Anyone ever try this with a charger?

[mick53]

Hi,

The specific charger I'm talking about is this one: http://www.dealextreme.com/details.dx/sku.936
but I suppose it would apply to others.

The indented grooves of this charger where the batteries lie are perfectly sized to insert US pennies.

Between 1962(?) and 1981(?) US pennies were made with 95% copper, the rest being zinc, or sometimes a combination of zinc and tin. (Pennies minted after 1982 are 99.2 percent zinc and 0.8% copper).

Anyway, copper is 3rd behind silver and gold, I believe, as a conductor of electricity.

Anyone ever try to use pennies of this vintage to fill in the gaps and then charge 14500 with this charger?

The only problem I can think of would be that the pennies would not seat perfectly against each other and might lose some connectivity.

I know there are aluminum spacers out there specifically designed for this but aluminum is way down the list for efficiency in conducting electricity.

 

[Benson]

Anyway, copper is 3rd behind silver and gold, I believe, as a conductor of electricity.

Nope, copper's better than gold. See here for one compilation of resistivity.

Anyone ever try to use pennies of this vintage to fill in the gaps and then charge 14500 with this charger?

The only problem I can think of would be that the pennies would not seat perfectly against each other and might lose some connectivity.

Definitely the main issue -- but even that probably wouldn't be enough to prevent it from working OK. I know stacks of 1mm or so magnets work OK in spite of numerous contact surfaces, but they have flat surfaces which make better contact.

I know there are aluminum spacers out there specifically designed for this but aluminum is way down the list for efficiency in conducting electricity.

Even if aluminum was "way down the list" (it's actually fourth, right after gold), the conductivity of the metal simply doesn't matter in this application. Contact resistance dominates, which makes the stack of pennies (regardless of alloy) not at all promising.

Just for kicks, I ran some numbers on a 14mm diameter, 15mm long spacer.

• Silver (pure):
  1.6 uOhm
• Copper (pure):
  1.7 uOhm
• Gold (pure):
  2.3 uOhm
• Aluminum (pure):
  2.7 uOhm
• Aluminum (6061-T6):
  4.0 uOhm
• Zinc (pure):
  5.9 uOhm
• Stainless Steel (304):
  67 uOhm
• Titanium (pure):
  76 uOhm
• Titanium (6Al4V):
  170 uOhm

Even with the worst conducting metal on that chart, Ti alloy, you would only have a voltage drop of 75 uV -- if you think you'll save money by finding (and keeping track of) a couple dozen vintage pennies instead of buying spacers, go for it, but the fact that they're mostly copper will not constitute an improvement.

 

[csshih]

haha.. in my UF 139 charger, I've been using spent brass to fill the gaps to charge rcr123as, they work perfectly fine!

I haven't even polished them!

btw, 38 special, if you wish to know.

 

[Tomahawk23]

I tried using live one's, but I lost a finger during the process.

 

[Benson]

I tried using live one's, but I lost a finger during the process.

It's bad when your spacer vents with flame...