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12v 5ah Lead Acid Battery Charging

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Sep 29, 2009
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Cleveland, Ohio
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I have a 12v, 5AH Sealed Lead Acid Battery.
I use it to power small projects I create overtime.
But sadly... It ran out of power. Now it is time to charge it lol.

I Purchased it from Radioshack, along with a 15v 1000mah DC Adapter.
Battery: **broken link removed**
Adapter: Not sold anymore... but 15v, 1000mah, Prt #no:273-1691

I need to know if there is a special way of charging it.. or if I can just stick the two together for 10 Hours.

Also if there is an online site that sells a semi-inexpesive charger, or has a free schematic for building one.

Thanks in advance.

The 15V DC adapter will require a current limiter circuit to charge this battery.

Here are a couple of cheap and quick methods to charge the battery.

1. Find a computer UPS with a failed battery. The battery is usually the first thing to go. Therefore, many computer shops have piles of these in the scrap. Many uses similar sealed lead acid batteries and already have all the circuitry to charge the lead acid battery. Use the existing circuit from the UPS to charge the battery. Simply attach the battery and plug into the wall. Wait several hours to a full day and the battery is charged. Because the UPS was designed for a battery with a lower capacity it will take some time to get it charged, but it will occur.

2. Find a small trickle charger for a motorcycle or lawn mower battery. You want a small one with a low charge current.

3. Get a 2 ohm 5 watt resistor and a cigarette lighter plug. Connect the resistor in series with the battery and the plug. Plug into your car and drive around. The alternator will charge the battery.

In all cases, you probably want to limit the charge current to 1A or less to be safe. Use an ammeter to verify the charging current. Also, in all cases make 100% sure you observe the correct polarity. Double and triple check the connections before plugging in. Batteries really hate reverse polarization. I know from experience and it was not pretty!


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You may also consider using a constant volatge charging with 13.8 volts using a LM317.


ur charger need an current limiter.. mean I -const ...the low cost powersupply doesnt have an limiter for 1A ..the range can be 1,0 - 1,5 A....If ur Battery low..mean about 10V ..and u connect the charger can be the chare current are 1,5A therfore the Powersupply getting hot ,because overload..u can make an I - U charger with an P canel Mosfet and TLV2372..i think i have an schematic for this..let me have an look...U must coll it...5W power lost...


Added after 5 minutes:


i find the schmatic


Please view these two links....they may help you

**broken link removed**

**broken link removed**

You won't need a current limiter. You can even use a DC power supply to charge it. I usually set mine to 14.1V As the battery charges, you will see the current drop to near zero on the ammeter.

Your 15V 1A charger voltage will drop below 15V if sourcing 1A. As the battery charges, current draw will decrease and the voltage will increase.


i use that circuit for many time u can control voltage and current

r5 for adj charger voltage

r3 for control current limit

here current limit abt 0.6 A

r3= 1ohm 1watt

transformer 220v ac to 18v ac - 25 V.A

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