Filling station

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The charger is a 13.5V adjustable switching power supply, an SP-500-13.5. This cost a little over $300 Canadian, which I opted for instead of something like a Rudman PFC20, which costs $1550 US. The power supply acts as a constant voltage charger, is power factor corrected, and very stable. The only problem was charging each battery one at a time. At first I did this, and as I was not driving the car often it was not a big deal. I'd simply move the charging cables when I thought about it. I knew one day I'd want to drive the car every day, so I needed a way to automatically switch the supply from one battery to the next. I thought this, or something I could adapt to do this, must exist already, but after several bouts with Google I had my doubts, so I decided to build one. According to Exide, Orbital charging is finished when the charging current falls to less than 2% of rated 20Ah capacity - which for the 34XCD is 1A. At the time I did not know how to build something that would detect the current change. For the amount I drove - 5 to 10 km - charging always finished in less than 2 hours, so I opted for a timed switch which had the benefit of being easy to conceptualize. This helped a lot: Practical Electronics for Inventors. There are two editions now - the old one has lots of errors.