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Old 04-23-2004, 12:43 PM   #1
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Default Basic Charger operation

My understanding is that most all chargers feed 5 amp of current into your standard 7.2 volt 6 sub-c battery pack.

Most RC chargers are peak detecting which means they have a program which detects the small voltage drop which occurs when the battery is full charged. When it detects this drop it either turns off or reduces the amperage down to a "trickle"

The small voltage drop which occurs when a battery is full charged is larger for a NiCAd than Nimh Battery, so a charger needs to have a second more sensitive program to detect that an NImh battery is fully charged.


Either kind of battery will heat up significantly if the charger continues at its 5 amp rate sending current to the battery.

If your charger did not have any peak detection, if you carefully monitor the temperature of you battery you can spot the point at which it is fully charged by noticing sharp spike up in the heat of the battery. You remove a Nimh battery from a charger as soon as the temperature reaches 120F degrees.

It will continue to gain temperature for few minutes after disconnected from charger.


My question is... I practical terms, when it comes to a single battery What do I really gain from expensive chargers over a cheaper charger, if I use a digital thermometer and carefully monitor the temp of the Battery as it charges.


Note: When I attach a voltmeter to a charger I notice that the volts climbs to about 10 volts during the charging process. Is it the charger which is programmed to increase the voltage slowly as it charges or is this a product of changes in the battery as it charges. In other words could I simply attach a 7 volt power supply up to a battery and charge it?
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Old 04-23-2004, 12:58 PM   #2
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Default Re: Basic Charger operation

Quote:
Originally posted by imjonah
My question is... I practical terms, when it comes to a single battery What do I really gain from expensive chargers over a cheaper charger, if I use a digital thermometer and carefully monitor the temp of the Battery as it charges.
You gain not having to stand around, watching your batteries as they charge, and holding a thermometer next to them...

Also, higher quality chargers will be built of higher quality components - so the consistency of the current, and quality of the charge, should be better.


Quote:
When I attach a voltmeter to a charger I notice that the volts climbs to about 10 volts during the charging process. Is it the charger which is programmed to increase the voltage slowly as it charges or is this a product of changes in the battery as it charges. In other words could I simply attach a 7 volt power supply up to a battery and charge it?
It's the battery voltage that rises, not the charger. The charger will actually be outputting a constant voltage, greater than that of the battery itself, to encourage the current to flow into the battery - not back into the charger!

You could connect a power supply directly - people used to charge packs using resistors connected across a 12v battery - but where is the control?
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Old 04-23-2004, 03:27 PM   #3
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Default Re: Basic Charger operation

Quote:
Originally posted by imjonah
Note: When I attach a voltmeter to a charger I notice that the volts climbs to about 10 volts during the charging process. Is it the charger which is programmed to increase the voltage slowly as it charges or is this a product of changes in the battery as it charges. In other words could I simply attach a 7 volt power supply up to a battery and charge it?
The charger put out a constant CURRENT. During charge, theinternal resistance in the battery raises, resulting in voltage rising.
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Old 04-23-2004, 03:30 PM   #4
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Default Re: Basic Charger operation

Quote:
Originally posted by imjonah
My question is... I practical terms, when it comes to a single battery What do I really gain from expensive chargers over a cheaper charger, if I use a digital thermometer and carefully monitor the temp of the Battery as it charges.
I'll bet you once in a while forget to watch, and the pack will damage, or maybe even die. So a reasonably charger will be payed by a few blown packs sooner or later....

You cant get anything out of a battery, which you havent put in - bad charge means bad performance.

Besides, life's too short for watching a charge process.
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