Talk:Memory effect

I am a little confused, but I don't pretend to know that much about the topic. The current articles says:

"Voltage depression does not occur in nickel hydride (NiMH) batteries"

and then in the same paragraph

"voltage depresssion in general is just as common (in NiMH batteries) as with NiCd"

Am I being stupid, or is there a contradiction here? Tompagenet 11:57 Apr 10, 2003 (UTC)

Ditto. Thadk 9:23, 2004 Jan 10, 2004 (UTC)

Taken from main page since it is clear that it contradicts itself and nobody seems to be able to fix it:

AdamW Jan 15, 2004

Voltage depression does not occur in nickel metal hydride (NiMH) batteries because the electrolyte does not crystalize, which is why these types of batteries have become increasingly in demand for most electronics that are repeatedly charged, like laptop computers and cell phones. Most advertising for NiMH batteries includes the claim that they are immune to the memory effect, although cell degradation and voltage depression in general are just as common as with NiCd.

Is the memory effect not a special case of hysteresis?

The "battery memory effect" is different than the "passive matrix memory effect" that hysteresis mentions. Should we just mention the other effect in the article, or do we need a different article with disambig ? --DavidCary 01:08, 3 Apr 2005 (UTC)

What Exactly Is The "Memory Effect"?

Can someone actually clarify what the memory effect is? I got the vague impression that it refers to an unwanted lower charging voltage for rechargeable batteries under certain circumstances ????

I didn't understand the original meaning either, but what I understood was that overcharging the battery leads to "clogging" of sorts, making the battery appear to discharge very fast - the voltage drops rapidly. However the drop is not caused by running out of power but simply increased resistance. 65.95.157.80 23:03, 6 October 2006 (UTC)[reply]

—

Memory effect is something you only see on satellite applications or similar cases when the battery is on a precise charge-discharge cycle. Some of the chemicials essentially become inaccessable and the battery capacity end up limited to exactly what is being used.

Here on terra firma the cheapest way to charge NiCds is with a cheap wall wart that delivers a roughly constant current slow charge. The problem is that when left on the charge for extended amounts of time the chemical reaction will slightly stabilize and will have less potential energy when it is used. This is called voltage depression but is always confused with memory effect. Fortunately, the reaction breaks down to the same basics as a normal reaction so next time you charge the cell it makes the proper bonds. This is why a discharge works.

The problem with devices that show these symptoms is that the EE who deisnged them gave them a cheap charger and didn't account for this efffect. The simple fix is to adjust the device to work with lower voltages to the cells can release all their enegery and be ready to take a good charge. The complex fix is to include a better charger and/or watch the rate of voltage drop over time to determine a battery is empty (as opposed to simply watching the voltage at an instant of time).

74.92.174.53 04:49, 25 December 2006 (UTC)[reply]

Other ways to kill batteries

This is probably not a common problem, but I destroyed many batteries by charging them on inverters (mostly NiCd). We use alternative energy (12 volt battery bank, solar panels, Trace inverter). My cordless phones, cameras, laptops, flashlights.. basically anything with a rechargable battery, would die within a few months. The battery would no longer take much of a charge.

I am told it has to do with the square AC wave that an inverter produces (normal AC power has a perfect sine wave, in theory). Coupled with most rechargable systems having a wall-wart (power cube) cheap transformer to step down to DC, the DC->AC->DC power ends up with 60 gaps per second. Most equipment seems to work fine, but not rechargable batteries (although a new InfoLithium I've tested seems OK so far...).

Solutions (haven't had any problems in years, since I figured this out): Create 12 volt DC->DC power supplies for the chargers when possible (12v or under), if over 12v then charge only on "clean" AC power (when possible), and buy lots of disposable batteries.

It would be nice if this article mentioned this, as it might prove useful to people wondering why their rechargable appliances were slowly dying after being charged on an inverter (like a "pocket power", or a car inverter). However, I have no verification of this effect, nor any actual facts as to why it would kill a battery, nor even if all inverters would caused it. Splarka 10:42, 13 August 2005 (UTC)[reply]

I am told it has to do with the square AC wave that an inverter produce

Generally speaking, "Horsepucky". You might cause the input transformer in some chargers to overheat, but a properly-designed charger wouldn't care much about the waveform; we run NiCd/NiMH chargers from an inverter all the time. I suppose two questions to ask are "What's the peak voltage from your inverter?" and "What's the RMS voltage?"

Atlant 22:45, 14 August 2005 (UTC)[reply]

Although, reading the labels on the devices would explain what the machine is rated for. As long as the ratings are similar the device doesn't care "Power is power is power". If there is no label or you do not have the qualifications to understand what is on the label we STRONGLY suggest you DO NOT ATTEMPT THIS. (Signed on behalf of) 24.222.209.78

YES, horsepucks! Your charger is busting the batteries because it needs to deliver a controlled current. Your photovoltaic charger is more suited to lead acid battery charging where a constant voltage is what's needed.

Frozen batteries

When the batteries are frozen this will reset the memory effect. ^{[citation needed]}

I took out this sentence, as it is ... just wrong. In order to "reset the memory effect," you'd need to reset the chemistry of the battery. 153.42.226.100 01:26, 13 December 2006 (UTC)[reply]

Memory Effect and Voltage Depression

As a one-time battery chemist I picked up some information on NiCd and NiMH battery misbehavior. Memory effect, as observed in satellites, can be reversed by deep dicharging the cell to below 1 volt and then recharging as normal. Voltage depression is usually caused by growth of large crystals of the active materials on the electrodes. When current is drawn, the cell cannot sustain normal currents because the surface area of the active material of the anode or cathode is smaller than normal. This large crystal size is often a result of extended trickle charging (C/10) common with cordless phones and other devices that have inexpensive charging circuits. Again a deep discharge then recharge can rejuvenate the battery. You may need to repeat this. The higher the charge rate the smaller the crystals and the higher the surface area of the electrode. The best solution to this problem is a sophisticated charging circuit in the device.72.85.166.20 16:56, 28 April 2007 (UTC)[reply]

Voltage depression and chemical reactions

I just cleaned up the article, someone put the following sentence into the article, so I've moved it here-- "(This section needs updating. Information supporting this fix is available in the Gates manual. Also, voltage depression is caused by an alternate chemical reaction, not crystals. The part about cell reversal is true.)"

Don't know if anyone can get anything out of this Binliner4 18:08, 25 September 2007 (UTC)[reply]

Impact of Airport Baggage Screening on NiCDs

I've noted on several occasions that my sonicare toothbrush goes from holding a charge for several brushings to holding enough for only 1 or 2 after I travel somewhere with my toothbrush in my checked baggage. This has happened when travelling through SeaTac Airport in Seattle. Does anyone know if there is an impact from the new TSA baggage screening devices on NiCD batteries? —Preceding unsigned comment added by 156.74.250.7 (talk) 21:35, 27 February 2008 (UTC)[reply]

Article title is misleading

Most of the text of this article discusses battery failures that are not caused by the memory effect -- in fact, there is very little description of the actual causes of the phenomenon. —Preceding unsigned comment added by 65.160.28.32 (talk) 19:58, 10 October 2008 (UTC)[reply]

Seriously, the actual cause and description of "memory effect" is not covered very well by this article -- maybe the article title needs to be changed? 70.170.97.116 (talk) 10:06, 22 October 2008 (UTC)[reply]