Fog lights / Batteries

[[XAP]Bob]

I'm ashamed of myself, my home made lights didn't do too well this morning, I think my old drill battery might be finally dying - it was a good workhorse*.
I might go to a cheapo store and see how cheaply I can replace it like for like, because they're good power sources, serious storage and decent power output! Else it's on to NiMH AA's I presume... (Any experience on the forums?)

On the other hand I had an excuse, why were there less fog lights on cars this morning (in the fairly heavy, freezing, fog) that there are on a clear day. Some 10% of cars didn't have any lights on, 20% had just sidelights (chocolate fire-guard territory).
I'm not the only one who noticed today, my driving colleagues said the same!

Bob


* A reconditioned drill, after 10+ years the drill started to fail, so I replaced it, but kept the old one as a one way only screwdriver etc.
When I finally dismantled it to get the battery into a portable format it was giving 5.4V (nominal 9.6V) it's managed a few months of being charged/discharged every day, but it's probably dead** now
** Dead = can't do at least two commutes (home and back to work)

PS - Homemade lights are Luxeon LEDs - pair up front at 160lmn running of 1A drivers, single rear at 140lmn on a 700mA driver. So battery needs to provide 5-32V

[kwackers]

Problem with drills and rechargeable power tools in general is they nearly always use cheap Chinese rechargables which have the lifespan of yoghurt left out in the sun.

Even some 'named' brands are pretty crap - Black and Decker for example, haven't had a B&D rechargeable tool that's been worth a carrot when it came to battery longevity. On the other hand I had a Bosch drill that lasted forever - in fact the battery was still OK when the chuck bearings finally gave up the ghost.

If I were you, I'd simply build my own pack from decent batteries. In the long term it'd be far cheaper.

[[XAP]Bob]

Hmm 10 years isn't yoghurt in the sun territory in my book, and this is a B&D.

Mind you chatting with a geek friend at work they suggested using a welder to refresh it... see instructables for more ideas.

It also does better when I remember to charge it each day - but it is on the way out unless I do something. I might try plugging a fat resistor across it over a weekend to fully discahrge it, that's meant to do good things to nicad batteries, and seems less risky than taking a welder to it.

If I went for AAs I'd be looking at a set of 8 I imagine(easy to get clips to store 8AA's)
To get the power and capacity I'd need, if I think about the lights as a 7.5W draw (probably not too far off):
8*1.5V=12V, 12V/7.5W=1600mA
Looking for 90 minutes run time (to give me some leeway) that's 2600mAh cells required, and close to a FULL discharge each day). Which is close to the top end of NiMH as i understand it.
And I want to add a couple more front lamps, with narrower beams pointing further in front of me, so that will put even more load on the battery pack.

Whereas drill batteries are easily capable of pushing that kind of load for hours (laptop batteries might be interesting)