Posted: Wed Apr 17, 2013 6:26pm

Our boat has 3 110ah leisure batteries which are less than 3 years old and well looked after but I think they may be failing. I can't remember what reading I should get from a multimeter to confirm, and whether I can check the whole bank together or need to test them individually. We've not been on a long run for a few months and won't be able to for some weeks but I have run the engine for quite a few hours for 2 days. I think there may be a little warranty left so need to confirm ASAP. Unfortunately we live 120 miles away! MIKE

Posted: Wed Apr 17, 2013 6:46pm

I very much doubt you will get them replaced under warranty. That is against manufacturing defects not sulphation cause by being left fully or partially discharged. If you have had them 3 years there was almost certainly no manufacturing fault. You need time to test batteries with a multimeter and you can not test them as a bank. If when you disconnect them from each other and let them stand overnight if one ends up with a much lower voltage than the others that one is faulty. If when charging them you see one cell gassing more than the rest then that cell is usually faulty.If the ends of the battery are bowing out then that battery is sulfated and has little capacity left. Charge them on the alternator for at least 8 hours or take them home and use a decent car battery charger for a full 24 hours each or maybe more. Disconnect and allow to stand for at least overnight. Measure the voltage and expect 12.7 to 12.8 volts. Anything much less than that indicates a faulty battery. Note the readings. Let them stand for another week and the voltages should be almost the same. If any have dropped that battery is faulty. However this does not measure capacity. For that you need to get them fully charged and then put a known load on them until the voltage reaches 12 volts. Then the load in amps X time taken will give a guide to the remaining capacity. Loss of capacity is not covered by the warranty. Typical domestic battery life is 2 to 4 years with some people killing them in months. Tony Brooks

Posted: Thu Apr 18, 2013 8:48am

Many thanks for your advice. My problem is logistics. Living 120 miles away and with other recent commitments we can only get to the boat every now and again, and then stay for 2/3 days. I’m not sure I could run the engine for 8 hours and don’t believe we could also manage without the batteries overnight. They are also located in a difficult place in the engine room and at 71, and with poor health, I know I can’t remove them for inspection or to take them home. If they need replacing I’ll have to pay the marina to do so and that will be expensive so I don’t want to do that without being sure it was necessary. Because my wife broke her rib falling off the boat last June we haven’t been able to use it as much as we usually do and this may have resulted in the batteries being run down. They still work but don’t seem to be fully up to par. We’re planning to go away on a 6 week trip at the end of May to replace an aborted one last autumn and I had hoped to confirm the battery situation before then. MIKE

Posted: Thu Apr 18, 2013 1:13pm

You specifically asked about using a multimeter so that is the advice I gave. A decent battery supplier should have rather expensive electronic devices for testing batteries but you would probably have to take them out. If you cruised to Evesham Marina then the battery distributors there might walk down to the boat and test them for you. Many yards have high rate discharge or load testers that would give an indication but unless the batteries are very well charged AND the tester is set for your battery capacity the result may be misleading. In any case that will not give you much idea about their remaining capacity. Unfortunately phrases like "seem to be failing" and "not up to par" are no help whatsoever in diagnosing possible faults. We need hard measurements like the voltage about an hour after stopping the engine and then again early the next morning (both with no significant electrical loads). What the charging current (amps) is at various times during the charging period plus the alternator output. Given these sort of readings over several days plus and idea of the electrical loads it may be possible to guesstimate what is wrong. However the normal thing is a much reduced capacity because of sulphation and that started from the moment you fitted the batteries. I expect to run my engine for between 2 and four hours a day with four being the more usual time. It will take perhaps 10 to 12 hours or more to fully recharge the batteries so anything less will lead to a degree of sulphaton. I can assure you that I sympathise with your predicament but unless you can get the batteries fully charged and tested I think your best course may be to simply pay up for a new bank. I bought three perfectly adequate 110 Ah batteries for around £200 last summer but then I do not expect them to last any more than two to four years - any more is a bonus. Tony Brooks

Posted: Thu Apr 18, 2013 4:07pm

Could you let me know where you bought those batteries? I can't find anything that low, and what do you think of sealed units as opposed to open cells? Bearing in mind the difficulty with access and my advancing age they seem like they may be more suitable.

Posted: Thu Apr 18, 2013 7:25pm

I bought them from my local vehicle electrical specialist who is an Exide stockist. I have also bought similar Tanya batteries from a local battery supplier. However I had to fit them. The electrical people were Thames Valley Electro-Diesel. However I had to lug them about and fit them. These were "apparently" sealed duel purpose calcium technology wet batteries but as is common at this price point you can lever the centre strip on the top up to give access to the cells. Moder calcium batteries should not gas until well over the typical 14.2 to 14.4 volts charging voltage so as long as you do not have any fancy charging systems fitted will not normally require topping up until cells start to fail. This type of battery has a larger than traditional "reservoir" capacity for each cell. Once you want truly sealed batteries you get into expense that can not be justified because sulphation will kill them just as fast as it would cheaper batteries and as I keep saying my suspicion is that yours have sulphated. Sealed AGM batteries have certain advantages over wet cells BUT you need to ensure you never exceed their maximum charging voltage and they are almost as prone to sulphation as cheaper ones. TO maximise battery life you need to match your use of them to their capacity and your charging regime and unless you are talking very expensive NEVER discharge them to below about 50% of capacity. That is about 12.25 to 12.3 volts with no significant load on them. Tony Brooks

Posted: Thu Apr 18, 2013 7:27pm

PS Using wet batteries that you can get into allows you to use a hydrometer to check the battery and that together with a voltage reading (after standing overnight at least) will allow you to assess the degree of sulphation. TB

Posted: Fri Apr 19, 2013 7:24pm

Many thanks for all of your advice. Believe it or not I was a mechanical engineer years ago but electrics sometimes elude me and batteries are like a foreign art, so thanks again.

Posted: Thu May 02, 2013 12:09pm

After testing the existing batteries as best I can I’ve decided to fit 3 new 110A wet batteries from Tayna along with a 20A Numax charger which is classified as a ‘Connect & Forget’. Tayna advised that the 20A version would be suitable for these batteries but now I’ve received it the box says suitable for up to 200A. Can you advise please? Secondly, despite the ‘Connect & Forget’ tag the instructions say you shouldn’t leave the charger connected to the batteries if you disconnect the mains supply as it will discharge the batteries, but obviously, there is no 240v supply when you’re cruising the canals so it would seem I must disconnect it from the batteries every time we go out which seems a chore. The batteries are in a box under the floor in the engine room and because of lack of space I planned to fit the charger underneath too on the side of the box. Is it really necessary to disconnect each time, and if so is there a suitable on/off switch I could fit? Thirdly, we have an inverter which we use to provide 240v on the cut and this is obviously connected to the 240v supply around the boat to which the charger would also be connected. Regardless of your advice above, I presume I would have to make sure the charger was disconnected from this supply if the inverter was on as I can see that the batteries would be supplying the charger with current to feed the batteries again and I presume this would not be a good idea?

Posted: Thu May 02, 2013 2:05pm

Is it alright to run the engine with the charger connected?

Posted: Thu May 02, 2013 6:29pm

Easy ones first. 1. The charger should be switched off and according to what you tell me about the instructions disconnected when the inverter is in use. If you leave it on it will flatten the batteries. 2. No harm will come from having the charger running with that alternator charging but depending upon the respecive voltages the alternator may shut itself down or the charger get itself confused once the batteries reach a certain state of charge. Again the instructions indicate it would not be a good idea to leave the charger connected when if it is turned off. Now the hard stuff. I do not have access to the technical documentation that I would need to form an independent opinion about leaving it connected with the mains turned off. If you made it clear that you expected to permanently wire it to the boat's system I think you have every right to a refund because you clearly can not. However I think Fit & Forget means that you can connect it to the batteries to charge and it will modify its voltage to ensure it will not damage batteries. You need to find out exactly how many milliamperes the charger draws form the batteries when turned off. If it is only 10 or so then I expect the car radio discharged more then that when it is turned off and also the inverter when left in standby, but I can not go against what Neumax say. If the instructions really do say it is only suitable for 200 amps then they are wrong. I expect it says 200 Amp Hours. The 200 Ah refers to the battery size it can charge from flat in a reasonable time not the amount it can top up and keep well charged. However the instructions make me wonder about the quality and reliability if it is left on for months at a time. My guess is that it is not a marine charger so may not be designed for that type of duty. Tony Brooks

Posted: Thu May 02, 2013 6:29pm

Easy ones first. 1. The charger should be switched off and according to what you tell me about the instructions disconnected when the inverter is in use. If you leave it on it will flatten the batteries. 2. No harm will come from having the charger running with that alternator charging but depending upon the respecive voltages the alternator may shut itself down or the charger get itself confused once the batteries reach a certain state of charge. Again the instructions indicate it would not be a good idea to leave the charger connected when if it is turned off. Now the hard stuff. I do not have access to the technical documentation that I would need to form an independent opinion about leaving it connected with the mains turned off. If you made it clear that you expected to permanently wire it to the boat's system I think you have every right to a refund because you clearly can not. However I think Fit & Forget means that you can connect it to the batteries to charge and it will modify its voltage to ensure it will not damage batteries. You need to find out exactly how many milliamperes the charger draws form the batteries when turned off. If it is only 10 or so then I expect the car radio discharged more then that when it is turned off and also the inverter when left in standby, but I can not go against what Neumax say. If the instructions really do say it is only suitable for 200 amps then they are wrong. I expect it says 200 Amp Hours. The 200 Ah refers to the battery size it can charge from flat in a reasonable time not the amount it can top up and keep well charged. However the instructions make me wonder about the quality and reliability if it is left on for months at a time. My guess is that it is not a marine charger so may not be designed for that type of duty. Tony Brooks

Posted: Thu May 02, 2013 7:32pm

Can you suggest a suitable switch I could install between the charger and the battery so that I could hard wire the charger and yet make it easy to switch it off as the charger will be located under the floor boards alongside the batteries? At the moment I'm thinking of hard wiring the 240v side through a wall switch with a neon indicator so that I can clearly see when that side is switched on and connected to the mains, and then hard wire the 12v end to the batteries via another 240v wall switch to make it easy to disconnect the charger from the battery.

Posted: Thu May 02, 2013 7:47pm

Every connection and set of contact in a circuit increases the volt-drop and for battery charging that is not ideal. You will need a DC rated switch rated at over 20 amps. I am sure you will find a selection on Google. Tony Brooks