Post by thread:[OT] Battery question

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

> 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.

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

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

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

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}

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