Which Method is Better for Charging Batteries: Economically & Scientifically?

[zorro]

Which method is more advantageous - economically as well as scientifically?
Charging a battery (rechargeable) just after its use or charging it fully after its complete discharge?

I read in my book that in the case of lead storage batteries, the PbSO₄ produced during discharge can be easily converted back into Pb and PbO₂ when freshly precipitated. Otherwise it changes its crystalline structure and ages to a less reactive from, which cannot be reconverted back to starting materials.

On the other hand, I read in the instruction manual of my car battery charger that frequent charging can reduce battery life so recharge completely only after full discharge. This is also written in my laptop's manual.

 

[pzona]

I'm not basing this on any type of science, but I've read that you shouldn't allow the battery to completely discharge. Also, you shouldn't overcharge it; once it's fully charged you should unplug it. I'm not sure what the chemistry is behind this as I've only covered about 4 weeks worth of material on batteries.

 

[zorro]

May be that depends on the type of battery.

 

[Borek]

Yes, it depends on the type of battery. It is so called memory effect.

 

[zorro]

Interesting. Thanks for sharing that Mr. Ph

 

[Robot B9]

What you described is called "sulfating" and will occur in normal automotive lead acid batteries if they are fully discharged a number of times. Some lead acid batteries, known as deep discharge, are more resistant to this.

Different battery chemistry (non-lead acid) may also suffer from similar problems.

 

[Redbelly98]

On the other hand, I read in the instruction manual of my car battery charger that frequent charging can reduce battery life so recharge completely only after full discharge. This is also written in my laptop's manual.

That statement puzzles me, since a car battery is recharged every time the car is driven.

 

[russ_watters]

Same for laptop batteries...

http://www.dell.com/content/topics/...sitelet/en/batteries_faq?c=us&l=en&cs=19#faq7

 

[Ivan Seeking]

Same for laptop batteries...

http://www.dell.com/content/topics/...sitelet/en/batteries_faq?c=us&l=en&cs=19#faq7

Really?

Q Should I completely discharge my battery before I charge it?
A No, with current lithium ion batteries this practice does not improve the runtime of the battery. This practice is a holdover from the days in which NiMH batteries were used.

For lead-acid batteries, by considering the slope of the first graph as a function of the percent discharge for each charge cycle, it is seen to be most efficient to fully charge the battery after each use and to minimize the percent discharge. Note that a car battery would typically discharge no more 5% before recharging.

There is the additional issue of battery voltage as a function of the percent discharge and the load. Considering the second graph [Source: Home Power #36 • August / September 1993], as the percent charge decreases, the voltage of the battery is reduced resulting in less power per percent drop in charge [an increasingly negative slope as the charge approaches zero].

A rule of thumb in industry is that you never want to discharge a lead-acid battery more than 50%. There is the additional concern that low voltage can damage systems or fail to reach the minimum threshold for operation.

For the second graph, C is the battery capacity in amp-hours, where C/X represents the discharge rate. The different curves are determined in large part by Peukert's law.

 

[zorro]

That statement puzzles me, since a car battery is recharged every time the car is driven.

Sorry for not being clear.
I am not talking about the battery inside the car.
I have a similar one-
http://www.google.com/products/cata...g_result&ct=result&resnum=1&ved=0CEkQ8wIwAA#"

 

[mheslep]

That statement puzzles me, since a car battery is recharged every time the car is driven.

Yes, but automotive lead acid batteries are typically recharged from 90-90% capacity back to 100%. They are not intended for frequent deep discharges, as depleting the battery a few times by leaving the lights on while parked will demonstrate.

 

[mheslep]

...
A rule of thumb in industry is that you never want to discharge a lead-acid battery more than 50%. There is the additional concern that low voltage can damage systems or fail to reach the minimum threshold for operation.

For the second graph, C is the battery capacity in amp-hours, where C/X represents the discharge rate. The different curves are determined in large part by Peukert's law.

50% discharge would apply to the 'deep cycle' or 'marine' grade of lead acid batteries, i.e. lead acid with heavy duty anode plates. Automotive motor-starter batteries don't want to see less than ~90-95% charge (~5% discharge) as you first noted.
http://www.windsun.com/Batteries/Battery_FAQ.htm#Starting, Marine, and Deep-Cycle Batteries

 

[Redbelly98]

That statement puzzles me, since a car battery is recharged every time the car is driven.

Yes, but automotive lead acid batteries are typically recharged from 90-90% capacity back to 100%. They are not intended for frequent deep discharges, as depleting the battery a few times by leaving the lights on while parked will demonstrate.

It sounds like you are actually agreeing with me, since both you and I are questioning the earlier statement that one should "recharge completely only after full discharge" for a lead acid battery. Am I missing something in what you are trying to say?

 

[mheslep]

It sounds like you are actually agreeing with me, since both you and I are questioning the earlier statement that one should "recharge completely only after full discharge" for a lead acid battery. Am I missing something in what you are trying to say?

If that's what you (and I) are responding to, yes I agree with you, the statement doesn't seem correct for automotive-lead acid.

 

[Ivan Seeking]

50% discharge would apply to the 'deep cycle' or 'marine' grade of lead acid batteries, i.e. lead acid with heavy duty anode plates. Automotive motor-starter batteries don't want to see less than ~90-95% charge (~5% discharge) as you first noted.
http://www.windsun.com/Batteries/Battery_FAQ.htm#Starting, Marine, and Deep-Cycle Batteries

True. However, I was referring to the limit, not the ideal or typical circumstance. Beyond 50% there is chance of permanent damage. This comes up for me when determining the absolute maximum run time [actually, volts vs load] before the system is automatically disabled. Deep cycle are good down to 50% in normal operations, but I have still been advised to never exceed that value in either case.

 

[russ_watters]

Really?

I wasn't very clear there. I was expressing surprise about the OP's statement that his laptop manual suggested a full discharge was needed for a laptop, similar to Redbelly's surprise about that issue for a car battery.

 

[JaredJames]

As someone who has a 'cream crackered' laptop battery, I noted on the packaging of my new one (and my mobile phone for that matter) that it says that allowing the battery to drop below ~10% capacity would start to "kill off the cells" and cause permanent damage.

These are the Li-ion type batteries. So far as both are concerned I generally try to discharge them down to the point the laptop and phone give me the "low battery" warning which kicks in at around 20% capacity. Just a relic of the past where I'm used to having to do that.

Does anyone know if this is detrimental to them? Should I simply plug them in any opportunity and keep them topped up or doesn't it matter? Also, does leaving them plugged once charged have an effect on lifespan (I read some type - can't remember which one - is damaged by leaving it on charge too long)?

 

[JaredJames]

Interesting site regarding batteries, I've put this in all three battery threads for reference:

http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

 

[Bogan69]

Hey this isn't neccessarily about Recharging betteries, but more about how normal batteries work. I am well aware that anions flow from the anode to the cathode, but i am wondering when the cations flow from the cathode along the wire, do they cancel out some of the negative charge on the wire?

 

[JaredJames]

Hey this isn't neccessarily about Recharging betteries, but more about how normal batteries work.

Thread title seems to disagree, along with the OP.