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Old Apr 10, 2011, 02:49 PM
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Lilienthal's Avatar
Littleton, CO
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Temperature Probe

My i206b came with a temperature probe. The manual doesn't say much about it, so I have a few questions:

1. The lead on the probe is only about 12" long and the probe port is on the opposite side of the charger from the charge and balance connections - so it is basically too short. Can the probe lead be extended without adverse effects?

2. When parallel charging multiple lipos, is it a waste of time to use the temp probe on just one of them? Does anyone use multiple temperatue probes?

3. Any recomendations on the temperature cut-off setting? Typically, I don't charge over 2C and my batteries heat up very little. I generally check each of the batteries once or twice during the charge cycle with my hand to see if any are getting warm.

Thanks in advance for your help.
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Old Apr 10, 2011, 03:00 PM
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Edmonton, Alberta, Canada
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What type of probe? Is the two wires two different metals? if it is, it is a thermocuple and you cannot extend it without using thermocouple extenstion wire (basicall the same two metals).

if it is not, it is a thermistor and you are fine.

In both cases, makes sure both wires are the same length.
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Old Apr 10, 2011, 03:01 PM
Jack
USA, ME, Ellsworth
Joined May 2008
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The temperature probes I've found in battery packs were 10K thermistors. If you put a Ohm meter on the leads you'll see a resistance reading and that resistance will go up and down with the temp if you hold the sensor (looks like a ceramic grain of wheat or small round capacitor) between you fingers.

A 10K thermistor will read 10,000 Ohms resistance at a temperature of 25C normally. The attached table is a temperature look up table for one brand of 10K, 3K, and 20K thermistors.

I checked the temperature probe I bought with my eLogger V3 and found it was a 10K thermistor also, so I was able to make and use my own temperature probes for that. The ones I made are smaller and can be put right inside a motor and up against the windings. In comparison tests they read with 1-3 degrees of the of Eagle Tree probes.

The thermistor had leads that were about 25mm long, I extended those with servo wire and the length of the wire (18" or so) changed the resistance a small amount but that not enough to be a concern for what I am using them for.

Jack
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Old Apr 10, 2011, 03:11 PM
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Littleton, CO
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Quote:
Originally Posted by DKNguyen View Post
What type of probe? Is the two wires two different metals? if it is, it is a thermocuple and you cannot extend it without using thermocouple extenstion wire (basicall the same two metals).

if it is not, it is a thermistor and you are fine.

In both cases, makes sure both wires are the same length.
Three wires. The manual doesn't say anthing except that it is 0-99 degrees C.
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Old Apr 10, 2011, 03:16 PM
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Three wires is a thermistor (two for current, one for more accurate measurement with no voltage drop on the non-current carrying line. Two measurement lines for 4-wires is most accurate).

Thermocouples can also handle >300 degrees, and thermistors much much less. So it's a thermistor.
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Old Apr 10, 2011, 05:43 PM
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jackerbes and NKNguyen, thanks for your help. Anybody have any thoughts on my other questions?
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Old Apr 10, 2011, 06:03 PM
Jack
USA, ME, Ellsworth
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Originally Posted by Lilienthal View Post
jackerbes and NKNguyen, thanks for your help. Anybody have any thoughts on my other questions?
I don't have a charger that monitors temperatures so I just put my hand on the pack every once in a while. As long as it is not more than slightly warm to the touch everything is OK.

At 130F/54C you can no longer keep your fingers or hand in contact with a surface. And batteries are already becoming or soon will be permanently damaged at that temp or a little more. So I don't think I want to see a battery get over 110F or so in charging.

Jack
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