Need Help for charging 12v Lead Acid Battery?

I need a charger for a 12v Lead Acid Battery for my Battlebot. I am planning to buy a UPS, detach and use the battery of the UPS to power motors and other stuff in the Battlebot and then recharge the batteries by connecting them back to the UPS charging circuit. Can my above be successfully implemented ? Please give me your opinions and suggestions as to how this can be implemented.   

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Vyger5 years ago
I have actually thought about doing the opposite. Using a big battery and hook it up to an UPS to increase the run time for extended power outages. (We get those every now and then) .
While UPS batteries are nice sealed units they don't have a large capacity. They probably will not give you that much run time. You might want to get something more along the line of a motorcycle battery.

Regular chargers are not to expensive and you might also find older ones for sale.
I have a newer fancy electronic one but I hate it because its always complaining about the condition of the battery, like when its completely flat so it thinks its shorted out. The best charger that I have is this old thing that I picked up at an auction for 5 bucks. It is a transformer and a rectifier. All it does it put out voltage no matter what and does not complain. I often use it to test components like glow plugs because it doesn't try to tell me that its not a battery, DUHH.
Jayvis Vineet Gonsalves (author)  Vyger5 years ago
Ok, so how if I use a 12v 7ah Battery for my robot? And can I use the circuit the circuit that I provided below to charge it?
Jayvis Vineet Gonsalves (author) 5 years ago
Thank you everyone for your replies, I have bought an Okaya 12v 7.2ah Battery and its charger for about 16$ which I feel is quite cheap :-)
A novel idea, but a UPS isn't designed to fast charge SLA batteries - usually a 10 hour rate. You can make your own charger fairly easily. Just bear in mind that you need a constant VOLTAGE supply to charge lead-acids.

So can I use this circuit as it seems to be fairly simple.
But the issue is about overcharging. How do I know when the SLA battery is charged?
The circuit there I dont' understand - the capacitor to the base of the transistor doesn't look right. There ARE plenty of SLA charger circuits out there- "full" is indicated nicely by the voltage across the battery.