EM waves drain batteries

[RichardR]

I have a friend whose batteries (car, truck, cellphone, cordless phone etc) always seem to go flat. He thinks there is some form of electro-magnetic wave (unspecified / unknown origin) around his house that is draining his batteries. I think he is just bad at remembering to charge his electrical equipment. Plus I think his car and truck batteries are old and when they go flat once they are likely to go flat again and really need replacing with new.

That said, I wonder if anyone here thinks it could make sense that some EM pulse could drain batteries. I seem to remember reading that after a nuclear attack the resultant EM pulse would cause most electronics to be fried, cars to stop etc. but always assumed this is because the electronic circuits would be fried, not the batteries. Does my friend's suggestion make any sense at all?

 

[Meffy]

I think it more likely he's using NiCd batteries and not discharging them all the way before recharging. That can reduce the charge capacity. Or maybe he's believing the battery life estimates given in product promotional material, which I think is often over-estimated (to put it mildly).

 

[patnray]

NiCads, especially, and lithium to a lesser extent, are very sensitive to improper charging cycles. They should be discharged as fully as possible before charging. When charging, charge fully. Do not charge for 10 minutes or so then disconnect, use the device, then reconnect to the charger.

Never, ever, put tap water in a lead-acid battery (cars and trucks). Always use distilled water. Tap water usually contains disolved minerals that can build up in the battery and create shorts between the plates. Lead-acid batteries, unless designed for "deep discharge", can be damaged by being completely discharged.

Even when properly cared for, rechargeable batteries do not have an unlimited life time. They will eventually have to be replaced. Also, all rechargeable batteries lose charge when not used.

It is far more likely to be a care and service issue than some mysterious EM field...

Edited for spelling/typo.

 

[Serenity]

I think it more likely he's using NiCd batteries and not discharging them all the way before recharging. That can reduce the charge capacity. Or maybe he's believing the battery life estimates given in product promotional material, which I think is often over-estimated (to put it mildly).

Keep in mind the NiCd memory effect is a myth, but you definitely want to avoid overcharging and deep discharging to prevent damage. See here:

http://www.repairfaq.org/REPAIR/F_appfaqe.html#APPFAQE_008

RichardR- As for batteries mysteriously discharging... on an episode of Ghost Hunters, it was noted that the investigators use the rapid depletion of batteries as evidence of spirits attempting to manifest themselves.

Seriously, I'd be surprised if an EM pulse is capable of that--I don't know, hopefully an engineer here could provide some insight. More likely your friend's charging efforts need to be looked at and/or his recollection of cell performance is biased.

 

[This Guy]

Keep in mind the NiCd memory effect is a myth, but you definitely want to avoid overcharging and deep discharging to prevent damage.

Years ago I over heard a store clerk at a Radio Shack I believe, explaining to a customer that there was a "memory chip" in Ni Cad batteries that caused them to go bad.

I started to say something, but under the circumstances, didn't feel it would be the thing to do. I knew the statement was wrong, but didn't know enough about how the batteries worked to explain why it was wrong.

As for the auto battery, should be easy to check the service date sticker on it. Most auto batteries have them, the stickers with the punch-outs that you remove to show the month/year the battery went into service. The battery likely shows it's expected service length. If it's near the end of that service length, it needs replacing. If it's early into the service length, there may be a problem in the electrical system. The alternator or regulator (regulators are often part of the alternators on newer cars) being the most likely suspects. Though the problem could be as simple as a dirty battery, causing a slow discharge between the terminals, or from the hot terminal to ground. Some soda water or baking soda and water, and an old tooth brush can do wonders for that. Often bad connections to the terminals are problems also. Loose or dirty terminals/connectors. There are metal brushes you can buy at auto parts stores that help clean the terminals, and the inside of the connectors.

Of course, it could be EM waves. He could put a tin foil cover on his autos and devices, and one for his head, as I'm sure EM waves would affect his brain also ;-)

 

[Dilb]

There's almost no way I can imagine an EM field draining a battery. Very strong EM radiation could cause it to heat up and increase the reaction speed, but that's a pretty obvious effect. Also, batteries tend to have metal around them (at least the little ones do, I'm not sure about car batteries), which shields the inside from almost any radiation less energetic than x-rays. Another way might be to iozine the air and provide a conductive path for electrons, but sparks are usually pretty obvious.

A battery is pretty much just a chemical reaction, and I don't know of any way to influence a chemical reaction with static EM fields either. I'd think nothing moves enough for magnetic fields to have an effect. Any electric field would be cancelled by the battery draining a tiny (unnoticeable) amount, building up a very small charge and restoring the normal voltage across it.

I highly doubt you can measurably effect a battery unless there's a path for electrons to flow.

 

[CaveDave]

NiCads, especially, and lithium to a lesser extent, are very sensitive to improper charging cycles. They should be discharged as fully as possible before charging.

No, they should be only discharged to their minimum per-cell voltage (which IIRC is 1.1 Volt/cell for NiCd and near that for other types (RTFM)
PLEASE read the _fine_ manuals that most batt. mfg's provide for the care and feeding of their products. They did not produce these just for their own amusement; you just *may* learn something useful, and get better service from your batteries than you expected!

When charging, charge fully. Do not charge for 10 minutes or so then disconnect, use the device, then reconnect to the charger.

Yes, that is true.
And always use a charger that is specified for the type, size, and rate-of-charge of the 'pack you are using. Complete the charge!

Never, ever, put tap water in a lead-acid battery (cars and trucks). Always use distilled water. Tap water usually contains disolved minerals that can build up in the battery and create shorts between the plates. Lead-acid batteries, unless designed for "deep discharge", can be damaged by being completely discharged.

Yes, that is absolutely true.

Even when properly cared for, rechargeable batteries do not have an unlimited life time. They will eventually have to be replaced. Also, all rechargeable batteries lose charge when not used.

Yes, that is true.

It is far more likely to be a care and service issue than some mysterious EM field...

Ditto.

Keep in mind the NiCd memory effect is a myth, but you definitely want to avoid overcharging and deep discharging to prevent damage. See here:

http://www.repairfaq.org/REPAIR/F_ap...ml#APPFAQE_008

Good reference and excellent point. Sam Goldwasser (and his contributors) has wonderful advice on a myriad of topics!

Years ago I over heard a store clerk at a Radio Shack I believe, explaining to a customer that there was a "memory chip" in Ni Cad batteries that caused them to go bad.

I started to say something, but under the circumstances, didn't feel it would be the thing to do. I knew the statement was wrong, but didn't know enough about how the batteries worked to explain why it was wrong.

As for the auto battery, should be easy to check the service date sticker on it. Most auto batteries have them, the stickers with the punch-outs that you remove to show the month/year the battery went into service. The battery likely shows it's expected service length. If it's near the end of that service length, it needs replacing. If it's early into the service length, there may be a problem in the electrical system. The alternator or regulator (regulators are often part of the alternators on newer cars) being the most likely suspects. Though the problem could be as simple as a dirty battery, causing a slow discharge between the terminals, or from the hot terminal to ground. Some soda water or baking soda and water, and an old tooth brush can do wonders for that. Often bad connections to the terminals are problems also. Loose or dirty terminals/connectors. There are metal brushes you can buy at auto parts stores that help clean the terminals, and the inside of the connectors.

Of course, it could be EM waves. He could put a tin foil cover on his autos and devices, and one for his head, as I'm sure EM waves would affect his brain also ;-)

All of the above is good advice.
Also, a bad automotive generator (rectifier sending AC to the batt. or regulator under- or over-charging will kill the batt.) . Heat is a lead-acid (and most other types) battery's worst enemy. Auto batteries fail during the summer, but reveal their failure in the winter.

Cheers,
Dave

 

[Meffy]

I don't know enough about the supposed NiCd memory effect to be sure whether it's mythical or not. I definitely get far better life out of my batteries using a charger that discharges each cell to a fairly low voltage first, then recharges to full. The reason behind it might be unrelated to the memory effect as usually described. ("Memory chips" notwithstanding! :-D)

Decades ago I built a Popular Electronics project that purported to "zap" memory-munged NiCd cells with a strong blast of current that (according to the project's story) would break up some internal chemical structure within the electrolyte. It worked almost every time, restoring close to full life to dozens of cells.

Now I use NiMH mostly, and the charger that can handle them and what NiCds I have left from the olden dayes.

 

[Ziggurat]

I have a friend whose batteries (car, truck, cellphone, cordless phone etc) always seem to go flat. He thinks there is some form of electro-magnetic wave (unspecified / unknown origin) around his house that is draining his batteries. I think he is just bad at remembering to charge his electrical equipment. Plus I think his car and truck batteries are old and when they go flat once they are likely to go flat again and really need replacing with new.

That said, I wonder if anyone here thinks it could make sense that some EM pulse could drain batteries.

No, it doesn't make sense. You need DC current to drain a battery. Electromagnetic radiation is, by definition, an AC electric field, and cannot drive a DC current directly. The only possible mechanism for contributing to draining the battery is if the field were somehow decreasing the resistance of some electrical pathway that allowed the battery to drain, such as ionizing surrounding air or directly heating the battery itself (which increases internal leakage current). But the magnitude of the EM radiation to do that would be HUGE, and there's nothing in anyone's house that could produce those kinds of fields by accident. Even if you wanted to do it on purpose, the worst you could do is just cook the things in a microwave, which probably isn't much different than sticking them in an oven, because the important mechanism is just going to be heating. You're going to get a bigger difference in the electrical resistance of air from changes in humidity than from any EM radiation you could possibly exposed to.

That having been said, rechargeable NiMH and NiCd batteries do have significant internal leakage currents, and will drain just sitting on the shelf much faster than alkaline batteries. That's why when you buy them, they always say to charge them before using for the first time, because they can't stay fully charged sitting on a shelf for months.

I seem to remember reading that after a nuclear attack the resultant EM pulse would cause most electronics to be fried, cars to stop etc. but always assumed this is because the electronic circuits would be fried, not the batteries.

That is correct. It's got nothing to do with the batteries themselves, because the currents involved aren't large enough. Old cars without any microchips probably wouldn't be affected at all, but it's hard to find those on the road now.

 

[Hellbound]

For more on EMP effects:

http://www.fas.org/nuke/intro/nuke/emp.htm

 

[Jimbo07]

You need DC current to drain a battery. Electromagnetic radiation is, by definition, an AC electric field, and cannot drive a DC current directly.

You mean, you haven't heard about the magic, invisible floating rectifiers?

 

[patnray]

No, they should be only discharged to their minimum per-cell voltage (which IIRC is 1.1 Volt/cell for NiCd and near that for other types (RTFM)
Dave

You are correct. That's what I meant to say. Excuse my awkward phrasing, and thanks for correcting it...

 

[MRC_Hans]

EM waves cannot directly discharge batteries, but they might interfere with connected electronics, making them draw excessive current. The imminent observation in such a case, however, would be malfunction of the electronic equipment (temporary or permanent), not battery life. Thus, quite apart from the unlikeliness that a certain household should be inside some strong EM field of unknown origin (again without observing the malfucntioning of various electrical and electronical utilities), the probability points in one or several of the following answers:

1) Inappropriate charging practices.
2) Purchasing substandard (and presumably cheap) batteries.
3) Unreasonable expectancies for battery duration.
4) Faulty observation.

Hans

 

[Dilb]

No, it doesn't make sense. You need DC current to drain a battery. Electromagnetic radiation is, by definition, an AC electric field, and cannot drive a DC current directly.

That's a bit off. AC is alternating current, and there's no need for an EM wave to actually have a current anywhere (although it will if it's propagating along a conductor). It's also possible to have a static electric field, and that won't drain the battery either. What you need is a current, and that involves some physical path for charge to flow.

True that an AC current shouldn't affect a battery either. It would damage it, but that's just an issue of batteries not behaiving like ideal circuit elements.

 

[Ziggurat]

That's a bit off. AC is alternating current,

Yes, I was being imprecise with my language - I meant the electric field of electromagnetic radiation is alternating. The point is, an alternating field doesn't produce a net flow of charge, unless (as pointed out above) you've got some magical invisible rectifiers floating around in the air.

and there's no need for an EM wave to actually have a current anywhere (although it will if it's propagating along a conductor).

I'm not talking about EM being a current, I'm talking about it inducing a current. Because at the end of the day, a battery (ANY battery) will only discharge if there's a current. It's possible that the current can be internal to the battery, but there's still got to be a current.

It's also possible to have a static electric field, and that won't drain the battery either.

Actually, that can, in principle, contribute to draining the battery. Typically there is some leakage current, though it's usually quite small, created by the electric field of the battery (even if it's only an internal leakage current inside the battery). Add on an additional static electric field and you can increase this leakage current. Adding on an alternating field, however, will produce no additional net current.

 

[CaveDave]

Decades ago I built a Popular Electronics project that purported to "zap" memory-munged NiCd cells with a strong blast of current that (according to the project's story) would break up some internal chemical structure within the electrolyte. It worked almost every time, restoring close to full life to dozens of cells.

Sounds like it was designed to burn off "whiskers" of electrode metal that can grow to short out the electrodes under some charging conditions.
from Sams repairfaq:
http://repairfaq.ece.drexel.edu/sam/aapsfaq.htm#adpsbat

NiCd Battery Pack Will Not Hold a Charge
This applies if the pack appears to charge normally and the terminal voltage immediately after charging is at least 1.2 x n where n is the number of cells in the pack but after a couple of days, the terminal voltage has dropped drastically. For example, a 12 V pack reads only 6 V 48 hours after charging without being used.

What is most likely happening is that several of the NiCd cells have high leakage current and drain themselves quite rapidly. If they are bad enough, then a substantial fraction of the charging current itself is being wasted so that even right after charging, their capacity is less than expected. However, in many cases, the pack will deliver close to rated capacity if used immediately after charging.

If the pack is old and unused or abused (especially, it seems, if it is a fast recharge type of pack), this is quite possible. The cause is the growth of fine metallic whiskers called dendrites that partially shorts the cell(s). If severe enough, a dead short is created and no charge at all is possible.

Sometimes this can be repaired temporarily at least by 'zapping' using a large charged capacitor to blow out the whiskers or dendrites that are causing the leakage (on a cell-by-cell basis) but my success on these types of larger or high charge rate packs such as used in laptop computers or camcorders has been less than spectacular. See the section: Zapping NiCds to Clear Shorted Cells.

and:

Zapping NiCds to Clear Shorted Cells
Nickel-Cadmium batteries that have shorted cells can sometimes be rejuvenated - at least temporarily - by a procedure affectionately called 'zapping'.

The cause of these bad NiCd cells is the formation of conductive filaments called whiskers or dendrites that pierce the separator and short the positive and negative electrodes of the cell. The result is either a cell that will not take a charge at all or which self discharges in a very short time. A high current pulse can sometimes vaporize the filament and clear the short.

The result may be reliable particularly if the battery is under constant charge (float service) and/or is never discharged fully. Since there are still holes in the separator, repeated shorts are quite likely especially if the battery is discharged fully which seems to promote filament formation,

I have used zapping with long term reliability (with the restrictions identified above) on NiCds for shavers, Dustbusters, portable phones, and calculators.

WARNING: There is some danger in the following procedures as heat is generated. The cell may explode! Take appropriate precautions and don't overdo it. If the first few attempts do not work, dump the battery pack.

Attempt sapping at your own risk!!!

You will need a DC power supply and a large capacitor - one of those 70,000 uF 40 V types used for filtering in multimegawatt geek type automotive audio systems, for example. A smaller capacitor can be tried as well.

Alternatively, a you can use a 50 to 100 A 5 volt power supply that doesn't mind (or is protected against) being overloaded or shorted.

Some people recommend the use of a car battery for NiCd zapping. DO NOT be tempted - there is nearly unlimited current available and you could end with a disaster including the possible destruction of that battery, your NiCd, you, and anything else that is in the vicinity.

There is more detail at the above link, near the bottom of the page.

Cheers,
Dave

 

[jj]

I can imagine one way an EM field would drain a battery. Power a transmitter with the battery. That will drain it.

Seriously, this sounds specious, to say the least. I'd pay more attention to how the batteries are stored, charged (if they are rechargable), and used.

Btw, NiCads did used to have memory effect, but that's mostly beat.

They do, however, especially with overdeep discharges, or even worse, cell reversal, have crystal growth that can puncture the separator. When that happens, bye-bye cell.

 

[Meffy]

CaveDave, you astonish me. That's exactly what it did, blast internal shorts. Huge capacitors weren't generally available back then -- not to hobbyists on low budgets anyway. :-} It was essentially a short-tolerant power supply. Never thought I'd see that info again. Thank you!

 

[Dilb]

Actually, that can, in principle, contribute to draining the battery. Typically there is some leakage current, though it's usually quite small, created by the electric field of the battery (even if it's only an internal leakage current inside the battery). Add on an additional static electric field and you can increase this leakage current. Adding on an alternating field, however, will produce no additional net current.

Got any sources for that? I'm not entirely convinced a battery will suffer leakage in a static electric field.. According to wikipedia (the only source I can find at the moment) the self discharge is non-current-producing, and is just the chemical reaction of the battery occuring. I can imagine some current due to conduction in the electrolyte, but is that current a significant part of the total leakage?

 

[CaveDave]

CaveDave, you astonish me. That's exactly what it did, blast internal shorts. Huge capacitors weren't generally available back then -- not to hobbyists on low budgets anyway. :-} It was essentially a short-tolerant power supply. Never thought I'd see that info again. Thank you!

Thanks, back at 'ya.
I found that (Sam's Repairfaq) about 2 years ago when I was researching battery charging, and ended up learning *far* more than I even suspected I didn't know

Ain't learnin' fun? It makes _my_ life worth livin'!

I think so.

Cheers,
Dave