nuckolls.bob(at)aeroelect
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 Posted: Wed Aug 12, 2020 8:19 am Post subject: ETX36D Charge/Discharge studies at 13.0 to 15.0 Volts |
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Okay, just finished the series of plots on the
ETX36D battery that EarthX donated to the cause
a few years back.
Did a series of charges at 13.0 to 15.0 volts with
constant current power supply. Note in the charge
plots, the voltage climbs slowly as the battery
charges but takes an upward 'jump' as the battery
achieves full charge and the BMS unhooks the battery
terminating the charge. Voltage rises to the power
supply's set point.
Note that ALL plots from 13.5 to 15.0 push enough
energy into the battery for the BMS to say "halt".
The 13.0 plot produces no such effect.
The discharge plots are similarly interesting.
Note that no matter what voltage of 13.5 or
greater, the battery acquires the same amount
of energy.
At 13.0V, energy imparted is about 1.8 AH,
a small fraction of the otherwise 11 AH full
charge.
From this experiment I deduce that the battery's
BMS considers 13.5 / 4 = 3.35 volts per cell to
be the full-charge target.
I further observed that the when connecting
the discharged battery to a 13.0 volt, 5A
supply . . . the initial charge current rose
to 5 amps! It just didn't stay there very
long. I need to get a multi-channel DAS
up and running so we can see voltage and
currents plotted together.
Nonetheless, I think it reasonable to assert
that fiddling with the voltage regulator on
the Revmaster engine with some hopes of
mitigating damage to a demonstrably FRAGILE
PM alternator is not useful. I have
further thoughts on that issue for a later
post.
Further, these experiments show that for
batteries fitted with an agile BMS, raising
the bus voltage will NOT offer the user
greater access to any un-exploited potential
for chemical energy storage.
Finally, fiddling with the voltage regulator
when substituting a BMS fitted battery into
an SVLA's system is of no benefit. The voltage
regulator can continue to supply ship's needs
while the battery takes care of itself.
I just received some new, A123 cells that I'll
survey for any variation in what we've seen
with the consumer product cells tested so far.
Bob . . .
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