auto disconnect when battery fully charged.

[urman]

I am looking to make a circuit for charging simple ni battery(9-12v) used in toys which automatically disconnect the supply when the battery is fully charged.

Please help me.
Thank you.

 

[Dragon Tamer]

What size is the battery? What type, Ni-MH or Ni-Cd? Do you want the power supply to disconnect by itself or do you want the battery to disconnect the power supply? Details man!

If it is a Ni-Cd or a Ni-MH battery, you could just use a MAX712 or MAX713 to charge the battery. They automatically stops charging when the battery is fully charged, and they're more than likely small enough to fit into your toy.

 

[audioguru]

What is a "ni" battery? is it an old Ni-Cad or newer Ni-MH?

A battery charger IC charges the battery then disconnects when the battery becomes fully charged. It is set differently for the different types of batteries. If a charged battery is used then it detects the charge and refuses to over-charge it.

I have a very simple charger that came with my Energizer Ni-MH AA cells. It simply uses a timer to disconnect the charger. But it is stupid because if cells that are already charged are used then it doesn't detect their charge, it severely over-charges them which makes them very hot. It also repeats a full over-charge if the mains power is cutoff then returns. It also over-charges Ni-Cad cells because they have a much lower capacity than Ni-MH cells.

 

[urman]

I want it for Ni-cd. I found a circuit with MAX712 but there are 2 or 3 component values are not given, probably it is depending on the battery value. But i dont know how to calculate them. Can you please tell me. thank you.

Here's the link for the circuit:
**broken link removed**

 

[urman]

What size is the battery? What type, Ni-MH or Ni-Cd? Do you want the power supply to disconnect by itself or do you want the battery to disconnect the power supply? Details man!

If it is a Ni-Cd or a Ni-MH battery, you could just use a MAX712 or MAX713 to charge the battery. They automatically stops charging when the battery is fully charged, and they're more than likely small enough to fit into your toy.

I want it for Ni-cd. I found a circuit for MAX712 to charge the battery. But 2 or 3 component values are not provided, probably it is depending on the battery voltage(which is for my application 7.5V, 9V, 12V). But i dont know how to calculate them. Can you please help me. Thank you.
Here's the link for the circuit:
**broken link removed**

 

[Mohammed Shameel A H]

I want it for Ni-cd. I found a circuit for MAX712 to charge the battery. But 2 or 3 component values are not provided, probably it is depending on the battery voltage(which is for my application 7.5V, 9V, 12V). But i dont know how to calculate them. Can you please help me. Thank you.
Here's the link for the circuit:
**broken link removed**

Bro,
This max712/713 both seem to be circuits which quickly charges our battery and doesnt seem to disconnect the charger when the battery is almost full. Does they stop the charging process when the battery is full?

 

[alec_t]

You have resurrected a 4-year old thread!!
To answer your question, the datasheet says:

The MAX712 terminates fast charge by detecting zero voltage slope, while the MAX713 uses a negative voltage-slope detection scheme.

It terminates charge, which in effect disconnects the charger. If you want actual disconnection you will need to sense charging current and operate a relay/contactor when termination is detected.