Monday, November 03, 2008

Building a replacement battery pack for a NiteRider 12V light

Since it was quickly getting very dark in the evenings, and I knew the "fall back" time change was soon to be upon us to make it even darker, my thoughts turned to bike lights.

More specifically, my thoughts turned to the general inadequacy of my current white-light setup... I've been using a little Cateye on the handlebars in blinking-mode (to get the attention of cars) and a bigger Cateye HL500 mounted down on the fork blade for trail/road illumination. But it just can't cut through oncoming cars' headlights, and on a trail with twists and turns, it has too narrow a beam.

Last year, I put the small Cateye on my helmet, to get around the HL500's focused beam; that wasn't bad, but the combo just wasn't bright enough. I started using these lights after my NiteRider halogen's battery pack finally died. I got several years' use out of it, but a replacement battery pack is over $150, and I was having a hard time justifying the expense.

So, having decided the current combination was just not cutting it, I weighed my choices: get a completely new system (maybe a hub generator? can't switch it between bikes very easily, and quite expensive. New-tech rechargeable LED stuff? Nice, but pricey) or revive the old one (but a new battery pack is almost as much as a low-end LED light!) But perhaps there was a less-costly option...

With nothing to lose, I tore open the NiteRider battery pack. Inside, it's just made up of commercial/industrial NiMH cells -- which are available on the 'net, if one looks around enough. The only label was "4500mAh JAPAN". Turns out, they are "4/3A" cells; e.g. 1/3 bigger than a regular A cell. What, you've never heard of an A cell? Think about it, though -- we're all familiar with AAA and AA batteries... does not their existence presuppose the existence of an A cell? And indeed, they can be had, but a lowly A cell packs not the 4500mAh we're looking for... even a regular 4/3A is only around 4000mAh. We must find the mighty Sanyo HR4/3FAUX to get what we desire!

I found 'em at TNR Technical, for $6.50 each (and you need 5 for a pack.) They're available with solder tabs, which we need; no extra charge. With tax ($2.36) and shipping ($9.95), my battery pack cost $44.81.

Once I had the batteries, all I needed to do was solder them together in the right order, swap the cables and molded casing over from the old battery pack, and charge it up. The batteries are set up in two rows of 2, with the fifth one located on top of those two rows, all wired together in series to give 12V. The factory pack used heat-shrink tubing and hot glue to hold everything together; I used a small amount of electrical tape and it worked fine.

When I cut the grey silicone casing off the factory pack, I probably sliced it more than I needed to. I had to use a several wraps of electrical tape in putting it back together, to ensure it would be waterproof. In retrospect, I would have tried harder to get the casing off without cutting it at all -- I'm not sure that's possible, but I think it could be done with some patience.

Summary: Works dandy! 1/3 the factory price.


eric davila said...

On this battery pack rebuild, did you use the same stock charger to charge the new batteries? I'm wanting to do the same, and want to avoid buying another charger.

SHould work, but wanted to make sure. good post btw.


BikeBoy said...

Thanks for finding this old post Eric! Yes, the original charger works fine, as you would expect. I've been running my replacement pack for a couple years now, no issues.