Storage Voltage for A123 ANR-26650-M1A

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Storage Voltage for A123 ANR-26650-M1A

Postby markz » Thu Nov 03, 2016 11:18 pm

I got 3.65 is absolute max, 3.6 is ideal max, nominal is 3.3V and min is 2.0V
Should I store my A123's at 3.2V or 3.3V?

Having a battery pack already assembled what is the best way to determine the health of my batteries?
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Re: Storage Voltage for A123 ANR-26650-M1A

Postby eTrike » Fri Nov 04, 2016 12:49 am

With LiFe such as A123 it is important to measure to the hundredth of a volt. Not much capacity above 3.45Voc, nor much below 3.15Voc. 3.30+ is fine. As long as your cells don't have an issue causing high self discharge it doesn't matter much, but higher is better if so. I've lost a few cells stored at 3.0V...
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Re: Storage Voltage for A123 ANR-26650-M1A

Postby okashira » Sat Nov 05, 2016 2:42 am

3.2. check after two weeks for weak (ie, high self discharge) cells.

Like all other lithium ion chemistry's, LiFe likes to be stored at as low as possible SoC.
Low as possible means.. balancing the following parameters: 1. time of storage vs 2. self discharge of the cells vs 3. cell wear from a single deep cycle.

great quality modern cells like Panasonic cells (especially extreme high volume cells like Tesla Model S cells) have very low self discharge which means you can discharge them to 5% SoC (3.2V per cell or so) and leave them there for years.

But lower volume cells need a little more monitoring. A123's pouch cells are great in my experience, however. I've kept them stored for a year and they hold like a rock with no measurable voltage loss. Maybe their cylindrical cells are the same way.
A123, panasonic, sanyo, samsung, lg, sony, all of these I would feel good about discharging to 5% for long term storage.

Lower quality manufactures like all chinese.. headway, ping, thundersuck, etc etc etc... totally different story.
Last edited by okashira on Sat Nov 05, 2016 2:43 am, edited 1 time in total. View post history.
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Re: Storage Voltage for A123 ANR-26650-M1A

Postby arkmundi » Sat Nov 05, 2016 3:18 am

3.2 to 3.3 V is fine.
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Re: Storage Voltage for A123 ANR-26650-M1A

Postby agniusm » Sat Nov 05, 2016 3:19 am

Voltage says nothing elpecialy for lifepo4. I think it should be 40-60% SOC
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Re: Storage Voltage for A123 ANR-26650-M1A

Postby eTrike » Sat Nov 05, 2016 12:26 pm

markz wrote:Having a battery pack already assembled what is the best way to determine the health of my batteries?

Good answers given above, but I missed this line. Do as okashira said and check self discharge. I prefer to do this when full as the self discharge rates are easy to see within a few days. If you're between 3.4-3.15V the self discharge can be higher but hard to discern unless your meter is capable of thousandths. Good cells might lose 20mV (0.020) in 3 years at 3.3V IME. I've not seen data which reflects beneficial lower SOC for LiFe (comparing 3.3-3.2V, excepting >3.4V) though I have seen data showing DOD is mostly irrelevant and not affected like other chemistries. If anyone can share relevant research data please do.
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Re: Storage Voltage for A123 ANR-26650-M1A

Postby markz » Mon Mar 20, 2017 5:05 pm

I just had to come back to do a quick check on the numbers.

Voc means Voltage Off Charger?
3.45V down to 3.15V is where the majority of the battery lives, or put another way where most of the discharge area on the curve is?

Also I think I missed something, is a full charge 4.2V or 3.6V?



eTrike wrote:eTrike » Thu Nov 03, 2016 10:49 pm
With LiFe such as A123 it is important to measure to the hundredth of a volt. Not much capacity above 3.45Voc, nor much below 3.15Voc. 3.30+ is fine. As long as your cells don't have an issue causing high self discharge it doesn't matter much, but higher is better if so. I've lost a few cells stored at 3.0V...
Last edited by markz on Mon Mar 20, 2017 5:07 pm, edited 1 time in total. View post history.
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Re: Storage Voltage for A123 ANR-26650-M1A

Postby spinningmagnets » Mon Mar 20, 2017 6:48 pm

3.2V, and store in a cold place.
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Re: Storage Voltage for A123 ANR-26650-M1A

Postby eTrike » Mon Mar 20, 2017 7:35 pm

3.6V or 3.65V is max(though at 0°C you can charge to 4.2V according to an older datasheet). Yes, the bulk of capacity is between 3.15-3.45V.

Voc = Voltage open circuit (resting voltage)
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