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nuckollsr(at)cox.net
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 Posted: Mon Feb 12, 2007 12:04 pm Post subject: Battery Tenders as recharging tools . . . |
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As promised, I've finished the first experiment to look
at the recharge characteristics of a Battery Tender. Take
a look at:
http://www.aeroelectric.com/Pictures/Curves/Battery_Tender_Recharge_1.jpg
I thought I'd looked at the Battery Tender performance
some time ago but data taken on this test suggests this is
the first time . . .
Note that the Battery Tender's 'size' is not a limiting factor
for putting energy back into a battery. The battery's terminal
voltage was climbing nicely at a rate commensurate with the
device's output rating of about 0.8 amps.
The surprise comes when the device switches from a charge to
sustain mode at just under 14.0 volts! To put this in
context, look at:
http://www.aeroelectric.com/Pictures/Curves/schumacher_3.jpg
Here we see a predictable rise in voltage as the battery's
chemistry converts incoming energy into stored chemical energy.
Note also that the rate-of-rise takes a decidedly upward inflection
sometime after the voltage climbs past 14.4 volts. This is typical
of most if not all rechargeable battery chemistries. This
characteristic is used to send a signal to truly 'smart' chargers
to announce a nearly full state of charge.
In the case for the Schumacher charger, we see that the profile
changes from constant current to constant voltage where the
battery is held in this "top-off" mode for about 2 hours. After
that time, the charger's output drops to the expected sustaining
level of about 13.0 volts.
Going back to the Battery Tender, we see that the recharge voltage
never rises to the inflection point indicating that the battery
is about full. Further, there's no dwell at some elevated top-off
voltage.
I'm discharging the battery again to measure how much snort the
Battery Tender put back into the battery. I'll then recharge it
again with the Schumacher charger and compare notes again.
This early look-see at the data suggests that admonitions
against using Battery Tenders as battery chargers is correct.
The Battery Tender doesn't get the job done based on what
we know of battery chemistry and the charging profiles
suggested by other manufacturers. The complaints I'd heard about
Battery Tenders was that they were "too small" . . . in fact they
appear to be quite capable with respect to energy output levels.
Instead, they are deficient in smarts necessary to (1) detect end of
charge, (2) hold at some elevated top-off level for a reasonable
length of time followed by (3) drop to a sustaining level that
doesn't charge the battery and simply offsets the battery's internal
self discharge currents.
Watch this space . . .
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
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| Posted: Mon Feb 12, 2007 8:37 pm Post subject: Battery Tenders as recharging tools . . . |
|
|
Good data to have. Would be interesting to compare to the Battery
Minder, which is similar in that it charges to around 14V at 1.33 amps,
then cuts back to 13.6 to maintain. I've been playing with it on a 1 yr
old CB35A, and a 7 year old CB35A that was dead when I started. Both now
show fully charged electrolyte specific gravity. I alternate, a few days
on each.
Robert L. Nuckolls, III wrote:
| Quote: |
<nuckollsr(at)cox.net>
As promised, I've finished the first experiment to look
at the recharge characteristics of a Battery Tender. Take
a look at:
http://www.aeroelectric.com/Pictures/Curves/Battery_Tender_Recharge_1.jpg
I thought I'd looked at the Battery Tender performance
some time ago but data taken on this test suggests this is
the first time . . .
Note that the Battery Tender's 'size' is not a limiting factor
for putting energy back into a battery. The battery's terminal
voltage was climbing nicely at a rate commensurate with the
device's output rating of about 0.8 amps.
The surprise comes when the device switches from a charge to
sustain mode at just under 14.0 volts! To put this in
context, look at:
http://www.aeroelectric.com/Pictures/Curves/schumacher_3.jpg
Here we see a predictable rise in voltage as the battery's
chemistry converts incoming energy into stored chemical energy.
Note also that the rate-of-rise takes a decidedly upward inflection
sometime after the voltage climbs past 14.4 volts. This is typical
of most if not all rechargeable battery chemistries. This
characteristic is used to send a signal to truly 'smart' chargers
to announce a nearly full state of charge.
In the case for the Schumacher charger, we see that the profile
changes from constant current to constant voltage where the
battery is held in this "top-off" mode for about 2 hours. After
that time, the charger's output drops to the expected sustaining
level of about 13.0 volts.
Going back to the Battery Tender, we see that the recharge voltage
never rises to the inflection point indicating that the battery
is about full. Further, there's no dwell at some elevated top-off
voltage.
I'm discharging the battery again to measure how much snort the
Battery Tender put back into the battery. I'll then recharge it
again with the Schumacher charger and compare notes again.
This early look-see at the data suggests that admonitions
against using Battery Tenders as battery chargers is correct.
The Battery Tender doesn't get the job done based on what
we know of battery chemistry and the charging profiles
suggested by other manufacturers. The complaints I'd heard about
Battery Tenders was that they were "too small" . . . in fact they
appear to be quite capable with respect to energy output levels.
Instead, they are deficient in smarts necessary to (1) detect end of
charge, (2) hold at some elevated top-off level for a reasonable
length of time followed by (3) drop to a sustaining level that
doesn't charge the battery and simply offsets the battery's internal
self discharge currents.
Watch this space . . .
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
|
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD |
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