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Old 12th April 2007, 09:05 AM   #1
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Arrow Charging batteries with a variable power supply

How to charge a normal lead acid car battery and an Absorbent glass mat 7ah battery

I have a diode built into my power supply

How can I build a charger that will maintain the battery for then needed, itís like a UPS type
Will it work if I use my 1.5A variable power supply and set the output to exactly 13.80 volt DC, will that charge my battery to 13.80 and maintain it without overcharging for a couple of years and without making gas builds ups

In my test itís a discharged battery and the power supply is set to 13,80V DC and if I connect the wires the voltage drop down to 13.40v and it charge at a rate of 0.20A, but why not 1A or 1,5A ?
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Old 12th April 2007, 02:19 PM   #2
protos is offline protos  Greece
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You can of course charge your battery like this.If the battery is very weak it will draw the maximum amperage of your ps before it limits.As it charges close to the maximum it will draw less and less current as the internal impedance goes up.In the end it may only draw 20 ma.You can give the battery a last top up at 14.2v for while.
If your battery is discharged and only draws .2A then this means your battery is dead and needs changing.
You can check this by trying to charge the battery a reasonable amount of time then disconnect the charger and after an hour check the voltage.A good battery will be close to 13v.
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Old 12th April 2007, 05:15 PM   #3
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I used my old screwed up 7Ah alarm glass mat type battery and opened it and pull all the rubber plugs of and added some battery acid and put the rubber plugs back and placed the plastic cover on top, but the huge problem is if the voltage goes higher than +- 12.80v the rubber plugs start flying with the plastic cover, but if I take the battery and let it sits without charge the voltage goes down to 12v and stays like this for long time until I take some wires and let it surge to make a nice red glow

So 14.2v will totally make the battery goes crazy, I already tried the standard 13.80v and that produce some gasses and pops the couple of rubber plugs
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Old 14th April 2007, 06:08 PM   #4
AndrewT is offline AndrewT  Scotland
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Hi,
I wonder if the acid is too strong.
Can you check the SG against the specification?

The automatic charger could be set to 3 levels. A constant current charge up to a limiting voltage just below your set voltage, maybe 13.5V, and then trickle charge to top up to 13.8V and then an even lower trickle to hold at 13.8V effectively a constant voltage charge.

But first you will need to adjust your set points on a known good battery. Does the absorbent battery get warm when near fully charged? A temperature sensor that overides the fast charge may be needed.
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Old 14th April 2007, 06:25 PM   #5
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It doesnít get warm it only likes building up gasses then the voltage get near 12.50v

Basically I added some acid to a deed empty battery

What will happen then the acid is too strong in a lead acid battery?
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