Electronics > Beginners
Why does my power supply act weird when being used to charge an auto battery?
jaunty:
I have an HP 6237B triple output power supply ... i thought i might see if i could use it to charge my severely drained auto battery (12 volts etc etc - you know the type) - but when hooked up it seems i cannot get the output level beyond just over 11 volts (cant' adjust it lower either!) - i can only vary the current and current won't go up too high (1.5A max) - would this have to do with some sort of interaction between the battery and power supply? or am i getting erroneous readings off the supply meters in this application? anyone have any experience with this or can explain?
I was thinking of using my cheap and cheerful chinese supply as a countercheck but didnt' want to blow it up
PA0PBZ:
Your power supply is fine, it doesn't go below 11V because that is the voltage of the battery it is measuring, and it will not go above that because the internal resistance of the battery is so low that you have to put a lot more amps in there to raise the voltage and your power supply is not capable of doing that. On the other hand, if you leave it connected (and the voltage setting is above 11V) you will see that the voltage will go up when the battery gets charged.
jaunty:
alright - yes hopefully it will go up LOL - though it got drained from sitting around for MONTHS (down to 7.5 V or so) so we will see if it's restorable ... it charged up to 11 ish volts after a few hours but seemed to plateau at that point and didn't seem to charge higher
james_s:
It may have a shorted cell, 11V is about where I'd expect a 5 cell lead acid battery to top out.
PA0PBZ:
--- Quote from: james_s on March 28, 2019, 03:49:35 pm ---It may have a shorted cell, 11V is about where I'd expect a 5 cell lead acid battery to top out.
--- End quote ---
If it starts to boil at 11V then yes, that could be the case. Also check the fluid level.
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