I spent a lot of time trying to find an economical replacement battery for my lighting system. Here is what I did:

I purchased the 6v, 4500m Ah NiMH battery to replace the Lead Acid battery that came with a Sigma Sport lighting system from the website Batteryspace.com. The new battery provided a much longer burn time at a much lower weight. For less than $30 I received a far superior battery than what came with my lighting system. Batteryspace.com also provided an assortment of connector sizes and I was able to match the one for my light. I did have to use the switch from my Sigma system because the switches for the light were located on the wire itself. This required some cutting and splicing of wires but something that anyone with a small degree of electrical skills can easily do. I had to splice the wire from my old system to the NiMH battery. The wire from the battery was the type that had the insulated hotwire surrounded by the wire from the negative terminal. This gave me a moment’s pause, but was not a problem. Just twist up the negative wire and splice it like any other wire. The only other modification I had to make was to the charger provided. It came with the male connector terminal (for the provided tips) attached. Because I need to plug the battery into the switch on my lighting system, I needed the female adapter plug attached to the charging unit so I could insert the correct connector tip. The only way I could do this was to splice the female end to the charger so I could use one of the tips Batteryspace.com provided. You could probably get an adapter for this, but it was more convenient just to splice it in (because I didn’t have the adapter). My only recommendation to Batteryspace.com would be to provide a couple of these adapters with their adapter tips. If you own a light that the switch is on the light itself you will not have any of the previously mentioned difficulties.
I liked the fact that this battery can easily fit into a seat pack. I have a full-suspension bike that does not have any water bottle mounts, so attaching my old battery always required creative use of zip ties and the battery still did not stay in place very well. It’s much easier to put the light in the seat pack. There was plenty of wire provided for my needs. This battery would work great for use with a helmet-mounted system as well because the battery is very compact.
I was ready to throw away my old Sigma lights altogether and get a new system until I decided to look for batteries for bike lights on-line. That is how I found Batteryspace.com. For less than $30 I was able to make my system better than it was when it was new. Batteryspace.com also sells bulbs and connectors and anything else you might need repair or customize your lighting system.
Batteryspace.com’s web site was very user friendly and included a search feature. They sell a tremendous amount of products for bike lighting, whether you want NiMH or Li-Ion battery. They also sell almost anything else to meet your battery needs for any application. I certainly recommend their site and will be a return shopper!

Brad Ditzler--Pennsylvania