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LiFePO4 chargers
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November 15th 18, 12:42 AM posted to rec.aviation.soaring
Graham Drinkell[_2_]
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Posts: 12
LiFePO4 chargers
At 20:09 14 November 2018,
wrote:
On Wednesday, November 14, 2018 at 2:56:35 PM UTC-5, kinsell
wrote:
On 11/14/18 9:03 AM, moshe... wrote:
On Tuesday, November 13, 2018 at 11:11:52 PM UTC-5,
kinsell wrote:
On 11/13/18 6:08 PM, bruce... wrote:
Mark, When K2 was fairly new on the market I contacted
them asking
if=
Battery Tender Jr. is okay and safe, they replied that it is perfectly
oka=
y and nearly the same as their charger. I also contacted Battery
Tender
Jr.=
with the reverse question and they said the BTJr is fine for
LiFePO4. I
us=
ed the BTJr for years on my K2 with no issues. They're about $25
on
intern=
et sites.
Have you measured the amount of charge you're getting into
the K2's?
=
It
will be considerably less than the rated amount due to using
lead-ac=
id
charger.
Also, if K2 has cell balancing capability, it won't be used
because
yo=
ur
Battery Tender doesn't put out enough voltage to make it
work.
=20
Many simple lead-acid chargers reach up to around 14.2-14.8
volts.
Tha=
t voltage would suffice to charge an LFP battery to well above 90%
capacity=
if it stays there for a while. If it quickly shifts to "float" at 13.5V
o=
r so then it won't do well in charging LFP. So simpler is better in
this
c=
ase. Measure what your charger does. And disconnect it after
several
hour=
s, don't leave it on "float".
=20
=20
Hate to break this to you, but at $24, the Battery Tender Junior
is one=
=20
of the cheapest chargers on the market, and is fully featured
with a=20
float mode.
=20
14.2 volts wouldn't begin to charge an LFP to "well over 90%" as
you=20
claim. If you found a charger that delivers 14.8 volts under
load, then=
=20
it would overcharge an SLA and would be considered defective.
=20
If you're going to spend big bucks for an LFP, you ought to get a
proper=
=20
charger for it. Still waiting to hear just how much charge the
K2's got=
=20
in them from a BTJ.
=20
-Dave
That's the conventional wisdom, but see experimental results he
https://www.powerstream.com/lithium-phosphate-charge-
voltage.htm
- well above 90% capacity even at a bit lower than 14V!
A cheap dumb 14.x volt fixed-voltage source with limited current
output
(an=
d perhaps aided by the battery's BMS) would charge an LFP just
fine. I'm
n=
ot saying that's the ideal charger, but in a pinch it would work well
enoug=
h. I am not happy with the several chargers I have that push SLAs
well
abo=
ve 14V (even above 15V), but they may be handy for LFPs.
Personally, I would fly a model aircraft with a lipo battery. Full
size, definitely not! They deform at high altitudes, with the
possibility of fracturing cells? The best bet is to use military spec
batteries that work in space?
Graham Drinkell[_2_]
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