This page is intended to provide builders of the battery desulfator circuit, as originally shown in Home Power Magazine, issue number 77, with additional information and very important corrections to the original diagram.
All those needing assistance to please submit your questions first to the desulfator News Group.
This basic circuit has been duplicated by many around the world. (Africa, India, Indonesia.....) Anyone with soldering skills can build the unit. There are many reports of successful battery reclamation after years of testing, so it can be safely said that this technique is valid. While there are a number of commercial units available now, this circuit represents the lowest cost way to rejuvenate tired batteries. Included are complete technical details so that anyone with typical electronics skills can adapt or modify the circuit to their specific needs.
The idea behind this pulse generating circuit derives from the fact that a sulfated section of a battery plate is covered with a nonconductive layer of sulfate crystals. These crystals insulate the plate from the electrolyte and are the cause of the increased resistance that makes a battery unuseable. However, a very fast risetime, high voltage pulse presented across the battery terminals will see these sections of crystals as capacitors, and the high frequency energy present in the pulse will readily pass through these capacitances. Over a long period of pulsing, the crystals are eventually broken down and returned to the electrolyte, promoting reduced resistance and lengthened battery life.
The main concern in presenting this information is to keep as many recoverable batteries in service as possible. Most batteries are discarded prematurely, due to sulfation rather than having reached their cycle limit. This represents a huge waste, and a potential resource. It is hoped that many tons of batteries can be kept out of the world's dumps by this simple technique.
suitable for most solar systems,
vehicle starter maintenance, and
gradual battery reclaimation.
There are several flavors of this circuit.
for large battery reclaimation,
electric vehicle maintenance,
high voltage systems, and
low level charging. Under
Using a resisitive load to measure battery condition is a standard method. For each battery type a standard load is defined, and if the voltage under load drops below a certain level, the battery is bad or in need of recharging. For small batteries this load can be typical, like a 5 Ohm load for a AA Alkaline drops the voltage at end-of-life to 1.0 Volts. Using a load across the battery (for a few milliseconds) is used by laptop computers to assess the charge status of the battery.
For big batteries the "standard" load resistor may get to be very small. However, given the availbility of good and fairly cheap(under $40) 3 1/2 digit digital volt meters, it is not necessary (or safe) to draw a big current spike out of the battery to measure its internal impedance. For my Dynasty UPS12-310 High output battery I use a 1 Ohm 1% 20 watt resistor shunted with a bar directly to the battery terminals. The resulting drop across the 1 Ohm resistor is eazy to measure with the voltmeter set to the 200 mV scale.
A fully charged 12.6 volt lead-acid battery will have an internal resistance of about 0.01 ohms. My Dynasty UPS12-310 high output battery is spec'd at 0.0033 Ohm. Determine the internal resistance of the battery by measuring the terminal voltage with open circuit, V, and then the voltage drop across an accurately known resistive load R, voltage DV. The internal impedance of the battery, Ri, is then given by Ri= DV * R / V.
Example: V=12.60 volts and DV= 81 mV Volt using a 1 Ohm 1% 20 watt Ohmite resistor. Ri= 0.081* 1.0 / 12.6 = 0.0064 Ohm.
The power dissipated in the resisitor is V*V / R = 12.52 * 12.52 = 158 watt. The resistor will get warm very quicky. If this experiment is not finished quickly, the temperature increase will change the resistance. This will make the measurement inaccurate and will burn your fingers).
Somebody on the email suggested pulling 200A, presumably using a 0.062 Ohm resistor. Pulling that much power (200 * 12.6 = 2.5KW!) has to be done fast indeed. Batteries of this size can be very dangerous.
Desulfator from Solar-Electric.com
Technical details on why pulse charging is good.
This shows that Ni Cads are similarly benefitted
Here is an email exchange on battery testing techniques.
A Battery Tester by Megger
http://www.btechinc.com/ Another battery tester.
http://www.powerdesigners.com/InfoWeb/design_center/Appnotes_Archive/A2615.shtm Further Battery testing info.
http://www.batterybes.com/ Commercial desulfator.
http://www.van-haandel-1.mywe b.nl/Download.html An article in Dutch about a desulfator with some interesting features. See page 2 for the schematic. Here is a translation to English of the most important details.http://users.pandora.be/vandenberghe .jef/battery/