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Universal Battery Charger project

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Dennis Thornton

Jan 1, 1970
0
I have several battery powered tools. Some are without chargers. I'd
like a universal charger that would handle any battery type from 7.2v
to 24v in any battery pack from any manufacture. Too many physical
configurations to expect a plug in setup so I'd use wires and clips to
connect.

I have a Hitachi UC 24YFA 7.2v thru v24v for both NiCD or NiMH. It
has 4 pins +, -, T, and S. I do not have a charger manual or a
Hitachi battery to disassemble, but I assume the T is for temperature
control by an internal thermistor and the S is for sensor and I think
this my biggest unknown (different internal resistor for each
voltage?).

How could I use this as a start for my project?
 
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Ian Stirling

Jan 1, 1970
0
Dennis Thornton said:
I have several battery powered tools. Some are without chargers. I'd
like a universal charger that would handle any battery type from 7.2v
to 24v in any battery pack from any manufacture. Too many physical
configurations to expect a plug in setup so I'd use wires and clips to
connect.

Do you care about the charging time?
If you don't mind a 12-14 hour charge, and all your tools use one
capacity of battery subc, ... then you might consider a simple current
limited power supply.
If the cells have a capacity of 1.8Ah, then a 180ma current limited
supply with a maximum voltage of some 30V would work fine.

A timer to cut it off after 12 hours might be nice.
Though you could simply use one of those mechanical "24 hour" timers,
which can be trivially modified to do this.
 
D

Dennis Thornton

Jan 1, 1970
0
C/10 for 12 hours would probably be ok, but I do hope for more.

I like to see the inside of a Hitachi battery to see what the "T" and
"S" are connected to. Again I assume a thermistor, but which one.
And I'm not sure about the "S". I think if I knew those two things
then I could hook it up to full capabilities.

As for now, it won't put out anything until the "T" circuit is happy.
Then it still might not until the "S" side finds something.
 
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