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johnjo
johnjo

Posted: Sun Nov 02, 2008 2:13pm

Post Subject: Batteries and inverters

I've just bought a 57ft NB and need to upgrade the batteries. I also need to re-wire the existing charger & inverters and associated wiring. Currently she has fitted a Sterling Advanced 4 step sw/mode charge/power pack; a Sterling combi charger 4amp/inverter 600w cont: [800w max] mod: 50hz sine wave; also as yet unfitted, a Sterling Inverter - 1800 Watt Cont: [2600 Intermittent] Input voltage 10-15V. Output 230v 50hz Mod: Sine Wave. Is any of this redundant or can I utilise it all and how & could I make use of both chargers say one for the starter and the other for the leisure? I have seen advice about splitting the domestic circuits, so could I spilt the circuits into three so as to utilise all three inverters, the lesser one to run, say the TV, the middle one to run the Fridge & the Freezer and reserve the larger one to run the W/Machine or Microwave. I have looked at Elecsol 125AH Deep Cycle batteries which have 5yr warranty [the main attraction] but they are wet batteries which can require topping up [out of sight, out of mind], and Numax leisure sealed batteries [Maintenance free]. I’ve seen a lot advice about Gel, Lead Acid etc: but what would be your choice of make & type [not necessarily either of the above]for the leisure and starter and could you explain why? Our requirements are 12v lighting [not LED yet], circulating pump, water pump, shower waste pump & household type under counter 240v fridge & a 240v freezer, 240v cold fill washing machine although this could always be used only when 240v landline is available, possibly a Microwave and plus the other usual 12v items, mobile phone, Laptop and occasional use of 12v 20” TV. Regards John

Tony-B
Tony-B

Posted: Sun Nov 02, 2008 5:32pm

Post Subject: Batteries and inverters

Dear John, I really can not advise you because you give me no idea about how the boat will be used, when it will be used, how long each electrical item will be in use and very little about the 12 volt loads. Before you can even think about spending any money you need to go onto my website and look in the maintenance course notes. Then follow the instructions to do a power audit and basic battery capacity/charging time calculations. http://www.tb-training.co.uk/16elect.htm#bmn 67. This will give you some idea about the size of battery bank you need but the actual calculations are rather more complex than those shown so it will not be totally accurate. Now we come to the battery chargers. I assume the Sterling Power pack is in fact a battery charger and not an alternator to battery charger. The power pack means it can supply part of the domestic needs as well as charging the battery up to its rated output, so this is the one I would use on the domestic batteries. The charger output of the Sterling Combi-unit can then be used to charge the engine battery. The manufacturers should be able to supply instructions and wiring diagrams. Remember it is no use trying to charge batteries when powering the charger from an inverter. NOW THE INVERTERS. You can not normally link several AC outputs together unless the equipment is designed to self synchronise with each other and I doubt those inverters are. Unless you want to split your onboard mains circuits into three parts and set up complex, fail safe, switches for when you are on shore power my advice is to forget it, sell the lot and buy a decent pure sine wave output inverter that will be large enough to work your washing machine. Until you try it there is no way you can be sure a particular piece of equipment will actual work on a modified sine wave inverter and the more electronics are involved the less likely it will be, so take care. Mains can easily kill people so I am not going to say anything more on this subject. THE BATTERIES – Unless you intend to use a long term shore power connection and a multistage battery charger to keep the domestic batteries well charged I am sure you are more likely to kill them by no keeping them fully charged that they are to fail from old age. Most batteries are only guaranteed against manufacturing faults, not owner neglect, so warranties are of doubtful benefit. Despite certain claimed advantages for “carbon”, AGM & gel batteries I can see little benefit in spending money on more expensive batteries unless you can keep them close to 100% fully charged all the time. I fit ordinary wet, lead acid batteries, deep cycle for the domestic bank and starting for the engine battery. I am not going to comment on makes on this public forum but if you are not able to keep the batteries fully charged almost any readily available make will do. Gel batteries and some AGM ones require a lower charging voltage if you are not to destroy them, so if you get ANY sealed battery please ensure you are told the maximum charging voltage and that you an adjust your chargers and charging system to comply. Tony Brooks

johnjo
johnjo

Posted: Sun Nov 02, 2008 5:41pm

Post Subject: Batteries and inverters

Crikey, don't you take any time off? I wasn't expecting a reply for at least a couple of days, anyway, MANY THANKS, even though I haven't supplied enough info for you to give as full a reply as you would have liked, however the info you have given gives me food for thought, so I'll go and re-read and make some decisions. Excellent forum. Regards John

Tony-B
Tony-B

Posted: Sun Nov 02, 2008 8:59pm

Post Subject: Batteries and inverters

John, the power audit may be better illustrated in the mechanical notes on the same site. I must get round to aligning them. Tony Brooks

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