battery test, do magnets deplete the charge?

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jon_slider
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battery test, do magnets deplete the charge?

I often store a flashlight attached to a magnetic cell phone holder in my car. The magnets are high strength Neodymium.
I use AAA Eneloop Pro batteries.

Someone suggested that the magnet would drain the battery.

So I did a 1 week test
After 7 days, an AAA Eneloop pro battery stored on a magnet dropped 7.3% in voltage from its fresh charge voltage.
A control battery, Not stored on a magnet, dropped 7.6% from its max voltage fresh off the charger.

conclusion,
storing a flashlight or battery, attached to a magnet does NOT speed up self discharge rate. If anything, the magnet actually helps the battery hold its charge better.

the difference in voltage drops between the two batteries was that the battery NOT on a magnet discharged 4% MORE than the battery stored ON a magnet. Imo the voltage differences are normal variation between cells, but there is certainly no Negative effect from storing a battery, or light, on a magnet.

Edited by: jon_slider on 05/17/2017 - 15:47
CRX
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What about li-ion cells? We need a test with them too.

SoCalTiger
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That’s a really smart idea to store the light on a magnet so that’s it’s not just rolling around in my glovebox or something. Good to know that there don’t appear to be any negative effects.

jon_slider
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CRX wrote:
What about li-ion cells? We need a test with them too.

Please do a test, and share your results
wolfdog1226
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Thanks,,,,,,,,,,,,,That is interesting. It makes me think how my Olight S10/S20 fare by always being attached to a vent and the vanity in the bathroom. It does not seem to affect them one bit. I would think if it did Olight and other dealers would not make them that way.

Obviously they have magnets on the bottom. A little different scenario. Your magnet most likely is stronger.

S20 on ML ~ 16 hours/day!

S10 used to shine on my Jimi Hendrix watch for my daily stretches. easier than using my phone app!! That “dummy” vent needs cleaning!

A failure is not a failure unless we fail to recognize that something needs to be changed.

CRX
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jon_slider wrote:
CRX wrote:
What about li-ion cells? We need a test with them too.
Please do a test, and share your results

Being honest I have strong magnets on a lot of my modded lights for years and have noticed no discernible effects in any chemistry although I haven’t done a specific test.

MorePower
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Magnetic fields will not affect the ability of any alkaline, NiCad, NiMH, or lithium ion cells to hold a charge. There’s no need to do any further testing.

sbslider
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MorePower wrote:
Magnetic fields will not affect the ability of any alkaline, NiCad, NiMH, or lithium ion cells to hold a charge. There’s no need to do any further testing.

agree with this, I would have questioned a result that showed otherwise. I would add this is for a static magnetic field, which the magnet produces. Not sure if a time varying magnetic field has an effect, but certain a static one would not.

btw, that is a nice way to keep a light at close hand.

MorePower
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sbslider wrote:
MorePower wrote:
Magnetic fields will not affect the ability of any alkaline, NiCad, NiMH, or lithium ion cells to hold a charge. There’s no need to do any further testing.

agree with this, I would have questioned a result that showed otherwise. I would add this is for a static magnetic field, which the magnet produces. Not sure if a time varying magnetic field has an effect, but certain a static one would not.

btw, that is a nice way to keep a light at close hand.

It shouldn’t matter whether the field is static or dynamic. The chemically stored energy in any of the consumer battery types will be unaffected.

RAW74
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Nice test, didn’t think a magnet would have made a difference in self discharge. By the way, did you get the airbag recall done on your Subaru? My shop has been doing a bunch of them for the past year! -Rick

jon_slider
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MorePower wrote:
There’s no need to do any further testing.

Thanks for your opinion. Please add evidence I can share with a friend who is a network security expert, that made the opposite claim, also without evidence.

RAW74 wrote:
. did you get the airbag recall done on your Subaru?

Yes. Thanks for checking Smile
MorePower
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jon_slider wrote:
MorePower wrote:
There’s no need to do any further testing.
Thanks for your opinion. Please add evidence I can share with a friend who is a network security expert, that made the opposite claim, also without evidence.

I realize that on the internet anyone can claim to be anything so there’s no reason for you to believe me, but I base my statement on 15+ years experience doing research and development work on batteries as well as what I learned in the numerous chemistry and physics classes I took to complete my degree in engineering.

As an aside, NiMH state of charge can’t be accurately determined by an OCV measurement, so the percent change noted in the first post doesn’t mean the cells lost over 7% of their hot off the charger capacity. Also, there’s enough variability in manufacturing that you’d need to test a lot more cells than a 1 to 1 comparison to determine whether any actual differences exist.

wolfdog1226
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^^
Looks like some of the quotes got mixed up!

A failure is not a failure unless we fail to recognize that something needs to be changed.

MorePower
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wolfdog1226 wrote:
^^ Looks like some of the quotes got mixed up!

Fixed it. Thanks.

jon_slider
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MorePower wrote:
I base my statement on 15+ years experience doing research and development work on batteries as well as what I learned in the numerous chemistry and physics classes I took to complete my degree in engineering.

Thanks, I believe you, but your comment is hearsay if I tell my friend your opinion.

How about a link that would be more than opinion?:-)

Otherwise, my test is the only evidence I have, and you are discrediting my effort but offering nothing in return.

See why your opinion is not evidence?

MorePower
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jon_slider wrote:
MorePower wrote:
I base my statement on 15+ years experience doing research and development work on batteries as well as what I learned in the numerous chemistry and physics classes I took to complete my degree in engineering.

Thanks, I believe you, but your comment is hearsay if I tell my friend your opinion.

How about a link that would be more than opinion?:-)

Otherwise, my test is the only evidence I have, and you are discrediting my effort but offering nothing in return.

See why your opinion is not evidence?

I completely understand where you’re coming from. Here’s a link about what types of chemical reactions may be impacted by magnetic fields.

Batteries store energy in chemical form, whether primary or rechargeable. When a circuit is completed, ions within the battery move, carrying charge, which allows a current to flow through the circuit. Self-discharge in rechargeable cells is due to side reactions that occur which “use up” the active materials that the battery uses to generate power. Static magnetic fields don’t have an impact on the speed of these side reactions, since they don’t involve radical pairs. The reactions that generate power also don’t involve radical pairs, so magnets won’t have an effect on them either.

jon_slider
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MorePower wrote:
Here’s a link about what types of chemical reactions may be impacted by magnetic fields.

Batteries store energy in chemical form

super helpful, Thank You
I have a lot more confidence now in being able to communicate effectively about the non effect of storing a battery on a magnet

much appreciate your time and understanding
have a Magnetic weekend! LOL