Chmielewski, Artur wrote:
>
> Many thanx for your answers concerning Ni-Cd pack. I think the Relay cord
> will be better solution than new Ni-Cd pack. And much cheaper ;-)
If you have an source for an cheap relay cord, let me know. I would
like one, but I don´t think, that I could get one below EUR 25,-, DM
50,-, which is the price I´d recently payed for new NiCd cells in my
pack.
As the listmembers might remember did I ask for experiences with NiMH
conversons.
I self had an defective pack and to choose between NiCd or NiMH.
The shop clerk at Conrad told me that NiMH cells will be dead at
temperatures we had last week, below 0° C. The Duracel PDF document
suports this too.
He told me also, I should expect an much higher self discharge. Extreme
high self discharge was my mayor concern, because of my experience with
such an battery (a full charged battery was dead after two weeks) and
the fact, that I already had an pack with high selfdischarge.
Duracell claimed, that there is lower memory-effect than with NiCd cells.
I never hadn´t problems with this effect and NiCd batteries, so I this
didn´t influenced my decision.
Interesting was the opinon of an company specialiced in charging equipment,
Cadex:
"For applications requiring a rigorous recharging scheme, the NiCd is by
far the best-suited battery. In an industry that runs on three shifts and
requires multiple recharges per day, for example, a NiMH would only last
about six months, a period that would not even outlive the manufacturer?s
warranty period."
and
"Many Public Safety Sectors that have experimented with the NiMH are
switching back to the NiCd because the NiMH battery in a portable radio
simply cannot provide the cycle count needed. During transmit, a high-power
radio draws two or more amperes of current and the NiMH is unable to
deliver the energy over the expected service life of the battery."
I decided against the high rated 150mAH noname 9V battery, because I doubt
(the shop clerk also) that it will real deliver that more power compared
with batteries of renowned companies like Varta or Panasonic.
I bought 3 9V block a 120mAh from Panasonic (they where marked "Made in
Germany", does Panasonic make batteries in Germany or are this rebranded
Varta cells?).
Inside the blocks you will find only two battery capsules a 3 and 4 cells
and not 7 seperate cells.
So it´s not possible to create a 12 cell battery out of just 2 blocks. The
orgin of the battery might be interesting if Vartas 9V blocks are made in
the same maner.
I connected three capsules a 4 cells by soldering them together with there
metal stripes and separating the capsules with the plastic separators which
were used in the 9V blocks. Two leads were connected and the whole thing
was wraped into shrink tube, making it an stable, compact unit. Someone has
to be carefully with soldering the leads (diameter and routing), the heigth
of the battery should not execede that of the original to fit into the
housing.
The new battery had an size of 1/2 to 2/3 of the orginal and weight the
half, 60 grams v.s. 120 grams, but with an slightly higher capacity of 120
v.s. 110mAH.
I didn´t made an 18V battery out of just two 9V blocks, because this would
have made it neccesary to connect two unit via leads (less stable) and the
(theoretical) possibility of damage into the pack due to the higher voltage.
There might be still a reason to create an 18V NiCd pack:
"Equipment that does not make full use of the available battery power by
cutting off before the cells are discharged to one volt drastically reduces
the available run time. Tests on batteries from a certain brand of cellular
phone that cut off at 1.15 volts per cell measured residual capacities of
60% and more. Not only does a high cut off voltage withhold valuable
battery energy but it inflicts harm to a NiCd over time because the battery
is not being exercised through its normal use.
Such a battery should periodically be discharged to one volt per cell by
some other means to prevent memory."
The battery check light on the pack stops lighten at an voltage around 14V,
so recharging starts at an voltage of 1.16V per cell. 14 cells would be
used more extensively down to 1V per cell.
I hadn´t the chance jet to test the refited pack at low temperatures,
because outside temperatures have risen to 7°C. I´ll give you notice when I
know more.
Regards
Richard
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