--- In [email protected], Bruce Napier <br...@...> wrote: > > Chas says on his Moore 2 Life blog that he has just had his third > alternator fail in five years and has been told "an average of between > 1 and 2 years is about right for an alternator being used every day > charging five domestic batteries". We're still on our first one after > nearly six years of charging four batteries. > > I've never heard that alternators should have such a short life - am I > just lucky? > > > All the best > > Bruce >
I think Chas has other problems such as Roger's post describes. As the majority (if not all) of our alternators are derived from automotive sources there is the odd occasion where "value engineering" ends up with a badly designed alternator but the vast majority of alternators should last far longer than two years. Alternators are inherently self limiting for current so (in theory) it should be impossible to cause any heat damage which includes blown electronics etc. In addition I have no idea how you can burn a rotor out because they only draw 3 to 4 amps unless there is an incipient manufacturing fault, however I know they do burn out. I have had an alternator run into a dead short on its main charging lead for perhaps half an hour without damage. Advanced regulators such as the Sterling device mentioned can never make the alternator deliver more current than it was deigned to, even the latest alternator to battery charger can not do that. However all such devices will cause the alternator to deliver more current than a normal voltage regulator during the second phase of charging and if there is any deficiency in the cooling then heat problems can occur. I also have a feeling that the fans used may not be optimised for long periods of low speed so trying to find and fit a larger fan could well help. Chas needs to look at the ambient engine area temperature and also the type of fan fitted on the alternator. Some Listers run "backwards" and if they are fitted with an alternator with a handed fan (not all are) then expect overheating problems. In fact fitting the Wong handed fan on any alternator can cause problems. I see many trad, rear engine boats with the engines closely boxed in and without adequate or suitably located air intake grills. I would always try to fit at least a 4 sq in (6 sq in is better) intake grill right behind the alternator. He also need to think back in case he upgraded the alternator but kept the original fan. Having said all that I know they do burn out in one way or another, especially when linked to certain advanced regulators. I put this down to a combination of poor designs and lack of cooling, but it can be mitigated by careful choice of advanced controller. For instance the Adverc pulses the alternator in 20 minute bursts so it has a chance to cool down between each high current burst (thats not why its done but it helps cooling). Lastly I have seen some calculations that cast considerable doubt upon the effectiveness of advanced controllers when fitted on systems that have been optimised for best performance and maintained. It seems a considerable, if not all, of the extra amps you see flowing when the device operates is used up in heating the battery and causing the gassing. Tony Brooks
