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Posted: Mon Sep 24, 2012 4:40pm

Post Subject: New Batteries

I need to replace my three 110Ah domestic batteries but I am confused by the variety of batteries available, i.e. sealed for life, deep cycle, gel filled. Could you please explain the terminology and advise what would be most suitable. Len on nb Hobbyhorse


Posted: Mon Sep 24, 2012 7:26pm

Post Subject: New Batteries

Dear Len, unless you can ensure your batteries are FULLY charged very regularly you will kill them from sulphation before they run out of cyclic life or develop an internal fault. This means that batteries are best considered as consumables with the expectation of replacing them between every two to four years. If you have any sort of advanced alternator controller or even one of the latest alternators charging in excess of 14.5 volts you stand a good chance of destroying any sealed batteries by driving the electrolyte off as gas - they actually have a valve allowing gas to vent. In this case it rules out all but wet open cell batteries unless you can adjust your charging device(s) to suit the type of batteries in use. Maintenance free batteries, AGMs and Gells are all sealed batteries. The last two do provide theoretical faster charges and discharges but in everyday use you may well not notice. These types are more expensive and claim a longer life, but note my comments about fully charging. Most sub-£100 batteries are probably constructed in a similar fashion to starting batteries (hence many being labelled as dual purpose) but give an acceptable life in the domestic battery role. True deep cycle batteries may well be a number of 2 volt cells or large 6v batteries. These will have a fr superior cyclic life to the normal wet open cell batteries that are used commonly used and may also be rated over 5 hours instead of 20 hours of discharge. This actually gives them a higher effective capacity than the numbers suggest but you pay for that, in some cases handsomely. Not a lot of use if you allow sulphation to kill them. Make sure that whatever you buy your charging systems do not exceed the batteries maximum charging volatge.You will have to fight to get this figure for cheaper batteries but they are normally more tolerant of over voltage as long as you top them up. The normal recommendation for ordinary boaters without shoreline charging or a significant solar and/or wind charging are ordinary wet open cell batteries and be prepared to change them regularly. If you can keep them fully charged the true deep cycle batteries will last maybe 10 to 15 years. I have sub £100 Exide dual purpose batteries. Tony Brooks

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