Baterias Ni-Mh

[zointz]

Boas,
Não sabia muito bem onde colocar isto, mas básicamento é uma explicação dos problemas das baterias NI-MH dado por um expert conhecido no mundo dos Prius. Este material foi traduzido com o Google tradutor e alguns ajustes meus.
O texto em Português não está excelente pelo que recomendo a leitura do texto em inglês.


Fala das Baterias Ni-Mh do Prius

Existem dois tipos de efeitos Memória, Efeito de memória de Carga e Efeito Memória de descarga. Ambos estes efeitos são relativamente raros, mas eles acontecem e Toyota fez um trabalho realmente bom, em primeiro lugar, para detectá-los e, em seguida, para limpa-los. Vamos dar uma olhada no que os causa e como eles são "limpos".

EFEITO MEMÓRIA CARGA
Efeitos de memória de carga são causados ​​por descargas repetitivas antes da bateria receber uma carga completa em relação ao seu limite superior.
Quando isso acontece a bateria não é capaz de assumir uma carga completa e de fato, irá relatar uma carga completa via nível de tensão
muito antes de a quantidade normal ou apropriado de Amperes terem sido admitidos. Toyota tem um sistema que de forma muito eficaz segue a tensão vs amperagem I/O e pode discernir de forma bastante eficaz quando existe o Efeito Memória de carga. De fato a sua literatura
indica que eles podem isolar esses sintomas e começar a reparação
até três meses antes que se torne duradoura e prejudicial para a bateria.

EFEITO MEMÓRIA DE DESCARGA
Efeitos de memória de descarga são causados ​​por cargas completas repetidas sem uma descarga completa. Quando isso acontece a bateria não é capaz de descargar por muito tempo antes de indicar uma queda de tensão acelerada, quando na verdade, a amperagem entregue é muito abaixo do que a bateria deveria ter entregue antes de manifestar tais baixas tensões.

RECUPERAÇÃO NiMH TÍPICO
Geralmente a indústria lida com tais problemas NiMH admitindo uma carga excessiva (voltagens mais altas que o normal) e, em seguida, os descargas com tensão mais baixas do que normalmente, especialmente quando existem várias células ou módulos em série. Isso muitas vezes e de forma eficaz e traz todas as células ou módulos mais perto um do outro em termos de capacidas e limpa todos os efeitos de memória muito bem. O que isto também faz no entanto, é gerar, por meio de eletrólise, uma quantidade anormalmente elevadas de hidrogênio e de moléculas H2 e O2, que causam prejudiciais pressões internas para a célula ou módulo. Estes gases podem ser ventilados, mas, então você solta uma parcela de seu eletrólito e consequentemente, alguma capacidade assim, a maioria dos fabricantes tentam evitar condicionando as repetitiva de baterias NiMH.

Outras desvantagens
Outro efeito colateral negativo desse tipo de condicionamento é que se alguém fosse capaz de reter os gases contidos na célula ou módulo
então, durante a reação de recombinação química das moléculas, um aumento de temperatura dentro das células ou módulos provoca a deterioração acelerada a menos que seja aplicada uma carga estável e baixa. Esta carga baixa e estável pode ser aplicado ás baterias fora do Prius, mas a tentativa de aplicar este tipo de carga para um Prius em movimento é quase impossível sem afetar severamente tanto o desempenho como a eficiência do
Prius.
Da mesma forma que pedindo que o cliente,tivesse de fazer a manutenção das baterias atravez de algum aviso era algo que a
Toyota achou que poderia ser negativamente recebido e passou muito tempo encontrar uma solução melhor.



Texto Completo em Inglês

Yes, I can speculate, I just hope I can make it comprehensible when
I do. I think that it is very possible that she was in the midst of
clearing or cleaning up what Toyota calls an HV Battery `Discharge
Memory Effect.' There are two kinds of `memory effects;' `Charge
Memory Effect & Discharge Memory Effect. Both of these memory
effects are relatively rare but, they do happen and Toyota has done
some really nice work first, to detect them & then, to clear
or `clean' them up. Let's take a look at what causes them & how
they are `cleaned' up.

CHARGE MEMORY EFFECT
Charge memory effects are caused by repetitive discharges before the
HV battery receives a `full' charge in respect to its SOC upper
limit. When this happens the HV Battery is not able to take on much
of a charge & in fact, will report a full charge via voltage level
long before the normal or appropriate quantity of amps has been
admitted. Toyota has a system that very effectively follows the
voltage vs. amperage I/O & can discern quite effectively when
a `Charge Memory Effect' is presenting. In fact, their literature
indicates that they can isolate such symptoms & begin remedial
processing up to three months before it becomes lastingly
detrimental to the battery.

DISCHARGE MEMORY EFFECT
Discharge memory effects are caused by repetitive full charges
before the HV Battery experiences a full discharge in respect to its
SOC lower limit. When this happens the HV Battery is not able to
discharge for very long before indicating, via an accelerated drop
in voltage, that it can no longer be discharged, when in fact, the
amperage quantity delivered is far below what the HV Battery should
have delivered before manifesting such low voltages.

TYPICAL NiMH RECOVERY
Generally the NiMH industry handles such problems by admitting
excessive (higher voltages than normal) charges & then lower than
normal voltage discharges; especially when there are several cells
or modules in series. This often & effectively brings all the cells
or modules closer to one another in SOC range holding capability &
cleans up any memory effects pretty nicely. What this also does
however, is generates, through electrolysis, an abnormally high
amount of hydrogen molecules H2 & oxygen molecules O2, which cause
harmful internal pressures to the cell or module. These gases can
be vented but, then you loose a portion of your electrolyte &
consequently some capacity so, most manufacturers try to avoid
repetitive conditioning of NiMH batteries this way.

ANOTHER DOWNSIDE
Another negative side effect of this type of conditioning is that if
one were able to retain the gases contained in the cell or module
then, during the chemical recombination reaction of the molecules, a
fairly healthy temperature increase transpires within the cells or
modules which heat causes accelerated deterioration unless a very
stable & low rate charge is applied. This low, stable rate charge
can be applied to batteries outside the Prius but, attempting to
apply this kind of charge to a moving Prius is almost impossible
without severely affecting both the performance & efficiency of the
Prius. Similarly, asking the customer, via DTC or MIL warning
lamps, to bring the car in for battery conditioning was something
Toyota felt would be negatively received in many ways and spent a
lot of time finding a better solution.

TOYOTA'S REMEDY – MOVE TARGET SOC
Toyota has a unique & patented way to handle `memory effect' by
causing the HSD to administer a `Target SOC' that has been moved
into a higher or lower point than normal. Normally, the Target SOC
is held somewhere around 60% and the system attempts to hold it
below 70% & above 50%. I say somewhere around 60% because ambient
temperatures & HV Battery temperatures cause the Target SOC
to `crawl' around a little.

TARGET SOC FOR CHARGE MEMORY EFFECT
Because the `Charge Memory Effect' has resulted from repetitive
discharges before reaching a full charge, the HSD moves the Target
SOC up the scale. If the normal Target SOC were say 60%, it might
be moved up as high as 70% and the HV Battery SOC would be held for
a relatively long but, specific amount of time at a Target SOC of
70%.

This has the same effect as the application of excessive voltage but
has none of the side effects of generating excess H2 & O2 gases &
pressures or the heat of the recombination reaction. While
operating in this new Target SOC range, the Prius performs almost as
efficiently as it did while in the `normal' 60% Target SOC range and
the HV Battery is put under significantly less stress; a very nice
remedy indeed.

TARGET SOC FOR DISCHARGE MEMORY EFFECT
Discharge Memory Effects come from repetitive charges without
reaching the full SOC discharge state. To remedy this memory
effect, Toyota designed the HSD to move the Target SOC down from say
a normal 60% Target SOC to a 50% Target SOC. Then the Target SOC
is held here for an extended but specific amount of time. This too
is much easier on the HV Battery than the typical NiMH conditioning
method & allows the HV Battery to continue delivering a very
efficient service while it is going through its remedial process &
without having to take the Prius in for HV Battery conditioning.

TIGHTER SOC TARGET TOLERANCE
During these cleansing or clearing events, the ±10% limit above &
below the Target SOC is held much more tightly than when things are
operating in the normal 60% Target SOC. During the `normal' Target
SOC which is generally around 60%, the system will allow us to go
almost all the way to 80% and almost all the way down to 43% both of
which greatly exceed the ±10% band that they system tries to keep us
in most the time. The system however, seldom allows the ±10%
limits to be exceeded when going through a `memory effect' removal
process.

FINALLY
I believe it is very possible that your lady was experiencing the
effect of having reached the upper limit of around 60% SOC that was
being imposed upon her car as it had likely experienced a `Discharge
Memory Effect,' had a 50% Target SOC imposed upon it, reached 60%
SOC or above while coming home & coasting down her long driveway,
stopped to wait for the cat to cross the drive & then the HV ECU in
concert with the HV Batt ECU started trying to peel off the extra
amps and keep her car within the narrow lower limit of the SOC.
Again, when the Prius is going through one of these
cleansing `Target SOC' regimens, the upper & lower 10% tolerances
are much more stubbornly held to by the system and consequently the
system was being very persistent in getting her HV Battery back down
where it needed to be.

Best Regards,
Wayne

[O_volt]

Bom trabalho!
Vê se te corrigem o título...falta lá um "a"