NiMh Battery Charger | Electronic Project Circuits

Posts Tagged ‘NiMh battery charger’

Fast NiMH – NiCd Battery charger by PIC16F84A

This battery charger charges a NIMH 5-pack battery used in the BiPed robot in less than 1 hour, and charges the 10-pack NiCd used in the Snuf robot in about 30 minutes. To prevent overheating of the battery, the charging current is turned off when the slope of the battery-voltage turns from positive into negative. A second termination-criterion of the charging process is provided for safety: the charge time is limited to about 1 hour.
In the figure 2 below you find the schematics of the Delta-U battery charger. The program for the utilized PIC 16F84A is given in this file nicd.asm *). The transistor Q3 serves as a current switch, and should be able to handle the charging current. The charge current is limited by R5. This resistor should be able to dissipate the energy supplied to it. The LM311 comparator, together with the PIC serves as a simple (non-linear) ADC. The absolute ADC-output value is not important, since only the change in battery voltage is considered. The charging current is switched off when the battery voltage is sampled (each second). The resistor pair R6/R8 should be configured such that the maximum battery voltage is measured in the range 0xE0 .. 0xE8 by the ADC. Then, since the ADC is non-linear, the ADC is sensitive enough to detect a negative slope in time. Since I had a surplus on LCD’s I used one to indicate the actual status of the charger. One or two LEDs could do about the same of course.

Read More Source:http://home.planet.nl/~j_havinga/BattCharger/BattCharger.htm
Thank you.

Be the first to comment - What do you think? Posted by admin - March 17, 2008 at 4:19 pm

Categories: Battery charger, Microcontroller Tags: nicd battery, NiMh battery charger, pic-microcontroller, PIC16F84

iPOD – MP3 Player Charger by MC34063

Portable iPod charger that you can use while away from your computer. The circuit is based around an MC34063 switchmode regulator. This has high efficiency so that there is very little heat produced inside the box, even when delivering its maximum output current. The circuit is more complicated than if we used a 7805 3-terminal regulator but since the input voltage could be 15V DC or more, the voltage dissipation in such a regulator could be 5W or more at 500mA. and 5W is far too much for a 7805, even with quite a large heatsink.

Read More Source:http://electronics-diy.com/electronic_schematic.php?id=139
Thank you.

Be the first to comment - What do you think? Posted by admin - January 2, 2008 at 11:18 am

Categories: Battery charger Tags: ipods, MC34063, NiMh battery charger, USB Battery Charger

USB port AA NiMH and NiCd Battery Charger by IC 393

I Find circuit Chartger battery AA NiMH for USB port.
I see to Good WEB : http://www.stefanv.com/electronics/

Detail :
In a recent blog entry, I complained about all the chargers and wall warts I need to carry with me when going on a trip. This project, which can charge a pair of AA Nickel Metal Hydride (NiMH) or Nickel Cadmium (NiCd) cells using a laptop’s USB port for power, arose to address part of that problem. (By the way, if you want to lighten your laptop load, take a look at the MoGo Mouse.)

Any USB port can supply 5V at up to 500mA. The USB standard specifies that a device may not use more than 100mA until it has negotiated the right to use 500mA, but apparently no USB ports enforce that requirement. This makes the USB port a convenient source of power for devices such as this charger.

There are commercially available USB AA charging solutions available, but they each have some drawbacks:

The USBCell is a 1300mAh AA NiMH cell with a removable top that allows it to be plugged directly into a USB port. No separate charger is needed. Unfortunately, the cell capacity is very low (most NiMH AA cells are 2500mAh these days), and each cell requires its own port.
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There is a two cell USB powered AA charger available, sold under a variety of names, but it charges at a very low 100mA rate. The distributor calls it an “overnight charger”, but at 100mA, a 2500mA cell would take about 40 hours to charge (40 instead of 25 due to the inefficiencies of charging at low currents).
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I found a 2/4 cell charger that can be powered by a USB port, auto adapter, or wall wart, but it is as large as the wall charger I’m trying to replace. Different ones can be found here and here, but these take 10 to 12 hours to charge 2500mAh cells.

The charger in this project is designed to charge two AA NiMH or NiCd cells of any capacity (as long as they are the same) at about 470mA. It will charge 700mAh NiCds in about 1.5 hours, 1500mAh NiMHs in about 3.5 hours, and 2500mAh NiMHs in about 5.5 hours. The charger incorporates an automatic charge cut-off circuit based on cell temperature, and the cells can be left in the charger indefinitely after cut-off.

Source :http://www.stefanv.com/electronics/usb_charger.html