Do you discharge a battery a little before you charge it?

[sixdogs]

When I was a kid helping out is a shop, the meticulous owner told me to ALWAYS turn the lights on for two minutes before a battery charge to drain off surface resistance to a charge.

Is this a wive's tale?

 

[RjCorazza]

Draining the surface charge is necessary prior to testing a freshly charged battery, but I have never heard anyone say to do that prior to charging a battery.
For batteries that I want an accurate test on, I let them sit for 24 hours before testing.

 

[Tinhack]

I worked in two dealerships (VW & Pontiac) in an earlier life. No one ever said to discharge a lead-acid battery before charging. Although the testers of the day did just that. They were nothing but a carbon-pile resister and two gauges--Amp and volts. There was no cool electronics like they have today in hand-held testers.

 

[scootr]

I'm calling wives tale on that. Another tale I used to hear was completely drain the battery before charging. Science has proven that batteries have a cycle life. If a battery has a cycle like of say 1500 full recharges, then it has a life of 3k 50% recharges. And everything runs better, draws less amperage, on a full charge vs low voltage. Less amperage draw reduces motor and component heat increasing efficiency.

 

[RjCorazza]

I worked in two dealerships (VW & Pontiac) in an earlier life. No one ever said to discharge a lead-acid battery before charging. Although the testers of the day did just that. They were nothing but a carbon-pile resister and two gauges--Amp and volts. There was no cool electronics like they have today in hand-held testers.

And yet the old carbon pile load testers are still the most accurate way to see if a battery is actually serviceable! I use a fancy electronic tester to track batteries over time only.

 

[DarkBlack]

Maybe a confusion with NiCad batteries which were to be discharged before recharging otherwise they developed a “memory” of the charge point, and would drop voltage faster after that discharge point on subsequent uses.

 

[chim]

Other than what DarkBlack mentioned, I never heard of discharging a battery except by simply using it normally. What would be the pointy of charging an already-charged battery?

 

[scootr]

Maybe a confusion with NiCad batteries which were to be discharged before recharging otherwise they developed a “memory” of the charge point, and would drop voltage faster after that discharge point on subsequent uses.

Yes but, NiCad is an obsolete medium.
LiFePO4 battery composition is way better, IMHO.

 

[Tinhack]

And the LiPo batteries don't need to be discharged. They keep going until dead anyway. I've been converting all my battery hungry items to rechargeable LiPo. Their output is a straight line on a graph then drops off instantly. I especially like the rechargeable AA and AAA batteries now. They output 1.5-1.6v. Not like the old NiCad of 1.2v fully charged.

 

[Roadworthy]

This is interesting but seems to have digressed from the original question. I have nothing definitive to add but thought the surface charge was on a fully charged battery actually putting it a bit above the stated battery voltage. That being the case why would one want to charge a fully charged battery?