cruiser Posted November 23, 2008 Share Posted November 23, 2008 Thanks to all who advised regarding my slowly discharging leisure battery. I disconnected the earth lead last Sunday and have monitored the situation on a daily basis. The battery is still losing about .04 volts daily, i.e: 12.95, 12.91, 12.86 etc. It's now down from 12.97 day one to 12.65 day seven. Having said that, it re-charges fully within about two hours. The positive lead is still connected, but surely that couldn't be responsible? So is my 4 year old (if original) battery kaput? Is there a magic trick I can perform to save it? Advice as always, much appreciated. In return, tips on banjo set-up and maintenance freely given. Country rocks.....but Bluegrass rules! Link to comment Share on other sites More sharing options...
fred22 Posted November 23, 2008 Share Posted November 23, 2008 I was in a Caravan Accessory shop the other day and a chap was buying a new leisure battery. He spent a good 10 mins trying to negotiate a part exchange price on his old one. The assistant got full marks for his coolness as the customer would not or could not see reason. Link to comment Share on other sites More sharing options...
Guest Tracker Posted November 23, 2008 Share Posted November 23, 2008 When buying a new leisure battery I always take a multimeter and check the battery voltage - looking for over 12.5 volts with no load - and of it is below that level I simply choose another one - it's my money so why not! However just because it is a lower voltage does not mean it is no good - it may only want a charge - but if the voltage is high I reckon that it must be a good 'un so why take the risk! Link to comment Share on other sites More sharing options...
spospe Posted November 23, 2008 Share Posted November 23, 2008 Cruiser The best way to check a leisure battery is to do a controlled discharge. 1) Make sure that the battery is fully charged and its stated ampere-hour capacity is known. 2) Choose some item of equipment which is not voltage sensitive, such as a reading lamp which uses filament bulbs and make a note of its wattage. 3) Turn on the lamp and time how long it takes for the battery to reach 11 volts. 4) As an example, if you had four, 10 watt lights on, that represents 40 watts in total, or nominally 3.33 amps. 5) Normally batteries are quoted as having a given capacity at a given discharge rate, for example the 20 hour rate. The 20 hour rate would be the current which would discharge a battery in 20 hours, so nominally for an 85 ampere-hour battery, this would be four and a quarter amps (close enough to 3.33 amps). Assuming an 85 amp-hour battery then the 11 volt point will be reached after about 70-75% of the capacity has been used and the battery should not really be discharged any further so as to avoid the risk of damage. 75% of 85 ampere-hour is about 64 ampere-hour and so on this basis, with a 3.33 amp discharge the battery should last for about 19 hours before it reaches 11 volts. NOTE: battery manufacture is not an exact science and the above example contains the words "nominally" and "about". Several approximations have been made, such as taking the battery voltage as being 12 volts when fully charged and that the discharge point is when 75% of the capacity has been used. Nevertheless if you follow the above guidlines, you will get a good idea of what the state of the battery is. As a guide, I recommend changing a battery when its capacity drops to about 70% of its quoted figure. So remembering that in the above example the battery should last for 19 hours (at 100% capacity), anything much below about 13-14 hours would mean time for a new one. As a final point, I have noticed that a characteristic of failing lead-acid batteries is that they seem to charge up very quickly, but then fail to either hold a charge. Hope that this helps ............ Michael Link to comment Share on other sites More sharing options...
Brambles Posted November 23, 2008 Share Posted November 23, 2008 cruiser - 2008-11-23 1:28 PM Thanks to all who advised regarding my slowly discharging leisure battery. I disconnected the earth lead last Sunday and have monitored the situation on a daily basis. The battery is still losing about .04 volts daily, i.e: 12.95, 12.91, 12.86 etc. It's now down from 12.97 day one to 12.65 day seven. Having said that, it re-charges fully within about two hours. The positive lead is still connected, but surely that couldn't be responsible? So is my 4 year old (if original) battery kaput? Is there a magic trick I can perform to save it? Advice as always, much appreciated. In return, tips on banjo set-up and maintenance freely given. Country rocks.....but Bluegrass rules! Your voltage readings are fine actually, as at this time of year your battery ambient temperature is a lot colder. However you say 2 hours to reach fully charged but I do not now what rate you are charging at and to what level. I would have expected it to reach fully charged a lot sooner, but probably what is happening is you are reaching full charge and then the battery is warming up slightly before 'full charge voltage' is reached. Next time you charge , check it every 15 mins and see if the cells are gassing, you should if quiet all around you actually hear the fizzing.. If gassing then all is fine and battery is charged. However this does not mean you do not have reduced capacity and a controlled discharge test or an electronic battery tester many battery stockists have will be able to check this. Tracker -- 12.6 volts should be your cut off for buying - below this I would not touch with a barge pole. However sometimes if desperate you have to, so lower limit would be 12.4 volts which is where sulphation of the lead plates starts. Which leads onto ..never store a battery for extended periods when voltage is below 12.4 volts. Jon. Link to comment Share on other sites More sharing options...
cruiser Posted November 24, 2008 Author Share Posted November 24, 2008 Thanks all as usual for replies, and Jon....the battery may have charged in less than 2 hours....I just didn't check it sooner. Anyway, hold everything. I checked today after the usual 24 hour gap, and the reading had only dropped .01 (12.65 to 12.64). So maybe it's just been finding it's level and will stay at that reading. I'll check again tomorrow and report back. Life doesn't get much more exciting than this, eh? Link to comment Share on other sites More sharing options...
Brambles Posted November 24, 2008 Share Posted November 24, 2008 cruiser, you might get lucky and it is a hot day tomorrow and your voltage rises!! The voltage is temperature dependant so you may well fall below 12.6 but does not mean anything is wrong. Unfortunately do not have to hand at moment a chart showing volt v temp. You also should bear in mind when you charge a battery the lead plates get charged with what is called surface charge. This is the plates acting like a capacitor and will hold the voltage up just below the point where charging of the battery can actually occur. This surface charge dissipates slowly over and hour or two, and may well be the initial voltage drop you are seeing. So all this is starting to point to quiescent current (standby for equipment) drain in your Motorhome. You really need a ammeter to measure this but I would not be surprised if it is 45 to 65 milliamps. As always, my advice is to disconnect the battery whenever you are layed up for more than a week. I have fitted a switch to mine and switch it off even when layed up for a few days. Jon. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.