Charging a Car Battery with a Bench Power Supply

Interesting... I'm certainly giving this some thought before going ahead with charging the car battery with my bench supply.

D from BC British Columbia Canada

So here's what I ended up doing...

While going through my junk collection to look for a power diode (There was some fear the power supply might have an overheat crowbar circuit the shorts the output.), I came across a headlight halogen bulb.. Good enough..

Dialed 13.8V on the supply. Shorted the leads and set the current limit to 2A. Put the halogen in series. Made connection to the battery.

Bulb glowed a bit. Power supply displayed a current of ~1.3A. The bulb is dropping some voltage. Up'd the voltage for 2A. I heard a relay click. That was a little scary.. :) I guess the power supply switched over to another secondary tap.

Then the power supply heatsink got too warm to touch. I lowered the voltage until I heard the relay click again. I figured the power supply would dissipated less if the regulator drops less voltage.

Left battery to charge overnight. Woke up this morning happy that I'm not on fire :P

Checked battery. The bulb is not glowing.

14V measured across the battery. Current at 380mA. (Was going for 13.8V..But consequences from the halogen.)

I believe it's charged.

D from BC British Columbia Canada

Most of these people have no clue.

Just set the charger to 14.4V, current limit 5-7A (ass-u-me-ing it's a

55 AH battery), and when the voltage reaches 14.4, give it 45 minutes more and turn it off, or turn the voltage down to 13.8 and leave it on float charge until you need it.

Have Fun! Rich

And you've probably shortened the life of your halogen bulb.

Cheers! Rich

Interesting little bit there.. I'm glad it's just a junkbox halogen bulb I'm using.

As per

" With a reduced voltage the evaporation is lower and there may be too much halogen, which can lead to abnormal failure. At much lower voltages, the bulb temperature may be too low to support the halogen cycle, but by this time the evaporation rate is too low for the bulb to blacken significantly. There are many situations where halogen lamps are dimmed successfully. However, lamp life may not be extended as much as predicted. The life span on dimming depends on lamp construction, the halogen additive used and whether dimming is normally expected for this type."

D from BC British Columbia Canada

This seems pretty overcomplicated. The regulator in the alternator isn't that precise either (usually somewhere between 14.2 and 14.7 volts).

--
Programmeren in Almere?
E-mail naar nico@nctdevpuntnl (punt=.)

The fuse is the least complicated means to protect the battery, if the bench supply has a crowbar.

As you point out, it may overcomplicate things if one worries about the bench supply sensing the voltage on the battery. But, if one is concerned about it, then the cicruit addition itself - a relay, pushbutton and diode - is hardly complicated.

Ed

Thanks mate - you ain't got a damn clue what you are talking about! You have just ruined my stuff - email me your address and I will damn well sue you. Blokes like you should not be allowed on these chat groups giving advice - you have no idea of the dangers you could cause.

d t y

Sorry chaps - that reply was aimed at "Roger the Dodger" - obviously named well as he dodges his responsibilities