Battery Desulfator


General

THIS PROJECT IS IN DEVELOPMENT. THE WEBPAGE IS BEING WRITTEN SIMULTANEOUSLY WITH DESIGN IN THE PAST TENSE AS IF IT WAS COMPLETED. IN OTHER WORDS, THIS THING MAY NOT WORK AS SHOWN.



In the middle of building a battery charger from a computer power supply, I discovered numerous articles on battery desulfation and desulfators. I began modeling one of the circuits and playing around with the various ideas put forth in the desulfation forums. This page is a collection of simulations and commentary possibly leading up to a hardware project.

SWITCHERCADII SIMULATION DIAGRAMS

Desulfator SWCADII Schematic Diagram
CIP charger schematic with battery simulation from Bjack


Desulfator SWCADII Plot Diagram
Simulation Plot of charge voltage and currents


In the plot above the V(vbat) voltage is the battery voltage plus the voltage across the capacitor C1.

Current through the battery, I(L5) = I(V1), is the inductor flyback current plus the current from the diode-bridge charging C1.

Changing the size of capacitor C1 appeared to inversely change the peak charging current. That is, a change from 100uF to 150uF decreased the charging current from 1.8 amps to 1.2 amps; a change from 100uF to 50Uf changed the curent peak from 1.8 to 2.2. This reaction was contrary to the "bigger is better" assumption for C1. I hadn't looked closely at the pulse envelope, or really thought about why this was occuring. It was illogicall to me, and there were a lot of value assumptions in this simulation.

Since I wanted to try a desufonator, and wanted to have it supply a small charging current, and the CIP circuit seemed to do this with one less inductor than the standard desulfator circuit, I decided to model it in more detail (eventually,as I was currently working on building a bathroom, playing with LED flashlights, and working on two old cars).


Desulfator SWCADII Plot Diagram
Simulation Plot of charge voltage and currents
with low transformer primary resistance


In the initial plot above, I had a transformer primary resistance of 5000 ohms that severely limited the output current capability. When I put in a more realistic 18 ohms, the plot changed radically.

Now the circuit does looked more like the standard desufator circuit with a low-current charger attached. The FET-drain peak voltages seemed very high in the simulation. The capacitor C1 size did not inversely change the peak charging current. It did change the level of non-pulsed charge current from which the current pulses rose.

The problem with the second plot is that it shows only 9 ms detween 27 and 36 ms after starting, it is not a stable circuit yet. When I ran a longer simulation, the 120 hz ripple dropped out of the picture and only the pulses remained. So charging with this circuit seemed to be only the power in the pulse width.

I have attached the text of the simulation after the references. Both the .NET file and the .ASC schematic file for SwitcherCAD are there.You can cut and paste it into a text editor, then save them with the proper extension to run in a simulator.


Hardware Construction Project

Sequenced Desulfator Schematic Diagram
Planned Desulfator Project


The desulfator shown schematically above is being simulated. So far it shows promise. It combines features from multiple sources and sequences through them using a simple arrangement of 555 timers. Microprocessors are great for things like this, but for many people the programming tools are not available.

The planned cycle has four steps. The first step is to pulse the battery for 15 seconds using a Charged-Induced-Pulse described by desufonator2. The second cycle is a settling period of 1 second. Third is a 100 microsecond pulse that shorts the battery (180 amps?) to remove dendrites. And finally, a 5 second period to measure the battery voltage.

Timer U2 pin 3 is high for 15 seconds and enables the pulsing timer U1. After 15 seconds of pulsing, U2-3 goes low, disabling U1 and triggering U3. U3 times out and triggers U4, which in turn times out and triggers U5. U5 is configured as an asable flip-flop and remains triggered until it is reset by timer U2 pin 3 again going high. the total time for U3, U4, and U5 is limited to 6.5 seconds by the off time of U2.

The high time for U2-3 is calculated as t1 = .693 Rt x C = .693(180k + 100k)47u = 15s. Worked backwards, Rt = t1/(.693C) = 15s/(.693 x 47u) = 280k).
The low time for U2-3 is calculated as t1 = .693 Rt x C = .693(100k)47u = 6.5s. Worked backwards, Rt = t1/(.693C) = 6.5s/(.693 x 47u) = 100k).


Sequenced DesulfatorBoard Layout
Desulfator Project Board Layout



The measurement circuit gets a reference voltage from the 555 timer for 5 seconds and compares it with the voltage across the battery. I don't yet know if anything can be obtained from battery measurements at the planned time, as the battery voltage will likely just be the charger surface charge. I will probably leave the measurement components off the circuit board until I can make some actual oscilloscope measurements. I would like to be able to drop the charger offline, or go to a maintenance charge, using the measurement circuit.

Q6 is a level shifter circuit that converts the battery voltage referened to the +voltage supply rail, into an equivalent voltage referenced to ground. The voltage across R28 is equal to: 2 X [ (Vbat/2) - .7 ]
Vbat=2 X [ (V,R28/2) + .7]

POINT % LOW % HIGH V LOW V HIGH BAT V LOW BAT V HIGH
U6-9 .49 .56 5.3 6.1 6.7 7.5
U6-8 .77 .84 8.3 9.1 9.7 10.5
U6-2 .9 .97 9.8 10.5 11.2 11.9
U6-13 1 1 10.84 10.84 12 12
U6-12 1 1 5.3 10.5 6.7 11.9


Alternate Power Supply Schematic Diagram
Alternate Power Supply (untested)




The Prototype



Prototype CIP




Prototype CIP




Testing

I have three dead batteries for testing. All were murdered by me. The Mustang started this project. It is a Everstart, from Walmart I think, and was fairly new when left to die in an unused Mustang for a year. Then I tried to recharge it and ended up overcharging it. The water in one cell boiled and is low. It reads about 3.42 volts and I think it is a lost cause.

The Honda was a good battery that went dead last winter on a trip to Indiana. It was dead only because someone left the dome lights on all nightand the next day. At -20 degrees, on a trip, with no voltmeter, you don't do much troubleshooting, so I just replaced the battery. It reads 12.35 volts but has been setting for a year on the basement floor. If it can be rejuvinated, It could be used in the Mustang.

The Suzuki came out of a Samurai and was used for a backup supply for a while. It has been on the garage floor for two years or so. Condition is unknown.

References

The first two references below have gone dead. These were links to the forum where the CIP desulfonator was proposed. I haven't been able to find any other references to the CIP desulfonator on my internet searches. Maybe this whole idea is bogus. I've started building a prototype, so I'll continue on it. If anyone knows what happened to the llinks, let me know.

http://p198.ezboard.com/Charged-Inductive-Pulse-Hybrid/fleadacidbatterydesulfationfrm13
The EZBoard forum for CIP desulfonators.

http://p198.ezboard.com/MiniCIP-12-volt-5-watt-555-based-PFET-CIP/fleadacidbatterydesulfationfrm13.showMessage?topicID=3.topic
desufator2's modification of a standard AC desufonator to a CIP desulfonator.

http://digilander.libero.it/bjack_italy/desulf/desulf.html
Bjack's desulfator P-Spice model of a lead-acid battery.

SwitchercadII Simulation Netlist and Schematic

desulfator-cip-bjack.net:

* E:\Program Files\SwCADIII\Battery charger\desulfator-cip-bjack.asc
XU1 0 N008 N009 N006 N010 N008 N007 N006 NE555
L1 N012 M1-DRAIN 100 Rser=162m
D1 M1-DRAIN N003 MBR745
C1 N012 0 100 Rser=.4 Lser=100n
L3 VBAT N003 580n
L4 VBAT VBAT 10n Rser=100m Rpar=10M Cpar=13p
L5 VBAT N011 200n
V1 N011 N012 12.65 Rser=.022
R1 N006 N007 15k tol=9 pwr=9
R2 N007 N008 270k tol=9 pwr=9
D2 N007 N008 1N4148
C2 N006 N008 .0047
C3 N006 0 100
R4 N006 N003 2200 tol=9 pwr=9
D4 0 N006 BZX84C15L
C4 0 N010 .01
V2 N001 N005 SINE(0 166 60)
M1 M1-DRAIN N014 0 0 IRF1312S
Q1 0 N009 N013 0 2N2907
R3 N013 0 15k tol=9 pwr=9
D3 N009 N013 1N4148
D5 0 N013 1N4148
D6 0 N014 1N4148
R5 N013 N014 22 tol=10 pwr=1
D7 N013 N006 1N4148
D8 N002 N003 MURS120
D9 N004 N003 MURS120
D10 0 N002 MURS120
D11 0 N004 MURS120
L2 N001 N005 15 Ipk=2 Rser=5k
L6 N002 N004 .685 Ipk=10 Rser=.5
R6 N004 N005 1T
.model D D
.lib E:\Program Files\SwCADIII\lib\cmp\standard.dio
.model NPN NPN
.model PNP PNP
.lib E:\Program Files\SwCADIII\lib\cmp\standard.bjt
.model NMOS NMOS
.model PMOS PMOS
.lib E:\Program Files\SwCADIII\lib\cmp\standard.mos
.tran 50m
K1 L2 L6 .999
.lib NE555.sub
.backanno


desufator-cip-bjack.asc: highlight, copy, paste into text file with.asc extention for schematic to run in SWCADII.



Version 4
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SYMBOL Misc\\NE555 -48 208 R0
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SYMATTR SpiceLine tol=9 pwr=9
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SYMATTR Value 1N4148
SYMBOL diode 400 1024 R180
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SYMATTR Value 1N4148
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SYMATTR Value 22
SYMATTR SpiceLine tol=10 pwr=1
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SYMATTR Value 1N4148
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SYMATTR InstName D8
SYMATTR Value MURS120
SYMBOL diode -64 -368 R270
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SYMATTR InstName D9
SYMATTR Value MURS120
SYMBOL diode 0 -272 R90
WINDOW 0 0 32 VBottom 0
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SYMATTR InstName D10
SYMATTR Value MURS120
SYMBOL diode 0 -192 R90
WINDOW 0 0 32 VBottom 0
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SYMATTR InstName L2
SYMATTR Value 15
SYMATTR Type ind
SYMATTR SpiceLine Ipk=2 Rser=18
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SYMATTR Type ind
SYMATTR SpiceLine Ipk=10 Rser=.5
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SYMATTR InstName R6
SYMATTR Value 1T
TEXT -512 632 Left 0 !.tran 50m
TEXT -376 -488 Left 0 !K1 L2 L6 .999


.end
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Copyright Dale Thompson,
28 August 2007 through
last revision on 18 November 2008.