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What generator to buy

We are looking to buy a generator for our 42 foot narrow boat. The main use for this would be to charge the batteries when doing a short days cruising. It would also be used to charge a laptop and mobile phones. We currently have an electric fridge, cd/radio and lighting which are powered by 2 leisure batteries. Any advice would be appreciated

Asked by: Mike Hodder  | 2.12pm, Saturday 25 February

WW says:

If you are cruising for just a few hours, it should be possible for the engine to charge the batteries well- especially if there is an external alternator controller.
If you want to purely charge the batteries from a generator, then you would ideally need, assuming you have two 110Ah batteries, a 20 to 30 Amp battery charger, to be powered by a generator. Any small generator would be able to power this, as the input would be a maximum 450W for a 30amp charger.
There are a few generators out there that have a DC only output, though they tend to be hard to find. Honda used to make one, though a second hand one might be possible. However, you then might need a invertor to provide basic 230V power for you laptop, etc.
Ideally, chose a 4-stroke generator, if you are having a petrol one, as the 2-stroke are expensive, noisy and tend to have very unstable voltage outputs! The very cheap open-frame generators that can be found online or in DIY stores tend to be extremely noisy and would soon make you have enemies from those moored nearby!
There are two main type of portable petrol generators, those which have a standard alternator, and inverter types. The former are cheaper, the latter produce a much more stable waveform- essential is you want to run a TV or delicate electrical equipment. They are more expensive though! However, for battery charging, or mobile phones/laptops, the ordinary ones are fine.
We used a Honda EX650 for many years- over 20- and only stopped using it because it was stolen! It produced 450W continous, 650W max, and was ideal for what you use. Although it is no longer available, there are other similar models around, both from Honda and other manufacturers. Looked after, with regular oil changes, sparkplug maintenance, etc, they wil last for many years. However, they are not waterproof and should ideally not be left running when it is raining, without some form of basic cover- that doesn't choke the exhaust, or prevent the cooling air from flowing.
A word of warning though- all petrol generators should be stored in a locker similar in construction to a gas locker- petrol vapour leaking out is very dangerous. You could store one in a self-draining cockpit, but that might not quite meet the boat safety standard. You also need to consider where to store the petrol (like in a gas locker).
There are also a few other considerations: always refil the generator on the land; preferably always run the generator on the bank as well, rather than on the boat.
Never even run a generator inside the boat, or even inside the back doors of the boat, or in an engine room- carbon monoxide will quickly build up, with potentially disterous consquences!
Also, a generator has an earth point; a length of cable, connected into the ground (like through a mooring spike) will give you a proper earth connection; many users of generators ignore this, which could be dangerous.

Mark Langley  | 5.48PM, Saturday 25 February

The problem with having a generator on a narrowboat is where to store it when not in use. The storage requirements for petrol (and equipment with an integral petrol tank), are the same as for gas; in a vented locker or in an open location where any spilt fuel or vapour will not enter the interior of the boat.
I would advise you to consider spending the money on improving the battery charging from the engine and possibly increasing the battery capacity.

Rupert Smedley  | 5.53PM, Saturday 25 February

Readers say:

As said before, the Honda is an amazing machine, ours runs all summer. Ventilated storage is essential, however the EU10i does have a fuel filler cap vent switch which should (but may not) prevent fumes being vented when not in use. Consider a solar panel and small charge controller.

Paul Douse  | 10.09AM, Wednesday 7 March

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