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Posted: Tue Nov 17, 2009 5:25pm

Post Subject: Battery Charging

Tony, I leave my boat in a marina for up to 6 weeks and to date have always isolated the electrical system, and left the batteries off charge. However as I have a Sterling Inverter/Charger on board and a connection to 240v landline I was considering leaving the batteries on constant charge (float). Will this be detrimental to the batteries, and would you consider it safe to leave the boat this way. Would I have to leave the isolators on, or as I am assuming they are connected on the output of the batteries, should I remove them to isolate the battery output whilst still allowing the batteries to remain on constant float charge. thanks Duncan


Posted: Tue Nov 17, 2009 5:53pm

Post Subject: Battery Charging

Dear Duncan, First the easy part. Sterling are a reputable supplier so as long as the charger part of the unit says it is multi-stage it would be best to leave it on all the time. There is one very low possibility that if the batteries are already in a poor state and the charger decides to do an automatic equalisation charge it just might finish the batteries off, but as I said its a very low and possibly theoretical scenario. I do not want you coming back at me if it did happen - hundreds of people do exactly what you propose without any problem. The harder part is for me to decide by remote control how your boat has been wired when you "assume". Connect a voltmeter across the battery bank with the isolators open and the unit off. turn the unit on and the meter may or may not jump up to a higher reading. If it does then you can turn the isolators off, if not you will have to leave them on. Unless the combi-unit has two charger outputs I would expect it to be connected to the domestic bank only. Typically you need not worry too much about the engine battery, but if you have concerns about its state of charge just lip a jump lead between the domestic bank positive and an engine battery positive making sure the clips can not fall off or short out to any metal work. The charger will then charge both banks but a fault on one bank could allow that bank to discharge the other bank, again not likely. Tony Brooks

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