# Re: [EVDL] How to Prolong Lithium-based Batteries - Battery University



## EVDL List (Jul 27, 2007)

*Re: [EVDL] How to Prolong Lithium-based Batteries - Battery University*

Hi Mark,

I'm not sure where you get 3.45vpc. My understanding was actually that the 3.6V limit has a lot to do with why LiFePO4 has a longevity advantage over Lithium Cobalt. Most iron phosphate cells I've worked with can actually withstand being charged to 4.2V like other cells, you just get very little additional energy storage going from 3.6V to 4.2V. From the manufacturer's standpoint, it's better to recommend a lower charge voltage so they can claim longevity than to specify a higher one and gain a couple % in specific energy (they'd still fall far short of lithium cobalt, but lose another major selling point).

In short, I think you're fine charging to 3.6.

-Ben



> [email protected] wrote:
> 
> > From: Mark Hanson <[email protected]>
> > Date: April 3, 2012 10:18:18 AM EDT
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] How to Prolong Lithium-based Batteries - Battery University*

=

Hi, (sorry, English is not my main language, but you can guess the main p=
art.)
=

>From what I have learnt it is probably also the electrolyte and it dont lik=
e "high voltages" + if it stays a long time at that stage. =

=

So if you have it for "float charge", say higher than 3.4, "forever", or ve=
ry long balancing times at low current, then I guess the damages will be to=
the electrrolyte in some kind of breakdown process there, and not due to t=
he "overcharge" or metal plating, not a overcharge in terms of Ah, bacause =
when they are full...they are full. At least in my experience they act almo=
st like a "capacitor" in the end of charge, so when you reach somthing lik=
e 3.50 (if charged at low rates) the voltage sudenly start to rise very sha=
rp when its "full", and almost all ions have probably now moved to the new =
place, But If you charge a cell at very high rates, it might also need the=
TIME to move down from the surface, similar to acceptance-phase in lead ac=
id, But I dont know how it is at a nano-scale. I dont know for sure what is=
happening in the structure after high rate chaging,, but it seems like it =
take some tiiiiime for the ions to find the right places much deeper down f=
rom the top surface and move in to the electrode material... =

=

Just guessing, based on some lab experience with lifepo4.
=

BTW, Thundersky SUCKS at winter temperature and the datasheets was a lie, =
at only -30 degrees C they are totally terrible in its discharge performanc=
e, =

I would not recomend using them at "high" rates below +10=B4C (inner cell t=
emp), or not above 0.3C @ 0 Degrees Celcius or below. =

Dont charge more than 0.3C at room temp, litium metal plating/dendrites mig=
ht permanent reduce its capacity, or in the long run..even might cause a fi=
re(?).
=

and no charging, at any rate below 0 or +5=B4C or so. It seems like it caus=
es permanent capacity loss. (lithium metal plating on the surface?) =

=

Do not touch the leaking electrolyte from the bad seal/cap, =

=

(or any leaks, condensing fumes from fire enter in to you lung e.t.c.) it p=
roduce one very nasty acid in contact with the water in your body (its not =
a "strong" acid, so you probably dont feel it first, but it can do very nas=
ty things to the body, even with its delayed effects of maybe 10-20 hours o=
r more it can do things in the blood and bone.... =

:-/ =

=

Protect the eye, as it probably can do terrible damages there very fast, I=
guess in seconds! =

=

=

Some facts and (warning) picture: http://www.medicalcare.se/pdf/EAPCCT2007_=
PosterNS.pdf ) =

=

http://en.wikipedia.org/wiki/HF_acid
=

=

/J
=

=


> From: [email protected]
> Date: Tue, 3 Apr 2012 22:34:54 -0400
> To: [email protected]
> Subject: Re: [EVDL] How to Prolong Lithium-based Batteries - Battery Univ=
ersity
> =

> Hi Mark,
> =

> I'm not sure where you get 3.45vpc. My understanding was actually that th=
e 3.6V limit has a lot to do with why LiFePO4 has a longevity advantage ove=
r Lithium Cobalt. Most iron phosphate cells I've worked with can actually w=
ithstand being charged to 4.2V like other cells, you just get very little a=
dditional energy storage going from 3.6V to 4.2V. From the manufacturer's s=
tandpoint, it's better to recommend a lower charge voltage so they can clai=
m longevity than to specify a higher one and gain a couple % in specific en=
ergy (they'd still fall far short of lithium cobalt, but lose another major=
selling point).
> =

> In short, I think you're fine charging to 3.6.
> =

> -Ben
> =

>


> [email protected] wrote:
> > =
> 
> > > From: Mark Hanson <[email protected]>
> ...


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