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[Ted_H]

I've been given an unused (still in the box) SLA battery however it dosent seem to wantto tke a charge ..has it been left on theshelf too long or is there a way of bringing it to life ....shame if it can only be ued as ballast !

[Peter Fitness]

From past experience I would say it's only good for ballast   but others may have some suggestions.


Peter.

[grendel]

I managed to get 3 whole boxes of 'brand new' unused but 3 year old SLA's (6v 10AH) 10 to a box, most of these were recoverable, some needed a quick burst (5 minutes at most) on a car battery charger to get the voltage up to a level where the standard SLA charger wouldnt report a fault, a few were ballast even after this.

[john s 2]

Some battery chargers will not attempt to start charging totally flat batteries seeing them as not there. If in doubt use a charger that just gives out amps, flash together the leads to see a spark. Also charging at a higher voltage may wake up the battery. Fingers crossed. John. 

[Ted_H]

Some battery chargers will not attempt to start charging totally flat batteries seeing them as not there. If in doubt use a charger that just gives out amps, flash together the leads to see a spark. Also charging at a higher voltage may wake up the battery. Fingers crossed. John.

Thanks john .. could you suggest a charger that gives out amps .. I have a 4A car battery chargr that "sparks" when the leads are touched together .. will that do ?

[john s 2]

Yes you could use this at a pinch. Its not a good idea to charge a 6v battery on 12v.The idea is to liven it up.so it can be charged at 6v. Your charger may  have a 12v 6v change over switch.Please think of amps as amount and volts as push or pressure.Most small pb batteries should be charged at say half an amp. If your batterys wake up then a few slow charges may restore them. Discharging between cycles of course. Good luck John.

[Ted_H]

thanks again john its a 12v battery i'm trying to wake up ... ill leave it a while on charge and see what happens
 

[john s 2]

Ill keep my fingers Crossed for you. If your battery wakes up. You could of course slow charge it by putting say a 12v buld in series to limit charge. John.

[Colin Bishop]

I think that once a lead acid battery is comatose it will never return to its 'as new' condition. It may appear to accept a charge with a raised voltage but will have no significant capacity. I rather suspect you are flogging a dead horse really.
Colin

[Ted_H]

im realy just wanting it to give a tug i have one last run and test before i think of selling it, and let my grandaughter have a sail of it .. its a brute so will take a few knocks .. lol

[grendel]

depends really a brand new unused / uncharged battery wont have suffered from sulphation of the plates, it may well just be low on voltage, through charge leakage, as long as it is charged properly after a few cycles it should be ok. the spec sheet online for the type I have quote a shelf life of a year (before charging) and a typical life of 5 years or 1000 charges, mine had been on the shelf for 3 years, and I guess about 2 out of the 30 were past it.
Grendel

[malcolmfrary]

A battery kept charged will not suffer sulphation, but during charging and discharging, not all of the chemical components that react on the surface of the plates go back exactly where they came from.  In wet cells, these bits that missed can sink to the bottom, in a gel cell, which can theoretically be used in any position, presumably the gel keeps them where they form.If the battery is left to its own devices, being left as a container of chemicals that will slowly react with each other, the lead, lead oxide and sulphuric acid will interact and leave lead sulphate crystals lying around.  These are not amenable to breaking down into lead, lead oxide and suphuric acid when charging current is applied, so the battery becomes a dead 'un, especially if it is a sealed one.
An illuminating read on [size=78%]http://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery[/size]