# basic battery charging

Discussion in 'General Electronics Chat' started by mechanicalman, Jul 25, 2011.

1. ### mechanicalman Thread Starter New Member

Jul 25, 2011
3
0
we have a 24V dc circuit. To allow for one action when teh power is switched off i thought about placing a 24V battery in series with the rectifier output using the rectifier circuit to charge the battery

As the float value of the transformer circuit appeard to be 37V dc. Do I need to regulate reduce this? if so how,

Could I use just a capacitor between 24V and oV? if so how do i decide on type and size. I want to operate a solenoid for a lowering valve for 30 seconds and a coil in a solenoid lock for a further 20 seconds. strady state 4VA, start inrush 60VA

I have previousely used charger, battery and realy and delatching switch which is a littl e complicated

many thanks

2. ### iONic AAC Fanatic!

Nov 16, 2007
1,450
71
A 24V circuit? What is it? What does it do? Placing a 24V battery in series with a rectifier output and using the rectifier circuit to charge the battery.
Can I assume that this rectified output is the 24V Circuit you mentioned above? Also, if you are intending to power this "circuit" with the battery in case of a power failure it would need to be connected in parallel and probably be isolated from the circuit.

Next: The proper charging of the 24V battery would be to begin with a bulk charge of about 28.8V, then switching to a lower current to finish the charge. Finally you would float charge at a low current at a voltage of about 27.6V
So ultimately the 37V you mention would be a battery killer, regardless of it's current capabilities. Yes you would need to reduce the 37V.

Are you asking if you could use a capacitor rated at 24V as a voltage regulator....No, don't think so.

Last edited: Jul 25, 2011

Dec 26, 2010
2,147
302
Why don't you post a schematic (diagram) of what you are planning to do. Verbal descriptions of circuits are hard to write, and even harder to understand.

4. ### #12 Expert

Nov 30, 2010
18,093
9,682
That was a perfect example of how hard it is to understand a circuit with no drawing. A "safety margin" of 50% over the battery voltage to charge a battery is, as Ionic said, a battery killer.

Must have drawings to stop the guessing.

5. ### SgtWookie Expert

Jul 17, 2007
22,202
1,793
Just to clarify, the only thing EngChick was referring to in her first two sentences was the voltage rating of the filter capacitor, and nothing else.

6. ### #12 Expert

Nov 30, 2010
18,093
9,682
I see now. Without a drawing, I thought this was about charging a battery.

7. ### mechanicalman Thread Starter New Member

Jul 25, 2011
3
0
I will post a circuit.

Basically I want to power a circiut in case of power failure

There is a transformer and rectifier to produce 24V DC it is measuring much over that wne no current is being drawn.

A 24 V battery will give the result, its just how to charge the batery. and how to ensure it is working when deeded if not always used.

8. ### mechanicalman Thread Starter New Member

Jul 25, 2011
3
0
So if the power is off, I want to power the circuit for 60 seconds. If i just connect a battery at 24 and 0 it will be killed by the mains powered 24V when it floats way above 28V

Is there a simple charging regulation circiit or do need a totally different circuit and a relay to switch it in.

File size:
13.3 KB
Views:
25