Lead Acid Battery Charger | Electronic Project Circuits

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Simple Charges Lead-Acid Batteries by MAX773

A flyback converter implements a current-limited power supply to charge lead-acid batteries. The MAX773 current-mode controller limits the output current and the flyback transformer provides isolation and flexibility for input voltages both above and below the battery voltage. The MAX471 current-sense amplifier monitors the charging current and feeds back to a threshold detector so that below a designed threshold the flyback converter can switch to a lower charging voltage for trickle-charge mode.

The circuit shown in Figure 1 charges lead-acid batteries in the conventional way: A current-limited power supply maintains a constant voltage across the battery (2.4V/cell or so, as specified by the battery manufacturer) until the charging current decreases below a current threshold defined by the capacity of the battery. At this point, the charger is placed in a trickle-charge mode. The current threshold is typically 0.01C, where C refers to the battery capacity, which is specified in ampere-hours. When charging a battery, the term “C rate” refers to the current required, in theory, to charge a battery to its full battery capacity C in one hour. In actuality, power lost during the charge cycle ensures that all batteries charged at their C rate take more than an hour to reach full charge. Ideally, you could charge a 5A-hr battery in one hour if the charge current is 5A. Also, ideally, a C/10 charge rate (500mA) charges the same battery in 10 hours. However, the power loss mentioned previously increases these charge times beyond the two time spans stated above.

Read More Source:http://www.maxim-ic.com/appnotes.cfm/an_pk/621

Be the first to comment - What do you think? Posted by admin - March 19, 2008 at 10:33 am

Categories: Battery charger, Switching power supply Tags: Automatic Battery Charger, lead acid battery charger, Switching power supply

12V input, 12V battery charger by 555,7815

The charger consists of two stages: The first is a capacitive voltage doubler, which uses a 555 timer IC driving a pair of transistors
connected as emitter followers, which in turn drive the voltage doubler proper. The doubler has power resistors built in, which limit the charging current.

BUY Lead Acid Battery Charger Electronic Module

The second stage is a voltage regulator, using a 7815 regulator IC. Its output is applied to the battery via a diode, which prevents reverse current and also lowers the voltage a bit. The resulting charge voltage is about 14.4V, which is fine for charging a gelled or AGM battery to full charge, but is too high as a trickle charger, so don’t leave this charger permanently connected to a battery. If you would like to do just that, then add a second diode in series with D3!

There is a LED connected as a charge indicator. It will light when the charge current is higher than about 150mA. The maximum charge current will be roughly 400mA.

Source:http://ludens.cl/Electron/12Vcharger/12Vcharger.html
Thank you.