[Elecraft] K2 alive again, yay!

[jerry]

Li-Ion is not hard to manage.  With a standard BMS, all you need is a
voltage-regulated and current-limited wall wart - quite routine 
nowadays.

                    - Jerry KF6VB


On 2021-07-21 05:40, Louandzip via Elecraft wrote:
> Oops.  That commercial pack is LiFePO4, not Li-Ion.  Doh.
> W7HV.
> 
>     On Wednesday, July 21, 2021, 6:38:50 AM MDT, Louandzip
> <louandzip at yahoo.com> wrote:
> 
>   There is a protected Li-Ion pack for the K2 available. With Lio-Ion,
> proper battery management is essential.
> 
> https://www.batteryspace.com/custom-lifepo4-18650-battery-12-8v-4500-mah-57-6wh-7a-rate-w-pcb-and-connector.aspx
> I briefly looked at putting together a LiFePO4 pack for the K2, but
> haven't yet done anything with that idea.  LiFePO4 is more forgiving
> and more lead-acid-like in its care a feeding.  Lower energy density
> than Li-Ion, but still much better than lead-acid.
> 
> Lou W7HV
> 
> 
> 
> 
>     On Tuesday, July 20, 2021, 7:52:06 PM MDT, jerry <jerry at tr2.com> 
> wrote:
> 
>  On 2021-07-18 19:50, Douglas Hagerman via Elecraft wrote:
> 
>> Next step, adding the the immensely heavy internal lead-acid battery.
> 
> *** I wonder how hard it would be to add instead a much lighter
> lithium-ion
> battery pack?  Individual 18650 cells are now routine at 2.5A-H, and
> available up
> to 3.5A-H.  The technology has gotten standardized, and you can buy a
> BMS ( Battery
> Management System ) card off the shelf.  The only hard thing is spot
> welding the tabs.
> A 3S1P ( three cells in series, 1 in parallel ) pack would probably do
> fine.
> 
>   I just got back from the garage where I repaired such a pack.  It was
> out of an 85W
> cordless vacuum cleaner.  Just four cells.
> 
>     Like any battery, the voltage varies with charge.  These cells are
> about 4.2V fully
> charged, and 3.4 when dead.  For three cells, that would be 12.8V fully
> charged, and 10.2
> when it's time to recharge.
> 
>     I got all set up to weld the cell tabs for an ebike project.  The
> ratio of energy storage to battery weight is much better than 
> lead-acid.
> 
> 
>                       - Jerry KF6VB
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