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Old 03-01-2007, 05:07 PM   #1
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Probably a silly battery question, lets say a 4300 Nimh pack was just one big cell..

rather than 6 seperate ones (still the same pack shape/weight) would it actually make any difference to the performance to have one big cell rather than 6 little ones?

As I figure, it would certainly make balancers and cell matching a thing of the past at least.

Just curious really.
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Old 03-01-2007, 05:24 PM   #2
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stick them in a box, jobs a good-un
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Old 03-01-2007, 05:27 PM   #3
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The are called batteries for the reason that cells are combined in series to create the necessary voltage. Each cell produces a certain voltage depending on the chemistry of the electrodes, and these cells are combined in series to add up voltages. The matching process is finding cells to combine with each other that are equally high voltage and capacity. So, one big cell would be of some mah rating, probably 24000, and only 1.2 volts
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Old 03-01-2007, 05:46 PM   #4
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well lipos use 2 cells in series, each cell produces a nominal 3.7 volts, so 7.4v in total... and to get higher capacity, the pair of cells can then be wired in parallel with another pair of cells with is where the naming convention comes from 2s1p for 2 cells in series, 2s2p for 2 series, 2 parallel... and the guys who fly might use 4s1p batts...

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Old 03-01-2007, 05:48 PM   #5
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That is correct.

A nickel metal hydride cell has two HALF-CELLS:

NICKEL for the Cathode (where reduction takes place, Ni2+ goes to Ni) and

NEODYMIUM/COBALT alloy (where oxidation takes place, they lose electrons)

the electrons from these power your car.

Now for both Nickel and the Ne/Co alloy, there is a constant known as the E*halfcell (electrical reduction potential in volts per halfcell) when hooked up to a Standard Hydrogen Electrode.

NO MATTER HOW BIG YOUR BATTERY IS the E*s remain the same!

The voltage of the battery = E*Ne/Co - E*Ni.

For NiMHs, this is usually around 1.2 V.

I hope this was clear.
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Old 03-01-2007, 06:16 PM   #6
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So basically.....

Quote:
Originally Posted by Yub, yub, cmdr!
That is correct.

A nickel metal hydride cell has two HALF-CELLS:

NICKEL for the Cathode (where reduction takes place, Ni2+ goes to Ni) and

NEODYMIUM/COBALT alloy (where oxidation takes place, they lose electrons)

the electrons from these power your car.

Now for both Nickel and the Ne/Co alloy, there is a constant known as the E*halfcell (electrical reduction potential in volts per halfcell) when hooked up to a Standard Hydrogen Electrode.

NO MATTER HOW BIG YOUR BATTERY IS the E*s remain the same!

The voltage of the battery = E*Ne/Co - E*Ni.

For NiMHs, this is usually around 1.2 V.

I hope this was clear.
7.2 volts for a single cell is possible but not with the chemicals currently in use but "who knows one day a battery might be made of something that can"?
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Old 03-01-2007, 06:23 PM   #7
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Quote:
Originally Posted by Mabuchi540
7.2 volts for a single cell is possible but not with the chemicals currently in use but "who knows one day a battery might be made of something that can"?
Oh man...think of the stink that would cause
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Old 03-01-2007, 07:01 PM   #8
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Yes. Any voltage is theoretically possible.
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Old 03-02-2007, 01:31 AM   #9
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To answer the origional question.

Performance would be roughly the same as using one of todays single cells.
We already have 1.2v 4300Mah (Nominal) cells, there is no need for a bigger version.

If you car actually moved, it would move very slowly.
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Old 03-02-2007, 11:05 AM   #10
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Actually the voltage of the battery depends on the A. Metal type, B. Surface area of the 2 metals that are used, C Type of liquid. Capacity depends on the A. Type, B. Amount of liquid between them and C. Metal type and thickness.
The larger the surface area, the higher the voltage is, using the same metal.
The more amount of liquid, the higher the capacity, using the same liquid and metal (up to a point, you need more metal (thicker plates) when you have more liquid).

How cells work: The liquid and the metal transform into different materials when electricity flows and in the end there is not enough left of untransformed material to maintain the voltage. In rechargeable cells you can convert the liquid and metal back to nearly original state by running current backwards through the cell. You can actually do this 3 or 4 times with standard Alkaline batteries too, before they start to leak or explode. My record Alkaline cell exploded at 13th recharge. This transformation can be noticeable on scales and for example in car batteries you weigh the liquid to see if the battery is charged.

The reason we use all these cell to create a 7.2 Volt battery, but not one cell is twofold. It's much easier and cheaper to build lot of machines that manufacture millions of nearly identical cells (that's right they're built by machines, not hand-wound) that can be used for RC cars, power tools and incredible amount of other equipment, than it is to build new machines for each possible use of cells. And we wouldn't be happy if there was only one manufacturer for RC cells and he suddenly decided not to make them anymore in that size so we would all have to change our cars or buy new ones to suit.

The reason rechargeable batteries are 1.2 volts instead of 1.5 volts is that when the first rechargeable batteries were made, technology wasn't advanced enough to fit enough wattage into the standard sizes so the "Powers That Be" decided to lower the voltage 20% so the batteries would last longer in use.

And to answer the question. It would work similar but the cell would be lot more expensive.

Now everyone go and get yourself a lemon, a copper nail and a iron nail. Stick the nails side by side into the lemon and use digital voltmeter to measure the voltage. See how it increases when you push the nails farther into the lemon (more surface area). Now try different type of nails.
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