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Battery Backup/Charger Circuit

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bravishbabum

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battery backup circuit

I am planning to design a circuit with the following considerations:

*A Li-Ion battery backup of ~= 6V(pack of two)
*A Li-Ion charger Circuit.
*Automatic switching between mains and backup without reset of the circuit.



LT1239 is more or less a suitable IC for the application.
Is there any other cheaper/alternate ICs or a solution using discrete components.??

Kindly suggest.
 

GSM Man

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li-ion battery backup circuit

Maxim/Dallas has a couple - look at the MAX1757 & MAX1758
 

bravishbabum

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charger circuit

Thankyou GSM MAN for the prompt and helpful reply.

Can we design a circuit using only discrete components and an op- amp for the same purpose??

This is how I assume:
When main supply is ON:
The op-amp will provide the constant current required for the LI-Ion recharge until the maximum rating is reached.
When the main supply is OFF:
The supply should switch to the battery backup without any reset in the load,which I suppose a diode can do.

But I don't have a clear picture of a final circuit.
Can anyone share/suggest?
 

GSM Man

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how to design a circuit with battery backup

bravishbabum said:
The op-amp will provide the constant current required for the LI-Ion recharge until the maximum rating is reached.
The Lithium-ion chemistry is very sensitive to the charging current and voltage, and they have to be carefully controlled. The cells are easily destroyed if not charged properly. Before attempting to design your own charging circuit I'd look carefully at the charging requirements. Maxim has some good application notes on their web site http://www.maxim-ic.com/appnotes10.cfm/ac_pk/5#42
 

bravishbabum

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li-ion charger circuit

If I opt for Ni-Cd or Ni-Mh rechargeable batteries is their a cheaper solution?

Is their any Maxim IC charger/supply switcher available for Nickel based batteries??(((like max1757/max1758 for Li -Ion batteries.)))
 

GSM Man

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battery charger,backup ,switch,ic

bravishbabum said:
If I opt for Ni-Cd or Ni-Mh rechargeable batteries is their a cheaper solution?.)))
Yes.

bravishbabum said:
Is their any Maxim IC charger/supply switcher available for Nickel based batteries??(((like max1757/max1758 for Li -Ion batteries.)))
Yes, look on the Maxim web site: www.maxim-ic.com. Also, you can look at what Microchip has to offer: http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2087
 

bravishbabum

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battery backup charger nimh circuit

It was really a helpful link ,Thank you for the support.

But I didn't get a single IC in DIP package(that will be helpful to develop the prototype)
Can you suggest me any IC in DIP package which serves the same purpose.
 

GSM Man

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li ion charger circuit

The big market for battery chargers addressing those chemistries is in small devices (cell phones, PDA, laptops, etc.). Those apps require small device packages so the manufacturers don't make those chips in DIP packages. Personnally, I don't know of any battery charger that will fit your requirement that's available in a DIP package.
 

movie_freak

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battery charger circuit with opamp

TI has various components for Battery charging, Battery Monitoring especially in 3.7V battery LI-ion area. And they claim an accuracy of 1% considering all the factors like aging, no of time charged discharged etc etc in estimating the available back up.

So, it may be worth trying


Surya
 

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