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LittleWing
LittleWing

Posted: Thu Nov 04, 2010 7:13pm

Post Subject: Charging Batteries with an Inverter

We have a Power Master 1500 pure sine wave inverter/charger. My understanding has been that if the engine is running, the inverter/charger is on, and there are no 240v appliances drawing power, then the recharging of the batteries would be handled by the charger function. And that as the batteries near 80% charge (or thereabouts) the charger would 'boost' the remaining charge in steps - so that the batteries would eventually be almost 100% fully charged and kept in good shape. But a fellow boater recently cast some doubt on this, and when I looked at the unit I noticed that the little light over the 'charging' mode is always dimmed (not bright like the little light over the 'inverter' mode). Question 1: Do these inverter/charger units only charge from a 240v landline, and not when running the engine? Question 2: If so, is there any way to fully recharge the batteries (2 x Vetus 165Ah sealed batteries) without a landline? We continuously cruise, and almost never come across a place where external 240v is offered.

Tony-B
Tony-B

Posted: Fri Nov 05, 2010 11:24am

Post Subject: Charging Batteries with an Inverter

Dear Jim, any charger, be it part of an inverter or not, will only charge the batteries when it is supplied with mains voltage from a landline or generator. If you tried to invert the battery supply and direct that to the charger the electricity the inverter uses to allow it to work would quickly flatten the batteries. I am very pleased that you rarely get the use of a land-line. Without seeing the charts for your inverter I fear that if it does work as you describe the volatge may well go high enough to damage SEALED batteries. I doubt you will ever get batteries fully charged using an engine driven source of 240V ac because of BWs 8am to 8pm engine running rule although a generator driving the inverter will help (I must caution you against a petrol generator unless you store it and its fuel in something like a gas locker). For CCers I fear its careful use of electricity, accepting shorter battery life and if you can afford it a significant solar array. The solar may well supply all your domestic electrical needs in the summer and make a significant contribution during the winter. If you leave the boat to go visiting for a week or so it will probably fully charge the batteries while you are away. Tony Brooks

LittleWing
LittleWing

Posted: Fri Nov 05, 2010 5:47pm

Post Subject: Charging Batteries with an Inverter

Thanks Tony Actually, looking at a PDF manual for the inverter, I see its settings are correctly set for sealed batteries, and as you infer, the 'stepped' charging would be for unsealed batteries. This inverter has a separate function for plugging in and handling solar panels, so that may be the way to go. I guess I've spent a year thinking I'm fully topping up the batteries to no avail. ... they don't seem to be running the lights & pumps as long as they did last year! Thanks again.

Tony-B
Tony-B

Posted: Sat Nov 06, 2010 8:11am

Post Subject: Charging Batteries with an Inverter

First of all check the maximum charging voltage for the batteries because modern automotive based technology can allow sealed batteries to be charged at open cell levels of around 14.4 volts or so and then it will be a matter of checking the inverter does not exceed this. My Vetus catalogue does not give a maximum charging voltage but it would be worth checking with Vetus because at the technology used in at least one of their types suggests it may accept "normal" charging voltages - but CHECK, do not just reset the inverter. I am not sure you will gain maximum effect if you connect a solar array to the inverter because of the type of voltage control it may use. The latest MPPT controllers make much better use of the panel's output so you can get a claimed 30% more charge than that provided by other technologies. Finally you may very well have damaged your batteries by sulphating them because they were very rarely fully charged. They have probably lost a significant part of their capacity now. I would advise that you consider the batteries as consumable items that you will replace every couple of years or so (some ccers get under a year from their batteries because they never get them fully recharged). This implies buying ordinary wet open cell batteries at lower cost as the most cost effective way. Tony Brooks

LittleWing
LittleWing

Posted: Tue Nov 09, 2010 7:23pm

Post Subject: Charging Batteries with an Inverter

Thanks again -- Unfortunately, the batteries are mounted on the swim right at the back under the deck and cannot be seen from the top at all. Further, the box they are mounted in has copper tubing and a diesel filter to a diesel boiler mounted on the accessible side, (no I didn't install this, a rather 'reputable' fitter did), and there is no place to fit them anywhere else. So, like you say, I must see these as disposable items and keep them in as good shape as I can. -- It may be to our benefit to fit new sealed ones when they are finished and use a small generator to top them up regularly and for other power uses. ANOTHER QUESTION: If a set of batteries totalling 330Ah were partially charged to, say, 12.2v, how long would it take to take them to near-full charge using a Honda EU 10i (1Kw) generator/inverter (for example)? Would the 2Kw model charger (EU 20i) fully charge them twice as quickly (or more quickly at all)?

Tony-B
Tony-B

Posted: Wed Nov 10, 2010 8:30am

Post Subject: Charging Batteries with an Inverter

Please ensure that you obtain the recommended maximum charging volatge for the sealed batteries from the supplier IN WRITING because modern sealed batteries may be able to be charged at the "normal" charging volatge and it would be a waste to set the charger to a lower volatge if you do not have to. I can not give a definitive answer to the question but I can give guidance. Using the 12v output on either generator will take days & days & days so apart from an emergency it is not a sensible option so what is normally done is to use the generator to drive the battery charger. Now complications come in because I notice you are quoting watts but as this is a AC device we need kVA and without the manual I suspect the Eu10 is not a 1kW output but more like 850kVA. If it is 1kW then its kVA output will be more, perhaps 1.2 kVA. So step one will be to obtain the kVA required to drive the charger in your inverter and the kVA of each generator. Then you can see which one will drive your existing charger. Also find the input required for a range of individual multi-stage chargers and pair them with either generator to find the most cost effective solution. Using either the engine alternator or a generator and charger will get you to perhaps 80% fully charged in a reasonable time but obviously a 10 amp charger will take far longer than a 50 amp one. The other 20% will take a very long time because however powerful the charger the charging current starts to drop so at perhaps 95% of fully charged you may only be charging with a few amps. We strive to 100% fully recharge the batteries but accept we rarely can when out cruising and probably never without an additional long term, but low output charging system. Remember generators are a target for thieves and BW impost an 8pm to 8am shut down period for engines and generators on boats that are not moving. Hence the advice about batteries being consumables. Tony Brooks

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