Hi,
I have two 12V batteries (Pb, these ) and I need to charge them somehow. I have 1.5A 12V power source (real out is 13-15V) and it will be great if I could use this one to charge. But I worry to just plug it.
Is there any circuit (DIY is ok too), that I will use and could just plug it and let it be over night, when it will be charged the circuit will cut the charging?
I had old Pb battery from UPS and when I let it on the power source over the night, it blowed up.
Thanks
The easiest way is with a "CC CV" (constant current, constant voltage) module from eBay. You'll need a DC adapter (~18V+, like from a laptop) for a supply for it.
General rule is that you charge batteries at a 10 hour rate. Your batteries are 2.3Ah (2.3 amps for one hour), so the charge rate would be .23A for 10 hours. If you're going to leave it charging in standby mode then the appropriate voltage would be 13.56V to 13.86V when at room temperature, as shown in the link below:
Chagrin:
The easiest way is with a "CC CV" (constant current, constant voltage) module from eBay. You'll need a DC adapter (~18V+, like from a laptop) for a supply for it.
Is it realy necessary to have 18V adapter? I'm using this 12V to power it when I'm near plug and I don't need batteries and the power source is already built in, so I will have to add one more power source, but it will not fit in the box 
And how does the CC CV module works? I plug battery, power source and what? Set V and A for charged battery and it will charge until it will be as setted? or what?
Thanks
Sealed Lead Acid (SLA) chemistry is what allows the CC CV mode. One important thing to understand is that the standby voltage is a limit that the SLA battery can tolerate (electrolysis and corrosion start at higher voltages). SLA also likes to have that standby voltage for a while (about three hours) as the last traces of lead sulfate are converted back into metallic lead.
parmanik:
Is it realy necessary to have 18V adapter? I'm using this 12V to power it when I'm near plug and I don't need batteries and the power source is already built in, so I will have to add one more power source, but it will not fit in the box
Yes. The module I linked takes DC in, puts DC out. You will need an additional AC/DC adapter.
parmanik:
And how does the CC CV module works? I plug battery, power source and what? Set V and A for charged battery and it will charge until it will be as setted? or what?
It has one potentiometer for the voltage and one for the amperage. You set the voltage that you want (13.56-13.86V), connect it to the battery, and it will show how much amperage is being used; you then set the amperage to an appropriate limit (.23A).
Not a "great" module but that's what you get for that price. I'm not aware of any better/decent, low cost, all-in-one device that you could use as a battery charger. A proper battery charger would cost at least 6x as much and I think that's what you're trying to avoid.