An electrical experiment – Monday 28 March 2022

We plan to visit marinas where practicable, especially when riding out bad weather. Marinas provide comfort; from most marinas we can go shopping for fresh food, we can have a proper shower, wash clothes and, in particular, connect to shore-power. But we will cetainly have to anchor from time to time; we will almost certainly have to anchor at the start of the trip when we head south down the the coast of Wales.

Bubble has a starting battery and just one domestic battery, of 140Ah. The more I read about domestic power for yachts and caravans the more it appears that the Watt-Hour capacity of the battery is of more use than the Amp-Hour rating, but I’ve never heard fellow boat-owners talking about the Wh capacity of their batteries. Commonly one hears the proud declaration ‘Oh I’ve got a bank of x batteries totalling y Ah’, where x and y are both much bigger than the resources at my disposal on Bubble. But I’ve never experienced a shortage of power on Bubble.

Away from shore-power, if motoring or motor-sailing I am confident that the domestic battery will be sufficiently charged to cover Bubble’s modest needs for a couple of days. As a matter of course the fridge is on continuously and the compressor, when running, draws several amps. The instruments including the VHF and AIS are usually left on as the AIS transponder has a useful anchor-alarm facility and my iPad, phone and laptop all need to be charged. All lighting aboard is LED so the current draw there is negligible, but the the fresh-water pump uses several amps as does the Eberspächer cabin heating system. The anchor windlass draws a huge current so I tend to run the engine when arriving at an anchorage and in advance of weighing the anchor when moving off. At sea the autopilot motor presumably draws a siginficant current and could do so for many hours at a time.

Diesel engines do not like idling so I don’t want to run the main engine to charge the batteries if we have to remain at an anchorage for some time.

Some people manage their power the ‘proper’ marine way by having one or more large solar panels and perhaps a wind-powered generator too. I would love to have these but Bubble is not replete with convenient places to mount them, and I don’t have a stainless fly-bridge on which to mount such things. I have a small solar panel but it kicks out little more than 1A in bright sunlight.

It occurred to me when contemplating a very expensive project to equip Bubble with more power-generating equipment, that even with the extensive use I get out of her, she’s at her berth in the marina, connected to shore-power, for most of the year. Almost all of my sailing is day-sailing from the marina, and power is of no concern then. Longer trips, though more frequent following my retirement, are only a few a year in number and for much of the time when cruising Bubble is visiting other marinas, and is also then connected to shore-power. It seems to me that the expense, work and added windage on the yacht to do a ‘proper’ job is difricult to justify in my own particular cirucmstances.

So I have just collected from Screwfix a small petrol generator, an Impax 800i. As the name suggests, it is a 700W machine, so it will not run an elecrtic heater or kettle, but I don’t need it to; nor will it be up to powering Bubble’s hot-water heater, just as a ‘proper’ solar/wind installation wouldn’t. All I plan to do is to connect it to the yacht’s power inlet when at anchor, if the batteries need a top-up, and see what happens. I don’t know at the moment whether or not the on-board Sterling battery- charger/maintainer will work when connected to the Impax, but the generator is an invertor model so it is claimed to be compatible with sensitive equipment such as PC chargers. We’ll see. But at under £200 it seems to be worth a try. I will report back as we go round …. that is if I ever need to run the generator in anger.

UPDATE AFTER TESTING ABOARD: it works fine when connected to the ship’s shore-power inlet and the Sterling battery charger charges the batteries as if connected to the mains. So the generator will be coming on the circumnavigation!

The little generator. I wonder if it will be any good.
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