Battery Backup Power Supply

[CMOS]

battery backup schematic

I am looking for a simple schematic of 12V unregulated battery backup power supply. When mains supply is on, the circuit charges the battery well as it supplies 12V output. When mains supply fails, 12V output is derived from the battery. The charger should be automatic with overcharge and deep discharge protection.
Battery type is 12V,7Ah Sealed Lead Acid.

Any help is appreciated. Thanks.

 

[flatulent]

microchip battery backup circuit

The usual method is to connect the ac supply to the battery through a diode and power your load from the battery. When the supply is off the diode keeps the battery from discharging through the ac supply output circuit components.

One thing to look out for when using an unregulated supply is trying to put more than 13.8 V on the battery. If your supply is more than this you can add a low drop out linear regulator to the supply.

 

[CMOS]

back up power supply cmos

Yes, I can build that circuit. But I am looking for an automatic battery charger circuit since 12V SLA batery is used as alternate source in my project. So I cannot keep it charging continuously. Also when in battery backup mode, the battery should not get drained completely. Thats why deep discharge protection is necessary.

 

[panalog9]

atmel battery backup

Here are a few links you can check out.

Microchip Intelligent battery charger. They also have a UPS reference design somewhere.
**broken link removed**

Atmel Battery charger reference design
http://www.atmel.com/dyn/resources/prod_documents/doc1659.pdf

Maxim - Battery charger design issues
**broken link removed**

Battery charging is not as simple as it looks, as you seem to know already

-pana

 

[CMOS]

12v backup battery circuit

Hi Panalog,
Thanks for your links. Those circuits are very much complicated and advanced. I would have built this if I was doing a project only on smart battery charger. But my application requires a battery backup and I just need a very simple automatic charger circuit with both cut-offs.

Anyways thanks for your reply.

 

[DavidP]

battery charger power supply

In parallel with the series diode connected between the positive tag of the bat. and the output of the PSU (anode towards the bat.) connect a 20-30 Ohm 5W resistor. This will charge the bat while mains is on. This method is working fine in alarm systems. As mentioned above the transformer should be circa 13.5 -14V

 

[CMOS]

battery backup for powwer from israel

Will it not reduce battery life due to overcharging?

 

[Luis2007]

Hey guys,

I'm wondering if anyone can help me, I need to build a backup battery power supply and I don't have the schematics. Does anyone have the schematics for this type of circuit? I'd greatly appreciate it.

 

[A.Anand Srinivasan]

Will it not reduce battery life due to overcharging?

the batteries impedance keeps on increasing due to the charging and hence the current decreases.... the battery reaches a state of equilbrium when the current from the supply is equal to the leakage current of the battery...

 

[aq_mishu]

check here my previous post...


it is a two stage charger that works fine and the battery can be left for unlimited time without damaging it... i am using it to charge my SLA and motor cycle battery...

Mishu~