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Looking for schematic of Lead-Acid charger

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Junior Member level 3
Jul 12, 2001
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I need a schematic for Lead-Acid charger. An article about Lead-Acid charger was published in May’s 99 edition of Elektor magazine, but unfortunately I can’t get a printed or electronic copy of that edition.

labc2 pcb

Check out the bq2031 from TI and releated app. notes. I have used this chip in a number of projects.
**broken link removed**

bq2031 charger

I really like: **broken link removed**

i also have a Sealed lead acid schematic with PCB witch is MUCH more suffisticated (temperature controlled) if you want this PM me.

switc boost mode bq2031

You charge lead acid batteries with a constant voltage charger. Just use an adjustable voltage regulater cicuit with current limit, adjust it for 13.8 volts for a 12 volt car battery.

You charge nicads with a constant current charger.
Hope this helps.

uc3909 charge battery 20a

A simple and working reliable circuit to charge Lead Acid batteries:

Build an unregulated power supply with series current limiting resistor. Example, for 12 Volt battery, use a transformer with 15V AC output, a bridge and a capacitor...

With a op. amp circuit, monitor the lead acid battery voltage. For 12 V applications, if it reaches to 13.8-14 V, disconnect the charger output using a relay. If battery level goes down to 11.5 V, re-connect the charger. This will recycle all day by itself.

With this circuit, the system don't produce excessive heat by using a regulator circuit, never overcharges the battery, and the circuit is very simple and reliable...

By adding an extra relay to the circuit, you can also protect from excessive discharging of the lead acid battery.

It work so nice, esp for portable lamps, and longer battery life...

bq2031 schematic

Be carefull .
13.8 Volt is the absolute maximum .
I'd reccomend 13.5 Volt to be on the safe side .

charger lead acid schematic

Betanorm`s Idea is the way I designed mine. I use a 741 as comparator and set regulated voltage on input using a zener diode then monitor the battery voltage on the othr input pin and set hesteresis with a feedback resistor output driving a bc107 to relay . workes realy well and can be used to charge accumulators gells lead acid

max pic code acid charge

Anyone has schematic for 20A lead acid and gel battery charger???

charger lead acid circuit

You can go up to even 14.0-14.5 Volts, and this will still be safe. It depends on how fast you prefer to charge your battery, so how powerfull is your charger. For example: check the charging voltage in a car lead acid battery.

With my method of charging, the lead acid battery is in cyclic use. If you apply 14.0-14.5V continuously, it is outside the safe area.

If you charge the battery fast, then the histeresis range should be wider.

Since there is a chemical reaction in the cell, final voltage per cell should not be constant and should depend on temperature.

Worst condition to be avoided is certainly discharging lead acid battery below 1.8 volts per cell. If you encounter this condition, your battery will never be powerfull again.

charger 24v 4a

I would not charge a car type Lead Acid batterry with more than 6 amps as this can cause the plates to buckle and can distroy the insulators. The cyclick method of charge is the best way to go . You must use a relay to switch the current on and tricle it with a resistor after you threshhold voltage has been reached.


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charge lead acid schematic

Hi im looking for a schematic
that uses a pic micro to do it
with a PWM, if not ill just do it
schematics no problem for me.
code, got PMW, regulating duty cycles
is the problem, via code.

bq2031 lead-acid charger circuit

I think cyclic method for charging Lead-Acid batteries is the best and the cheapest method. If you charge the L-A battery with continuous DC current, charging voltage should be monitored preciselly. Otherwise voltage for cyclic charge will destroy the battery for continuous charge.

lead acid charging controller by pic

hi guys!

i have designed a 24v,4A low cost battery charger works in simple constant current mode as stand alone.also it is possible to control its output current/voltage by a microP or even a computer port,if an a/d card is available.

its docs (sch & pcb)in protel format is available.
if u want it respond to this letter!


circuit charger bq2031

A normal charge voltage over a regular car battery (lead-acid) is about 14.4 V. When the battery starts to draw very much lower current at this voltage it is about full charged. The generators of cars use to set this constant charge voltage by measuring the ambient temperature. So I would say that this voltage is temperature dependent.

Should you charge with constant current, then go over to trickle-charge (short intermittent charge with low current) when the battery voltage has risen to about 14.4 V (approximately). More data on the temperature dependency on this voltage could be found in manuals and application notes from the manufacturer of your particular battery, or of similar type.


On 2002-03-09 09:56, MITSUKO wrote:
Be carefull .
13.8 Volt is the absolute m@ximum .
I'd reccomend 13.5 Volt to be on the safe side .

mitsuko capacitor

Try, In there the have good application notes for different type of battery chemistry.

Anyone has schematic for 45-60A Lead-acid gel battery charger?

mypooka said:
Hi im looking for a schematic
that uses a pic micro to do it
with a PWM, if not ill just do it
schematics no problem for me.
code, got PMW, regulating duty cycles
is the problem, via code.

Dear Friends
Excuse me for lating.I was busy two past weeks.

A little about The Charger:
it is an off line flyback charger designed for charging 24V lead-acid batteries @ 4A.Switching freq. of
75Khz reduces the size of charger and increases quality at the cost of EMI which must be filtered.
Unitrode UC3844 controller is selected for several benefits:
-it works in current mode thus is more stable than voltage mode SMPS
-it has short circuit protection
-due to internal under/over voltage look out there is no need to special supply for the IC
-also it is a low cost controller IC
for switch a high voltage NMOS (2SK794) is selected , thus MAX input voltage can be higher than 250V.
also the ckt works @ MIN input voltge of 170V.
input and output are isolated by a tight CTR optocoupler.
The core is TDK :pQ3230 ,it has a small size ,good heat sinking and good shielding.
Primary: 42 turns,0.7mm,in 2 layers
Scondary:7turns,2*0.9mm,in 1 layer
Primary aux :6 turns,4*0.5mm,1 layer
Secondary aux :6 turns ,4*0.5mm,1 layer
Output voltage @ 25°C=27.6V
Output voltage TC=-3.9mV/°C
Short circuit current=4A ;Duration=infinite
there are 4 controlling signal in secondary side:
CSEN=current sense,it is linearly proportional to output current (Io=0A:CSEN=0)(Io=4A:CSEN=2.5V)
VSEN=output voltage,it is linearly proportional to output voltage(Vo=0:VSEN=0)(Vo=27.6V:VSEN=
CCON=current control,by this signal u can control output current according to :
Io=0.4+1.44*CCON ; 0V<CCON<2.5V => 0.4A<Io<4A
VCON=voltage contrlo,by this signal u can control output voltage according to :
Vo=13.8+5.52*VCON ; 0V<VCON<3.5V => 13.8V<Vo<33.12V
if the board works stand alone or its control pins are open,it works in simple constant current/constant
voltage mode.Exciting VCON & CCON by a micro controller or other means can change output
characteristics ;also there is a DIPSWITCH in secondary side which can be used for controlling output
voltage level .RESERVED resistors must be calcuated for this reason.
As u see your external control is not in closed loop , thus there is no unstability problem.Also converting DIGITAL PWM to ANALOG can be done by a simple RC low pass filter.


Unitrode/TI App. Notes (
SLUA055.PDF : "Simple Switchmode Lead-Acid Battery Charger " contain useful info. about lead acid
batteries and charging algorithms.
offline charger designing and closing the feedback loop.
SLVA061.PDF : "Understanding Boost Power Stages in Switchmode Power Supplies" for flyback

Power Integrations INC. App. Notes (
All of App. Notes Are Recommended,specially for flyback transformer design and construction,EMI and

Re: Lead-Acid charger

goodboy_pl, can be this design modified for higher current more than 4 A ?

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