batteries - what is 'equalisation'?

[snowleopard]

batteries - what is \'equalisation\'?

i have heard that a sulphated battery can be revived by overcharcing for a few hours at around 15.5 volts, causing heavy gassing. i believe this process is called 'equalisation' and some battery chargers have a cycle which will do this.

i asked Sterling if theirs did and was told yes.

having bought the sterling charger rather than the more expensive dolphin i find out that it doesn't have the programme i wanted. they say equalisation is just another word for 'absorbtion' or 'bulk' charging.

where did i go wrong?

while on the subject of batteries, the absorbtion charge voltage can be set to 14.4v for gel or sealed batteries or 14.8v for standard lead-acid. mine are 'maintenance free' lead acid, i.e. normal batteries which don't need topping up - would you call these 'sealed'?

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[pandroid]

Re: batteries - what is \'equalisation\'?

I think equalisation is just another word for the 'absorbtion' phase (NOT the 'bulk' phase) that most 3 stage chargers carry out. It uses a smaller voltage and limits the current that a battery can take to allow it to come up from about 80% charge to close on 100%. A battery shouldnt gas in this process - thats the whole point.

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[bedouin]

Re: batteries - what is \'equalisation\'?

I have tried a couple of things to revive my old batteries - both "over-charging" for a few hours, and adding tablets bought from Halfords. While these may have made a bit of an improvement, it is not enough to make the batteries useable this season, so a new pair are required for this season.

As to the charging voltage. The important distinction is whether you can (and are willing to) top up the electrolyte. If you can get to the cells to add distilled water then it's okay to use 14.8V, otherwise stick to 14.4V which shouldn't cause the electrolyte to boil.

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[pvb]

Equalisation...

Few marine leisure battery chargers in the UK seem to offer equalisation, which is supposed to help prevent flooded lead-acid batteries from ageing prematurely. What happens in equalisation is that after the charger gets to the end of the absorption phase it continues to push current into the battery until the voltage stops rising (this is usually at 15.5 to 16.0v). By doing this, it's supposed to dissolve the lead sulphate crystals which have formed on the plates. Equalisation can only be done on flooded batteries - never on gels. For boat use, equalisation might be done say once or twice a month. Because the battery voltage gets very high, it's advisable to do the equalisation with all loads disconnected, otherwise damage could occur to light bulbs, electronics, etc.

The current generation of Sterling chargers have something which they call an "automatic 7-day de-sulphation cycle" - this might be equalisation.

You're probably best using the "sealed" setting for your maintenance-free batteries.

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[charles_reed]

Re: batteries - what is \'equalisation\'?

Equalization

In any cyclic application, a series of batteries will always need to be equalized from time to time in order to ensure that the battery cells remain at the same voltage throughout the pack.

No two battery cells or batteries are created equal. During both charge and discharge each and every cell/battery will react in a minutely different way to its neighbour. This could mean that each battery may be holding a different quantity of charge. In order to get the most out of the total battery pack it is necessary to make sure, as far as possible, that each and every battery is holding a similar amount of charge.

During the charge cycle the voltages of the different batteries will very. In order to bring them all to the same level it is necessary to give some a slight overcharge in order to bring the other up to full charge.

Equalization is done by allowing the voltage to rise while allowing a small constant current to the batteries. The voltage is allowed to rise above the normal finish voltage in order to allow the weaker batteries/cells to draw more current. The stronger batteries will not be adversely affected providing the current is gently and the period and frequency of overcharging are not too high and great respectively. The stronger batteries will absorb the overcharge by giving off heat by gently boiling and gassing more heavily. Once the weaker batteries have absorbed the required current, the equalization charge can be halted. The equalization time should be long enough to bring all the batteries up to a full state of charge. As the time factor will very the most reliable way to check the charge states is by a voltmeter on each cell or individual battery.

Really sophisticated battery charging and monitoring systems do not require the use of an equalization charge and are able to charge all the batteries fully including the weaker ones without overcharging the strong ones.

In these systems, each battery is fitted with an electronic clamp, which gradually reduces the amount of charge going into the fully charged batteries as the finish charge progresses. This means that the weaker batteries receive more current to bring them up to a full state of charge and the strong batteries are prevented from being overcharged unnecessarily. The drawback with these sophisticated systems is their cost. The price of each battery clamp can be in the order of 1/5 the cost of each battery.



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[Anchorite]

Re: Another miracle-worker?

Not too far from the subject: Accastillage Diffusion (AD), France's biggest
chandlery chain does a glossy FREE catalogue of 450 pages. Page 291 shows
an appliance called MEGAPULSE by Novitec. This is connected directly to
the battery and claims to reactivate old and apparently useless batteries
by dissolving the sulphate deposits....
Has anyone heard of or used (or swears by or at) one of these?
Price is 76 Euros, say £50.

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[charles_reed]

Re: Another miracle-worker?

The technique is pretty old-hat and generally accepted as being feasible.

There are a number of proprietary manufacturer's especially in the US (Redi-Pulse being one).

For a fairly easy explanation and DIY view this website http://www.flex.com/~kalepa/desulf.htm

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[saturn]

Re: batteries - what is \'equalisation\'?

in my industry equalisation is just another word for boost charge, generally used on a new battery to bring it up to fully charged .or used when for some reason the battery has become low in capacity and you want to charge quickly.
equalisation will charge at near max output of charger (check voltage)and on some chargers will just drop of more slowly than in normal mode.
i would say that if you had a charger with a equalisation facility and you used it say monthly (checking specific gravity if you can)it would be very useful.lead acid batteries enyoy a constant charge -discharge cycle.constant trickle charging and little use they do not.lead acid "maintainance free" batteries that still have caps on each cell for inspection imo are not and if you boost charge check electrolyte level.

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[smb]

Re: batteries - what is \'equalisation\'?

Ditto re Sterling. I asked the same question and got the same reply only to find a different interpretation of equalisation once I bought the unit. The instructions do indeed refer to 'equalisation' at 14.4/14.8 volts but obviously this is less than the 15.5+ advocated by most sources as neccessary to remove sulphation.

Never sure if I was deliberately mis-sold by the blurred terminology or just bought into someone elses view of the best approach, but voted with my wallet and subsequently went to Adverc for my alternator regulator and battery monitor etc.

BTW, constant current or bulk stage on a three stage charger. Can anyone tell me if this should hold at 100% of charger output or 100% of what the batteries will gladly accept which reduces as their voltage rises?


Steve



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[charles_reed]

THE latter nm

nm

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[anabel]

Re: Another miracle-worker?

Anchorite,
Would you be able to let me have Web site address of 'Accastillage Diffusion (AD)
mentioned by you in recent post??
Thanks.
Anabel

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[jon_bailey]

Re: batteries - what is \'equalisation\'?

Last year on a FIAMM marine battery had a voltage problem. Took battrery out and found one of the cells was low on acid - topped up with distilled water recharged but still no good.

The good thing about this battery is that it is wet cell so can check SG of acid using a cheap (Draper) tester. This confirmed that cell was 'dead'. Did the equalization/desulphation trick and then sg of acid checked out fine and used for the whole of last year without problem. Recently charged the battery after winterisation and after top-up of all cells and normal charge, all cells checked out fine i.e. sg of 1.275, even the 'duff' one from last year.

Not sure how old battery is or how much longer it will last but it makes you wonder how many viable batteries get thrown out?

The lesson here is use wet cell, non sealed batteries.

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