New Additions
x86 Instruction Chart
8087 FPU Instruction Chart
9 Volt Battery Chargers
Solid State Circuit Breaker (20V 650mA)
Spice BJT Model Viewer
Ohm's Law Calculator
Prime Factorization
Convert a Decimal Fraction to a Simple Fraction
Example POV-Ray Animation
Example Virtual Machine
Locating a Gunshot with an Array of Microphones
Software Defined Radio
Salt Flats & Aeromods
Audio Amp + Spice References
Image Processing
KFC 'Secret' Recipe
Neddy's Brownies
Ham and Cheese Muffins
Railroad Tracks
The Bike Shed
The Guy That Invented Fire
Mods for the TRS-80 Color Computer

9 Volt Battery Chargers

Test Results

Type Nicad Akaline Ni-MH Akaline Nicad
Capacity mAh 100 ? 120 ? 120
Start Voltage 7.61 4.25 2.45 6.81 7.06
1 Resistor mA 7.2 11.4 .1 11.2 9.7
2LED+NPN mA 10.8 10.8 .1 10.8 10.8
2NPN 15V Supply 10.05 11.32 .1 11.32 11.31
2NPN 19V Supply 11.42 11.43 .1 11.44 11.43


  • '1 Resistor Only' charging currents vary by as much as 58%. It is not reliable. It is dangerous with short circuit.

  • 'A' and 'E' were claimed to be new but were actually worn out.

  • Battery 'C' is defective or was damaged by a charger that did not speak Ni-MH

  • 'B' and 'D' were broken internally, probably during shipping at -40C.
Back Next

Charge Rate

Wall Warts

Simple 1 Resistor Battery Charger

Constant Current Battery Charger from 2 LED's and a NPN Transistor

9V Battery Charger from 2 NPN Transistors

Adjustable Charge Rate Battery Charger from Op Amp

0 - 160 mA Adjustable Charge Rate Battery Charger

Test Results

741C Cheat Sheet

Sparks and Flames


Copyright © 2020