[Elecraft] Internal Impedance of Li-Ion Battery Packs

[Bob]

Most LIFePO4 battery discharge curves are based on the full C rate

This is an example of a battery you might be interested in.  20 AH, 20 Amp
Max CONTINUOUS Discharge Current.  There isn't a good "standard" for what
the capacity is based on.  You need to check with each vendor.  LiFePO4
batteries are very Coulomb-efficient -- what goes in is what goes out, and
this tends to keep your capacity very close to rated values no matter what
the load is.  It also means that unlike SLA batteries, a LiFePO4 doesn't
get hot charging or discharging (at least not at 20 Amp values) -- this is
because the internal resistance is so darned low -- so there is little
wasted energy in a charge/discharge cycle.

My Bioennno 30 AH rated battery, tested at C/4 rate of 7.5 amps (the limit
of my test equipment), provided me with 29.88 AH of usable capacity, and
that was stopping the test at 12.00 volts, which is several volts higher
than absolute minimum (8.8 volts).  Speaking of which, I would highly
recommend you stop using your battery when the terminal voltage falls below
12.00 volts -- there will be very little remaining capacity at that point
anyway.


http://www.bioennopower.com/collections/12v-series-lifepo4-batteries/products/12v-20ah-lifepo4-battery

That 7 pound battery is $198 including the charger, and will outperform a
40 AH SLA battery (will last 5 to 10 times longer, will weigh 1/5th as
much).

73, Bob, WB4SON



On Mon, Aug 4, 2014 at 9:02 AM, Bob N3MNT <bob at hogbytes.com> wrote:

> Another *KEY* consideration, especially since you indicate it is a rare DX
> location ( I read as air travel required) is what you will be allowed to
> take on the plane.  Even if the battery meets your electrical and weight
> requirements it will be of little value if you can't get it There.  I echo
> the LiFePo selection as they a are safer and more closely alighed with the
> operating range of ham equip.
>
>
>
> --
> View this message in context:
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