Electronic Circuits and Projects Forum

Hi John, hi Eric,

the idea of reverse charging (which is indeed connecting the charging device the other way round (+ to - and - to +)) isn't new at all.

Reverse pulsing is also used to manufacture double sided PCBs. Applying steady DC vias and through holes normally become considerably small on both sides of the PCB. Applying reverse pulsing the vias become as smooth as the plain surfaces.

Having this in mind I made an experiment with a very tired motorbyce battery. I could observe what happened inside the battery because its container was made of transparent material. One electrode in a battery turns into pure lead with a ligh grey surface. Both electrodes were almost black when I first charged the battery.

Charging of that 6.5Ah battery was terminated manually at 7.2V battery voltage. After five hours the battery voltage was again down to 4.5V. So I tried the above described method. The analog Ammeter of the 25A max charger clicks very loud when polarity is changed reaching the end of the scale, so I assume the reverse current is somewhere in the 100A range.

Anyway, after 6 full charge and discharge cycles the battery is almost like new. 24 hours after a charge cycle the battery voltage is stable at 6.5V.

I'm a very cautious person, and that's the reason why I don't use protective clothing or goggles.

Attachment: PCB with and without reverse pulsing.

Regards

Hans

hi Hans,
I appreciate that reverse charging a 'low discharged battery' is old technology.

Its the way your earlier post reads that concerns me.

It appears to say " while charging a battery, its OK to occasionaly reverse connect the charger to the battery for 250mS during the charge cycle"

If you reversed connected a charged battery to a charger it would either blow the dc fuse or the rectifiers.

Its a procedure I would NOT recommend to any novice.

I dont see the connection between battery charging and copper deposition in pcb production.

Originally Posted by ericgibbs

.

I dont see the connection between battery charging and copper deposition in pcb production.

Hello Eric,

I guess you'll agree that both of them are electrogalvanic or electrolytic processes.

Hans

Originally Posted by Boncuk

Hello Eric,

I guess you'll agree that both of them are electrogalvanic or electrolytic processes.

Hans

hi Hans,
I agree the electro technology is the same.

My concern is a Newbie is going to try this desulphate idea and finish up blinded and/or disfigured if the battery explodes.

The problem is, which I am sure you are aware, a current of 100A could easily weld the 'temporary' contact in place so that it couldn't be disconnected before the battery blew.

BTW, I have seen the 'weld' take place, when a guy used a pair of car jump leads the wrong way around.
He couldnt get them off and the jumps leads melted.!

Is it just me or does it seem kind of silly to try to come up with a completely electrical method to desulfinate batteries? Aren't there chemical methods to desulfinate lead acid cells?

Originally Posted by Sceadwian

Is it just me or does it seem kind of silly to try to come up with a completely electrical method to desulfinate batteries? Aren't there chemical methods to desulfinate lead acid cells?

I only know of mechanical methods to do that - completely remove the affected electrodes and replace by new ones.

I watched this at a Turkish battery shop where they also make customer specified batteries. Got my glow plug battery (model engines) made there: 2V/75Ah - lasted one year without charging.

In the "modern" world batteries are "ex & hopp" items.

Hans

Originally Posted by Sceadwian

Is it just me or does it seem kind of silly to try to come up with a completely electrical method to desulfinate batteries? Aren't there chemical methods to desulfinate lead acid cells?

There used to be a chemical on sale for adding to the battery acid, I suspect it was another scam.
I havn't seen it advertised for some time, perhaps others have.

The best way to take out a battery from sulphation is to add distilled water and charge it at 1/20th of the original rating and for longer time, say 2 days.
as the recovery starts and cells get warmer, better reduce the current still to 1/30 or so. We were able to recover cells in this process.

But , one check is needed whether lot of SHEDDING had already taken place, and if so the positive plates may not sustain.

Hence I ask, what physical material difference is there in a truly new battery vs an old one, over time the back and forth electrolytic response does result in buildup of material, mainly from impurities in added water. I have NEVER seen true distilled water used in the recharging of a large lead-acid cell. The best I've seen is a refill from a long term water bottle sitting idle, which becomes slightly acidic over time from atmospheric carbon.