Can Mixing Different Battery Brands Damage Your Devices?

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The discussion highlights several common myths encountered in electrical engineering, such as the belief that mixing battery brands can damage devices and that leaving a car battery on a cement floor will drain it. It also addresses misconceptions about safety during electrical storms and the functioning of cell phones. The idea that a rubber strip can make a car invisible to police radar is humorously noted as a favorite myth. Additionally, the conversation touches on the concept of a car acting as a Faraday cage, providing some safety from lightning. Overall, these myths reflect a mix of misunderstandings and outdated beliefs in the field.
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These are some of my favorite myths I have encountered in my EE career...

1. NEVER mix Duracell and Eveready batteries in the same flashlight
2. Never leave your car battery on a cement floor, it will ground out and drain itself ( A metal shelf on concrete is OK)
3. Never use a wireless phone during an electrical storm
4. You are safe from lightning in a car because it isn't grounded
5. Cell phones use satellites to communicate (what are those big towers for?)
6. I need 100 ohm coax so I will just use 2 50 ohm pieces in series

MY FAVORITE:
7. For $20 you can by a rubber strip at the truck stop to ground your car and make it invisible to police radar. (Watch out for lightning though..)
 
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manzana said:
2. Never leave your car battery on a cement floor, it will ground out and drain itself ( A metal shelf on concrete is OK)
Someone posted a thread about this recently. The problematic claim was worded, "Never leave a car battery on a cement floor. It will ruin it." The last sentence is ambiguous, but is meant to warn that fumes from the battery will ruin the cement floor. But, because of the ambiguous wording, it's easy to suppose it means the cement floor will ruin the battery.
 
manzana said:
These are some of my favorite myths I have encountered in my EE career...

1. NEVER mix Duracell and Eveready batteries in the same flashlight
2. Never leave your car battery on a cement floor, it will ground out and drain itself ( A metal shelf on concrete is OK)
3. Never use a wireless phone during an electrical storm
4. You are safe from lightning in a car because it isn't grounded
5. Cell phones use satellites to communicate (what are those big towers for?)
6. I need 100 ohm coax so I will just use 2 50 ohm pieces in series

MY FAVORITE:
7. For $20 you can by a rubber strip at the truck stop to ground your car and make it invisible to police radar. (Watch out for lightning though..)

Those are pretty good. I've heard many of them, and yes they are pretty silly. What's worse is barring cell phone usage at gas stations (petrol stations) citing safety reasons. That's just a load of hooey.

There might be a touch of truth to #1 though. When you change batteries, preferably you should change them together and use batteries of the same brand. The issue is that since the battery cells are in series, as is typically the case with a flashlight ("torch" for all you European yahoos people), as the battery depletes there is a real chance that the cell with the least amount of charge will find its polarity reversed. When this happens it will very likely corrode and may damage the flashlight (torch).
 
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manzana said:
4. You are safe from lightning in a car because it isn't grounded

there's a lot of truth in this one as well. BUT NOT because it isn't grounded, but because it is a reasonable Faraday cageDave
 
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davenn said:
but because it is a reasonable Faraday cage
Poor Faraday, why are there some many people that want to catch him and lock him in?
 
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hahaha
 
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manzana said:
7. For $20 you can by a rubber strip at the truck stop to ground your car and make it invisible to police radar

this one reminds me of something else from days gone by
Cars were sold with or could be added later, a leather strap from the car chassis that the other end would bounce along the road
It was said to ground static build up in the car that was reported to be one cause of people getting car sick ( motion sickness)
I have never done any research into it, so don't know if there is any truth or if it is just another "old wives tale" ? :)

Dave
 

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