Battery Backup (Lead Acid Battery)
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Posts: 46,084
I've built a few Alarm Systems using the BS2 and employed a battery
backup system using a standard battery pack as per ideas given in
this group (Using diodes). Using the same setup, I had hoped to
employ a Lead Acid Battery I got from B.G. Micro and have it stay
charged until needed. Anyone have any ideas on this? I have never
built a battery charger circuit before in which the battery was also
powering the device when main power was cut.
It seems to me Tracy or someone here mentioned at one time something
about how to connect the battery so that it's always got a trickle
charge. Remember, this is powering a BS2 Alarm System, so I want to
keep it simple.
To whomever did recommend a circuit at one point that preserved a
battery's charge, could it have been setup using a simple diode?
I will attempt yo search the archives as well...Thanks.
Chris Savage
backup system using a standard battery pack as per ideas given in
this group (Using diodes). Using the same setup, I had hoped to
employ a Lead Acid Battery I got from B.G. Micro and have it stay
charged until needed. Anyone have any ideas on this? I have never
built a battery charger circuit before in which the battery was also
powering the device when main power was cut.
It seems to me Tracy or someone here mentioned at one time something
about how to connect the battery so that it's always got a trickle
charge. Remember, this is powering a BS2 Alarm System, so I want to
keep it simple.
To whomever did recommend a circuit at one point that preserved a
battery's charge, could it have been setup using a simple diode?
I will attempt yo search the archives as well...Thanks.
Chris Savage
Comments
I had a need also to charge Gel Cell batteries. After the major blackout we
had here (Southern Ontario) in late August, I decided I needed a solution
that would charge and maintain my battery collection.
There were a few requirements that I had:
- simple
- would maintain a battery on charge indefinitely without the worry or
overcharging it
- low cost
- readily available components
Looked at several options and came up with a circuit using an LM317 and a
handful of components. Take a look at: http://www.projectx.com/Kits/GelCell/
It has full schematics, parts lists, theory of operation, setup instructions
so you can DIY.
John - VE3SVE
Original Message
From: Chris Savage [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=B0_BngUsyI4X--WX846SpSt3hIPW4QN-6XhmRvQR-qt1YBhv4UqF2bsUasWLWyWzEdgkjXzs3rxWykSx2MJkrw]knight_designs@y...[/url
Sent: Sunday, November 30, 2003 10:54 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Battery Backup (Lead Acid Battery)
I've built a few Alarm Systems using the BS2 and employed a battery
backup system using a standard battery pack as per ideas given in
this group (Using diodes). Using the same setup, I had hoped to
employ a Lead Acid Battery I got from B.G. Micro and have it stay
charged until needed. Anyone have any ideas on this? I have never
built a battery charger circuit before in which the battery was also
powering the device when main power was cut.
It seems to me Tracy or someone here mentioned at one time something
about how to connect the battery so that it's always got a trickle
charge. Remember, this is powering a BS2 Alarm System, so I want to
keep it simple.
To whomever did recommend a circuit at one point that preserved a
battery's charge, could it have been setup using a simple diode?
I will attempt yo search the archives as well...Thanks.
Chris Savage
To UNSUBSCRIBE, just send mail to:
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and the battery to keep a trickle going. There's a few IC's out there that
do a better job by monitoring the batteries voltage directly. Or perhaps
consider just running the circuit off the battery 100% of the time and
supplying a big enough charger to do both the battery and circuit draw.
The biggest thing to be aware of is that all batteries technologies are not
created equal, and lead-acid batteries have a totally different
charging-curve than ni-cad or lithium-ion bats. All batteries are subject to
damage or even explosion if over charged. That being said, if you're
interested in a lead-acid trickle charger I could probably pick out the
proper resistor values that would do the job. How big of a lead-acid battery
are you using. Ni-Cads are a little trickier, and lithium -ion batteries are
way beyond the scope of this course....
Mike Sokol
www.modernrecording.com
mikes@m...
" One should not increase, beyond what is necessary,
the number of entities required to explain anything"...
-William of Occam-
Original Message
From: "Chris Savage" <knight_designs@y...>
To: <basicstamps@yahoogroups.com>
Sent: Sunday, November 30, 2003 10:53 AM
Subject: [noparse][[/noparse]basicstamps] Battery Backup (Lead Acid Battery)
> I've built a few Alarm Systems using the BS2 and employed a battery
> backup system using a standard battery pack as per ideas given in
> this group (Using diodes). Using the same setup, I had hoped to
> employ a Lead Acid Battery I got from B.G. Micro and have it stay
> charged until needed. Anyone have any ideas on this? I have never
> built a battery charger circuit before in which the battery was also
> powering the device when main power was cut.
>
> It seems to me Tracy or someone here mentioned at one time something
> about how to connect the battery so that it's always got a trickle
> charge. Remember, this is powering a BS2 Alarm System, so I want to
> keep it simple.
>
> To whomever did recommend a circuit at one point that preserved a
> battery's charge, could it have been setup using a simple diode?
>
> I will attempt yo search the archives as well...Thanks.
>
> Chris Savage
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>backup system using a standard battery pack as per ideas given in
>this group (Using diodes). Using the same setup, I had hoped to
>employ a Lead Acid Battery I got from B.G. Micro and have it stay
>charged until needed. Anyone have any ideas on this? I have never
>built a battery charger circuit before in which the battery was also
>powering the device when main power was cut.
>
>It seems to me Tracy or someone here mentioned at one time something
>about how to connect the battery so that it's always got a trickle
>charge. Remember, this is powering a BS2 Alarm System, so I want to
>keep it simple.
>
>To whomever did recommend a circuit at one point that preserved a
>battery's charge, could it have been setup using a simple diode?
>
>I will attempt yo search the archives as well...Thanks.
>
>Chris Savage
Hi Chris,
One simple solution is STMicroelectronics' PB137 regulator, a three
terminal 13.7 volt regulator designed to float-charge 12 volt Pb-acid
batteries. Find the data sheet on the Mouser site, where they cost
50 cents ea.
-- Tracy
> Chris,
> I had a need also to charge Gel Cell batteries.
> There were a few requirements that I had:
> - simple
> - would maintain a battery on charge indefinitely
> without the worry or
> overcharging it
> - low cost
> - readily available components
> Looked at several options and came up with a circuit
> using an LM317 and a
> handful of components. Take a look at:
> http://www.projectx.com/Kits/GelCell/
John,
While this looks like an excellent charger, my
project calls for the battery to be charged until
needed. Perhaps it's beyond the scope of asking in
the group (Since it's really more about the power
supply for a BS2 and not the BS2 itself). However, I
was hoping to be able to have my BS2 run off a
Wall-Wart or home-made supply (Which will include both
5VDC & 12VDC outputs) and then if the AC power fails,
the Lead Acid Battery would take over powering the
circuit.
Recently I have watched discussion regarding battery
backups in BS2 circuits, and as I stated earlier, I
was a part of an earlier one myself, but I wasn't sure
if the same circuit would apply or not. I don't want
the Lead Acid Battery to potentially lose it's charge
over time, or, if when needed by the circuit, get low,
then remain that way until next time it's needed.
I guess what I'm asking is this: If you run the
battery power to the regulator through a diode and do
the same thing with the DC power from the Wal-Wart of
supply, will the supply keep the battery charged
through leakage via the diode.
Somewhere back a ways was a discussion about
this...But my connection keeps getting dropped
everytime I start searching it seems... =(
=====
Chris Savage
Knight Designs
324 West Main Street
Montour Falls, NY 14865
(607) 535-6777
http://www.knightdesigns.com
__________________________________
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> You should be able to add a resistor directly
> between the transformer output
> and the battery to keep a trickle going. There's a
> few IC's out there that
> do a better job by monitoring the batteries voltage
> directly. Or perhaps
> consider just running the circuit off the battery
> 100% of the time and
> supplying a big enough charger to do both the
> battery and circuit draw.
I could use a standard charging circuit if I have a
relay switch over to the battery (While disconecting
the battery from the charging circuit), however, I've
no experience with that particular type of circuit.
That is, switching without resetting or locking up my
BS2. Any insights?
> The biggest thing to be aware of is that all
> batteries technologies are not
> created equal, and lead-acid batteries have a
> totally different
> charging-curve than ni-cad or lithium-ion bats. All
> batteries are subject to
> damage or even explosion if over charged. That being
> said, if you're
> interested in a lead-acid trickle charger I could
> probably pick out the
> proper resistor values that would do the job. How
> big of a lead-acid battery
> are you using. Ni-Cads are a little trickier, and
> lithium -ion batteries are
> way beyond the scope of this course....
This battery is, I believe a 12V 7mAh...
=====
Chris Savage
Knight Designs
324 West Main Street
Montour Falls, NY 14865
(607) 535-6777
http://www.knightdesigns.com
__________________________________
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> Hi Chris,
> One simple solution is STMicroelectronics' PB137
> regulator, a three
> terminal 13.7 volt regulator designed to
> float-charge 12 volt Pb-acid
> batteries. Find the data sheet on the Mouser site,
> where they cost
> 50 cents ea.
Thanks Tracy...I will look it up...Hopefully this chip
will help.
=====
Chris Savage
Knight Designs
324 West Main Street
Montour Falls, NY 14865
(607) 535-6777
http://www.knightdesigns.com
__________________________________
Do you Yahoo!?
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If you have a sealed Pb-acid battery, it can be charged continuously
at a constant voltage of around 13.6 to 13.8 volts. It will
self-regulate to accept only the charging current that it needs. For
example, if it is already charged, a 7 amp-hour battery will only
suck up 10 or so milliamps. If the battery discharges during a
power outage, then, when the power comes back, it will take a few
hundred mA for a period of time and then taper off back to the 10 ma
level.
You asked about the charging circuit and maybe a diode, so you can
both run your security system and keep the battery topped off at the
same time. Very simple with float charging. Simply put the battery
and the circuit in parallel on the 13.7 volt charger. No diode
necessary.
;
; 13.7 volts
wallwort+--| PB137 |----o
;
`
' +| |+
| battery circuit
| | |
o
o
'
Notice that the PB137 touts as a feature that its leakage is only 10
microamps, back into the regulator when the wallwort is disconnected
or loses power. That is so that the battery won't discharge back
into the regulator, and that means you don't need a blocking diode
there. The dropout voltage of the regulator is 2 volts, so you need
a wallwort capable of 16 volts.
BTW. there are quite a number of Pb-acid chargers available in the
form of wallworts (very cheap, too), but you can't use those in the
above circuit. That is because they are (usually) automatic fast
chargers, that allow the battery to fast-charge up to 14.2 volts, and
then, when the current tapers off, the charger automatically switches
back to 13.8 volt float charging. You can't run that in parallel
with a circuit, because the circuit might hold the charger at the
dangerous 14.2 volt level and overcharge and dry out the battery.
What you want is a float charger for your backup, period.
-- Tracy
>--- Tracy Allen <tracy@e...> wrote:
>> Hi Chris,
>> One simple solution is STMicroelectronics' PB137
>> regulator, a three
>> terminal 13.7 volt regulator designed to
>> float-charge 12 volt Pb-acid
>> batteries. Find the data sheet on the Mouser site,
>> where they cost
>> 50 cents ea.
>
>Thanks Tracy...I will look it up...Hopefully this chip
>will help.
>
>
>
>=====
>Chris Savage
>Knight Designs
>324 West Main Street
>Montour Falls, NY 14865
>(607) 535-6777
>
>http://www.knightdesigns.com
>
> Hi Chris,
> If you have a sealed Pb-acid battery, it can be
> charged continuously
> at a constant voltage of around 13.6 to 13.8 volts.
<trimmed>
> Notice that the PB137 touts as a feature that its
> leakage is only 10
> microamps, back into the regulator when the wallwort
> is disconnected
> or loses power. That is so that the battery won't
> discharge back
> into the regulator, and that means you don't need a
> blocking diode
> there. The dropout voltage of the regulator is 2
> volts, so you need
> a wallwort capable of 16 volts.
<trimmed>
Tracy,
This sounds like exactly what I need...Not what I
expected, but then, I wasn't familiar with the PB137.
I guess I'll have to get a few of these, and thanks
for the info. This project has set on the bench for
awhile because it's for my own personal use (As are
all experimental projects)...I bought the battery to
tinker with ideas, but probably should've read a few
books on these type of batteris. But thanks again for
the crash course.
=====
Chris Savage
Knight Designs
324 West Main Street
Montour Falls, NY 14865
(607) 535-6777
http://www.knightdesigns.com
__________________________________
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This might be a solution for you.
http://www.farcircuits.net/battery2.htm#2battery This charger uses the
UC3906 chip specifically for sealed lead-acid batteries. I don't have the
magazine article with me right now, but it provides one voltage and current
while the battery is charging, another for the last 5-10% of charge, and a
third when the battery is topped off.
If you know any amateur radio operators (or are one yourself), find a copy
of the 1992 Radio Amateur's Handbook by the ARRL. This project appeared in
Chapter 27, figure 66. I just received the circuit board and IC, but I
haven't assembled it yet so I can't give any real feedback.
Also, I found this while searching Google for project above...
http://www.geocities.com/vk3em/sla-charger/sla-charger.html This also uses
the UC3906 chip. There is a higher parts count, and I haven't read the
article closely enough to know if its better, but at least it has the theory
of operation of the chip.
Good luck!
Brian, N7QJB
>Message: 14
> Date: Sun, 30 Nov 2003 13:20:22 -0800 (PST)
> From: Chris Savage <knight_designs@y...>
> Subject: RE: Battery Backup (Lead Acid Battery)
>
> --- "John D. Kerr" <jdkerr@p...> wrote:
> > Chris,
> > I had a need also to charge Gel Cell batteries.
> > There were a few requirements that I had:
> > - simple
> > - would maintain a battery on charge indefinitely
> > without the worry or
> > overcharging it
> > - low cost
> > - readily available components
> > Looked at several options and came up with a circuit
> > using an LM317 and a
> > handful of components. Take a look at:
> > http://www.projectx.com/Kits/GelCell/
>
> John,
> While this looks like an excellent charger, my
> project calls for the battery to be charged until
> needed. Perhaps it's beyond the scope of asking in
> the group (Since it's really more about the power
> supply for a BS2 and not the BS2 itself). However, I
> was hoping to be able to have my BS2 run off a
> Wall-Wart or home-made supply (Which will include both
> 5VDC & 12VDC outputs) and then if the AC power fails,
> the Lead Acid Battery would take over powering the
> circuit.
>
> Recently I have watched discussion regarding battery
> backups in BS2 circuits, and as I stated earlier, I
> was a part of an earlier one myself, but I wasn't sure
> if the same circuit would apply or not. I don't want
> the Lead Acid Battery to potentially lose it's charge
> over time, or, if when needed by the circuit, get low,
> then remain that way until next time it's needed.
>
> I guess what I'm asking is this: If you run the
> battery power to the regulator through a diode and do
> the same thing with the DC power from the Wal-Wart of
> supply, will the supply keep the battery charged
> through leakage via the diode.
>
> Somewhere back a ways was a discussion about
> this...But my connection keeps getting dropped
> everytime I start searching it seems... =(
>
>
> =====
> Chris Savage
> Knight Designs
> 324 West Main Street
> Montour Falls, NY 14865
> (607) 535-6777
>
> http://www.knightdesigns.com
have a couple of complete kits.
Brian, N7QJB
Original Message
From: "Brian Grimm" <n7qjb@m...>
To: <basicstamps@yahoogroups.com>
Sent: Monday, December 01, 2003 11:43 PM
Subject: RE: Battery Backup (Lead Acid Battery)
> Chris,
>
> This might be a solution for you.
> http://www.farcircuits.net/battery2.htm#2battery This charger uses the
> UC3906 chip specifically for sealed lead-acid batteries. I don't have the
> magazine article with me right now, but it provides one voltage and
current
> while the battery is charging, another for the last 5-10% of charge, and a
> third when the battery is topped off.
>
> If you know any amateur radio operators (or are one yourself), find a copy
> of the 1992 Radio Amateur's Handbook by the ARRL. This project appeared
in
> Chapter 27, figure 66. I just received the circuit board and IC, but I
> haven't assembled it yet so I can't give any real feedback.
>
> Also, I found this while searching Google for project above...
> http://www.geocities.com/vk3em/sla-charger/sla-charger.html This also
uses
> the UC3906 chip. There is a higher parts count, and I haven't read the
> article closely enough to know if its better, but at least it has the
theory
> of operation of the chip.
>
> Good luck!
> Brian, N7QJB
>
> >Message: 14
> > Date: Sun, 30 Nov 2003 13:20:22 -0800 (PST)
> > From: Chris Savage <knight_designs@y...>
> > Subject: RE: Battery Backup (Lead Acid Battery)
> >
> > --- "John D. Kerr" <jdkerr@p...> wrote:
> > > Chris,
> > > I had a need also to charge Gel Cell batteries.
> > > There were a few requirements that I had:
> > > - simple
> > > - would maintain a battery on charge indefinitely
> > > without the worry or
> > > overcharging it
> > > - low cost
> > > - readily available components
> > > Looked at several options and came up with a circuit
> > > using an LM317 and a
> > > handful of components. Take a look at:
> > > http://www.projectx.com/Kits/GelCell/
> >
> > John,
> > While this looks like an excellent charger, my
> > project calls for the battery to be charged until
> > needed. Perhaps it's beyond the scope of asking in
> > the group (Since it's really more about the power
> > supply for a BS2 and not the BS2 itself). However, I
> > was hoping to be able to have my BS2 run off a
> > Wall-Wart or home-made supply (Which will include both
> > 5VDC & 12VDC outputs) and then if the AC power fails,
> > the Lead Acid Battery would take over powering the
> > circuit.
> >
> > Recently I have watched discussion regarding battery
> > backups in BS2 circuits, and as I stated earlier, I
> > was a part of an earlier one myself, but I wasn't sure
> > if the same circuit would apply or not. I don't want
> > the Lead Acid Battery to potentially lose it's charge
> > over time, or, if when needed by the circuit, get low,
> > then remain that way until next time it's needed.
> >
> > I guess what I'm asking is this: If you run the
> > battery power to the regulator through a diode and do
> > the same thing with the DC power from the Wal-Wart of
> > supply, will the supply keep the battery charged
> > through leakage via the diode.
> >
> > Somewhere back a ways was a discussion about
> > this...But my connection keeps getting dropped
> > everytime I start searching it seems... =(
> >
> >
> > =====
> > Chris Savage
> > Knight Designs
> > 324 West Main Street
> > Montour Falls, NY 14865
> > (607) 535-6777
> >
> > http://www.knightdesigns.com
>
> Hi Chris,
> If you have a sealed Pb-acid battery, it can be
> charged continuously
> at a constant voltage of around 13.6 to 13.8 volts.
<message trimmed>
Tracy, the battery (I am at the shop now) is a
Universal Battery UB1213, Non-Spillable Sealed
Lead-Acid Battery. Says on it:
Constant Voltage Charge Volt Reg Init Current
@20 degrees Celcius
STANDBY USE 13.5-13.8V NO LIMIT
CYCLIC USE 14.0-15.0V 0.38A MAX
(That was supposed to be a table)
> Notice that the PB137 touts as a feature that its
<trimmed>
Also, what is the PB137? I looked at my VR listing
last night and did not see that part # listed. Does
it cross with something else?
Thanks!
=====
Chris Savage
Knight Designs
324 West Main Street
Montour Falls, NY 14865
(607) 535-6777
http://www.knightdesigns.com
__________________________________
Do you Yahoo!?
Free Pop-Up Blocker - Get it now
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> Chris,
> This might be a solution for you.
> http://www.farcircuits.net/battery2.htm#2battery
<trimmed>
No schematic, circuit diagram or pics... =(
> If you know any amateur radio operators (or are one
> yourself), find a copy
> of the 1992 Radio Amateur's Handbook by the ARRL.
<trimmed>
I do know one (N2UZQ), and if I ever hear from him
again, I will see if he has it. Until then I am going
to attempt Tracy's idea. Meanwhile, if you do happen
to build it, post for us how well it works. Thanks!
=====
Chris Savage
Knight Designs
324 West Main Street
Montour Falls, NY 14865
(607) 535-6777
http://www.knightdesigns.com
__________________________________
Do you Yahoo!?
Free Pop-Up Blocker - Get it now
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>> Hi Chris,
>> If you have a sealed Pb-acid battery, it can be
>> charged continuously
>> at a constant voltage of around 13.6 to 13.8 volts.
>
><message trimmed>
>
>Tracy, the battery (I am at the shop now) is a
>Universal Battery UB1213, Non-Spillable Sealed
>Lead-Acid Battery. Says on it:
>
>Constant Voltage Charge Volt Reg Init Current
>@20 degrees Celcius
>
>STANDBY USE 13.5-13.8V NO LIMIT
This standby charging is what the PB137 does. It is a 13.7 volt regulator.
>CYCLIC USE 14.0-15.0V 0.38A MAX
These batteries can be fast charged to a voltage of 14 to 15 volts.
Some automatic or "two- or three-step" fast chargers have been
mentioned in response to your query. An automatic fast charger is a
more sophisticated circuit. It has to limit the initial current, to
less than 0.38 amp in this case, and they have to know when to
switch from fast charging at the higher voltage back to standby
charging at ~13.7 volts. A fast charger can be designed to power an
external load as well as charge the battery, but it has to monitor
the battery current separate from the load current. The best ones
also monitor temperature, too. Like I said, more sophisticated.
You have a 12 volt, 1.3 amp-hour battery, I think.
The current limiting on the PB137 is about 2.5 amps, which is not
well matched to a 1.3 amp-hour battery. But in standby use, it
should not be a problem. Many batteries are self-limiting in
standby, and the "NO LIMIT" designation suggests that it might be
true of this battery. A way to be safe about it is to use a 16 volt
power adapter rated at about 400 milliamps. That would serve to
limit the inrush current to the battery should it become severely
depleted.
Charging at 13.7 volt is typical at around room temperature, say from
40 to 100 Fahrenheit. Very cold environments take a higher voltage,
and very hot places a lower voltage. All these gritty details are in
manufacturer's literature.
>
>(That was supposed to be a table)
>
>> Notice that the PB137 touts as a feature that its
>
><trimmed>
>
>Also, what is the PB137? I looked at my VR listing
>last night and did not see that part # listed. Does
>it cross with something else?
Go to http://www.mouser.com, and enter "PB137" into the search box.
It will come up there, and you will also find a link to technical
info, a pdf data sheet here:
http://www.STmicroelectronics.com/stonline/books/pdf/docs/6278.pdf
The battery needs to be matched to the current drain of the system
and the length of time the battery would have to cover a power
failure. And the risk factors of having it fail in a longer than
expected power failure.
I've used this chip. But not for solar chargers. It works there
too, but its quiessent current of 4ma and its dropout voltage of 2
volts are not that great for small solar apps.
-- Tracy
>
>Thanks!
>
>
>
>=====
>Chris Savage
>Knight Designs
>324 West Main Street
>Montour Falls, NY 14865
>(607) 535-6777
>
>http://www.knightdesigns.com
>
>__________________________________
>Do you Yahoo!?
>Free Pop-Up Blocker - Get it now
>http://companion.yahoo.com/
>
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>Subject and Body of the message will be ignored.
>
>
>Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
been in constant use since then and works as advertised. Have had the same
battery for all this time and it is still in excellent shape.
Al, W3AL
Original Message
From: "Brian Grimm" <n7qjb@m...>
To: <basicstamps@yahoogroups.com>
Sent: Tuesday, December 02, 2003 1:57 AM
Subject: [noparse][[/noparse]basicstamps] Re: Battery Backup (Lead Acid Battery)
> I also forgot about A&A Engineering (http://www.a-aengineering.com/).
They
> have a couple of complete kits.
>
> Brian, N7QJB
>
>
Original Message
> From: "Brian Grimm" <n7qjb@m...>
> To: <basicstamps@yahoogroups.com>
> Sent: Monday, December 01, 2003 11:43 PM
> Subject: RE: Battery Backup (Lead Acid Battery)
>
>
> > Chris,
> >
> > This might be a solution for you.
> > http://www.farcircuits.net/battery2.htm#2battery This charger uses the
> > UC3906 chip specifically for sealed lead-acid batteries. I don't have
the
> > magazine article with me right now, but it provides one voltage and
> current
> > while the battery is charging, another for the last 5-10% of charge, and
a
> > third when the battery is topped off.
> >
> > If you know any amateur radio operators (or are one yourself), find a
copy
> > of the 1992 Radio Amateur's Handbook by the ARRL. This project appeared
> in
> > Chapter 27, figure 66. I just received the circuit board and IC, but I
> > haven't assembled it yet so I can't give any real feedback.
> >
> > Also, I found this while searching Google for project above...
> > http://www.geocities.com/vk3em/sla-charger/sla-charger.html This also
> uses
> > the UC3906 chip. There is a higher parts count, and I haven't read the
> > article closely enough to know if its better, but at least it has the
> theory
> > of operation of the chip.
> >
> > Good luck!
> > Brian, N7QJB
> >
> > >Message: 14
> > > Date: Sun, 30 Nov 2003 13:20:22 -0800 (PST)
> > > From: Chris Savage <knight_designs@y...>
> > > Subject: RE: Battery Backup (Lead Acid Battery)
> > >
> > > --- "John D. Kerr" <jdkerr@p...> wrote:
> > > > Chris,
> > > > I had a need also to charge Gel Cell batteries.
> > > > There were a few requirements that I had:
> > > > - simple
> > > > - would maintain a battery on charge indefinitely
> > > > without the worry or
> > > > overcharging it
> > > > - low cost
> > > > - readily available components
> > > > Looked at several options and came up with a circuit
> > > > using an LM317 and a
> > > > handful of components. Take a look at:
> > > > http://www.projectx.com/Kits/GelCell/
> > >
> > > John,
> > > While this looks like an excellent charger, my
> > > project calls for the battery to be charged until
> > > needed. Perhaps it's beyond the scope of asking in
> > > the group (Since it's really more about the power
> > > supply for a BS2 and not the BS2 itself). However, I
> > > was hoping to be able to have my BS2 run off a
> > > Wall-Wart or home-made supply (Which will include both
> > > 5VDC & 12VDC outputs) and then if the AC power fails,
> > > the Lead Acid Battery would take over powering the
> > > circuit.
> > >
> > > Recently I have watched discussion regarding battery
> > > backups in BS2 circuits, and as I stated earlier, I
> > > was a part of an earlier one myself, but I wasn't sure
> > > if the same circuit would apply or not. I don't want
> > > the Lead Acid Battery to potentially lose it's charge
> > > over time, or, if when needed by the circuit, get low,
> > > then remain that way until next time it's needed.
> > >
> > > I guess what I'm asking is this: If you run the
> > > battery power to the regulator through a diode and do
> > > the same thing with the DC power from the Wal-Wart of
> > > supply, will the supply keep the battery charged
> > > through leakage via the diode.
> > >
> > > Somewhere back a ways was a discussion about
> > > this...But my connection keeps getting dropped
> > > everytime I start searching it seems... =(
> > >
> > >
> > > =====
> > > Chris Savage
> > > Knight Designs
> > > 324 West Main Street
> > > Montour Falls, NY 14865
> > > (607) 535-6777
> > >
> > > http://www.knightdesigns.com
> >
>
>
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