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'[AD]: Battery surplus'
2001\04\26@140529 by jamesnewton

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The postal code for Tucson is 85710 for anyone who is interested in
calculating the UPS shipping cost. In fact, just click on this and enter
your City and Postal code.
wwwapps.ups.com/servlet/QCCServlet?action=packageinfo&origcountry=US&
origincity=Tucson&origpostal=85710

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{Original Message removed}

2001\04\26@144411 by Tcrist

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Ok, for people who are filtering out [OT]: but got the [AD]: after I changed
the topics, Tim's email address is
.....tcristKILLspamspam@spam@TRITRONICS.COM

I've set this email to reply to him so if you just hit reply, you should be
ok.

Tim is taking a chance on billing people for shipping here. If I find out
that anyone doesn't pay up, be prepared to get kicked off the list at least.

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{Original Message removed}


'[AD]: Battery surplus'
2001\05\07@215511 by Brian Reed
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I received my box of batteries today - sweet!

Has anyone determined the battery model used?  They seem to
be from BYD, one of two models.  From http://www.bydbattery.com
click on "Products List" and see AAA400 & AAA500.  The
"Nominal Capacity" of each is 400 or 500 respectively ... is that
a mAh capacity rating?

Thanks,

- Bri
-

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2001\05\07@220823 by Ethan Swint

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Most of the AAA NiMH batteries I've seen give a capacity of 500 - 600 mAh,
so that would be in the ball park.  If anyone got an extra box of these and
doesn't want all of them, I would like some (~20 packs or so?) for a home
hobby project.

Ethan Swint
.....Ethan_SwintKILLspamspam.....baylor.edu

{Original Message removed}

2001\05\07@221746 by Bob Ammerman

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Does anybody know a part number and source for the connector to mate with
the one on the battery? (both a PC mount connector and a wire tail
connector, preferably).

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

{Original Message removed}

2001\05\08@010532 by Bob Blick

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>Has anyone determined the battery model used?  They seem to
>be from BYD, one of two models.  From http://www.bydbattery.com
>click on "Products List" and see AAA400 & AAA500.  The
>"Nominal Capacity" of each is 400 or 500 respectively ... is that
>a mAh capacity rating?

I tested a pack and got 380mAH (19 mA for 20 hours) after charging it at
100 mA for 6 hours.

-Bob

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2001\05\08@075038 by Martin Wehner

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Hi everyone-

about a week ago, Tim Crist sent out boxes of batteries for the cost of
shipping only. I was one of the people who wanted to get one, but didn't
e-mail him fast enough.
He told me, however, that a few of the people received double-shipments by
accident.
Is there anyone out there willing to send me one of those boxes they received
by mistake?
My zip-code: 02171 (Boston area)
I am willing to pay shipping, even if it's all the way from the West coast.

Thanks-

       Martin



-------------------------------------------
Martin Wehner

e-mail: <EraseMEmartinspam_OUTspamTakeThisOuTcyclotomic.com>
web:    http://www.cyclotomic.com/~martin
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2001\05\08@093841 by Olin Lathrop

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> about a week ago, Tim Crist sent out boxes of batteries for the cost of
> shipping only. I was one of the people who wanted to get one, but didn't
> e-mail him fast enough.
> He told me, however, that a few of the people received double-shipments by
> accident.
> Is there anyone out there willing to send me one of those boxes they
received
> by mistake?
> My zip-code: 02171 (Boston area)
> I am willing to pay shipping, even if it's all the way from the West
coast.

I got a double shipment here in the Boston area.  These boxes are quite
heavy and a hassle to ship.  I don't know which town is 02171, but could you
come to Littleton Common to pick it up?


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olinspamspam_OUTembedinc.com, http://www.embedinc.com

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2001\05\08@102307 by Lawrence Lile

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Tim told me they were supposedly rated 550 mAH.

I've built up a 12V stack of them that is theoretically 10 Amp-Hours.

I'm probably going to build a charger based on the Maxim MAX713 charge
controller

http://dbserv.maxim-ic.com/quick_view2.cfm?pdf_num=1666

They have a reference design all ready for a NIMH charger that looks pretty
straighhtforward.  They also have the thing in kit form as an eval kit.  I
don't have a price yet on their eval kit, probably not expensive, though.

http://www.maxim-ic.com/BuyMaxim/Sales.htm

So far, I've been charging with just a voltmeter attached, with an old car
battery charger through a current limiting resistor.  I watch the voltmeter
for a negative voltage slope, then quit.    I know from reading datasheets
that NIMH batteries have a negative voltage slope when fully charged.  What
I'm unclear on is, is the negative voltage slope measured :

1.  When there is no charging current

or 2.  When charging current is flowing?

I find the voltage floating all over the place while these batteries are
charging, and I can't imagine finding the negative voltage slope after
watching the voltmeter wander up and down so much while charging with about
2 amps.  For instance, I watched the voltage during charging go from a peak
of 13.05 volts, down to 12.8 volts, back up to 13.1 volts, wander down to
12.9, then back up to 13.2.  All this time, the batteries had about 2 amp
charging current. No way they were near charged.    Anybody got any
clarification on this?


-- Lawrence Lile

{Original Message removed}

2001\05\08@105439 by David VanHorn

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>
>So far, I've been charging with just a voltmeter attached, with an old car
>battery charger through a current limiting resistor.  I watch the voltmeter
>for a negative voltage slope, then quit.    I know from reading datasheets
>that NIMH batteries have a negative voltage slope when fully charged.  What
>I'm unclear on is, is the negative voltage slope measured :
>
>1.  When there is no charging current
>
>or 2.  When charging current is flowing?

When charging current is flowing.
Also, the charging current is from a constant current source.
Otherwise, the small droop will be masked.
One further wrinkle, it's NICAD that has the negative droop.
NIMH just flattens out.


>I find the voltage floating all over the place while these batteries are
>charging, and I can't imagine finding the negative voltage slope after
>watching the voltmeter wander up and down so much while charging with about
>2 amps.  For instance, I watched the voltage during charging go from a peak
>of 13.05 volts, down to 12.8 volts, back up to 13.1 volts, wander down to
>12.9, then back up to 13.2.  All this time, the batteries had about 2 amp
>charging current. No way they were near charged.    Anybody got any
>clarification on this?

Charge from a constant current source, and all will be revealed. :)

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2001\05\08@112336 by Dan Larson

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On Tue, 8 May 2001 09:23:01 -0500, Lawrence Lile wrote:

>Tim told me they were supposedly rated 550 mAH.
>
>I've built up a 12V stack of them that is theoretically 10 Amp-Hours.
>
>I'm probably going to build a charger based on the Maxim MAX713 charge
>controller

I've used these chips for charging my robot battery packs. The MAX712 is the
device to use for NiMH because it terminates on zero slope. The MAX713 terminates
on a negative slope. Those are the only two differences between them. The only
down-side is that they will drop into fast charge for 15 minutes or so in a
power input glitch. I am actually using the MAX712 with the zero slope termination
on my NiCd packs simply because it terminates sooner. My robots sit connected to
there chargers when not in use so I don't like cooking those cells too long
and the 712 drops into trickle charge sooner, especially after a power glitch.

{Quote hidden}

I think the chips work by spacing samples out over many minutes, so the distance
between two samples can be as much as 15-20 minutes (IIRC) and I imagine that
this acts as a low pass filter and thus the longer intervals show the slope
better.

Dan

>
>
>-- Lawrence Lile
>
>{Original Message removed}

2001\05\08@160448 by goflo

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Been using 2 sets of 4, Sanyo NiMH 1500 mah for a couple
of years now in an old NEC portable. Avg load ~130 ma,
12-13 hours duration before low batt led, with regular
use - I've got a background utility running which tracks
time powered-up.

Chging scheme is LM239 configured as 1A constant-current
source (because that's what was in the junk box).

I monitor chging V & T - The batteries tracked the voltage
droop per the data sheet closely at first, but the effect
disappeared early on.

I was never able to observe the described temp behaviour.

What is very noticeable is the rate at which V_chg increases
with increasing ambient T.
I would'nt accuse my methods of rigor, but perhaps acquiring
predictable chging data requires a constant temp environment?

Hmmm, use # 819 for a Peltier beer chiller...

regards, Jack


David VanHorn wrote:

{Quote hidden}

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2001\05\08@162700 by Peter Tiang

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> I monitor chging V & T - The batteries tracked the voltage
> droop per the data sheet closely at first, but the effect
> disappeared early on.
>
> I was never able to observe the described temp behaviour.

   That's weird, did you observe the temp close
   to the cell or outside the battery pack ?

>
> What is very noticeable is the rate at which V_chg increases
> with increasing ambient T.

   If I remembered correctly, you should be
   monitoring the pack voltage when the current
   source is removed.

   This will take care of the voltage drop due to
   charging current which will vary with cell
   impedance (which is a function of T).

   Incidentally, this method of "pulsed" constant
   current charge is better at preventing dendrites
   formation in the battery cells.

> I would'nt accuse my methods of rigor, but perhaps acquiring
> predictable chging data requires a constant temp environment?

   As explained above.

Regards,
Peter Tiang

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2001\05\08@172508 by goflo

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Peter Tiang wrote:
>
> > I monitor chging V & T - The batteries tracked the voltage
> > droop per the data sheet closely at first, but the effect
> > disappeared early on.
> >
> > I was never able to observe the described temp behaviour.
>
>     That's weird, did you observe the temp close
>     to the cell or outside the battery pack ?

Thermocouple probe of a Wavetek 28XT taped to a cell.

{Quote hidden}

Checked the data sheet, no mention of measurement protocol.
I bet you're right. I'll give it a try, thanks.

regards, Jack

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2001\05\09@025140 by Peter Tiang

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> >     That's weird, did you observe the temp close
> >     to the cell or outside the battery pack ?
>
> Thermocouple probe of a Wavetek 28XT taped to a cell.

   At full charge the rate of change in cell temperature
   is typically only 1C/min. What's the resolution of your
   28XT (dependent on your thermocouple range) ?

   Most battery charger that supports dT/dt termination
   does so when the rate reached 1C/min or when a
   negative slope occurs.

{Quote hidden}

   I checked some 5 years old charging plots that
   I had, the voltage droop for NiMH is much more
   pronounced on the off-current curve than the
   on-current curve (almost flat).

> regards, Jack
>

Cheers,
Peter Tiang

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2001\05\09@152426 by goflo

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Peter Tiang wrote:

>     At full charge the rate of change in cell temperature
>     is typically only 1C/min. What's the resolution of your
>     28XT (dependent on your thermocouple range) ?

Display reads either 0.1 deg F or 0.1 deg C increments.

>     I checked some 5 years old charging plots that
>     I had, the voltage droop for NiMH is much more
>     pronounced on the off-current curve than the
>     on-current curve (almost flat).

Put a partially discharged pack on the chgr, periodically
interrupted the chg to measure V - Seems to behave as you
suggest. Droop point was about 30 mv lower than the data
sheet shows, but ambient T was near 90F...
Think I'll put an old computer to work running the chgr,
keep track of environmental factors, and see if the data
makes any sense.

Thanks for the help, Jack

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