Thoughts

Julian on April 15th, 2013

Some solar charge controllers include a load disconnect function. In most cases it just switches off the load when the battery voltage drops below a pre-determined level. Sure it provides the ultimate fail safe against a flat battery, but it’s a crude device. Imagine the scenario: you’re in the shed late at night – it’s [...]

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Julian on April 8th, 2013

This is a story of unintended consequences. When I designed the PWM5, I thought it would be a useful feature to be able to switch off the flashing blue LED. And a few people have agreed that it does come in handy. But not for the reason I had in mind! The blue LED is [...]

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Julian on April 5th, 2013

I keep coming back to the idea of an MPPT Solar Charge Controller. It would be the maximum power point tracking version of the PWM5. But there’s an idea buzzing around inside my head which I have to research before I can begin the design process. It’s the thought that there might be a coincidence [...]

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Julian on August 29th, 2012

I’ve been looking around for a twilight switch (dusk to dawn switch) for 12 volt appliances. It’s a device which closes a switch when the ambient light level falls below a certain level – ideal for turning on a light when it gets dark. There are very few available, and none of them does exactly [...]

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Julian on March 12th, 2011

Electric cars are coming, slowly! Here are some thoughts about how the industry will develop. Battery charging is not the whole story Batteries must be replaceable as well as rechargeable. The idea of re-charge points in filling stations is frankly laughable. Waiting 6 hours for a fill up is nonsensical. Re-charge points in shopping centres [...]

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Julian on March 10th, 2011

It was always my intention to follow up the design of the PWM5 with a MPPT (maximum power point tracking)┬ácharge controller. But it hasn’t happened – for a number of reasons. Firstly, there’s a simple economic argument. The 30% or so of extra power that MPPT squeezes out of a solar panel can be obtained [...]

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Julian on November 21st, 2010

I was asked recently if the PWM5 can be used in a 24 volt system. If the 24 volt battery is actually two 12 volt batteries (connected in series) then the answer is a qualified yes. Qualified because this can’t be done with a single solar panel. The diagram shows how it should be configured. [...]

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Julian on November 3rd, 2010

Bootstrapping is the process of picking one’s business up by its own bootstraps, or in other words, using one’s own products or services to increase business efficiency. My product controls the process of charging lead-acid batteries from solar panels which gives me free electricity. So to bootstrap my business, I need to use that free [...]

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Julian on September 26th, 2010

During the summer my solar array expanded a little with the introduction of a new 80W monocrystalline solar panel. I now have around 60 watts of amorphous and 80 watts of silicon. The panels are all connected in parallel inside the box on two chunky aluminium bus bars. A long run of 15A mains twin [...]

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Julian on July 15th, 2010

It may be possible to upgrade the specification of the PWM5 to a maximum current more than 4.8 amps. I really want to rate it for use with solar panels up to 100 watts which have a short circuit current around 6 amps. The 4.8 amp current limit is pretty arbitrary really. It was chosen [...]

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