Custom café racers, bobbers, trackers, scramblers – all are aiming for that clean and very uncluttered look from behind the engine to the rear wheel. The two major challenges are the airbox and the electrics. The airbox can be replaced by neat, small pod filters (with carb jetting to suit). The electrics, however, can be more of a challenge. At the heart is the old lead-acid battery – big and heavy. If this can be minimised it could be mounted out of sight under the seat with its associated wiring. However, the challenge is the size, weight and orientation. New technology in the form of lithium batteries is often the answer. A quarter the size and one-fifth the weight (1.5 lbs versus say 9 lbs) for an equivalent 12 to 14 amp-hour battery with +270 Cold Cranking Amps (CCA) – more than enough to start a T100 Bonneville (see picture showing lithium versus lead-acid batteries). But they are expensive (4 x lead-acid) and high technology. They are small, light, powerful and flexible (can be mounted in any orientation) but they are also more sensitive and it is important to understand this or catastrophic failures of the battery and sometimes other electrical components can occur.
Four things to know:
A lithium battery has a different charging cycle and regime to a lead-acid battery. So one needs to use a lithium trickle charger for these (see picture showing Shorai and Optimate lithium chargers) and not a standard lead-acid charger.
If the CCA is exceeded the lithium battery warranty is typically voided (electronics within the battery will show the manufacturer if this has occurred).
If the lithium battery’s resting voltage goes below 12.8 volts then the warranty is also voided. In practice this means the battery should be trickle charged periodically – say once per week – and especially so for bikes with ECUs (fuel injection).
Do not let a lithium battery fully discharge and then use it again. If this does happen and the bike is then ridden then there is a real risk of unbalanced charging and catastrophic failure (burn and melt) of the battery and other electrical components (such as electronic ignition and voltage regulator). (see picture of battery and electronic ignition failure of this type on a BMW boxer)