Leisure Battery voltage 3.85

[eppiblue]

Apologies if this sounds like a stupid question, - Is it now completely useless, ie do I need a new LB or do I just need to go for a 30 min drive?

[francophile1947]

If it's that low you won't have done it any good, but it's worth trying to charge it - it'll take longer than 30 minutes though One of those £12.99 intelligent chargers (often sold by Aldi and Lidl) is probably your best bet, but it'll be on charge for several days.

[bigdaddycain]

Aye, there's no harm in seeing if it'll hold a charge, good luck.

[hembramacho]

I thought my LB was knackered when it lost most of it's charge (can't remember what it went down to, but is way lower than it should have been). Got a CTEK intelligent charger (the more expensive type of Lidl/Aldi variety ) and it was brought back to life. Might as well give it a go.

Cheers

Andrew

[g8dhe]

Yup a good solid drive for as long as possible or put it on a charger for 24-48 hours at least. If its a fairly new battery and not been discharged too long then it will recover but it will have shortened its life by a few months.

[lpgimports]

If it is a proper leisure battery it should recover, they are made in a different way than a normal starting battery. Leisure batteries give low amps for long periods to low states of charge if required not large amps for short periods like a starting battery..

Paul

[haydn callow]

In future it would be wise to use a cheap voltmeter (multi meter) and keep a check on the battery....best not to let it drop below 11 volts before recharging.....this applys to any battery. Also if you let it drop to very low voltages there is a good chance you will blow the main fuse if you start the engine. If this happens it will never charge untill the fuse is replaced.....Check this hasn't happened in your case......(put a volt meter across the terminals and with the engine running you should read about 14 volts +/- ...if it still reads 3.5 then the fuse is probably blown)

[scanner]

If it is a proper leisure battery it should recover, they are made in a different way than a normal starting battery. Leisure batteries give low amps for long periods to low states of charge if required not large amps for short periods like a starting battery..

Paul

But there is low (about 10 volts) and there is waaaaaay too low - 3.85 volts. As said above it may recover, but if it does it won't be anywhere near a 100% recovery.

[lpgimports]

It's never a good idea to run a battery till it has nothing left but the construction of a leisure battery is such that they are designed to handle much greater abuse in the form of deep cycling.

You can even recover car batteries that have deep discharged if you do it slowly and with an intelligent charger and desulfation kit. Have a friend that does loads nt had time to play around with this as yet.

Paul

[eppiblue]

I took it for a spin for 40 mins last night and checked the LB voltage when I got back and was just under 12V.

Sometimes I only run the stereo from the LB when parked up, Im guessing that would run for quite a while before going flat?

[g8dhe]

You need to leave a battery for an hour or two after charging to get real figure, a fully charged Lead Acid will be about 12.6-12.8v under no load, but it will depend exactly on the chemistry involved, there are several variations.
At the other end it will be about 11.8 - 12.0v when discharged again under no load, with a load on then it will drop to about 10.5v as a minimum when fully discharged.
So I think you would be best to get a bit more charge into the battery if possible, otherwise you may find that within a few days it will be totally flat again. Most L/B have a capacity in the order of 80-95Amp/Hrs so a 40 minute run even if it was putting 10Amps into the battery for all that time will only be 10*40/60≈6Amp/Hr so you have a while to go yet before its fully charged.

[haydn callow]

as stated above, a reading of 12 volts is to all intents FLAT.

[dandywarhol]

Very bad move to take it out to charge it off the alternator - you've probably now completely f~cked any chance of recovering it now with such a large charge going into it!

Why didn't you take lpg's advice and slow charge it with an intelligent charger???????????

[g8dhe]

The problems caused by sulfation occur two ways;

• Normal use, sulfates build up over time and in general are the cause of battery failure after a few years. Electrically it tends to cause additional internal resistance which affects both charging and discharging currents, but also it mechanically causes problems to the lead plates by distortion and flaking
• The other problem is when a battery is discharged and then NOT recharged for some considerable time, not hours or just a few days, but several weeks or months and is made worse if the cells are not fully filled with electrolyte.

Once sulfated it takes a lot more time to convert the secondary sulfation back into sulphuric acid, but this is normally achieved by passing large currents but for very short periods (less than a second) through the battery and is what you will see many special charging circuits are all about. In general a battery can be charged at quite large currents (20-40Amps) quite happily provided that the temperature is not allowed to exceed the normal limits for the battery or allowed to exceed a charging voltage of 14.6 volts (varies slightly ±0.1v depending on specific battery type etc) once you exceed 14.6v then gassing starts to occur and you loose electrolyte.

Plenty of good reading at Wikipedia or Battery University if you need to know more

[dandywarhol]

That info is good for starter batteries Geoff - I still don't think its good to belt a high alternator current through a leisure battery for that length of time if its in as poor a discharged state as this one is...........................