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'Battery self discharge....'
1997\10\14@172439 by Steve Smith

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In a message dated 14/10/97  20:03:55, you write:

<<   Now, another question ...

        Do nicads self-discharge when not in use ?
                If yes Then
                        this method becomes half useless
                End If
        Loop
 >>
Yes all secondary cells have a self discharge rate found in the battery data
sheets and generally expressed as n/C where C is the capacity in AH uasally
at the 10 hour rate and n the percentage of self discharge over a giiven time
eg .001 per day ect.
Nicads have lower self discharge rates than NiMh battries but are prone to
develop a 'memory' if only charged and discharged to part of their capacity
by far the best soulition to self discharge is a sealed lead acid battery but
the power to weight raito is much lower than Nicads very useful in stationary
aplications but not so good in portable equipment. (remember the old Luagable
telephones) lead acid battries.
Charging methods can be optimised to reduce cell memory in Nicads by using a
discharge cycle to ensure the battery is flat before commencing a charge
cycle.
It may be worth taking a look at Cyclon battries sealed lead acid but with a
very high discharge rate and very good power to weight raito made by Gates
energy products in US. These can be opperated in any orientation and give a
life expectancy in excess of a sealed Nicad the self discharge values are
very low on this product also.


Cheers Steve.........

1997\10\15@105019 by Matt Bonner

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Steve Smith wrote:
>
> In a message dated 14/10/97  20:03:55, you write:
>
> <<   Now, another question ...
>
>          Do nicads self-discharge when not in use ?
>                  If yes Then
>                          this method becomes half useless
>                  End If
>          Loop
>   >>
> Yes all secondary cells have a self discharge rate
..snip..
> It may be worth taking a look at Cyclon battries sealed lead acid but with a
> very high discharge rate and very good power to weight raito made by Gates
> energy products in US. These can be opperated in any orientation and give a
> life expectancy in excess of a sealed Nicad the self discharge values are
> very low on this product also.
I've recently been playing with rechargable alkaline.  Apparently they
have a low self-discharge (they're already charged off-the-shelf), have
no memory problems, can be recharged up to 150 times.  I don't know
their energy density, but it's at least as good as NiCad.  Need their
own type of charger, though.
--Matt

1997\10\16@214825 by Dave Mullenix

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Matt wrote:

>I've recently been playing with rechargable alkaline.  Apparently they
>have a low self-discharge (they're already charged off-the-shelf), have
>no memory problems, can be recharged up to 150 times.  I don't know
>their energy density, but it's at least as good as NiCad.  Need their
>own type of charger, though.

I did some experiments with these batteries when they first came out.  I
used a set of four penlights to power a pocket LCD TV.  I'd turn the TV on
and let it run until it turned itself off and note the time.

After 25 discharge/charge cycles, their capacity was down to that of a set
of NiCads.  This seems to be consistent with what the manufacturer claims
for their lifetime.

They'll do better if they're recharged before they's run completely down.
NiCads are the only batteries that thrive on deep discharge cycles.

Dave

1997\10\17@090210 by Jack Warren

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>
> NiCads are the only batteries that thrive on deep discharge cycles.
>
> Dave

Careful.  I know you mean 1 volt per cell when you say "thrive on deep
discharge cycles".  You can discharge a single Ni-CD cell to 0 volts, but to
do that with a battery (2 or more cells) WILL reverse charge the weakest one.
After that, the pack is rather worthless...


Jack Warren
(I REALLY like the Rayovac Renewals!!!)

1997\10\17@090411 by Andy Kunz

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>They'll do better if they're recharged before they's run completely down.
>NiCads are the only batteries that thrive on deep discharge cycles.

There's a lot to getting the most from NiCd's (NiCad is a Sanyo TM, btw).
Anybody interested should ask on newsgroup rec.models.rc.land and see the
flurry of confusion it generates.

Andy

==================================================================
Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865
         Hardware & Software for Industry & R/C Hobbies
       "Go fast, turn right, and keep the wet side down!"
==================================================================

1997\10\17@090830 by Andy Kunz

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>Careful.  I know you mean 1 volt per cell when you say "thrive on deep
>discharge cycles".  You can discharge a single Ni-CD cell to 0 volts, but to
>do that with a battery (2 or more cells) WILL reverse charge the weakest one.
>After that, the pack is rather worthless...

R/C Car racers (including pros) will discharge their packs to 0V per cell,
and connect the + to - terminals (multiple cells) together for storage.
NiCd's do not like to be stored with a charge.

I typically run my packs down to .8V at 60A before recharging.

Andy

==================================================================
Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865
         Hardware & Software for Industry & R/C Hobbies
       "Go fast, turn right, and keep the wet side down!"
==================================================================

1997\10\17@142035 by Eric van Es

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Andy Kunz wrote:

> >They'll do better if they're recharged before they's run completely down.
> >NiCads are the only batteries that thrive on deep discharge cycles.
>
> There's a lot to getting the most from NiCd's (NiCad is a Sanyo TM, btw).
> Anybody interested should ask on newsgroup rec.models.rc.land and see the
> flurry of confusion it generates.
>
> Andy

Aye - see what its gone and done to this here list!

--
Eric van Es               | Cape Town, South Africa
spam_OUTvanesTakeThisOuTspamilink.nis.za | http://www.nis.za/~vanes
LOOKING FOR TEMPORARY / HOLIDAY ACCOMODATION?
http://www.nis.za/~vanes/accom.htm

1997\10\19@201505 by Dave Mullenix

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Just a note on Renewal rechargable alkaline cells:

I live in Madison, Wisconsin, home of Ray-O-Vac, and they provided a speaker
for our local ham club.  He stated that one of the reasons Ray-O-Vac decided
to get into rechargeable alkaline cells is because their research showed
that ham radio operators are almost the only people to ever get anywhere
near rated lifetime from their nicads.  This is because they habitually
carry a spare battery pack and run each pack down to zilch before switching
to a fresh pack.  (We don't discharge to the point where a cell might be
reversed, of course.)

He said that most people buy nicads, use them a few times, grossly
overcharge them between uses or take them out of the charger before they're
fully recharged and consequently find the cells are dead after five or ten
recharge cycles.  They figured that Renewals, which give at least 25
recharge cycles before they're down to nicad energy levels, would give most
users the best buy for their money.

One other tidbit I picked up: the difference between ordinary dry cells and
heavy duty dry cells is that the heavy duty dry cells have slighty purer
chemicals.  I always wondered about that.

Dave, N9LTD

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