# Pulse charging SLA batteries

Discussion in 'Off-Topic' started by survivalsys, May 16, 2011.

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1. ### survivalsys Thread Starter New Member

Apr 15, 2010
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I have scoured the net, sites like battery university and nowhere can I find any real info on what voltage, minimum current, on off times to create a pulse charger for a 12V SLA battery. Some say short duration high voltage pulse (what is high). Some mention Bedini pulse charger which I personally think is rubbish. Some mention a 1 sec pulse etc etc.

Does anyone out there know anything about what parameters to set when building a pulse charger. I have build a high voltage (500V) low amp circuit and when I pulse the battery it makes a clicking sound.

Any advice would be appreciated !!

2. ### #12 Expert

Nov 30, 2010
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The high voltage thing isn't a very clear statement because the voltage at the terminals of the battery will be the battery voltage plus the internal resistance of the battery times the input current. A "high pulse" would be a high current pulse. Of course the high current is driven by high voltage, but there are limits. Dropping 500 volts into a 12 volt battery will probably just make a clicking sound as the voltage arcs inside the battery. Not a smart thing to do.

The usual way to go about it is to start with the amp-hour rating of the battery and charge in proportion. 1C or C/1 means to pour current into a battery at a rate that will amount to its capacity in one hour. Most chargers do less than that because there is a real danger of warping the insides with heat.

4 instance, if the internal resistance of the battery is 1 ohm and you try hitting it with 500 volts, the voltage on the battery terminals would become 12 V + 500 volts while 500 amps pours into the battery. See the fallacy?

You must think in terms of current.

4 instance, a 12 volt transformer will produce 12 radical 2 peak volts (minus the rectifier loss). About 16 volts. If you put a capacitor on this and feed it to the battery, the battery will accept some current and it will be almost DC. How much current depends on the condition and size of the battery. If you do not add a capacitor, the rectifier will give the battery pulses of current from zero to whatever that peak current was when the capacitor was connected.

That's a start. Ask some more if you have a better idea what you want to know now.

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3. ### survivalsys Thread Starter New Member

Apr 15, 2010
3
0
This is the battery specs:
Specification:
Cells Per Unit = 6
Voltage Per Unit =12
Normal Operating Temperature Range = 25oC±5oC
Capacity = 20Ah@20hr-rate to 1.75V per cell @25oC
Weight = Approx. 5.90 Kg
Max. Discharge Current = 200 A (5 sec)
Internal Resistance = 14m ohm
Operating Temperature Range = Discharge: -20 ~60 Charge: 0oC~50oC Storage: -20oC~60oC
Float charging Voltage = 13.7 to 13.9 VDC/unit Average at 25oC
Recommended Maximum Charging Current Limit = 6A
Equalization and Cycle Service = 14.6 to 14.8 VDC/unit Average at 25oC

Will say a 50 - 60 volt pulse of short duration and @ 6.9A be sufficient do you think ?

Apr 20, 2004
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