"storage charge" for li-ion / 18650 - chargers and voltage

littlebattery

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Hey guys -

My question is regarding li-ion individual cells and storage charging - I cannot find a _single_ li-ion/18650 charger that is advertised as having a 'storage mode' - yet I see the same advice on storage, discharge down to around 40-50%.

I have a little background with li-po packs - for those it is drilled home that you really (REALLY) need to partially discharge / put a 'storage charge' on them if they will not be used for a while. I only use my li-po's a few times per year, so i have a "nice" RC-car style balanced charger that will discharge them down to 3.85 volts per cell (and then they go in a refrigerator :) )

Am I missing something? Do li-ion's degrade at full charge / temp to a much lesser degree than Li-po? Do I just not know how to search correctly [ :) ] ?

Anecdotally, I have a few 3400mah orbtronic ICR's, some from about 18 months ago, some new; none have seen a ton of use, but i do notice that the new ones are taking > 3000mah, and the 'old' ones are 2500-3000.

Thanks!

(FYI specifically i have a mix of protected ICR and unprotected IFR & IMR, mostly in 18650 size, a few 18350, cr123, and cr2; although I haven't found any info that is specific to charge, storage profiles for the different chemistries.)
 

HKJ

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My question is regarding li-ion individual cells and storage charging - I cannot find a _single_ li-ion/18650 charger that is advertised as having a 'storage mode' - yet I see the same advice on storage, discharge down to around 40-50%.

Very few charges have it, one is the SkyRC MC3000, but it is a rather expensive charger.
A "trick" is to discharge the battery and then charge it in LiFePO4 mode, then it will end up around 3.6V to 3.7V

Many people to not bother with storage mode, the cell will deteriorate a bit faster, especially when stored in warm places, when stored cool it is not that important.
 

Enderman

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Almost all RC lipo chargers have a storage mode that charges/drains your lipo to 50-75% capacity.
I don't know why few flashlight chargers have this feature, maybe because they assume you use the flashlight often and want to keep it topped off.
I would suggest you just drain the battery by turning the flashlight on for a bit if you plan to store it, and also store the lipo in a cool dark place like a closet or something.
Just as you do with potatoes!
 

littlebattery

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@HKJ thanks for the reference to the mc3000; yup looks like that does do storage. and yup $200 is pretty pricey.

What I'm thinking about doing short-term is picking up a garbage 4-slot 18650/universal charger off ebay ($10), remove the guts, and solder on an rc-plug & balance-connector in their place - to use with my existing RC li-po pack charger. A little more cumbersome than the mc3000, but setup for storage mode is pretty easy with the touchscreen model i have, so I hope it will work well as a 1-4cell ICR "pack".

I am hoping I can hold out for another 'advanced' charger until i find one that does cr2 through 18650 with no adapters.
 

StorminMatt

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Another option is to charge your batteries on something like a VP2, and pull them when the voltage reads 3.9-3.95V. They will then rest to about 3.8-3.85V. This DOES require babysitting, though.
 

Gauss163

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Another option is to use a general purpose CC/CV charger, e.g. the $35 RD DPS5015 50V/15A buck regulator discussed in this BLF thread on DIY bench power supplies.
RD_DPS5015_Constant_Voltage_current_Step_down_Pr.jpg
 

stephenk

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Another option is to charge your batteries on something like a VP2, and pull them when the voltage reads 3.9-3.95V. They will then rest to about 3.8-3.85V. This DOES require babysitting, though.
I just did something similar on the DRAGON VP4 Plus during a refresh cycle, pulled the cells at approx. 40% charge, and ended up with resting voltages in the 3.6V to 3.7V range.
 

Greebe

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Just curious if discharging to 3.8v or so is as effective as charging up to that same voltage with a charger that does a storage charge? I wonder if one way is better?
 

vicv

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only thing that matters is the voltage not how it got there. That's if you're worried about it. You already have a hobby charger. Just use that. Get a couple niobium magnets and stick cells to the alligator clamps with them. No need for building a slotted charging dock. For 18650 get one of the 4x18650 battery holders that hold the cells in parallel with 4 red and 4 black wires coming out. Works great for charging
 

iamlucky13

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Just curious if discharging to 3.8v or so is as effective as charging up to that same voltage with a charger that does a storage charge? I wonder if one way is better?

If you really want to split hairs, charging to full and then discharging to storage voltage means an extra cycle on the battery compared to charging to and stopping at the storage voltage in the first place, so the latter is hypothetically slightly better.

But we're talking about batteries in storage. The nature of this kind of use means you can not accrue very many cycles this way. And cycles that discharge only to around 50% at a moderate rate are not very stressful on the battery. The practical effect on long term battery life will be minuscule.

So unless somebody else is aware of anything significant that I forgot, I'd say do whichever is more convenient.
 

Gauss163

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From a health perspective it, it matters little if you start from above or below to reach SOC. The direction might play a small role in the actual SOC attained, esp. if the charger does not taper off the current at the end in order to better attain the target. But this too matters little since we do not need much precision for this purpose.

As a general rule of thumb, target 40-60% capacity for storage (higher the longer the storage time). The long term goal is to keep the cells balanced around the 50% capacity mark for as much of their life as possible, since this inhibits many internal processes that cause degradation.
 
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novarider

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only thing that matters is the voltage not how it got there. That's if you're worried about it. You already have a hobby charger. Just use that. Get a couple niobium magnets and stick cells to the alligator clamps with them. No need for building a slotted charging dock. For 18650 get one of the 4x18650 battery holders that hold the cells in parallel with 4 red and 4 black wires coming out. Works great for charging

A Lipo charger will charge 18650 batteries? Hmmm I have a very nice Lipo charger for my rc cars I never thought about using it for my flashlight batteries!

Where would I get one of these holders to use with my charger?
 
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Gauss163

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A Lipo charger will charge 18650 batteries? Hmmm I have a very nice Lipo charger for my rc cars I never thought about using it for my flashlight batteries!

You can use any CC/CV charger that is programmable to the proper termination voltage and charge current. This of course includes RC / hobby chargers, but also many cheaper general purpose CC/CV chargers.
 

novarider

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You can use any CC/CV charger that is programmable to the proper termination voltage and charge current. This of course includes RC / hobby chargers, but also many cheaper general purpose CC/CV chargers.

I may have to look into this. My rc setup is way over the top and a bit cumbersome to charge one or two 18650 batteries tho. It's a Cellpro powerlab 6 and I power it off of two computer server power supplies at 24V. Much easier to just plug in my Nitecroe d2 charger. I will have to do some thinking about this.
 

vicv

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A Lipo charger will charge 18650 batteries? Hmmm I have a very nice Lipo charger for my rc cars I never thought about using it for my flashlight batteries!

Where would I get one of these holders to use with my charger?

I can't post links but I'm sure if you search for it you'll find it
 

novarider

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Now I am researching using magnets to attach leads from my charger. This sounds very promising
 

novarider

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I meant soldering wires directly to the magnet. Just because you have seen something before doesn't mean everyone else has. I personally had no idea magnets were safe to use to conduct electricity.
 
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