Charging a 6V battery

C00P · Senior Member

Charging a 6V battery

T1 Terry · Guru

The battery is severely sulphated and will not accept a charge. The risk with higher voltage charging a genuine gel electrolyte battery is creating bubbles of gas between the plate and the gel electrolyte, oxygen on one plate and hydrogen on the other. These bubbles will not disperse resulting in no contact between plate and electrolyte in that area and that results in lost capacity. Gel batteries require a lot of care, over voltage or over current charging wrecks then along with excessive discharging as both cause gas bubbles to form. You can try a pulse charge to see if the plates can be recovered but I don't think you will have much success unfortunately, I think the battery may have gone to battery heaven.

T1 Terry

C00P · Senior Member

Thanks Terry, I thought it would be something like that.
I'll give it a suitable funeral at our local recycling depot...

C00P

Jaahn · Guru

Hi COOP cry

I have rejuvenated a few LA batteries over the years. Similar to yours too. I would leave it on the 100ma input and keep checking the voltage now and again. It may start to fall after some hours as the sulphate breaks down. If that continues till if falls to about 7.5 V then you have succeeded. If not then ditch it. It should not be left for days and days. It is only 5 ahr so no more than double that input.

The chances are good that it will succeed contray to what others say, but not knowing the history ???

good luck Jaahn

Warren-Pat_01 · Guru

Hello COOP, I'd do what Jaahn suggested.

If & when it comes "good", leave it to settle for a short while & then discharge it down to about 5.9v & then recharge it again. See modernsurvivalblog.com/alternative-energy/battery-state-of-charge-chart/

Leaving batteries to sit on the shelf for long periods without some sort of activity does not do any of them any good. You can get small 3-stage chargers to keep them on float.

Best of luck.

T1 Terry · Guru

Please let us know which technique you use and the result, an actual real life recovery of a Gel electrolyte battery isn't very well documented and just because it works with an AGM or flooded cell doesn't mean it will work with a Gel electrolyte battery, but no harm in trying so give the ideas suggested a go.

T1 Terry

PeterD · Guru

Any dead flat battery will not accept much current when you commence to charge it. Don't raise the voltage to force current into the battery. That causes overheating and damage to the battery. Leave the charger on 6 V for a while and let nature take its course. When you start to see the battery accepting current then you put a 2 A diode in the circuit and put the PSU on 7.2 V and complete the charging. The PSU may just not regulate too well at low currents.

I have had GEL batteries that have been flat for a considerable time and have come up with gentle charging. Give it a try, you have nothing to loose but your smokers cough.

C00P · Senior Member

PeterD wrote:

I have had GEL batteries that have been flat for a considerable time and have come up with gentle charging. Give it a try, you have nothing to loose but your smokers cough.

Not even that- never smoked. What's the purpose of the diode?

THanks for all the suggestions, folks. I'll give that approach a go and let you know if it works. It hasn't gone to the undertaker's yet wink .

C00P

-- Edited by C00P on Thursday 18th of May 2017 11:41:39 PM

PeterD · Guru

The diode is to drop the voltage into the battery by 1/2 V or so. His 7.2 V op from the PSU could be a bit much for the battery.

Hylife · Guru

Gell batteries do dry up and do eventually fail beyond repair.
They are only $19 from Jaycar, just buy a new on and loose the worry.
https://www.jaycar.com.au/6v-4ah-sla-lantern-battery/p/SB2498

6v-4ah-sla-lantern-batteryImageMain-515.

On second thoughts, just buy another torch. Those old Dolphins are ancient tech. A cheapo $5 LED model from Kmart would outperform a Dolphin.

-- Edited by Hylife on Friday 26th of May 2017 09:45:37 PM

Bagmaker · Senior Member

Last century, the advertisement for Dolphin torches showed a fellow accidentally dropping the torch off a cliff, it bounced down to the water below and shone the whole way.
My father used to point out that his took that sort of abuse to get the thing to turn on in the first place!

Gotta agree with Hylife though, update a decent LED torch

macka17 · Guru

I Second LED's.

I've got "several" chuckle. ALl from China.
(65\70% work on arrival but they do replace)

Last one. (in post). $24 del.

60mm Lens dia. Drives with 4 x 18650 battery's and 9 x XM-L bins
(equal to globes).

Throws a HUGE white beam, 500 + metres.
and WILL blind you if looked into.
Waterproof to 2 mtrs. Drop direct fall 2 mtrs.
and fits IN hand.

Another one . $7.50 del. will outshine. out beam any, globe Dolphin.

If you still have Dolphin. You can Probably? get an LED as straight swap
for globe.
But LED Torches with modern Battery's really do outdo the older ones.