0
\$\begingroup\$

I've a defective charger for a small LED torch light, its output is 4.2V / 500mA.

I may not find an alternative one, so I'm considering modifying a mobile phone charger as following:

  • The mobile phone charger has output of 5V / 1 or 2 Amps.
  • I put at the output three diodes: 1N4007, and two schottky diodes of about 0.1V voltage drop each: 0.65 + 0.2 = 0.85 V
  • So the output becomes: 5-.85 = 4.15V (edited )

Is this voltage adequate and suitable to charge the battery? Is it safe to use? Let me know your thoughts.

Thanks in advance

\$\endgroup\$
  • 1
    \$\begingroup\$ Add a schematic if possible. Charging Li+ improperly can yield spectacularly pyrotechnic events. \$\endgroup\$ – Peter Smith Jul 21 '18 at 12:21
  • 1
    \$\begingroup\$ Likely unsafe. The forward volt drop of a diode depends on current and this means the output will rise about 4.2 volts when delivering low currents. Go buy one. \$\endgroup\$ – Andy aka Jul 21 '18 at 12:35
  • \$\begingroup\$ Phone chargers are not chargers, they are constant-voltage power supplies. \$\endgroup\$ – user253751 Jul 23 '18 at 2:58
0
\$\begingroup\$

The original charger had only 4.2V which leaves no room for a charger driver

This means the charger had the charging logic inside.

A diode is still conducting a small current even under it's forward voltage.

You better use a dedicated module like this one that can be modified for 500mA, using a diode will overcharge or even destroy your battery

| improve this answer | |
\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.