battery charger

[aamir1]

guyz i need a automatic u.p.s battery charger circuit for 12v 10a battery plz some one help me and provide me the schemetic for it please

 

[ronv]

Here is one designed by Chemelec.

**broken link removed**

 

[bountyhunter]

Here's a much better one that accurately regulates and is also temp compensated. If you just want a simple charger, omit the circuitry in the left half which is end of charge detection. This has been working for about 15 years keeping my motorcycle battery topped off, which is a 12V lead acid battery rated at about 15 A-Hr.

 

[3v0]

Some IC solutions.

**broken link removed**

https://www.ti.com/lit/an/slva378/slva378.pdf

 

[colin55]

**broken link removed**

The output voltage on this circuit is too high. It should detect 13.75v.



EDIT (3v0) repaired link.

 

[bountyhunter]

The output voltage on this circuit is too high. It should detect 13.75v.



EDIT (3v0) repaired link.

The one I posted is adjustable. You can set it to any value from about 12 - 15V.

 

[colin55]

This is all you need:

**broken link removed**

BATTERY CHARGER - world's simplest automatic charger
This is the world's simplest automatic battery charger.
It consists of 6 components, when connected to a 12v DC plug pack. The plug pack must produce more than 15v on no-load (which most plug packs do.) An alternative 15v transformer and a centre-tapped transformer is also shown. A centre-tapped transformer is referred to as: 15v-CT-15v or 15-0-15
The relay and transistor are not critical as the 1k pot is adjusted so the relay drops-out at 13.7v.
The plug pack can be 300mA, 500mA or 1A and its current rating will depend on the size of the 12v battery you are charging.
For a 1.2AH gel cell, the charging current should be 100mA. However, this charger is designed to keep the battery topped-up and it will deliver current in such short bursts, that the charging current is not important.
This applies if you are keeping the battery connected while it is being used. In this case the charger will add to the output and deliver some current to the load while charging the battery. If you are charging a flat cell, the current should not be more than 100mA.
For a 7AH battery, the current can be 500mA. And for a larger battery, the current can be 1Amp.

SETTING UP
Connect the charger to a battery and place a digital meter across the battery. Adjust the 1k pot so the relay drops out as soon as the voltage rises to 13.7v.
Place a 100R 2watt resistor across the battery and watch the voltage drop.
The charger should turn on when the voltage drops to about 12.5v. This voltage is not important.
The 22u stops the relay "squealing" or "hunting" when a load is connected to the battery and the charger is charging. As the battery voltage rises, the charging current reduces and just before the relay drops out, it squeals as the voltage rises and falls due to the action of the relay. The 22u prevents this "chattering".
To increase the Hysteresis: In other words, decrease the voltage where the circuit cuts-in, add a 270R across the coil of the relay. This will increase the current required by the transistor to activate the relay and thus increase the gap between the two activation points. The pull-in point on the pot will be higher and you will have re-adjust the pot, but the drop-out point will be the same and thus the gap will be wider.
In our circuit, the cut-in voltage was 11.5v with a 270R across the relay.
Note: No diode is needed across the relay because the transistor is never fully turned off and no back EMF (spike) is produced by the relay.

 

[bountyhunter]

That relay is still likely to chatter, the design would be better if it had some positive feedback. The feedback voltage to the base of the transistor is derived from the battery. Notice that when the relay is activated, it disconnects the current going to the battery which will mean the battery voltage drops, turning the transistor off and reconnecting the current (battery voltage goes back up) and the cycle repeats.

That type of circuit used to be called a reflex oscillator.

 

[colin55]

The circuit does not chatter or "hunt." Build the circuit before making any stupid statements.

 

[bountyhunter]

The circuit does not chatter or "hunt." Build the circuit before making any stupid statements.

Speaking of stupid statements, I'll close my contributions to the thread by saying IMHO, this design isn't worth the time it would waste to build it and using it would shorten the life of ANY lead acid battery if used as a maintenance charger for a UPS system. It has a horrific tempco thanks to the fact it has no reference and the voltage feeds back straight into the base of a transistor, ergo it will not properly charge the battery (not hold it at the correct float voltage). That 0.6V VBE (with it's -2mV/C tempco) is reflected up to about -45 mV/C at the battery since it's divider ratio is about 14V/0.6V. Second, IT HAS NO GAIN. After the battery reaches the turn off point and disconnects the current as the relay opens, the battery volatage drifts down through the region where the transistor will turn off..... but not sharply. The transistor driving the relay wanders through the linear region until it loses enough gas to release the relay coil again. The transistor should be replaced by an op-amp so at least the relay would turn on and off sharply, and you could apply some positive feedback (hysteresis) to keep it from turning on and off so much.

And for the record, this is the worst way to maintain a lead acid battery: never send a relay to do a transistor's job. You need a circuit that regulates the battery to the correct float voltage continuously and suppliess small current to hold it there to prevent sulphation and keep the electrolyte from freezing in cold weather. Lead acid battery makers supply specific information about the proper cell voltage to hold for sustained float charge.

Orther than that..... it's wonderful.

Build the circuit before making any stupid statements.

On a clear night, look out a window and count all the stars you can see. Double that, and that's probably how many battery charger circuits I have designed and built in the last 30 years.

 

[colin55]

First of all, who says he is going to use the charger in freezing weather. Just because you live in a snow country, doesn't mean the charger is going to the Yukon's.
Secondly, a small contant current eventually dries out the battery.

 

[bountyhunter]

guyz i need a automatic u.p.s battery charger circuit for 12v 10a battery plz some one help me and provide me the schemetic for it please

Just to attempt to correct other erroneous info contained in this thread, the correct float voltage for any "12V" lead acid battery used rarely (as back up power) is certainly not 13.7V, it is lower to avoid boiling away electrolyte:

After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since it's main purpose is to keep an already charged battery from discharging.

Note that for long term float service, such as backup power systems that are seldom discharged, the float voltage should be around 13.02 to 13.20 volts.

http://www.solarnavigator.net/battery_charging.htm

The battery maker may have a specific voltage/cell recommended, refer to data sheet.

 

[colin55]

Who said the float charge is 13.7v???

 

[ronv]

They are correct the voltage in post 2 is to high. To correct it change R1 t0 250 ohms, R2 to 2.4K and Rx to 2 ohms. This should give you a current linit of around 300Ma and a charge voltage of 13.8 which will give you a pretty good range of temperature without gassing.

Opps, forget that one I calculated the diode drop backwards.

Make R1 210 ohms, R2 2.2k and Rx 2 ohms. Now you have 13.75 volts at 300 ma.

 

[colin55]

A float charge of 300mA for 10AH battery is far too high.
We experienced a 10mA float charge for a 1.2AH 12v battery completely dried out the battery in 3 years.

 

[ronv]

A float charge of 300mA for 10AH battery is far too high.
We experienced a 10mA float charge for a 1.2AH 12v battery completely dried out the battery in 3 years.

300ma is the maximum charge current in the circuit. The float is voltage controlled not current controlled.

 

[colin55]

300ma is the maximum charge current in the circuit. The float is voltage controlled not current controlled.

The float current will decrease but any constant current will gradually disassociate the electrolyte.

 

[ronv]

https://www.powerstream.com/SLA.htm