Lithium ion batteries losing charge in iron mine? - Page 1
Forum section: electronics / beginners

author: Derick Freese
author_rank: Contributor
timestamp: September 21, 2015, 03:51:50 pm
content: I saw this post on another forum and thought it would be well suited to this place. No one has come up with an answer there, and I doubt anyone there is an EE there, so let's give this a shot.This is the original post:He also mentioned this in regards to what's being affected:Any ideas? One suggestion is that the iron is what's causing the effect, but I don't see how.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 21, 2015, 05:01:05 pm
content: I can think of a couple of possibilities, but none seem likely.1. Rapid pressure change as you went down the shaft caused mechanical stresses in battery/battery monitoring circuitry that resulted in warning. Don't know how deep the mine was, but you could possibly test this theory by letting the cameras sit on a high building for a few hours and then take the elevator down. Or do similar tests on a long airplane flight.2. Induced currents from the mine power system. Your were probably closer to high current supply lines than is typical in above ground situations.

author: Jeroen3
author_rank: Super Contributor
timestamp: September 21, 2015, 05:02:18 pm
content: High humidity? Condensation?

author: rt
author_rank: Regular Contributor
timestamp: September 21, 2015, 05:24:18 pm
content: Temperature drop? Lithium voltage will drop with temperature and in particular for high current draw (camera flash, etc).Although I thought mines often got warmer as you went down.In any case I think what these people need is a device for their batteries to extract that last drop of "wasted energy" when their camera cuts off ..... hmmmmrt

author: Derick Freese
author_rank: Contributor
timestamp: September 21, 2015, 05:31:42 pm
content: Temperature drop, maybe. I've never had an issue going from the roof of a tall building to the ground, so I doubt pressure changes are the issue. Mines do get cooler the lower you go, especially if they have started to flood. This was an abandoned mine, so no electricity. Someone did speculate that there could be differences in the magnetic field around the area, but I'm not sure if it would be strong enough to affect battery charge.

author: mij59
author_rank: Frequent Contributor
timestamp: September 21, 2015, 05:33:55 pm
content: High temperature affecting the battery gage of the camera, the battery gage sensing a high temperature but the battery still being cold.

author: Derick Freese
author_rank: Contributor
timestamp: September 21, 2015, 07:54:19 pm
content: After several hours of being in a mine, things have a chance to get acclimated to the temperature. The battery isn't going to be at much different of a temperature than the camera, especially if it were kept switched off until use. There might be high humidity, but it's still not going to be higher than the humidity here in Florida, which doesn't seem to affect my lithium batteries.I'm waiting for this gentleman to visit the mine again and see if the problem persists, and if it's just his cameras, or other lithium ion battery powered devices as well.

author: jitter
author_rank: Frequent Contributor
timestamp: September 21, 2015, 08:13:46 pm
content: Putting a battery inside an iron box won't cause it to suddenly drain, so an iron mine isn't going to do that either.To answer this question, a lot more data is needed than we are presented here. I'm thinking of things like temperature down in the mine and up top, duration of the visit, the time it took after going back to the surface for the charge level to return to normal, etc. Also I wonder about how the camera measures the charge level of the battery and if a sudden change in temp could lead to condensation that would affect that measurement.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 21, 2015, 10:09:35 pm
content: Note that there is no actual drain on the batteries since they recovered to a full charge indication when they returned to the surface. This is most likely a sensing problem, though it could be a voltage drop with no change in chemistry.

author: Derick Freese
author_rank: Contributor
timestamp: September 22, 2015, 06:51:30 am
content: Here's some more information:NC is North Carolina, USA, NS is Nova Scotia, Canada. Temperature is in Celsius.Both of these cameras a Canons, although one is a DSLR and one is a point and shoot. 5 degrees is pretty cold, plenty cold enough to cause condensation. I would expect other gear to have condensation issues, though.

author: Psi
author_rank: Super Contributor
timestamp: September 22, 2015, 07:02:52 am
content: Could be a bug/memleak in the code which is triggered by a rapidly changing reading for magnetic north from the imu due to so much iron.Yeah it's pretty far fetched, just the only thing I can think of.That, or maybe the magic cave pixies didn't like having their photos taken

author: Derick Freese
author_rank: Contributor
timestamp: September 22, 2015, 07:11:10 am
content: Spinning the camera around would do the same thing. The only reason a camera would know which way was north other than a compass is GPS. Since GPS doesn't work underground, it wouldn't know that magnetic north is deviating from normal.

author: Strada916
author_rank: Frequent Contributor
timestamp: September 22, 2015, 07:15:12 am
content: Could be due to strong magnetic fields. O0

author: Psi
author_rank: Super Contributor
timestamp: September 22, 2015, 07:16:56 am
content: Quote from: Derick Freese on September 22, 2015, 07:11:10 amSpinning it around is still slow compared to the change that could happen in a randomly magnetised area.In some situation's/interrupt interactions you only see bugs when things change drastically from instruction to instruction

author: pickle9000
author_rank: Super Contributor
timestamp: September 22, 2015, 07:21:56 am
content: First, no clue.Second, I hope to learn something, good thread just keep aliens out.

author: canibalimao
author_rank: Regular Contributor
timestamp: September 22, 2015, 07:22:13 am
content: That could be ghosts sucking all the energy in the battery to stay alive

author: TSL
author_rank: Regular Contributor
timestamp: September 22, 2015, 09:55:23 am
content: If this is an active mine it could be RF interference from the leaky feeder comms system

author: Derick Freese
author_rank: Contributor
timestamp: September 22, 2015, 12:34:35 pm
content: No, these mines are all abandoned. That's how you gain free access to a mine, you wait until it gets abandoned.

author: KerryW
author_rank: Regular Contributor
timestamp: September 22, 2015, 03:31:40 pm
content: My guess:The presence of large amounts of iron is increasing the inductance in the switching regulator circuit, requiring longer ON time to let the current build up. A lower battery voltage would also require a longer ON time. If the camera is determining battery state by the ON time required to regulate the voltage, it would think the battery was low.

author: Derick Freese
author_rank: Contributor
timestamp: September 22, 2015, 03:45:43 pm
content: I'm seeing if he has a multimeter to test battery voltage. Sure, it's an extra piece of kit to drag down the mine, but it's for SCIENCE

author: Derick Freese
author_rank: Contributor
timestamp: September 23, 2015, 04:42:16 pm
content: This might be the answer:http://www.ansto.gov.au/ResearchHub/Bragg/CurrentResearch/ScientificHighlights/Magnetismofbatteries/index.htm

author: nbritton
author_rank: Frequent Contributor
timestamp: September 24, 2015, 02:37:42 am
content: Quote from: Strada916 on September 22, 2015, 07:15:12 amSo far I'm liking this idea the most.https://en.wikipedia.org/wiki/MagnetiteGo stick a neodymium magnate over the battery to see if you can duplicate the effect. I don't think the magnate will damage the camera, but I would double check google just to be sure.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: September 24, 2015, 02:59:24 am
content: Lithium ion batteries are used in proximity to very strong rare earth magnets in the RC hobby, with no observed ill affects. Magnetic fields are very unlikely to affect the battery, but perhaps there is some Hall effect going on in the sensing circuit. If that were the case orientation relative to the field of the camera would matter. You probably hold the camera in a relatively consistent position when checking battery state (not upside down for example) so this might not have shown up in your first experiences, particularly if the field orientation was vertical.Next time down in the mine it might be worth seeing if 90 degree rotations of the camera in at least two orthogonal directions changes anything.