Salvaging Lead Acid Batteries

Working on a previous project to make a prototype Pi UPS I pulled a number of salvaged lead acid batteries out of the scrap bin.

Battery Resuscitation through Desulfation

Battery Resuscitation through Desulfation

It quickly became apparent that the batteries were all flat and as each had a terminal voltage of around 0.5V they appeared to be beyond life ever again. Not surprising considering the number of years they had lived in the scrap bin without ever having a charge.

Initial attempts to put a charge into them and get them going again were without success. Even over voltage-ing them a little to get them started failed miserably. The best of them was taking around 10 micro amps. After leaving them on charge for 5 days or so the situation had not improved. So what were we looking at ? Maybe they had dried out, maybe the plates had fallen apart and were now mush or maybe being overly discharged the plates were caked irretrievably in insoluble hard lead sulphate crystals.

There are plenty of miracle cures for dead lead acid batteries and desulfation. Frankly I am rather sceptical of most of them. But for some reason I thought although slightly implausible desulfation was a fun hack to try. Chemical means to reverse the crystal build up were out as the batteries are sealed units. So it was time to rummage through the internet for ideas and then hit the scrap bins again for parts. The circuit I settled on is here Pulse Desulfator Doc. This formed the basis and the prototype as shown in the photo was a derivation of this.

Having nothing to loose other than a bit of time constructing and debugging it I set too to build it. The inductor was a hand wound approximation, the logic inverter shown in the schematic was replaced with a simple transistor based inverter using a 2N2222 NPN transistor and the mark space ratio of the 555 astabel circuit needed adjusting. Probably because the inductor value was a touch lower than it should have been. But in the end it appeared to be working.

Now the acid test (see what I did there….). From the picture you can just see the ammeter on the bench PSU showing the battery taking a charge of 200 milli amps. So success. It took 2 days of float charge plus the desulfator pulsing away to get this recovery. Over this period the input current could be seen steadily increasing, whereas before with a stable DC supply it had just sat there and done nothing. The open circuit voltage of the battery at the time of writing now shows 4.5 volts so there is a way to go yet. It could be a couple of weeks or so before the battery is as recovered as it ever will be. In reality I can’t see them ever being “as new” however a trick worth knowing about and trying when salvaging neglected lead acid batteries.

Not to self if trying this with an old car battery check the electrolyte levels first and be prepared to except that the plates could just be mush and the battery beyond recovery.

December the 14th Build Day

On december the 14th we had our monthly build day at Access Space. We had a large array of 3D printers and electronic projects
being worked on, some of the things that went on throughout the day include...
- 3D Printing parts to improve the hack space
- Laser Cutting
- Tinkering with electronics

3D Printing parts to improve the hack space

We have been hosting our meet-ups at Access Space for around 9 months now. From the start Access Space has very kindly given us a space in there Refab Lab for us to store and use our 3D Printers. We where asked to put forward suggestions for in ways witch we
could improve the hack space. We discussed with Access Space about making it an easier space to work in. We decided to create and print some coat hooks. We drew up some 3D coat hooks in Open SCAD, a free open source 3D CAD programme.

3D Printed coat hook being drawn up in Open SCAD

Once the object had been Compiled and Rendered it was exported as a STL file, it could then be sliced and printed. altogether we
printed four of the coat hooks, in total we had three printers on the Job. Including the small foldable, portable printer that
has been made by one of the group members (we will try any get picture).

3D coat hook being printed

This above is this is the finished product. The coat hooks where mounted on to a pice of wood witch was screwed on to a shelving
unit.

Laser Cutting

One of the 3D printers that was brought along to the build day was a SUMPOD Delta, this printers X,Y and Z axis sit on three
threaded rods. Some pieces where designed using Ink Scape (a 2D open source CAD programme) and laser cut. The pieces where to
mount the stepper motors on to the printer.

SUMPOD Delta 3D Printer

Among all of this we also had some people with Arduino's creating projects, including light synthesisers.  

We would also like to thank Access Space for providing us with a work space and access to tools and machinery in there Refab Lab.
The next meet up will be held at Access Space on the on January the 27th.

You can keep in contact with us by following us on Twitter @SHHMakers or on our forum at: https://groups.google.com/forum/#!forum/sheffield-hardware-hackers