on the edge

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Greg Black

gjb at gbch dot net
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If you’re not living life on the edge, you’re taking up too much space.

FQE30 at speed


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Worthy organisations

Amnesty International Australia — global defenders of human rights

global defenders of human rights

Médecins Sans Frontières — help us save lives around the world

Médecins Sans Frontières - help us save lives around the world

Electronic Frontiers Australia — protecting and promoting on-line civil liberties in Australia

Electronic Frontiers Australia


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(Coming soon…)


(Coming soon…)

Software resources

GNU Emacs


The FreeBSD Project

Wed, 03 Nov 2004

A question for the electrical engineers

Bought the third battery in 22 months for the BMW today. They are not all that expensive, but this is still a bit over the top. Can’t complain about the batteries themselves, as my use is contraindicated for lead-acid batteries—the battery gets used for maybe 15 to 20 starts on a track day and then sits idle for four to six weeks, with the only action being the slow drain from the immobiliser and radio LEDs. Clearly, this use pattern is never going to work well.

So I’ve been thinking about solutions. My current favourite is some sort of solar-powered trickle charger. This seems good to me because it would trickle charge during the day and the on-car electronics would trickle discharge during the night, so maybe the battery would give me decent life. But I’m not an electrical engineer and I’m not sure how right I am. Nor do I have any idea if this sort of thing is available off the shelf or if it would be easy to build one. Obviously, if it cost more than about $100 all up, it would be unlikely to pay for itself.

I had considered one of those baby batteries that they use in real race cars on the grounds that it would be easy to remove from the car for intermittent trickle charging via a timer in the workshop, but discarded that idea because I don’t think those batteries have enough grunt for events with night work like the Grand Prix Rally or a Duttons Rally. On top of that, if the battery was out of the car, the immobiliser wouldn’t work and Shannons wouldn’t be pleased. So I think some method of charging the battery in the car is probably the only way to go.

So, if you know the answers to the above and are willing to share, I’d love to hear from you.

Update: I’ve been pointed to Jaycar, who appear to have exactly what I need for $50. Cool.