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Battery memory effect: a thing of the past? Answered

do I have to let my batteries run out before recharging? Why cell phones seems to have unlimited battery life cycle and some others things don't? What about my iPhone? It would be great to charge it a little bit every time I'm at any computer but I have this kinda fear to riun it's battery life...


lead acid and lythium batterys do not store memory. but still some alcaline and other types do so first see what type of battery is it and then decide the best charge/discharge cycle.

I find that with NiCad's it is possible to bring them back by shooting them with 50v.ac for 10 seconds. this blows the wiskers off the internal stuff and they work good as new. I do this to NiCad's for battery drill motors. Sometimes I need to blast them several times. If you hear them start to crackle you have gone too far maybe. Short Zaps.

A few years ago I gave a buddy of mine an ancient laptop with a dead NiCad battery. He said he put the battery in a deep freezer and somehow it worked again. He wasn't a very technical person. I didn't believe him. I researched to find out if that was possible. Here' what I still remember. The chemicals inside the NiCad cells crystallize over time. The memory effect happens when they are partially crystallized and can't take a full charge. When they fully crystallize the cells stop taking a charge at all. Freezing them causes the crystals to become brittle and more easily broken. Partially crystallized cells are more likely to work than fully crystallized cells. In my test, I froze 3 ancient laptop batteries in a deep freezer for about a week. Then dropped them a few times from about 2 feet onto the garage floor while they were still frozen. After I thawed them out for a few days, only one of them worked and it would only hold about 1/2 the charge it did before. I suspect there wouldn't have been a problem subjecting the individual cells to a rock tumbler or something because they're metal. The cells very hard to get out of the plastic shell without breaking something and even harder to put back in. I think it could be done, but exploding batteries scare me too much to find out. From what I've read, the newer batteries don't have that problem because they're made of different chemicals and the physical structure inside is different. I've never seen the NiCad memory effect in any of the laptops I've serviced with the other battery types. Several clients tell me they've had it happen, but many of my clients have some odd laptop superstitions. I'm always skeptical of what they tell me. My professional opinion is anything resembling a memory effect in a modern battery would have to be caused by individual cells going bad. It's not the same thing. WARNING: Don't try the freezer experiment with a modern laptop battery EVER. Batteries do occasionally explode or catch fire without provocation subjecting them to abuse beyond their normal parameters is just asking for trouble. Be careful! - Chris

Newer batteries still have a hughe problem. Especially if used in notebooks. Heat... Most notebooks heat up that batterie to much, wich shortens theyr lifecycle dramatically. But there's an easy way to avoid this. Only have the batterie in your notebook if you intend to use it or charge, but don't leave it there all the time. And if you're not gonna use it for a long time, leave it charged to 40-50% in the fridge (some companys even write that into the instructions)

I agree completely. Heat is a big problem, but then so is cold. Lithium Ion batteries require a certain operating temperature range. Too hot = bad. Too cold = bad. Just right = Not as bad.

I've actually seen battery heaters on a few surplus sites. They're described as leftovers from laptop battery manufacture. The few times I've ever dissected a rechargeable battery pack, I've never seen anything that looked like a heater.

I'm not sure how that would work in a laptop. I suppose they wouldn't actually work if the battery was too cold to function. I'm from Florida. I've never seen REAL cold. Or even snow. I can't say personally how the cold effects laptops. They may kick in when the battery decides the lower temperature limit is approaching. If they have heaters, that might explain part of the battery drain problem vs. a cell phone.

Either way, though I have to say the 'memory effect' isn't the same as it was with the ni-cads. Maybe there is something similar, but I've never seen it on the new ones. When we have bad notebook or tool batteries to scrap, I take out the cells. I check which one's take a charge and dump the rest in the recycle / scrap bins. Free batteries are a good thing. Every bad battery had at least one bad cell. with the ni-cads, nearly every cell would take a fraction of a charge or none. With these new one's they either charge all the way or the don't it seems like.

I've never noticed the thing about leaving it in the fridge. That makes sense though, because the chemical reactions inside would slow down. You would probably have to wait for it to warm up again before you use it. I'm going to check some of the manuals at work tomorrow and see if I can find that instruction. Thanks for the tip.

nicad battery's are purty much the only battery's that get a memory

memory effect is only something with NiCad batteries, which are banned in europe now anyway Lithium Ion batteries can be damaged by deep discharging them, so you should try and keep them above 10%, however

Just dont overcharge them, dont pop something on the charger and forget about it for a couple months.


9 years ago

NiMH have some "memory" consequences, although nothing like the older NiCads. It's probably OK to recharge without fully discharging, but it's probably best to let them discharge if possible. Newer Lithium-ion batteries don't have the memory effect at all. In fact, if they are drained too far (~30% of the total), they will stop functioning altogether.