Custom Bike Light solutions are becoming more and more popular with the price of standard Bike Light Kits increasing and with such kits often not offering the best solution for the rider. Even if you do purchase one of these kits, replacement batteries can be very expensive, sometimes running close to the cost of a new bike light kit. It seems for these reasons and others that people are opting to build their own bike light systems from scratch, reducing the overall cost and getting a custom solution to suit their needs better than a standard product could.
There is quite a lot of information on the internet regarding bike lights and bike light kits which is where we have looked to gain a little greater knowledge in the subject. This along side talking with customers has enable us to gain a greater understanding of what is required from a bike light battery.
Modern bulbs can now operate at high levels of brightness; the efficiency of these bulbs is also increasing however it is still the case that you need quite a high amount of power to run them effectively. This means that the battery used to power the bulb needs to have a high capacity to give a worth while run-time; unfortunately this brings up issues of size, weight, and price of the battery.
Which type of battery?
This very much depends on what type of light (bulb) you are using and how you intend to use it (frequency and required run-time).
There are many different types of bike light systems for the various type of rider, off-road, urban, rural, commuter etc. this is important when selecting the type of bulb; when looking at the type of battery to be used, bike systems can be split into two broad categories:
1, lights to make you able to be seen
2, lights to able you to see.
The first, are generally low power bulbs which quite often come as an enclosed unit with the batteries enclosed in the bulb case, taking standard cells, AAA, AA, C or D depending on the size of the unit. These type of systems tend to work find using good quality Alkaline batteries if you are an infrequent user, only going out once or twice a week in the dark. A more frequent user may be better off using rechargeable batteries; they may not last as long in between charges but you will get better life in the long run.
The second type of bulbs will generally require a custom built rechargeable battery to power them; this is our main area of interest. In the past Sealed Lead Acid batteries were commonly used because of there robust nature, and they were the only rechargeable system that could deliver the kind of power required to run such bulbs. The main drawbacks of these batteries are the size and weight, a general 12V 7Ah battery can weigh up to 2.65Kg and measure 151mm x 97.5mm x 65mm, and on a bike, these need to be kept to a minimum.
As rechargeable technology developed Nickel systems started to become available with firstly Nickel Cadmium (NiCd) and then Nickel Metal Hydride (NiMh). NiCd batteries are very robust which is good for this application however they do not exhibit the same energy to weight ratio (energy density) of the more modern NiMh cells. An example of this is taking a D size cell (61.5mm x 33mm, 180g), a NiCd D cell can give you 5Ah capacity, a NiMh can now give you up to 10Ah, this is pretty standard that a NiMh cell of the same size will give you around twice as much capacity than NiCd.
Many people will have heard about Lithium-Ion batteries, these batteries again have an increased energy density over NiMh so a battery of a smaller size can deliver the same capacity with Lithium-Ion. We do not currently deal with the manufacture of custom Li-Ion battery packs although it is something we are looking for the future so currently the best system we can offer is using NiMh.
A NiMh bike light battery will be made up of a number of cells strung together in series in a given configuration. Each cell has a voltage of 1.2V, therefore a 6V battery will have 5 cells and a 12V battery will have 10 cells. The voltage rating of the battery must match that of the rated voltage of the bulb or slightly over (generally only 1.2V greater), a lower voltage will not run the bulb effectively, if at all.
The power rating (W or Watts) of the bulb is important; the higher the power rating, the more current the bulb needs to power is and hence a higher capacity battery will be needed to cope with the current drain. Unfortunately with batteries, as you increase the capacity, this size of the battery increases and with it so does the cost. The important thing to remember is the higher the voltage and power rating of your bulb, the larger and more expensive your battery will be.
The weight and size of the battery pack is a very important factor; the size and weight of the battery pack will relate to the electronic specifications outlined above, however the shape of a battery pack can be worked with and there are may different ways a battery can be configured. Packs can be built to fit into a bike drinks bottle, to strap onto the frame of the bike, or fit into a carry bag, there are many alternatives available.
Cell Pack Solutions offer NiMh solutions most commonly using NiMh cells to make up battery packs of varying voltges to meet the specifications of the bulbs. Check out the range of Uniross cells we have available for use in bike light applications.
