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'[OT] Battery question'
2005\12\05@170447 by fred jones

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There are a lot of smart minds here so I thought I'd check with you all.  I
am interested in building a magnetometer.  I know that manufacturers
commonly use Gel Cell batteries because they are non-ferrous and won't
interfere with the mag.  With the power capacity to weight efficiency gain
with using a Nimh battery pack, I'm trying to find out if they are ferrous
or not.  Are there any battery experts here that know the answer?
Thanks,
FJ


2005\12\05@172443 by Mike Hord

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> with using a Nimh battery pack, I'm trying to find out if they are ferrous
> or not.  Are there any battery experts here that know the answer?

http://en.wikipedia.org/wiki/Nickel

Nickel is ferromagnetic.  Bad sign!

Mike H.

2005\12\05@172719 by Howard Winter

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Fred,

On Mon, 05 Dec 2005 16:04:45 -0600, fred jones wrote:

> There are a lot of smart minds here so I thought I'd check with you all.  I
> am interested in building a magnetometer.  I know that manufacturers
> commonly use Gel Cell batteries because they are non-ferrous and won't
> interfere with the mag.  With the power capacity to weight efficiency gain
> with using a Nimh battery pack, I'm trying to find out if they are ferrous
> or not.  Are there any battery experts here that know the answer?

Well I'm no expert, but I just tried a magnet on an NiMH battery (both of which I had beside my keyboard - sad
or what? :-) and it seems they have a magnetic casing, probably steel, which I think is the common way to
package most primary cells these days.  Duracells seem to give the same result.  If you can get old-fashioned,
non-leakproof "ordinary" cells, they will have a zinc casing with a cardboard wrapper so will be non-magnetic,
but I'm not sure they make them any more!

Cheers,



Howard Winter
St.Albans, England


2005\12\05@185448 by fred jones

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Ahh, good idea.  I was afraid of that.  Thanks!
FJ
-------------------------------------------------------------------------------------
Well I'm no expert, but I just tried a magnet on an NiMH battery (both of
which I had beside my keyboard - sad
or what? :-) and it seems they have a magnetic casing, probably steel, which
I think is the common way to
package most primary cells these days.  Duracells seem to give the same
result.  If you can get old-fashioned,
non-leakproof "ordinary" cells, they will have a zinc casing with a
cardboard wrapper so will be non-magnetic,
but I'm not sure they make them any more!

Cheers,



Howard Winter
St.Albans, England


2005\12\05@190556 by William Chops Westfield

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On Dec 5, 2005, at 2:04 PM, fred jones wrote:

> I'm trying to find out if [NiMH batteries] are ferrous or not.

Nickel is magnetic even without being ferrous; I don't know if there is
enough metallic nickel in NiMH batteries to matter.  OTOH, I think all
NiMH batteries that I've seen have been in steel cans, but I don't
know whether that's required...

Lithium Polymer would seem like a good candidate, aside from it's
tendency to explode :-(

BillW

2005\12\05@204123 by Steve Halla - VIR

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Ferrous materials, contain iron, and are therefore magnetic to some extent,
depending on the concentration of iron in the product.

Here is a list of chemicals found in NiMh batteries, here is an alphabetical
list:

Nickel - as nickel hydroxide
Nickel - as nickel oxide

Nickel - as nickel powder

Potassium Hydroxide

Sodium Hydroxide

Zinc - as zinc metal

Zinc - as zinc oxide

Zinc - as zinc hydroxide

Aluminum

Cobalt - as cobalt metal

Cobalt - as cobalt oxide

Cobalt - as cobalt hydroxide

Lithium Hydroxide

Manganese

Lanthanum

Cerium

Neodymium

Praseodymium

Steel - as battery container (mostly magnetic)



Regards,



Steve







{Original Message removed}

2005\12\06@143539 by Peter

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On Mon, 5 Dec 2005, fred jones wrote:

>
> There are a lot of smart minds here so I thought I'd check with you all.  I
> am interested in building a magnetometer.  I know that manufacturers commonly
> use Gel Cell batteries because they are non-ferrous and won't interfere with
> the mag.  With the power capacity to weight efficiency gain with using a Nimh
> battery pack, I'm trying to find out if they are ferrous or not.  Are there
> any battery experts here that know the answer?
> Thanks,

Nickel is magnetic but has no remanence. In theory you should be ok if
the batteries are very far away from the detector. 2 meters or so shoudl
do it.

Fyi the terminals of most discrete parts and ICs are ferrous and will
have a remanent field after being exposed to magnets (like the Earth)
for a while. If you care about this then you can degauss the circuit
(with care). If not, just mount it far from the sensor with the
batteries.

Peter

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