--- In [email protected], "ap4098" <brook...@...> wrote: > >> > > > Unfortunately the question is not the correct one for the information I think > you want. > > The starter battery will be replenished in less than half an hour according > to the experts but I doubt that will be fully charged. I would say that > unless you are an inveteracy long distance cruiser each day then the chances > of you getting your batteries fully charged are close to zero. > > In four hours the alternator either alone or with one of the fancy additions > will get the batteries 80% charged or so BUT from then on the time taken to > replace (say) one amp hour gets progressively longer as the batteries near > fully charged. It is said that this could take ANOTHER 10 to 12 hours using > alternator alone. It is easy getting to 80% of fully charged and fancy charge > controllers will shorten this time but it is doubtful if they will make a > significant difference to the time needed to get to fully charged. > > If you do as most boaters without external charging sources do and just > concentrate on getting your batteries to 80% fully charged or so then treat > them and expendable and expect them to last between two and four years. This > is why it is often said that the most cost effective batteries are the > cheaper open cell wet lead acid batteries even though the vendors are trying > to push us towards sealed cells. > > Leaving your batteries at around 80% fully charged will result in a gradual > loss of capacity caused by a permanent change in the batteries insides. The > equalisation charge mentioned in another post will help to mitigate this but > not totally resolve it and in any case equalisation charging is far more > important for batteries that have been left on float or maintenance charge > for long periods NOT those using alternator charging. > > If you are intent on maximising the batteries life then you need an > alternative form of long slow charging that will go on for many hours. A > shoreline and multistage charge is probably the best but a fair sized(Watt+) > solar panel and controller will also do a fair job on a "holiday" boat whilst > it is tied up and you are at home. > > My advice would be to either get an ammeter and voltmeter fitted and learn > how to interpret them OR get a Smartguage but please note that as batteries > loose capacity because of that chemical change I mentioned the Smartguage > will show 98% charged or whatever based on the actual capacity and not the > capacity the batteries were sold with. > > IF you want a better answer (but still not perfect) you need to work through > the calculations you will find in http://www.tb-training.co.uk/Poweraudit.htm > > Tony Brooks
Hi Tony, Thanks for that - Iknew you would be lurking with the answer somewhere! Could you explain why the 80% problem is far worse on boats than cars. My car averages say 30min. journeys per start and the battery is about 10yrs old and still going strong ! Regards Pete www.thecanalshop.com
