Hobbycharger questions

lightseeker2009

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Jul 29, 2009
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If I want to extend the chargers wires, how much effect will this have on termination voltages etc?
I doubt it will have any effect at all when I lengthen the input wires. But what if I put on twice as long wires on its output side?
 
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moderator007

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Jan 1, 2010
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According to a online wire sizes calculator. Stranded 18awg should have around 6 ohms per 1000 feet. If your charging leads are stranded 16awg it has a resistance of about 4 ohms per 1000 feet. 4 feet of 18awg should have about .0261 ohms. 4 feet of 16awg should have about .0163 ohms. Voltage drop at 3 amps across 4 feet of 18awg should be about .0783 volts. 16awg about .0489 volts. The 2 feet of wire you already have is exactly half these values. All the calculations were based on standard stranded wire. Most hobby chargers use silicone high strand count wire. The value for silicone wire would even be less than these calculations.

I dont think it will make much of a difference if any.
 

SilverFox

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Hello Lightseeker2009,

It actually depends on the charger. Some chargers are very sensitive to wire length and others aren't. This usually only effects charging Li-Ion chemistry. With longer wires, you may find that your ending voltage on the cells is a little lower. I don't think it has any impact on NiMh chemistry.

Tom
 

s.urfer

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Aug 16, 2010
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If it is an older type, they sometimes use the leads as resistors. Thus the electronic might malfunction in terms of current accuracy. Charge termination should be OK, though.

If it is a relatively new charger, it should not cause any real problems. The termination voltage is reached a bit earlier, because the longer wires add voltage drop, but the good chargers will remain charging with reduced current. Which will also reduce the voltage drop in the longer wires, to the point where it doesn't matter anymore.
 

Russel

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Jan 31, 2009
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Some hobby chargers, such as the FMA Cellpro 10S, require the use of balance leads while charging, even if you are only charging one cell. You might consider this an inconvenience, but it has the advantage of cell voltage measurement without the influence of charge lead voltage drop. Basically, when charging a single cell, the balance leads measure the cell voltage at the cell without significant current running through them, while the charge leads supply the charge current. Because the balance leads are measuring the voltage at the cell the voltage drop from the (separate) charge leads is not a concern, at least with respect to voltage measurement. You do, of course, want to have charge leads sufficient for the charge current so that they don't heat up or cause excessive resistance.
 
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HKJ

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It will usual not affect the termination voltage any significant amount. With LiIon cells the current is low when the charge is terminated (usual 1/10 of charge current), this reduces the influence of cable resistance.
 
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