George and Dragon Posted June 19, 2019 Report Share Posted June 19, 2019 What I really want to know (having convinced myself that i do need new batteries) is what do the letters and numbers in LX31MF actually mean? Which must I keep the same and which don’t matter? I have a bank of 4 sealed 12V batteries. 3 are Lucas LX31MF, the other is another brand but the same part number. Are these AGM? They were already installed when I bought the boat. They don’t have a date of installation marked but since the range on the label finishes at December 2014 my guess is they’re at least 5 years old. Unfortunately they’re barely holding any charge - finish cruising at 6 pm by 8 the following morning they’re down to 12.3V despite only running lights and the fridge overnight. I have a MCS monitor built into the 12V distribution panel - change over with to display battery voltage (domestic and starter) the ammeter shows the same value whichever bank is selected so presumably only on domestic. I’m normally on a marina attached to shore power and the domestics are kept charged by a Waeco charger, there’s also separate alternators for domestic and starter batteries. There is some corrosion on the steel parts of the terminal clips (I thought they should be brass) but there’s no furring. Link to comment Share on other sites More sharing options...
Tony Brooks Posted June 19, 2019 Report Share Posted June 19, 2019 I go by width, heigh, depth (all of case), terminal type and terminal layout plus capacity or CCA. Then I might, If I am lucky get a three digit number like 644. Add that the type of battery you want (start, deep cycle, leisure, Sealed Lead acid, open cell lead acid and so on and you should be able to find suitable batteries that fit an do the job. I feel manufactuers' destinations are not that much more than marketing. If you are changing a whole bank then it does not matter what you fit as long as you can connect them, they fit the space, have sufficient capacity and are of the type you feel is best for you. I and some others prefer open cell lead acids while others swear by sealed or AGMs. Take your pick. Link to comment Share on other sites More sharing options...
George and Dragon Posted June 25, 2019 Author Report Share Posted June 25, 2019 I managed to unconvince myself from buying new batteries: after a day when they took no charge whatsoever despite running for 4 hours, the voltage at the distribution board showing 10.3 and the fridge completely defrosting. The following morning the rested voltage was back to 12.2 and they happily took charge and powered the fridge and inverter. Very strange. Since then no problems, we got back to the marina and they're happily on charge. ❓I found something that suggested that the battery part numbers (31 etc) refer to the case design. Can anyone confirm this? Link to comment Share on other sites More sharing options...
WotEver Posted June 25, 2019 Report Share Posted June 25, 2019 5 minutes ago, George and Dragon said: I found something that suggested that the battery part numbers (31 etc) refer to the case design. Can anyone confirm this? Yes, that’s absolutely correct. 6 minutes ago, George and Dragon said: The following morning the rested voltage was back to 12.2 and they happily took charge... You are aware that 12.2V is ‘flat’ aren’t you? Link to comment Share on other sites More sharing options...
mrsmelly Posted June 25, 2019 Report Share Posted June 25, 2019 4 minutes ago, George and Dragon said: I managed to unconvince myself from buying new batteries: after a day when they took no charge whatsoever despite running for 4 hours, the voltage at the distribution board showing 10.3 and the fridge completely defrosting. The following morning the rested voltage was back to 12.2 and they happily took charge and powered the fridge and inverter. Very strange. Since then no problems, we got back to the marina and they're happily on charge. ❓I found something that suggested that the battery part numbers (31 etc) refer to the case design. Can anyone confirm this? They will be happy on hook up at a marina. If they realy were at 10.3 then they will be knackered anyway if they have done that before. If they are cheapo sealed batteries at a minimum of five years then they are disposable consumeables and you have done well. I am happy to get two years out of mine at less than a hundred quid each. Much though depends on time on hook up and time cruising and cycling the batteries. Link to comment Share on other sites More sharing options...
Alan de Enfield Posted June 25, 2019 Report Share Posted June 25, 2019 15 minutes ago, George and Dragon said: we got back to the marina and they're happily on charge. I would suggest that your 12v appliances are actually running off the charger rather than the batteries. The batteries are totally 'shot' and if you turned the charger 'off' the batteries would be flat and the appliances would 'shutdown' - probably within minutes. Link to comment Share on other sites More sharing options...
George and Dragon Posted June 25, 2019 Author Report Share Posted June 25, 2019 38 minutes ago, WotEver said: You are aware that 12.2V is ‘flat’ aren’t you? Yes, and clearly there's something wrong - we should be able to last more than 24 hours without cruising. But I ain't putting hundreds of quids into new batteries until I'm certain they will charge from the engine 30 minutes ago, Alan de Enfield said: I would suggest that your 12v appliances are actually running off the charger rather than the batteries. The batteries are totally 'shot' and if you turned the charger 'off' the batteries would be flat and the appliances would 'shutdown' - probably within minutes. Not quite. Link to comment Share on other sites More sharing options...
mrsmelly Posted June 25, 2019 Report Share Posted June 25, 2019 8 minutes ago, George and Dragon said: Yes, and clearly there's something wrong - we should be able to last more than 24 hours without cruising. But I ain't putting hundreds of quids into new batteries until I'm certain they will charge from the engine Not quite. They have done well if indeed they are five years old. Batteries are like diesel, they are consumable items, even expensive ones need replacing. Your sealed ones are cheapo disposables like I use and they have done you proud. Boating aint cheap, new batteries are just part of the territory. New batteries will transform your electrics. Link to comment Share on other sites More sharing options...
matty40s Posted June 25, 2019 Report Share Posted June 25, 2019 Most modern chargers and inverter chargers will NOT charge under a certain voltage as a safety feature....if one of the batteries has faulted out or shorted, it might blow up if the bulk charge of over 14.5 or even worse, equalization charge is allowed to be put through it. The only way of trying to charge those batteries properly is off the boat with a decent auto trickle charger for a day or two..you will then find out whether they hold charge or not. My guess from your description is not. The only other thing I can think of to take them down that low is if you left the 240v immersion on when you went out cruising. Link to comment Share on other sites More sharing options...
MtB Posted June 26, 2019 Report Share Posted June 26, 2019 10 hours ago, George and Dragon said: Yes, and clearly there's something wrong - we should be able to last more than 24 hours without cruising. But I ain't putting hundreds of quids into new batteries until I'm certain they will charge from the engine ^^^This^^^ I'm not sure why no-one else has suggested it, but to me the symptoms sound as though the charging system on your boat isn't working correctly. Do you have a multimeter? Link to comment Share on other sites More sharing options...
David Mack Posted June 26, 2019 Report Share Posted June 26, 2019 On 19/06/2019 at 14:09, George and Dragon said: Unfortunately they’re barely holding any charge - finish cruising at 6 pm by 8 the following morning they’re down to 12.3V despite only running lights and the fridge overnight. The fridge is a huge consumer of power. If you are trying to eke out limited battery resources, switch the fridge off overnight ( and don't open the door). Link to comment Share on other sites More sharing options...
George and Dragon Posted June 26, 2019 Author Report Share Posted June 26, 2019 9 hours ago, Mike the Boilerman said: I'm not sure why no-one else has suggested it, but to me the symptoms sound as though the charging system on your boat isn't working correctly. Do you have a multimeter? Yes, that occurred to me. How does a multimeter help me? 4 hours ago, David Mack said: The fridge is a huge consumer of power. If you are trying to eke out limited battery resources, switch the fridge off overnight ( and don't open the door). Understood. Link to comment Share on other sites More sharing options...
WotEver Posted June 26, 2019 Report Share Posted June 26, 2019 3 minutes ago, George and Dragon said: How does a multimeter help me? When you start the engine with the multimeter black wire on the alternator case the voltage on the B+ connection on the alternator (red wire from the multimeter) should jump up in value compared to when the engine is off. After a while (could be a few hours) that voltage should be in excess of 14.2V. With the engine running there should be very little voltage (less than 0.2V) measured between the alternator B+ and any of the battery positive posts (red multimeter cable onto alternator, black onto battery). I’m going to assume that your multimeter isn’t a D.C. Clamp type but if it is then charging current measurements are essential troubleshooting steps although the two tests I’ve itemised above are a good start. Link to comment Share on other sites More sharing options...
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