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Q & A

Charger Playing Up?

During the winter, the only electricity our narrowboat uses is for the three stage charger which charges only the 3 domestic batteries. The consumption is much higher this winter than previously, consuming more in 22 days than it has previously done in three months. When we check the boat the charger is always in trickle mode. The batteries are in their 8 year but behaved normally whilst cruising for 3 months during the summer. We did notice that the charger fan has recently started cutting in whereas previously we didn't even know it had a fan. Any ideas as to what may be the problem and the steps to take, please?

Asked by: Clive Dutson  | 7.52pm, Wednesday 28 January

WW says:

I am sorry to say that it sounds as though your batteries have come to the end of their useful life. The charger is working much harder to keep them topped up, but the charge is being lost. The fan running indicates that the charger is getting hot charging the batteries, which will account for the higher electricity consumption.
I am assuming that the cells are all properly topped up with distilled water; if not topping them up may temporarily alleviate the problem, but the batteries do need to be replaced. Eight years is a very good life, it shows what can be achieved with good maintenance and a multi stage charger.

Rupert Smedley  | 11.22PM, Wednesday 28 January

The trickle charge setting of the charger does not actually deliver a fixed current into the battery, it charges it at a voltage designed to maintain a fully charged battery in peak condition, compensating for the self discharge current. If the battery is failing, the self discharge current will be higher and it will consume more trickle charge power than a healthy battery, hence the charger will consume more mains power.

Rupert Smedley  | 5.14PM, Tuesday 3 February

Readers say:

Thank-you, Rupert. I fear you are right about the batteries - I was hoping to match the 10 years a neighbouring boat has achieved!
I can't quite get my head round the physics of this though. As the charger can't consume any less power then the trickle charge and, when we visit the boat, the green trickle charge is always showing how can we be consuming extra power? Presumably the charger 'thinks' the batteries are fully charged otherwise it wouldn't switch to trickle. Somehow the voltage must drop to switch to higher charge rate and consume extra power - can this really be happening? If you can stop my brain hurting I'd be very grateful.

Clive Dutson  | 11.24AM, Thursday 29 January

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