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Battery life

How long can I expect a well maintained bank of 3 leisure batteries to last? They're five years old and the inverter had just started switching off after quite a short time, with the alarm light coming on.

Asked by: Paul Taylor  | 11.00am, Thursday 29 June

WW says:

Five years is a fair lifetime for a set of batteries, but it does depend on type and usage. It certainly sounds as if the batteries are failing; however it is usually just one that drags down the whole bank.
You can often get a little extra life by isolating the bad battery; if you disconnect the individual batteries and monitor the voltages of each one, the voltage will be lower or drop faster on the bad battery than the good ones. Then reconnect the two good ones to tide you over until you get a new set. Do not be tempted to just replace just one battery. Batteries connected in parallel to form a high capacity stack must be exactly the same age and type.

Rupert Smedley  | 12.22PM, Thursday 29 June

I agree that a great deal depends on how the batteries are treated and how they are maintained. If you regularly take a lot of power out of them and then leave them in a discharged state for any length of time, they will fail quite quickly.

  • Having tungsten lights on continuously and frequently using 230-volt domestic appliances through an inverter are two good ways of running the batteries down. Leaving them in this state for any length of time will encourage sulphates to build up on the battery plates which makes it more difficult for them to be recharged. They should also be checked regularly and topped up with deionised water if necessary.

  • On the other hand, if you are more frugal with the use of electricity and regularly use a three-stage charger to keep the voltage up between cruises, they should last at least five years and, sometimes, much longer.

  • The type of battery also makes a difference, although it is not always easy to determine what type you are being offered. Cynics will tell you that there are only two types of battery - Traction batteries and starter batteries. Assuming that you don't want, or can't justify the expense of traction batteries, you have to decide whether the leisure batteries you are being offered have the heavier plates the manufacturers claim or whether they are simply starter batteries with a different label.

  • Speaking personally, I bought a set of Elecsol batteries (now unavailable) in 1997 and I replaced them in 2014 - not because they had failed but as a precaution because I was afraid they might finally give up the ghost while we were away cruising. This is obviously exceptional but it shows that you can get many more years from a set of batteries if you look after them.

    Graham Booth  | 11.11PM, Thursday 29 June

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