/Schematics/Power supply/Automatic battery charger

Scooter battery problems, anyone?

Why automatic? Because it automatically starts the charging procedure when battery voltage drops below a certain predefined value and stops after the voltage has risen above the maximum allowed value. Setup can't be easier, just connect two alligator clips to battery terminals and plug the device in mains. This way it can stay connected for months and the battery will never overcharge. This comes very very handy when you have a scooter or a real motorcycle that you don't drive during the winter time. Because we all know what happens to a battery when not used and especially during the winter.

You can download the schematics at the bottom of this page by clicking on red "download" button.


Device consists of two main parts; power supply with current and voltage regulation (2 x LM317) and voltage monitoring circuit with switching relay. The charging procedure starts when voltage drops below 12.6V, and finishes when it gets to 13.8V. These values are not fixed and can be adjusted with trim-pots. The maximum charge current can also be adjusted with DIP switches. Voltage is not that critical but it must not be below 13.85V so that the charging procedure can stop.



It is mounted inside a plastic project box with three LEDs: green – powered on, yellow – charging in progress, red – wrong battery polarity (switch + and -).


Schematics are from Info elektronika br. 41, only the PCB is adjusted for different relay and additional power regulators.

Author (sent by): RazoR

Download counter: 21,533

Rate: (2.88, votes 1429)


Date: 09-06-2010

Lokalna verzija ove stranice: Automatski punjač akumulatora


Bookmark and Share Comments (16)

comment [16]

necesito que me digas los Nombres de los Materiales Por Favor y en Donde se Conecta La Corriente, Me podrias dar mas especifico el Diagrama Por favor agradecere muchisimo

comment [15]

da li bi mi netko mogo poslat popis elemenata ??? bio bih jako zahvalan !

comment [14]

Real smart to use a relay in a battery charger to charge batteries that might emit hydrogen gas.

comment [13]

I've contacted him for the updated schematics...
IP: n/a

comment [12]

Incomplete schematic. Have the PCB layout but no full schematic ..... need to see the values of the resistors near the DIP switches, we do not know the values of the electronic parts used near the LM317. Please attach the full schematic. Anyway good job!!

comment [11]

So, THIS is a trickle charger then :)
IP: n/a

comment [10]

hi trax. why to use with trickle charger? why another charging unit? makes no sense. that is not the reason. he uses an own power supply. look at his photos

comment [9]

I guess that he made this regulator so it can work with Trickle Charger: http://en.wikipedia.org/wiki/Trickle_charging
IP: n/a

comment [8]

the trick. constant limiting @ maximum current through the lm317 (1,5A) und constant regulation with a pot. sorry bro. you can do better. ;)

comment [7]

ly fallen down to the lowest voltage. and now you take the accumulator and use it, because, you think that the accumulator is full. the accumulator will be destroyed very quickly, because of the low voltage, when starting a scooters engine. sorry to say that: this device is bulls***. it would be better to keep the accumulator directly connected to a current limiteded constant-voltage charger at 13,6...13,8 Volts. you already have the needed parts in your charger ;) lm317 and a potentiometer. this will do

Comment page: 12>

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