2 Volt Accumulator.

[EF80TVVALVE]

Hi all

Just thought I would share this with everyone. I was offered this little Exide DTG a short while ago which looked to be in fairly good condition although previously used. Today a local battery supplier filled it for me and for no cost at all which was very nice of them. They were quite amazed to see such an old battery and were interested to know its use.

Here's a photo of it now, I was advised go give it a few deep charge cycles to help get the plates reacting again so I will be doing this over the next few days.

[G6Tanuki]

Lovely! I always loved the old accumulators in glassware that looked like something from the shelves of a Victorian apothecary.

Do you know how it was stored before it came into your posession?

The 'traditional' way to decommission/store an accumulator was to charge it fully then drain out the acid - that reduced the chance of the plates sulphating.

If it was left stood with the acid in it, self-discharge will have taken the terminal-voltage down to zero in a few months and then sulphating is almost inevitable. You used to be able to get 'battery reviver pills' containing some obscure chemicals [EDTA?] that were alleged to reverse the sulphating but I don't think they really helped that much.

[EF80TVVALVE]

Honestly, I have no idea how it was stored. The plates do look barely used though and the positive plate still had a smooth and level surface suggesting that it hasn't had a hard life. Hopefully it was done as you said and decommissioned properly. I'll update the thread on how it goes. I'm going to use it on the KB 163 that I bought from another forum member, the manual for the radio suggests that with a 20Ah battery I should see around 15 hours of use before recharge. I wonder how well it will do this after 60 years or so of slumber!

[emeritus]

A chemist colleague who had worked on battery research at GEC told me that charging a badly discharged lead-acid battery at a low current can be beneficial. Sulphate is a poor electrical conductor, and applying normal charging current can give rise to local heating due to the current being concentrated into the conductive areas between the sulphation. As sulphate and lead have different coefficients of thermal expansion, the consequential local heating can result in shedding of active material and loss of capacity. I use a suitable wattage filament bulb in series for current limiting when restoring old batteries. Never tried it on an old open one like yours but it has worked on salvaged 12V SLA's that showed zero volts and initially refused to draw any charging current: it was sometimes several days before enough current started flowing to make the bulb glow.

[Bazz4CQJ]

In recent years, quite a few people have gone with the idea that some lead acid cells can be helped by feeding them with a pulsating voltage. I built a "pulsator" from a kit and I'm convinced that it does help batteries which are affected only by sulphation (I understand the we Brits have now agreed to 'sulfation'). Of course, other problems can adversely affect LA batteries.

Looking at the signal fed to a 12 volt battery on a scope, the pulsator is feeding 16V spikes at a frequency of a few kHz, the width of the spike is too short to resolve on my 20MHz scope. The connecting leads have to have very low inductance.

B

[EF80TVVALVE]

Thanks all for the replies, I thought it would be best to get it on charge as soon as possible from it being filled. I dug out my Amplion Convette and connected the battery to the heater supply and set it up to give a charge voltage of about 2.4v with a current around 470mA until the 2v. 5a charger I sourced turned up. That came today and I've been charging it on that since.

At first it didn't look too great, there were no signs of reaction on the negative plate but after 6 hours it began to show signs of life. Its been on charge for almost 2 days now and it looks like it's coming along well, there is very good reaction on both plates now and the charge is holding much better than before.

I'm just finishing off a HT battery for the set and then I'll give it a run and see how it performs.

[G6Tanuki]

I hope you get it back to some usable level of charge-storage!

I remember something from ages ago about re-activating lead-acid batteries which was basically charge-a-bit, discharge-a-bit, charge-a-bit-more, but with the 'charge' periods being double the discharge-periods, so you essentially got a staircase-effect going on, gradually putting a bit more charge into the battery with each step. This was claimed to recover more storage-capacity than just charging continually, though of course it took a lot longer.

I'd be careful to avoid charging to the extent where significant 'gassing' occurs - in an old battery you risk having the active spongy-lead separating from the plate-supports. A buildup of flaked-off plate material was sometimes sufficient to actually reach the bottom edge of the plates, causing a shorted cell.

[Bazz4CQJ]

My recollection is that the advice used to be to let them generate a little bit of gas, but generating lots of gas just decomposes water in the electrolyte and is probably is not beneficial.

B

Overlapping posts with Tanuki

[EF80TVVALVE]

Thank you both for the advice, this is the first lead acid battery that I'm pulling out of retirement so I'm taking it on board. I was advised by the manager of the battery store to give it a charge for a couple of days to get the plates reacting again and they look to be doing that very well now. I don't want to risk any damage so I'll follow the advice and put it on a radio and let it run for a while. I'll see how long it takes for the voltage to drop this first time and see how it improves over the next few charge/discharge cycles.

[EF80TVVALVE]

Here's a photo of it powering the heaters on my Telsen radio, it's quite happy doing the job and the voltage under load is still at 2v which is a good sign.

[emeritus]

Chargng a previously-dead battery at a low rate until the plates have revived should avoid shedding. I charge from a 1960's trickle charger with a series filament bulb to limit the current, reversion to the traditional method in the days of DC mains, when accumuators were often charged using a lamp board. With a suitable series load the battery voltage will regulate its voltage as the sulphate of the plates gets converted back to sulphuric acid. According to my 1940's book, gassing charge should be limited to 15 mins in a battery that is charged daily, and full charge is indicated by no change in terminal voltage for 10 to 15 mins wth the cell gassing copiously. Full charge indicated by a voltage of 2.6 to 2.7 Volts at 60 °F, but this assumes that acid of the correct specific gravity was used initially..

[akuram1]

When I started in the trade that was the first job in the morning taking them off charge to wait for the customer to collect. I can’t really remember much about the procedure now but one I do remember was it was difficult to avoid the acid burning holes in clothes even with some sort of protection. Wonderful when we gave it up as the demand fell away. I think we charged sixpence a time. Happy days.

[Bazz4CQJ]

That's a very pleasing looking bit of kit. Even if it's no longer in peak condition, it may well be good at coping with the modest load of your heaters.

B

[EF80TVVALVE]

I'd really like to see the types of rigs that the various radio/cycle stores/garages had in order to charge these accumulators, some do sound very primitive and dangerous when reading posts of previous threads etc but I've never seen any photos of them.

This particular battery has done very well this evening, I'm giving up playing with the sets now and it's still absolutely fine and performing well. I'm sure it will be good enough, even if it doesn't reach its previous capacity if it can give me a few hours a week then that will be enough.

Just out of interest, the charger I bought is a 1970s Hammant and Morgan 2v 0.5a and states its for accumulators on the instruction card. I presume this will also charge larger batteries that state to charge at 1 amp but just take longer to reach full charge? I have an Oldham O50 due to be rebuilt and this states to charge at 1 amp, but I don't really want a collection of chargers

[Bazz4CQJ]

Does your accumulator still have any info on showing what its original capacity was?

B

[HamishBoxer]

I have a new old stock 2V accumulator but uncertain whether I should use it or not.

[NottsIan]

Originally Posted by G6Tanuki

You used to be able to get 'battery reviver pills' containing some obscure chemicals [EDTA?] that were alleged to reverse the sulphating but I don't think they really helped that much.

I've read somewhere that EDTA is not soluble in sulphuric acid so the revivers don't work well. If the acid is drained out and the cell flushed with distilled water a solution of EDTA can help remove sulphation after which the cell should be refilled with fresh acid and slowly charged. I've not yet had the opportunity to test this myself.

[EF80TVVALVE]

I believe this Exide DTG was originally 20Ah and the Oldham was 50Ah. Hamishboxer, I also have a couple of NOS ones that I picked up not too long ago, but it almost seems a shame to use them! I'll be keeping mine as they are. Some used ones do turn up on the usual sites but they sometimes sell for more than they're really worth, plus there's a chance they could arrive damaged like this Exide did. I had to find all the parts of the lid in the parcel and glue it all back together before resealing. I've added some photos so you can see it's 'before' state

[Lucien Nunes]

I'd really like to see the types of rigs that the various radio/cycle stores/garages had in order to charge these accumulators,

I wrote about a fairly high-output unit here:
Crypto battery charger thread
I have since managed to obtain the correct switchboard that was missing when I posted the thread.

Post 11 shows a catalogue page scan with a couple of the popular Davenset chargers using Tungar rectifiers.

[Hartley118]

Seeing your accumulator has triggered memories of school physics lab experiments such as the Wheatstone Bridge and Potentiometer. This type of Exide accumulator was used as the constant source of EMF connected to the metre length of resistance wire which had a ‘knife edge’ adjustable contact for finding the balance point.

As far as I recall, this type of ‘block plate’ cell design was ideal for a long life in relatively low constant current applications, but wouldn’t, for example, be suitable for a car starter battery requiring lower internal resistance.

Martin