Tracker Posted April 6, 2015 Share Posted April 6, 2015 As I understand it a fully charged 12 volt battery should show a no load voltage of around 12.75 volts, or between 12.7 and 12.8 volts depending on which website you read. I have a one year old Enduroline unused starter battery which has been kept charged every three months with a Ctek multistage charger and now over 24 hours since the charger was disconnected the voltage is 12.98. Can anyone explain please why it is so high and is it a good sign or a bad sign as I once had a leisure battery that showed over 13 volts a day after being fully charged but it had greatly reduced capacity in the real world of use. Thanks. Link to comment Share on other sites More sharing options...
Derek Uzzell Posted April 6, 2015 Share Posted April 6, 2015 12.98V seems high for a fully charged, fully-rested ordinary wet-acid starter battery. Are you certain your voltmeter is not over-reading? Link to comment Share on other sites More sharing options...
terry1956 Posted April 6, 2015 Share Posted April 6, 2015 Hi, nothing wrong, rest the battery a bit longer and check again. Remember a 12v battery is made up of 6 cells of 2.2volts each so thats just over 12volts off the charger.over time this will go down to 12volts when rested. Michael Link to comment Share on other sites More sharing options...
Solomongrundy Posted April 6, 2015 Share Posted April 6, 2015 I have a couple of digital voltmeters (robbery at £1.04p each) connected to my starter and leisure batteries. The starter battery reading is 12.8v all the time when the Motorhome is idle on the drive and the Solar panel charged leisure batteries are reading on this sunny day 14.2v - it does go down on poor weather days but has never dropped below 13v. Are these readings about right? Link to comment Share on other sites More sharing options...
Tracker Posted April 6, 2015 Author Share Posted April 6, 2015 Solomongrundy - 2015-04-06 4:37 PM I have a couple of digital voltmeters (robbery at £1.04p each) connected to my starter and leisure batteries. The starter battery reading is 12.8v all the time when the Motorhome is idle on the drive and the Solar panel charged leisure batteries are reading on this sunny day 14.2v - it does go down on poor weather days but has never dropped below 13v. Are these readings about right? Yes is the short answer - but if you want to check the true state of your batteries you would need to disconnect the solar panels and everything else for a day or two and then see what happens to the voltage. Be aware that leaving the panels connected to some regulators without a battery load connected can damage the regulator. Link to comment Share on other sites More sharing options...
Tracker Posted April 6, 2015 Author Share Posted April 6, 2015 Battery has been off charge for another 11 hours today and when checked (again with two different digital voltmeters - both recently checked against a professional unit) the voltage had RISEN to 13.01 volts? The garage was cold this morning and quite warm this evening so I'll check it again in the morning to see if that is the explanation as I seem to recall reading that batteries, like us, prefer warmth to work at their best! Link to comment Share on other sites More sharing options...
kevina Posted April 6, 2015 Share Posted April 6, 2015 My 18 month old Victron gel batteries sit at 13.0 volts for weeks after being fully charged (built in digital voltmeter). In fact, after a full b2b charge when we return from the continent I don't need to charge them again until the next trip several months later. I leave the solar panel disconnected. Kev Link to comment Share on other sites More sharing options...
Guest peter Posted April 6, 2015 Share Posted April 6, 2015 Tracker - 2015-04-06 6:57 PM Battery has been off charge for another 11 hours today and when checked (again with two different digital voltmeters - both recently checked against a professional unit) the voltage had RISEN to 13.01 !Eureka!!!!!!!!!!!!!!!! Tracker has discovered the phenomenon of the self charging battery. And is destined to become a multi millionaire. (lol) Link to comment Share on other sites More sharing options...
PeteH Posted April 6, 2015 Share Posted April 6, 2015 HI Digital Voltmeters, when the internal battery is "Dying" for some obscure reason seem to give a high Reading. I have 3 of the things. and it appears to happen with them all!. So if you have readings which could be "Suspect". checking or changing the internal battery. Might be the answer? (mine are the 9V type PP3). A standard 12V Lead Acid battery in good condition and fully charged will (should) show 12.6Volt or above after being rested for at least 1 Hour. Anything below is part discharged or suspect. I don't know the truth of this but "New" batteries are alleged to come only 75% Charged (about 12.5V)? Pete Link to comment Share on other sites More sharing options...
Tracker Posted April 6, 2015 Author Share Posted April 6, 2015 I too have three digital multi meters, one good 'un and two cheapies, and they all read within .02 volts of each other and all have new or fairly new batteries. Like yourself, when I get strange or unexpected readings the first thing I suspect is the meter! Link to comment Share on other sites More sharing options...
Southender Posted April 7, 2015 Share Posted April 7, 2015 Solomongrundy - 2015-04-06 4:37 PM I have a couple of digital voltmeters (robbery at £1.04p each) connected to my starter and leisure batteries. The starter battery reading is 12.8v all the time when the Motorhome is idle on the drive and the Solar panel charged leisure batteries are reading on this sunny day 14.2v - it does go down on poor weather days but has never dropped below 13v. Are these readings about right? The 14.2v is what`s coming out of the regulator and going into the battery. It is not what the resting voltage of the battery. Even on poor days solar panels still produce power hence the 13v you are seeing. Link to comment Share on other sites More sharing options...
Brambles Posted April 8, 2015 Share Posted April 8, 2015 Tracker, Its probably normal. There are various things which can raise the settled rest voltage. Calcium batteries will tend to be a little higher than the standard 12.65volts at 100% charged for an antimony battery. Also a lot of starter batteries now contain Calcium, Silver, Tin or other exotic metals and elements, even arsenic. Now depending what plate the additional elements are in can increase or reduce the voltages, and generally Silver or Tin will increase the charge voltage required and reduce gassing at 14.4 volts. As a battery ages various elements added can migrate from one plate to the other polarity plate and affect how the battery operates. It can result in when a battery is well past its best the settling voltage starts to rapidly increase and can be used as an indication the battery is on the way out. However in your case I suspect you are actually seeing the effect of an over charged battery beyond its 100%. Charging to 14.4 volts end point results in 100% charge, but charging to say 14.7 volts end point (or using pulse width charging) can result in a battery now being over 100% charged. The battery acid gets stronger and settling voltage rises. I think this is what you are seeing. Now this is actually very bad for a battery and is typical of what solar charging does if the battery is never being discharged. A good Solar charger will not attempt to charge again until it sees the battery voltage fall below a set point. All to prevent over charging. Reason over charging is bad is the stronger acid will cause erosion of the positive plate. So while sulphation is less, erosion is greater. What you would be better doing is discharging the battery a bit before you recharge it, then seeing what the end voltage after resting is like. You may find it more in line to what you expect as battery will be closer to 100% rather than say 105%. It is not good to repeatedly do a full charge cycle once charged .... just because you can. It results in an overcharged situation. Car batteries are not designed as standby batteries and do like to be used si give it a bit of exercise now and again and it should last well as a back up spare battery, but better still only buy a battery when you need one and keep an older battery as an emergency battery and then it does not matter so much if it fails through non use. Even putting your new battery in your vehicle and keeping the older one as an emergency back up. Just my ramblings for what they are worth. If it does not make sense thats because I have not checked wot i rote. p.s. I have some new AGM batteries next to me here and they settle at 13.2 volts and over last 2 months have fallen to 13.1 volts . A pair which are 4 years old and well used settle at 12.8 volts and are about 50% original capacity . So voltage can be misleading unless you know what it is meant to be for the particular battery. Link to comment Share on other sites More sharing options...
kevina Posted April 9, 2015 Share Posted April 9, 2015 I've just found a 240 page document entitled "Electric Vehicle Battery Systems" and in the midst of it (which is why I'm posting so late!), in the vrla battery section is a formula: SOC = 84 x ocv - 984 ( where soc - state of charge & ocv = open circuit voltage) A few quick calculations will see that 100% charged gel/agm battery is 12.9v (though in my batteries case a final figure of 992 works better) Apparently the state of charge graph for a vrla battery is linear hence the simple formula. Tracker, is your Enduroline possibly an agm battery? Kev Link to comment Share on other sites More sharing options...
Tracker Posted April 9, 2015 Author Share Posted April 9, 2015 Many thanks Jon and Kev for your helpful insights, and I think Jon is right about overcharging and loss of capacity as the same overly high voltage accompanied by a loss of capacity eventually happened to the two Vartas that I bought when I first installed a solar panel and with the benefit of hindsight maybe the regulator was not good enough to charge to the batteries needs rather than all the time. I live and learn! It's one of these Kev - http://www.tayna.co.uk/019-Enduroline-Car-Battery-950CCA-P8385.html Using the formula SOC = 84 x ocv - 984, (12.96 x 84) - 984 = 104.64% I've been using a multistage Ctek charger and I was under the impression that these chargers, with their voltage maintenance stage, had built in protection against over charging a battery? The more I learn the less I know! Link to comment Share on other sites More sharing options...
Tracker Posted April 9, 2015 Author Share Posted April 9, 2015 I've been looking at battery load testers like these - does anyone have any experiences of them, good or bad, and do they do the job of telling one how good or bad a battery really is at accepting and holding it's charge? https://www.google.co.uk/?gws_rd=ssl#q=12+volt+battery+load+tester Link to comment Share on other sites More sharing options...
Guest Joe90 Posted April 9, 2015 Share Posted April 9, 2015 No direct experience, but I suspect like most things you get what you pay for, here's one for a mere £220. http://isswww.co.uk/act-612-battery-tester?gclid=CJq6nbnq6MQCFUyWtAodZxYAQg Or I guess you could just pop out to your van on your front drive, and leave it say for 20 hours with an assortment of lights, and the TV on, and see how your battery holds up. ;-) Link to comment Share on other sites More sharing options...
StuartO Posted April 9, 2015 Share Posted April 9, 2015 I agree, if you need to test your leisure batteries, just leave the MH off an EHU and put some lights on to draw 5 or 10 amps, then monitor the decay in battery voltage over 12 hours or so. That should give you a clear enough indication of whether your batteries are still up to the job. You could even do that while you are in occupation on a site, by disconnecting the solar panel and leaving the lights on during the day. Then in the evening hook up the EHU again to recharge overnight. Testing them more exhaustively or precisely will have very limited value and if you have a deep urge to do so which you cannnot suppress, get some counselling instead!. Link to comment Share on other sites More sharing options...
kevina Posted April 9, 2015 Share Posted April 9, 2015 VRLA Battery Formula Just to clarify that the formula quoted above is only valid for vrla batteries, ie GEL and AGM. Link to comment Share on other sites More sharing options...
Tracker Posted April 9, 2015 Author Share Posted April 9, 2015 StuartO - 2015-04-09 10:31 AM Testing them more exhaustively or precisely will have very limited value and if you have a deep urge to do so which you cannnot suppress, get some counselling instead!. I'll take that as humour Stuart as I am not looking to be offended today! To me it makes sense to have some idea how good your batteries are before trundling off on a long weekend without ehu or engine running and I don't think that switching on led lights and tv would do that. In the old days you unscrewed the caps and checked the SG of the electrolyte and whilst not perfect it was quick, cheap and gave you a good idea about what state the battery was in. So as these battery testers exist and many of them are cheap why not have some idea? After all you generally know how much gas you have and how much diesel you have so why not the third essential element - battery capacity? There is little point in having two x 100 ah batteries that act as if they are fully charged but in reality are only capable of holding 20 ah each? Link to comment Share on other sites More sharing options...
Guest Joe90 Posted April 9, 2015 Share Posted April 9, 2015 Have a close look at your leisure batteries, all the ones I've ever had despite being labelled maintenance free had cunningly hidden caps under the impressive plastic " Maintenence free" labeling across the top, then you could unscrew the caps and check the electrolyte ;-) As for cheap testers, well I just bought some cheap Lafuma "style" chairs, instead of £150 each, these Lafuma "style" ones were £30.............they are crap and will be on the first boot sale, you know the old saying, and at my age why on earth did I fall for it ;-) Link to comment Share on other sites More sharing options...
StuartO Posted April 9, 2015 Share Posted April 9, 2015 Tracker - 2015-04-09 10:50 AM StuartO - 2015-04-09 10:31 AM Testing them more exhaustively or precisely will have very limited value and if you have a deep urge to do so which you cannnot suppress, get some counselling instead!. I'll take that as humour Stuart as I am not looking to be offended today!.... Actually I wasn't referring to you personally, merely the general risk of getting too anal about leisure battery health, as i found myself doing a while ago. Link to comment Share on other sites More sharing options...
Brambles Posted April 9, 2015 Share Posted April 9, 2015 By far the best way to test a battery is to actually use it. Link to comment Share on other sites More sharing options...
Tracker Posted April 9, 2015 Author Share Posted April 9, 2015 Brambles - 2015-04-09 3:18 PM By far the best way to test a battery is to actually use it. Thanks for that tip Jon - but with respect that's not a lot of help if you are far from home 2 days into a 4 day stay with no ehu and a flat battery! Link to comment Share on other sites More sharing options...
Guest Joe90 Posted April 9, 2015 Share Posted April 9, 2015 The problem is, you can test them all you like, our leisure battery died quite suddenly with no real prior warning, had only been in use just over a year, and we were away at the time, I had to go and buy a new one..........in France....not a big deal really, apart from the fact I may have ended up with a starter battery, but it's still going strong....... stop stressing , you'll still be able to have a brew on the gas hob, even if you have to light it with a match (!) :D If you really think it's a bit long in the tooth, or getting past it's best, perhaps a new one is the way to go, they don't last forever as I'm sure you know. Now does anyone know where I can get some good quality aluminium camping chairs :D Link to comment Share on other sites More sharing options...
Tracker Posted April 9, 2015 Author Share Posted April 9, 2015 Joe90 - 2015-04-09 6:35 PM stop stressing Not stressing at all - just trying to ensure the things that tend to give one a lot of grief are not close to giving said grief - common sense more than paranoia as I see it! A motorhome is a complex and often poorly designed and thrown together assortment of components some of which are of dubious quality and the best thing one can say about it's overall reliability is that thank heavens that it does not have to take off and land as well! Murphy's law and Soddes Law both apply equally which means that anything that can fail will fail at some point and the components that you least expect to fail are the ones that catch you out! If only motorhomes were designed and assembled in their entirety by Toyota or Honda! Link to comment Share on other sites More sharing options...
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