Author Topic: Verification of Charging Circuit  (Read 2732 times)

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Offline MastermimeTopic starter

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Verification of Charging Circuit
« on: February 20, 2013, 07:01:04 PM »
Hi guys,

Last question for this project.
I am building this  charging circuit (left side of schematic) and I feel like I am doing something wrong.  Perhaps shorting something out?

I feel like something is up with my transistor configuration is up.  My understanding of them is not complete, but I thought I got the gist of it

Thanks


Please help quick
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Offline jwatte

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Re: Verification of Charging Circuit
« Reply #1 on: February 20, 2013, 07:38:38 PM »

I think the NPN has the collector/emitter reversed if you consider the battery a load for the charger. Using a MOSFET may be better. You also need a current limiting resistor on the base, and perhaps a base bleed resistor between base and ground, too.

What is supposed to happen when the switch is left vs right? As far as I can tell, when the switch is left, it will attempt to parallel the two batteries, whereas when it is right, it will attempt to series them.

Btw: I would not hook that circuit to the rest of the pieces until it worked exactly like I want. Too much risk of burning things!
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Offline MastermimeTopic starter

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Re: Verification of Charging Circuit
« Reply #2 on: February 20, 2013, 08:33:43 PM »
Thank you for such a quick response.  You are exactly right, run in series, charge in parallel (I only have a 7.2v charger).


Quote
I think the NPN has the collector/emitter reversed if you consider the battery a load for the charger

I'm not sure if its my schematic skills or my misunderstanding.  In my circuit, I have emitter connected to ground of the top battery and the collector connected to the ground line of the charger.  Is this correct?

I think my schematic is correct.  No shorts right?  I dont want to ruin the batteries.

Quote
Btw: I would not hook that circuit to the rest of the pieces until it worked exactly like I want. Too much risk of burning things!

I dont!
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Offline newInRobotics

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Re: Verification of Charging Circuit
« Reply #3 on: February 21, 2013, 02:29:06 AM »
What are You trying to achieve with Your charger-transistor-batteries circuit?
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Offline jwatte

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Re: Verification of Charging Circuit
« Reply #4 on: February 22, 2013, 12:44:54 PM »
The implicit answer I deduce from above is to be able to charge the batteries without removing them using only a 7.2V charger.

The arrow in a transistor should point in the direction of conventional current. When charging, conventional current will go the other direction than the transistor arrow points.
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