extra cash?

A: If a special is being built where space is extremely limited, or if space under the seat is required for an additional electronic module such as a Power Commander or a Bazzaz or any other ECU remap, or if a race bike is being built where every gram saved could make a difference, then Lithium-ion batteries are well worth the cost. If, however, a regular road bike needs to have its failed or depleted battery replaced, then a regular AGM replacement is normally perfectly okay.