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Battery type detection - rechargeable or not?
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siliconmike
electronics forum addict


Joined: 21 May 2005
Posts: 73

PostPosted: Fri Jun 09, 2006 7:22 am    Post subject: Battery type detection - rechargeable or not? Reply with quote

I'm building a battery charger to charge a single AA size NiMh/Cd using
a micro.

How to detect if the user inserted a rechargeable battery?

How to detect polarity of battery (if it is flat) ?

Mike
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Robert Baer
electronics forum Guru


Joined: 25 Mar 2005
Posts: 1159

PostPosted: Fri Jun 09, 2006 8:06 am    Post subject: Re: Battery type detection - rechargeable or not? Reply with quote

siliconmike wrote:

Quote:
I'm building a battery charger to charge a single AA size NiMh/Cd using
a micro.

How to detect if the user inserted a rechargeable battery?

How to detect polarity of battery (if it is flat) ?

Mike

If a cell is totally "flat" then it may be impossible to reliably

determine the polarity via electrical means: it may be shorted or open.
If a cell is very low (say under 200mV), again it may be impossible
to reliably determine *correct* polarity, as misuse could have
reverse-charged the cell.
Naturally, if the cell is effectively open, it will not be possible
to electrically determine if it was inserted into the charger (use a
mechanical detector or mechanical means allowing insertion in only the
preferred direction).
Since you stated "rechargeable", there is no reliable way to
electrically determine if a fresh or new cell is a rechargeable or not.
The Eveready Renewal cells were alkaline rechargeable and had the
same electrical characteristics as non-rechargeable alkalines; both
similar to the carbon-zinc cells.

Have fun.
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Pooh Bear
electronics forum Guru


Joined: 24 Mar 2005
Posts: 3507

PostPosted: Fri Jun 09, 2006 11:38 am    Post subject: Re: Battery type detection - rechargeable or not? Reply with quote

siliconmike wrote:

Quote:
I'm building a battery charger to charge a single AA size NiMh/Cd using
a micro.

How to detect if the user inserted a rechargeable battery?

How to detect polarity of battery (if it is flat) ?

It's rare that a battery is completely flat so I reckon both could be done by
checking to see if there's a voltage at the terminals.

Graham
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GregS
electronics forum Guru


Joined: 12 May 2005
Posts: 355

PostPosted: Fri Jun 09, 2006 12:50 pm    Post subject: Re: Battery type detection - rechargeable or not? Reply with quote

In article <1149837775.144734.265450@h76g2000cwa.googlegroups.com>, "siliconmike" <siliconmike@yahoo.com> wrote:
Quote:
I'm building a battery charger to charge a single AA size NiMh/Cd using
a micro.

How to detect if the user inserted a rechargeable battery?

How to detect polarity of battery (if it is flat) ?

Most all flat batteries are shorted. Perhaps charging a battery
for a short time and measuring the voltage. Near 1.2 volts, likely
to be a rechargable type.

greg
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Richard Henry
electronics forum Guru


Joined: 13 May 2005
Posts: 748

PostPosted: Fri Jun 09, 2006 2:28 pm    Post subject: Re: Battery type detection - rechargeable or not? Reply with quote

"GregS" <szekeres@pitt.edu> wrote in message
news:e6bqpn$ag1$1@usenet01.srv.cis.pitt.edu...
Quote:
In article <1149837775.144734.265450@h76g2000cwa.googlegroups.com>,
"siliconmike" <siliconmike@yahoo.com> wrote:
I'm building a battery charger to charge a single AA size NiMh/Cd using
a micro.

How to detect if the user inserted a rechargeable battery?

How to detect polarity of battery (if it is flat) ?

Most all flat batteries are shorted. Perhaps charging a battery
for a short time and measuring the voltage. Near 1.2 volts, likely
to be a rechargable type.

Add: severely limit the charging current, while monitoring voltage and
temperature.
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