Finally got around to testing my Li-Ion batteries

fyrstormer

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When I first got into this hobby around 2008, I understood that lithium-ion batteries have a finite lifespan, but I didn't have any way to monitor the ravages of time, except to try to notice when a battery didn't seem to hold a charge for very long. Also, I didn't have a label-maker at the time, so I didn't print labels for the batteries with the dates I purchased them, so I could track their ages.

Well, thanks to my RC hobby, I now have a super-fancy charger that can charge multi-cell LiPo/LiCo/LiFe/NiMH/Lead batteries, as well as discharging them to measure their residual capacity, so I set to work testing my stash of RCR123s and 18350s. I charged each battery using my normal charger, then let it sit for a day, then tested its residual capacity. Here's what I found:

CIMG6450.jpg


All in all, about 2/3 of my battery stash has lost more than half of their original capacity. I'll be making a trip to Best Buy to recycle some batteries in the very near future.
 

desmobob

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I'm into R/C also, and have a few different chargers. It's handy having a hobby charger! Being able to charge/discharge and then measure capacity is a great feature, and a good reason to invest in a good charger. I regularly test all my R/C batteries; particularly my flight packs for glow-powered models. I write the date and mAh measurements on the batteries with a Sharpie so I can keep track of how they're holding up.

I just got my first light that uses RCR123 cells so I bought a charger and some extra cells and promptly charged them up. Now, I realize my Lithium ions not currently being used should probably be kept at "storage charge" so I'll probably use my iCharger to discharge them to the healthy level until I need to use them.

I need to find/make a battery holder for them so I can easily use my hobby charger with them. What did you use?

Take it easy,
Bob
 

fyrstormer

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I used a charging cord with the plug cut off and two small neodymium magnets soldered onto the wires. The magnets will stick to any ferrous-metal electrodes, such as the terminals of an RCR123 battery.

I don't know if lithium-ion batteries have the same need to be kept at a storage charge the way LiPo batteries do.
 

desmobob

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I used a charging cord with the plug cut off and two small neodymium magnets soldered onto the wires. The magnets will stick to any ferrous-metal electrodes, such as the terminals of an RCR123 battery.

I don't know if lithium-ion batteries have the same need to be kept at a storage charge the way LiPo batteries do.

Thanks for the information. I hope storing Lithium ion batteries fully charged doesn't degrade them. Mine seemed to be at about 75% charge when I received them (like when buying LiPos) so I assumed that was the case. And we all know about assuming.... :)

I just did some web searching and here's a quote from Fran Hoffart, Applications Engineer for Linear Technology in Milpitas, CA, from an article entitled "Proper Care Extends Li-Ion Battery Life" from the April 2008 edition of Power Electronics: "For maximum storage life, batteries should be stored with a 40% charge (3.6 V) at 40°F..."

Another article from the "Battery University" site says, "
Do not worry too much about the state-of-charge; a cool and dry place is more important than SoC."


Thanks again,
Bob
 

fyrstormer

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I think a lot of it is because rigid cylindrical cells can't out-gas like LiPo batteries can. So whatever gaseous chemicals might try to escape from the cell, they are forced to remain inside the cell until the battery is used and the chemical reactions that produce the electric charge are able to resume their reactions.
 

Gauss163

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I just did some web searching and here's a quote from Fran Hoffart, Applications Engineer for Linear Technology in Milpitas, CA, from an article entitled "Proper Care Extends Li-Ion Battery Life" from the April 2008 edition of Power Electronics: "For maximum storage life, batteries should be stored with a 40% charge (3.6 V) at 40°F..."

Another article from the "Battery University" site says, "
Do not worry too much about the state-of-charge; a cool and dry place is more important than SoC."

As always on the web, be very wary of claims made without any scientific basis. BatteryUniversity has been blacklisted by Wikipedia for this and other reasons, e.g. see this Wikipedia Talk entry (Reliability of Battery University as a source).
 

fyrstormer

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I'm not talking about destructive venting, I'm talking about the generation of gasses that remain inside the cell. LiPo batteries are encased in pouches which can stretch, allowing gasses generated during discharging to escape the chemical matrix of the cell, and only a small portion of those gasses will ever be reclaimed during recharging. Whereas, cells with metal cases don't stretch by any measurable amount, forcing gasses generated during discharging to remain embedded in the chemical matrix of the cell, where the reactions that produced those gasses can be more easily reversed.
 
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