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Sunday, 19 August 2007

How do we get electricity?

Boaty info:- Earlier inland boats just took a lead from the engine battery to run a light bulb, then people wanted more, so extra batteries were fitted. The trouble was sometimes people ran the batteries so low that they wouldn't start the engine. The solution was to split the batteries, one battery solely started the engine, the others did the domestics and a simple relay switch split the charging process.

Things moved on, boats got longer and more complex. The longer the boat, the longer the cables, the greater the voltage drop, so thicker cables were needed. But equally, more and more sophistication meant more and more power was wanted, and also people wanted more domestic appliances. Voltage drop is reduced if you double the voltage, so many boats now use a 24 volt system, Lily being one. Most lorries use this voltage so there are many parts that can be used from their parts bins, and the amount of current needed for a given wattage required by a lamp or motor is halved, greatly reducing the cable size required. But we still want home comforts, so we need 240 volts, and the alternating current needed to drive them, so the modern inverter was designed.

The inverter multiplies up the voltage to 240 volts and then magically makes it alternate from positive into negative. Unfortunately more modern equipment needs more than just an alternating current to make it work, it also needs it to be very close to the sine wave profile of the standard mains voltage. Clever engineers have mimicked this almost exactly and now electronic equipment works happily on the current modern inverters generate. Lily Pad has what is known as a combined inverter/charger and this wonderful device generates 3.5 kW of AC power, but also, when we get back to base and plug into the mains, also charges up the battery bank and keeps them in perfect condition.

Ah, batteries! There are all sorts of batteries available. Normal car batteries are fine for starting engines, but they do not like being heavily discharged. Domestic use in boats will tend to do this, so slightly different types are made to be leisure batteries. These come in all sorts of sizes, and at the Loughborough Boat Festival this year I saw a boat take delivery of some enormous batteries, heaven knows what they weighed but I know I was very glad I didn't need to move them into position. On Lily Pad we have a battery bank built up of 12 individual 2 volt cells, supplied by Harborough Batteries. These are similar to those used on electric milk floats and they are set in a metal locker on the starboard side of the rear deck and I think they weigh about 1/4 ton.


eeyore said...

Glad to see you have posted on this subject.

Whenever we boaters get talking the conversation tends to gravitiate to three subjects: batteries, enginew and toilets.

I look forward to posts on the others shortly.

eeyore said...

I just noticed the earlier post that covered the toilet subject!

A full discussion and description of your engine-including position, horsepower, age, transmission and reliability- is, therefore, expected soon.

Emma said...

I would like to know more about how you get your internet connection?

Emma said...

Hi guys!
I hope you are doing ok and things are all running smoothly. It would be great to come and visit...(mind you it may be hard to find you) I hope you have GPS fitted! If you do I am sure you could add a link in so we can keep proper track of where you are! :)
Carol you need to have a go at posting dont just leave it up to Ian!!
I hope to see you soon. :)