It depends on the type of battery, if its lead acid its in deep discharge and it depends on how long its been discharged, but they can recover if you just leave it on trickle charge for a few days, maybe use a half sine wave pulsed charge voltage to nudge it back to health....

If its NiCd or NiMH then it should accept the charge okay, as it isn't accepting the charge then maybe its time to throw them away (environmentally of course).

John.

Assalamu Alaikum, You have advised me to use trickle charger. Thank you for your advice. But it is a 6V sealed lead-acid Batteryof 4.5Ah. MAX CURRENT RATING IS 1.3A BUT NO VOLTAGE RATING. What voltage should I apply?

If you do manage to revive this battery (I think it is probably too badly sulphated by now) make sure to not discharge below 5 Volts. Below this voltage is the deep discharge point where recovery is difficult. If possible fit a voltage cut-off to the application.

To be honest, I've never had much luck with those sealed lead acid batteries, once deeply discharged they just sulphate up...

To try and get some life back into it I would leave it on charge at 7.50 volts for a few days if it hasn't picked up current in that time its not worth trying to force it, even if you could squeeze some charge into it it will always have a very low capacity...

I've used these batteries for 20 odd years and when they give up its usually a case of buying another.... Sorry not much hope for this one by the sounds of it?!

John.

Standard charging for the SLA is 6.9V

Boost charge for the SLA is 7.2V

For others if this sounds familiar,

std charge is 1.15V/cell (or 13.8 for 12V) boost charge is 1.2V/cell (or 14.4 for 12V)

I have gone through such battries for long 6V , 4.5 AH ,were common with portable emergency light system , there are two or three plastic seals on the top you can break open to see for sulphation ,dry electrolyte etc most problably you will see it ,there is little you can do about it but replacement , 1V or 2 V is too low to recover the battery charge , 5.5V was lowest cuttoff for discharge , charging voltage between 7.25 - 7.50V with 1.35A was specified rating ,try it withgood charger

go to www.triplebatterylife.com

Lead acid batteries do not like complete discharge and then sitting. The lead sulfate formed during the discharge chemical reaction is soft putty at first, but within a few hours turns hard and brittle, often cracking into 'alligator skin' and falls off the plates if jostled. The hard lead sulfate is very resistant to the 'charging' reverse reaction because it has a very dense surface once it hardens.

Such a battery is usually not salvageable, and what you describe is certainly not trying to restore.

If Sulfated the normal battery charger may not be able to to charge the battery. In a lead acid battery as it discharges in the chemical reaction a sulfate is formed. Once the saturation point is reached this sulfate starts to crystallize on the lead plates. The sulfate will act as a insulator. We all ways used a charger with variable out put to force current through. Has to be monitored quite frequently. As the sulfate in solution is changed back to acid dropping the saturation point, the crystallize sulfate will start to dissolve. The current and voltage will come up on this type of charger. It will over charge the battery. A sulfated lead acid battery can be restored just usually not the same. Will take many discharges and charges to get the crystallized sulfate back it to solution. Finish charge voltage on a lead acid battery is 2.5 volts per cell. This was done on industrial batteries where the value was worth the time. If the battery is small more economical to replace it then spend the time.

The solution for your battery problem was repeated many times.

Go and buy a new battery which will give you confidence. It is damn cheap any way.

Nadeem

There are battery chargers available via post that use a high frequency pulse to break down the sulfite but they are only able to help batteries that have not sat around in a discharged state for a long time. Battery Tender will do this. There are others. But a new battery will be less frustrating.

I have used a homemade de-sulphator with great success on 12v & 6v lead acid batts that would not charge at all- this unit applies 100v pulses at 1khz, & is powered by the batt if above 6v, or by another batt in parallel, or a batt charger, thru an isolating inductor- it may take 1-2 days- it has succesfully rejuvenated SLA batts also- there are plans on the web how to make.

The previous by CA1 may have some merit. I've resurrected some rechargeable batteries by using a bench variable metered power supply that has CURRENT LIMITING. I'll begin with 100-200 mA (and starting from 0-volts then upward) and see if the battery then wants to accept a charge (the current will decrease?). If the battery seems to be accepting the charge (current drops with time) then increase the voltage gradually (with patience) to no more than about 100 mA. If not, disconnect battery increase the ps voltage to about the par voltage and set the current limit to perhaps 1 AMP; and then just manually and intermittantly connect the battery while watching where the current goes. See no change (current keeps going to 1 amp?), then reduce the current limit to about 1/2 and repeat. If it seems to charge after about an hour or so, disconnect and verify the terminal voltage after 12 hours. Not/dead? Then it is done. It's always trial and error.

Sometimes the various types of batteries will come around (for reasons as explained previously). Sometimes. Beyond that, chunk the baby and just replace it with new. After all, nothing lasts forever. But we tried, huh?

Get a new battery and make sure you never deep discharge it.

Even if you manage to get it working again, you have done serious damage to this battery already and it will never be reliable.

Most posters have told you this already, they are completely right!

Nice to see you again, Andy:

I think that debate of WTC is over now.

6V battery is cheaper than all that talk. I suggested that too.

Regards;

Nadeem

Hi Nadeem,

nice to hear from you too.....

We both think alike.......

Stay healthy.

Andy G.

Hello Andy:

Yes it happened before that we spoke the same truth. I got out of WTC debate as it was heating up and the debate became very acromonious and even reading started hurting me emotionaly. So, I bowed out. In USA we still feel the pain.

I am not keeping up with the ongoing discussions but this one caught my eye.

However, sometimes I go in and just read quietly and learn what others are saying about the topic.

Regards;

Nadeem Butt

10042007