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yamyam
yamyam

Posted: Wed Dec 16, 2015 12:48pm

Post Subject: Battery charge

Hi just brought this boat it's got a 2000 Barrus shire engine with main alternator 90 amp for leisure batts did have a 50 amp but replaced it and small alternator for starter battery we've got two 2000 inverters we found out the 4 batts where knackered replaced with 4 new 160 gel batteries I'm only using two batteries at moment has when engine is on they only really charge to 13.8 I haven't seen batteries above 14 since had boat do I need the 4 batteries has we have washing machine iv been told I could run boat with two batteries hope you can help thanks Wayne

Tony-B
Tony-B

Posted: Wed Dec 16, 2015 2:33pm

Post Subject: Battery charge

As far as the engine battery alternator goes it will be fine because as long as the engine is in good condition it only takes a few Amp Hours to start it. The domestic bank and alternator is another matter. Without a lot more information and data about your charging regime and electricity use my immediate impression, given the 4kW (assuming you mean 2000 Watts each) of inverter and talk of washing machine, is that you have ruined a very expensive set of batteries by gross undercharging. You also have 640 Ah worth of battery capacity(when new) but you are presently only using 320 Ah. I would question the selection of Gel batteries unless you are 100% sure you know how to and can look after them. This implies some form of battery monitoring that you have not mentioned. You will kill such batteries just as fast as a cheap set unless you keep them all but fully charged for most of the time. Your inverters will draw about 400 amps at full output and that will totally flatten the batteries in less than an hour or half an hour with just two. Before any one can answer your question YOU, and I mean you, need to work through the power/energy audit and charging calculations that you will find samples of in the course notes on tb-training.co.uk. That will tell you how much battery capacity you need to provide and how long you need to charge for each day. Only then can your question be answered. One further point. The greater the output of an alternator the lower its maximum voltage so your 13.8 volts could be caused by a faulty alternator or in could be because the batteries are flat. At present I suspect the latter. I think if you ran the engine at 1000 rpm or more for over 8 hours you may well see the voltage creep up. You also need to be aware that a "standard" alternator may be set to charge at a too high voltage for gel batteries so you need to get the maximum charging voltage from the manufacturer or dealer and then check that your alternator will not exceed that figure. If you tell me all about your charging regime and the results of your power/energy audit I will advise further.

Tony-B
Tony-B

Posted: Wed Dec 16, 2015 6:37pm

Post Subject: Battery charge

Yet another point. Gel batteries often have a lower maximum charging voltage than is normal for automotive derived alternators so if you were replacing Gels with Gels the alternator might have been modified to provide the lower maximum voltage and if so that might explain the 13.8 volts. However if you replaced as set of wet,open or closed cell batteries this will not be the case.

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