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Toyota Confirms: Li-Ion Batteries Have a “Memory Effect”

By Joe Levi May 3, 2013, 11:05 am
speed chargers

We all know how important batteries are in our modern electronics. They’re also becoming an increasingly vital part of our vehicles. For people in both camps, the latest news from Toyota is disheartening: Li-Ion batteries have a “memory effect”.

Ni-Cad Batteries

When the traditional, land-line telephone evolved from a corded beast into a clunky — but wireless — beast, there was much cause for celebration. The battery technology of the day was Ni-Cad (Nickel Cadmium). Batteries based on this technology were used in everything from cordless phones to satellites orbiting the planet. There were two significant problems that plagued these batteries.


First, after thousands of charge/discharge cycles to within 2% of the same state of charge, the battery would develop a “sudden drop” in voltage.  To many electronic devices, this drop would make the battery appear “dead”.  NASA figured this one out because their batteries could only be charged when the sun was shining on panels, and the satellites usually used the same amount of energy to power them while they were in Earth’s shadow. It’s extremely unlikely that any consumer electronic device would be subjected to conditions that would reproduce this problem. Scientists at GE’s Battery Business Department in Gainesville, Florida published a paper describing the “memory effect”, but didn’t convey that Earth-bound consumers should never run into this condition, and later retracted their paper, but the damage in the public-eye was already done.

What kind of battery technology powers V’GER?

Second, there was another issue with Ni-Cad batteries that presented symptoms similar to that discovered by NASA and GE: “voltage depression” or “lazy battery effect”. This results from repeated overcharging, but can generally be “fixed” by subjecting the battery to a few deep cycles.

Eventually new technologies were introduced, eventually bringing us to today’s Li-Ion and Li-Polymer batteries. Unfortunately, to the typical end-user who wants their electronics to be fully-charged, keeping the battery on the charger for extended periods of time only increases the effect, and makes the usable per-charge lifespan of the battery lower — even with the new technology.

Li-Ion Batteries

Lithium Ion and Lithium Polymer batteries are found in almost every electronic device today. Cell phones, smart watches, and even hybrid and electric vehicles are powered by these technological gems. According to a new study, even our latest and greatest battery technology isn’t immune from the dreaded “memory effect”, though you’re not as likely to see it as you were with Ni-Cad batteries. That’s the good news.

Samsung Li-Ion Battery
The battery inside your cell phone is likely Li-Ion

There’s a lot of physics and technical information behind why batteries present this “memory” when discharging, and if you’re interested in all that, I highly recommend the article at Phys.org that I’ve linked below. For this article, however, suffice it to say that Li-Ion has the same problem as older battery technologies, just not as visible. Luckily, the “solution” is the same today as it was two decades ago.

How to Defeat the Memory Effect of Li-Ion Batteries

We’ve all got to realize that we can’t get rid of the “memory effect” problem. It’s inherent to the technology — and likely to batteries in general. But now that we know about it, we can adapt and minimize the impact the “memory effect” has on our electronics. It’s fairly simple, which may be one reason why it’s not widely adopted. Keep the following rules in mind:

  1. Realize that your batteries don’t like to live at the very top or the very bottom of their charge capacity. Don’t keep your devices on the charger after they’re fully charged. Similarly, don’t leave them dead in a drawer for expended periods of time either.
  2. Every once in a while, completely discharge your device, then completely charge it up again. Do that a few times in a row. This will help “condition” the battery and will ensure that you get better use of its capacity. Doing this will reduce the rated lifespan of the battery, but it will get you more practical use out of it and prevent a premature death.

That’s it. Pretty simple, right? Ironically that’s what HAM Radio operators have been telling us for many decades, and those guys really know their stuff!

Sources: Nature.com; Phys.org
Image Credits: MichaelKnows.com; Star Trek: The Motion Picture


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