Switch Mode Power Supply

[hamid159]

Anybody can help me with smps battery charger?I have 12v,160Ah battery.i want to charge it with smps circuit.i've tried a lot to find such a circuit but I couldn't.Please anyone can help me???

 

[pinout]

Hi Hamid159,
I haven't got a cicuit for you but this link may help you get started and understand the process.
https://www.ti.com/lit/an/slua055/slua055.pdf

There are other articles that show the charging voltage/current relationships.
This commercial product shows a good diagram on page 2 of the stages of charging.
**broken link removed**

Also just as a cooment you will require a power supply of around 16V at 16A if you charge at the C/10 rate.

If I find a suitable circuit I'll post later.

 

[hamid159]

16V will be much greater for battery to work properly...isn't it????

 

[pinout]

Although lead acid batteries are referred to as 12V, they are often at much higher voltages than this during their charge/discharge cycle.
It does seem high though and you may be able to get away with a bit lower, but the nominal fully charged cell voltage is around 2.4V so with 6 cells, you have 14.4V terminal voltage.
To get any current into the cell near a fully charged state you need a supply of greater voltage, hence the 16V suggestion.

Fig 1 in the ti.com pdf is a good picture of the cell behaviour. It shows the sharp rise in cell voltage as the cell is fully charged and you will not be able to see this unless your charging voltage can supply a voltage greater than the 14.4V calculated above.

I'm not an expert in this but did study this area some time ago, so open to other comments and suggestions.

 

[sreepss]

Try TOPSWITCH series converters. Its Easy to design and smooth working.
http://www.powerint.com/products/product-archive/topswitch

 

[nilses]

Very good observations.
I also studied this around 1981 when my Cortina's alternator stopped charging the battery in the middle of the winter.
The Lucas alternator was equipped with an electronic regulator costing around 50 UK Pounds at that time.
I built a replacement regulator with parts I already had in my toolbox,estimated cost 1 UK Pound.

 

[pinout]

Just to add, if you want to keep the circuit simple a power supply with around 13.5 to 13.8Volts with a current limit (preferrable constant current mode) of 8A to 10A could be used.

The constant current mode will charge your battery at around the C/20 rate to start.
The 13.5V will then charge at constant voltage getting slower as the charge current drops off tthrough the cycle as the battery charges.
At near full charge the PSU will be at the 'float' charge.

Things to be aware of:
This is not the fastest charge method as the current will decrease during the charging time, but that may not be an issue for you.
This is not good for a flat battery as you should start at a lower current to avoid damaging the cells.
It's not great for the float charge part as this can be temperature dependent, so you could over charge and loose electrolyte over time. A possible solution if you have a microcontroller in the design is to add a resistor and relay such that when fully charged the relay switches off leaving a series resistor in the output charginging circuit to set the float current.