what is the purpose of a diode with the rechargeble battery?

[sunnystar]

what is the purpose of a diode with the recharageble battery? is that true, to prevent the incoming voltage from the adopter being reversed otherwise battery gets short??

 

[wp100]

Hi,

Can you do a circuit diagram so we can better see what you mean.

 

[D.A.(Tony)Stewart]

Diodes in addition to 1-way switches for current are also thermometers with a small negative temperature coefficient (NTC) on forward voltage and can be used to sense battery completion of charge by a temperature rise which can then drop the control voltage to a safe float voltage or cutout entirely. This is most useful in multi-cell batteries. If one cell is dead or a low voltage short, then voltage or current feedback is not a safe sensor to use for charging the battery.

How, where the diode is used depends on design details you omitted in your question.

 

[sunnystar]

circuit of rechargeable battery is attached

 

[Audioguru]

The diode prevents the battery from discharging into the charger when the charger is turned off or when there is no power to the charger.
Why is there a switch that shorts the battery and maybe causes a fire?

 

[sunnystar]

switch is there to power ON the circuit

 

[Audioguru]

switch is there to power ON the circuit

No.
The switch in your schematic SHORTS the battery when it is turned on. It connects the positive terminal of the battery to the negative terminal of the battery which will release the magic smoke.

 

[sunnystar]

which will release the magic smoke means??

 

[Audioguru]

which will release the magic smoke means??

All electronic parts have lots of magic smoke packed inside. When the current is much higher than the rating of the part then some or all of the magic smoke escapes.:laugh:

 

[sunnystar]

u mean to say switch shud not be there?

 

[betwixt]

I think Audioguru is playing with you!

What he is pointing out is the switch in your schematic appears to be across the battery. If you close the switch a high current will flow and something will overheat badly, possibly starting a fire. In a schematic it is often impossible to avoid crossing lines so it is very important to show whether they are actually connected to each other or not. Convention is to use a round blob (a big dot) when the crossing wires are joined and either no blob or a 'bridge' (like the symbol on a map) when they are not joined.

Answering your original question, the diode is to allow charge into the battery but prevent it going back to the charger port if the supply is turned off. The diode will only conduct when it's anode has more voltage on it than it's cathode. In your diagram, it means if the charger voltage is higher than the battery voltage, current will flow into the battery and charge it. If the charger voltage is lower or not there at all, the diode will prevent the battery conducting back to the charger port.

Brian.

 

[sunnystar]

thanku so much brian sir for your great help and time.... :razz:

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