Measure charge during charge??

S

steamer

Guest
--I've been having trouble figuring out how to know when a battery
is fully charged. That is, sure, I can measure its voltage after
disconnecting the charger, but how could I do it in series, so to speak,
*during* the charging process? Dumb guy here..

--
"Steamboat Ed" Haas : Yet another genius
Hacking the Trailing Edge! : without a job...
http://www.nmpproducts.com/intro.htm
---Decks a-wash in a sea of words---
 
Ed,
What kind of batteries and charger are we talking about here?
Richard
 
how to know when a battery is fully charged
"Steamboat Ed" Haas (steamer)
Click to expand...
Temperature.
When input current no longer adds to the *charge* of the battery,
that current starts making the batteries warm.
Modern battery packs / chargers sense this.
 
steamer wrote:
--I've been having trouble figuring out how to know when a battery
is fully charged. That is, sure, I can measure its voltage after
disconnecting the charger, but how could I do it in series, so to speak,
*during* the charging process? Dumb guy here..
Click to expand...
Just wait some time and it will be fully charged.
 
On Thu, 10 Feb 2005 21:39:19 GMT, Jim Meyer
<weekendlazyness@gmail.com> wrote:

steamer wrote:
--I've been having trouble figuring out how to know when a battery
is fully charged. That is, sure, I can measure its voltage after
disconnecting the charger, but how could I do it in series, so to speak,
*during* the charging process? Dumb guy here..

Connect the voltmeter in series with the batteries and charger.
Click to expand...
---
LOL, thats just _cruel_!

--
John Fields
 
John Fields wrote:
--I've been having trouble figuring out how to know when a battery
is fully charged. That is, sure, I can measure its voltage after
Connect the voltmeter in series with the batteries and charger.
LOL, thats just _cruel_!
Click to expand...
why ?!
 
Some commercial battery chargers have a switch that "samples" the
battery voltage by momentarily disconnecting the charging circuit and
connecting an instrumentation circuit (to measure the voltage).

To do it manually without disconnecting wires, you could use a DPDT
switch or a relay to switch between the charger and a voltmeter.

Depending on the type of battery, voltage is usually the best indicator
of full charge, or as others have mentioned, temperature can also be
used.
 
On 10 Feb 2005 12:56:20 -0800, "JeffM" <jeffm_@email.com> wrote:

how to know when a battery is fully charged
"Steamboat Ed" Haas (steamer)

Temperature.
When input current no longer adds to the *charge* of the battery,
that current starts making the batteries warm.
Click to expand...
---
That's not necessarily true. For instance, when a lead-acid battery
is being charged with a constant voltage current-limited charger (as
it should be), the amount of current the charger will force into the
battery will decrease as the battery's voltage increases toward its
fully charged value, with the result that it will run cooler as it
gets more and more fully charged.

I don't think it's true, either, for batteries which are charged with
a constant current, since what heats a battery up is the power its
internal resistance is dissipating with current passing through the
battery. Since the internal resistance of a battery _decreases_ as it
charges, and since the power the battery dissipates is:


P = I˛R

Then, for a constant I, as R descreases P (and temperature) must also
decrease.
---

Modern battery packs / chargers sense this.
Click to expand...
---
Yes, but not for the reason you state. Generally, the temperature
measurement is made in order to allow the batteries to be charged at
the highest possible rate, and then when they start to overheat the
rate is cut back in order to keep the batteries from getting damaged.

--
John Fields
 
steamer wrote:
--I've been having trouble figuring out how to know when a battery
is fully charged. That is, sure, I can measure its voltage after
disconnecting the charger, but how could I do it in series, so to speak,
*during* the charging process? Dumb guy here..

Connect the voltmeter in series with the batteries and charger.
Click to expand...
 
On Thu, 10 Feb 2005 21:55:57 +0000 (UTC), ILYA <ilia_sa@comtv.ru>
wrote:

John Fields wrote:
--I've been having trouble figuring out how to know when a battery
is fully charged. That is, sure, I can measure its voltage after
Connect the voltmeter in series with the batteries and charger.
LOL, thats just _cruel_!

why ?!
Click to expand...

---
Here are the relevant pasts quoted so they make sense:

<QUOTE>
On Thu, 10 Feb 2005 21:39:19 GMT, Jim Meyer
<weekendlazyness@gmail.com> wrote:

steamer wrote:
--I've been having trouble figuring out how to know when a battery
is fully charged. That is, sure, I can measure its voltage after
disconnecting the charger, but how could I do it in series, so to speak,
*during* the charging process? Dumb guy here..

Connect the voltmeter in series with the batteries and charger.
Click to expand...
---
LOL, thats just _cruel_!

--
John Fields
<END QUOTE

---
Now, what was it, specifically, that you wanted to know?

--
John Fields
 
"steamer" <steamer@sonic.net> wrote in message
news:12NOd.6313$m31.75918@typhoon.sonic.net...
--I've been having trouble figuring out how to know when a battery
is fully charged. That is, sure, I can measure its voltage after
disconnecting the charger, but how could I do it in series, so to speak,
*during* the charging process? Dumb guy here..

--
"Steamboat Ed" Haas : Yet another genius
Hacking the Trailing Edge! : without a job...
http://www.nmpproducts.com/intro.htm
---Decks a-wash in a sea of words---
Click to expand...

Tried it by measuring the weight before and after charging ?
Since charge is put in, the weight will increase, thus the amount of weight
is a measure for charge...
Might even build a clever circuit that disconnects leads when the weight is
enough (eg using a spiral spring or so...)
;-)
 
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