Thursday, 16 October 2014

Forum

We slept late. By the time we'd come to our senses and had something to eat, there didn't seem to be a   pressing need to travel anywhere. We want to be in Nantwich on Sunday morning, and that's only just down the road. The main issue is keeping the batteries charged when we're not moving. And this has one or two facets.

1. It's not good for an diesel engine to be run cold, or with no load.
2. You mustn't run your engine in gear while stationary, because of the damage the turning of the prop can do to your immediate canal environment.
3. Running your engine faster than idle speed is noisy – which can be annoying for both you and your near neighbours.
4. Running your engine slow may not get your alternators to the speed where they are generating proper amounts of electricity.

So, with time on my hands today, I decided to ask the on-line Canal World forum what speed my engine needed to run to get the alternators charging properly. I was pleasantly surprised with the responses, in that several knowledgeable contributors posted comments and interacted with both me and each other.

The answer, however, was not entirely clear. There were several issues, but there seemed to be one fundamental contradiction. The alternator spins faster than the engine, by an amount determined by the sizes of the pulleys connected by the drive belt. My alternator pulley is half the size of the engine pulley, meaning it should spin twice as fast. But the official chart for the alternator suggests that, even at that ratio, it will generate very little electricity at cruising speeds and none at all when the engine is just idling. My voltmeter indicates, however, that it certainly generates a charge voltage even at idling speed.

So I have a conundrum. But I also have a lot more information than I had yesterday. One of the comments suggested purchasing the sort of meter that you can put around a cable to indicate the current flowing through it. I'd forgotten about these – though I should have remembered the AA man using one a year ago with my car. So I feel a birthday present coming on – just have to work out where to get Amazon to send it to as we travel down the Shroppie over the next few days.

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