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Forum index » Electronix » Basics
battery charging
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Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Fri Jul 07, 2006 12:04 am    Post subject: battery charging Reply with quote

Hi

I have been looking at schematics for battery charger. All the circuit I
have seen so far seem to stop the charging to the battery from the source.
most of them uses a pnp transistor to bypass the charge battery , therefore
creating a link from the source + to ground.
http://www.aaroncake.net/circuits/charger1.htm
Anyhow, the battery voltage will eventually decrease, and the charger will
go again , and again ....
How would i go about it so that the charger don't start again.

thanks

ken
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Jamie
electronics forum Guru


Joined: 24 Mar 2005
Posts: 597

PostPosted: Fri Jul 07, 2006 12:33 am    Post subject: Re: battery charging Reply with quote

Ken O wrote:

Quote:
Hi

I have been looking at schematics for battery charger. All the circuit I
have seen so far seem to stop the charging to the battery from the source.
most of them uses a pnp transistor to bypass the charge battery , therefore
creating a link from the source + to ground.
http://www.aaroncake.net/circuits/charger1.htm
Anyhow, the battery voltage will eventually decrease, and the charger will
go again , and again ....
How would i go about it so that the charger don't start again.

thanks

ken


use an SCR in series with the output?

using a current pulse sensor when you put the
dead battery on line should be used to auto switch
the SCR on. or use a m-pushbutton switch.

Scr's will hold in the on state until the current
being past drops below its holding spec.
thus if you put the + on the anode side and use
the cathode as the output and switch the SCR via
the gate when you want the charger to start you will
be all set.
i've seen this type of charging switch used in many
cases where you don't want the charger to come back
on.



--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5
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Rich Grise
electronics forum Guru


Joined: 24 Mar 2005
Posts: 3971

PostPosted: Fri Jul 07, 2006 8:21 pm    Post subject: Re: battery charging Reply with quote

On Thu, 06 Jul 2006 20:04:19 -0400, Ken O wrote:

Quote:
Hi

I have been looking at schematics for battery charger. All the circuit I
have seen so far seem to stop the charging to the battery from the source.
most of them uses a pnp transistor to bypass the charge battery , therefore
creating a link from the source + to ground.
http://www.aaroncake.net/circuits/charger1.htm
Anyhow, the battery voltage will eventually decrease, and the charger will
go again , and again ....
How would i go about it so that the charger don't start again.

thanks


You could do this with a relay. Wire it such that the "start" switch pulls
in the relay, which provides power to the charger. Also, pick off that
power and supply the relay coil in parallel with the switch (maybe with
isolation diodes). When the charger finishes its cycle, use that signal
to open the lead to the relay, which drops out and removes power until
you press the start switch again.

Good Luck!
Rich
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ehsjr
electronics forum Guru


Joined: 03 May 2005
Posts: 863

PostPosted: Wed Jul 12, 2006 2:54 pm    Post subject: Re: battery charging Reply with quote

Ken O wrote:
Quote:
Hi

I have been looking at schematics for battery charger. All the circuit I
have seen so far seem to stop the charging to the battery from the source.
most of them uses a pnp transistor to bypass the charge battery , therefore
creating a link from the source + to ground.
http://www.aaroncake.net/circuits/charger1.htm
Anyhow, the battery voltage will eventually decrease, and the charger will
go again , and again ....
How would i go about it so that the charger don't start again.

thanks

ken



The circuit shown on that page will never shut off
current to the battery completely. There is a path
from the 18 volt supply through R1 (500 ohms) and
R7 (.2 ohms) to the battery, regardless of anything
else that happens.

I guess the designer's idea was this: The ~8 mA through
that path, once the battery is fully charged, should make
up for any self discharge, keeping the battery at full
charge.

Ed
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Ken O
electronics forum Guru Wannabe


Joined: 27 Oct 2005
Posts: 116

PostPosted: Fri Jul 14, 2006 12:58 pm    Post subject: Re: battery charging Reply with quote

"ehsjr" <ehsjr@bellatlantic.net> wrote in message
news:Y28tg.7838$aL2.377@trndny07...
Quote:
Ken O wrote:
Hi

I have been looking at schematics for battery charger. All the circuit I
have seen so far seem to stop the charging to the battery from the
source. most of them uses a pnp transistor to bypass the charge battery ,
therefore creating a link from the source + to ground.
http://www.aaroncake.net/circuits/charger1.htm
Anyhow, the battery voltage will eventually decrease, and the charger
will go again , and again ....
How would i go about it so that the charger don't start again.

thanks

ken

The circuit shown on that page will never shut off
current to the battery completely. There is a path
from the 18 volt supply through R1 (500 ohms) and
R7 (.2 ohms) to the battery, regardless of anything
else that happens.

I guess the designer's idea was this: The ~8 mA through
that path, once the battery is fully charged, should make
up for any self discharge, keeping the battery at full
charge.

Yes , this is why I am looking for a method the the charger will not come
back on once the battery is charged.

ken
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