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.

Below are two tables which give general information about the common cells used and configurations of bike light batteries. The information is for use as a guideline, if you can’t see what you require please contact us and we will do our best to provide a solution to your problem.

Common Cell Types

The cells listed here are designed specifically for use in packs and have a flat top and are not suitable for standard use.

Cell Type	Capacity (mAh)	Height (mm)	Diameter (mm)	Weight (g)
4/3A	3800	67.0	17.0	52
1867	4100	67.0	18.5	62
C	4000	50.0	25.8	75
D	9000	61.5	33.0	166

Typical Configurations

This table shows some configurations of various batteries we have done in the past, this is by no means a conclusive list, it simply shows examples, and these configurations can be made using any size of NiMh cylindrical cell.

Configuration	6V Battery	12V Battery	13.2V Battery
SBP
NESTED
BIKE BOTTLE

At this point I think it is worth mentioning the termination of the battery. There are thousands of different connectors out their and it is very difficult to match the right ones without either seeing pictures or actually physically having the right connector in your hand. Even then it can be difficult with connectors like jack plugs/sockets, polarity is important and as we only see one end of the application it can be very difficult to get the connector right. The easiest thing is for us to supply the battery with plain flying leads and for you to fit the required connector to these leads. If however you would like a connector fitted then the more information you can get to us the better.

A final point is chargers; the charging of rechargeable batteries is often overlooked and not deemed to have great importance, this is however a false belief. Charging has a huge bearing on the performance of you battery pack, and charging your battery right is very important. Cell Pack Solutions provide a range of battery pack chargers manufactured by Ansmann. These chargers are some of the best around, all but the base model are intelligent chargers which automatically detect the current state of charge of the battery. They automatically detect when the batteries are fully charged and switch to trickle charge so there is no worry about overcharging the battery. We would strongly recommend the use of one of these chargers with your battery pack to gain the best possible performance and life from your bike light battery.

To make it easier we have put together a page of standard products which you can order from this site directly saving both time and money; see the link below for our standard product range.

Bike Lights Standard Products Page

We are always interested in designing new products, if you can’t find a standard product to suit please contact us via e-mail quoting ‘Bike Light Battery’ or speak to one of our team on 0191 427 4577 and we will be happy to help.