lead acid battery maintenance.

[Johan Wagener]

Lead Acid batteries die when they discharge completely right? What do I need
to keep my battery alive? Will a simple 12V DC power supply do? Is there a
more advanced circuit that can be used to charge the battery and to keep it
charged?

 

[Tweetldee]

Lead-acid batteries will become permanently damaged if completely discharged
and left in that condition for a long period of time. Usually, though, if
the battery is in good condition before it's discharged, and then fully
recharged shortly thereafter, no damage will be done.
In order to keep your battery from being damaged, get a small trickle
charger that's designed to be left on the battery indefinitely. Bring the
battery to a fully charged state by running it in an automobile, then
connect the trickle charger.
A good trickle charger (also called float charger) is available from Harbor
Freight at www.harborfreight.com. It's item # 42292-1VGA, and is only $7.49
USD. Search for "float charger"
Cheers!!!
--
Tweetldee
Tweetldee at att dot net (Just subsitute the appropriate characters in the
address)

Never take a laxative and a sleeping pill at the same time!!
"Johan Wagener" <pil(nospam)@webmail.co.za> wrote in message
news:5rudnTBz2pvmv1yiU-KYgw@is.co.za...

Lead Acid batteries die when they discharge completely right? What do I
need
to keep my battery alive? Will a simple 12V DC power supply do? Is there a
more advanced circuit that can be used to charge the battery and to keep
it
charged?

 

[Steve]

A lead acid battery may recover from being fully discharged but each time
that happens, the life of the battery is shorted considerably. A full
discharge is about the worst type of abuse of a lead acid battery..

Most boat owner know that they should not run their expensive 'house
batteries' below 50% of capacity and normally try to do a recharge at about
75%..

I have 800 AH of deep cycle batteries in my house bank on my boat. That
amounts to a $600 investment.. You can bet I never neglect them..

Steve
s/v Good Intentions

 

[Jeff Wiseman]

Johan Wagener wrote:

Lead Acid batteries die when they discharge completely right? What do I need
to keep my battery alive? Will a simple 12V DC power supply do? Is there a
more advanced circuit that can be used to charge the battery and to keep it
charged?

1. They can with certain circumstances,
2. A very high quality charger (or a low quality one if you don't
need it long)
3. Absolutely NOT!
4. Most definately!

You really should check out http://www.batteryfaq.org

- Jeff

 

[mikem]

Johan Wagener wrote:

Lead Acid batteries die when they discharge completely right? What do I need
to keep my battery alive? Will a simple 12V DC power supply do? Is there a
more advanced circuit that can be used to charge the battery and to keep it
charged?

Johan,

here is something I recently posted on one of the aviation
newsgroups: I think it is relevant to your question:

---------- Forwarded message ----------
Date: Fri, 7 Nov 2003 12:12:26 -0700 (Mountain Standard Time)
From: MikeM <...>
To: Pacer15P@...
Cc: Short Wing Piper Maillist <swpc@shortwing.org>,
aeroelectric-list@matronics.com
Subject: Re: Battery Chargers

On Thu, 6 Nov 2003 Pacer15P@... wrote:

Mike,

Read your response about chargers and snake oil and agree with your
comments.
I would appreciate your help with my questions.

Hi Dick,

hope you dont mind if I also forward my reply back to the list.

What charger, amp size, etc., would you recommend to slightly
charge or maintain a std lead acid 35 series aircraft battery?

By "maintain", I assume you are concerned about what happens to
the typical G35 aircraft battery during times when the aircraft
is not flown regularly (say bi-weekly).

The answer is complicated. As long as the aircraft is flown
once every couple of weeks, assuming that the generating
capacity in the aircraft exceeds the current being drawn by the
instruments, avionics and lights, (meaning that the reserve capacity
is available for charging the battery), and that the voltage
regulator gets the battery voltage up to 14.2+ Volts for the
duration of a flight, then you dont need to do anything
involving external chargers.

If the aircraft generation capacity or regulation is suspect,
then instead of tinkering with chargers, you really should fix
the root cause (which is install enough generating capacity,
adjust the voltage regulator to produce said 14.2+ V, fly the
airplane an hour or two every two weeks, etc.)

The reason for the "every two weeks" statements above are based
on the physics of flooded-cell batteries. There are two parts to
prevent degradation of a battery which is sitting unused for
periods of weeks to months. Lets call this "battery
maintenance". Note that "maintenence" only needs to be done when
the aircraft is not regularly flown, as in the winter months.

First, you need to keep the battery from discharging itself even
after disconnecting anything that draws current, which should be
the case if you turn off your Master. Second, you need to
periodically stir the acid in battery to prevent the acid from
stratifying with the lowest specific gravity on top.

All lead acid batteries loose charge just by sitting around. at
100 deg F, a G35 will loose 10%-20% of its capacity per month.
In cold weather, the self discharge rate is much lower. So if
you want to maintain a battery near full capacity, you have to
replace the charge lost due to self discharge. It requires only
~ 0.25A to make up for the leakage.

Preventing self discharge is usually accomplished by "floating"
the battery using a voltage-limited charger, which puts out 13.5
+-0.1 V open-circuit. Most commercial automotive chargers such
as you would get at Sears or Checker are not voltage limited
accurately enough to leave them connected to a battery for more
than 24 hours!!! They are suitable for recharging a run-down
battery, but they must be manually disconnected after a few
hours.

The better models of the automotive chargers have a time clock
shutoff which means you dont have to drive back to the airport
to shut off the charger. If you have the disipline, you can
"maintain" an unused battery through the winter months by giving
it an 4-6 hour charge every 30 days or so, relying on the clock
in the charger to shut it off, otherwise you have to drive back
to airport to disconnect the charger.

One of the primary causes of loss of capacity of batteries is
sulfation of the lead plates; Sulfation happens when the battery
is allowed to sit around in a partially or totally discharged
state for long periods; sulfation is minimised by keeping the
Specific Gravity of the acid high (fully charged) see:

http://www.sierrasolar.com/design/b_leadbattery.htm

The acid in a stationary battery (not being sloshed around in a
car, boat, motorhome, airplane) will stratify, meaning that the
Specific gravity at the top of the battery will be much less
that at the bottom. Due to low SG at the top, the top parts of
the plates will sulfate first, reducing the capacity and cold
cranking amperage of the battery.

The solution to stratification is to mechanically stir the acid,
which happens normally if you take your battery for a ride in
the car, or for a flight in the airplane. However, if the
airplane/car is parked for six months, what then?

A good substitute for mechanical agitation is to periodically
(once every two weeks or so) connect the battery to a charger
whose voltage is set to 14.4+ V for a few hours. In the industry
this is sometimes called "equalization", but the primary benefit
comes from charging the battery hard enough to evolve gas
(hydrogen at one plate, oxygen at the other). The bubbles rise
through the acid, stirring it as they go, mixing the weaker acid
with the stronger.

So, for total automatic unattended maintenance of batteries, the
charger has to float at 13.5V continuously, and every two weeks
or so, it needs to bump up the voltage to about 14.4V while
delivering a few amps for a few hours, and then revert back to
the float mode. If the aircraft is flown regularly, then you
dont have to bother with equalization.

Is it feasible to leave the master switch "on" to activate the
solenoid and charge/maintain the battery thru the cigar
lighter circuit?
Do you think this might create any unforeseen
problems such as overheating the solenoid if left unattended
for several days at a time etc. Or is this just a plain bad
idea?

Its just a bad idea. Overheating of the solenoid shouldn't be a
problem, because the solenoid is rated for it. However, your
charger has to deliver approximately 1.5A to the coil in the
solenoid, plus whatever unswitched loads there are in the aircraft (like
the fuel gauges)

Suppose someone unplugs your charger? Now the solenoid/gauges
will kill your battery. Its not hard to wire in a fused
connector which will allow direct access to the battery with the
master off.

Is it possible to overcharge a battery with today's low
amp chargers?

Yes.

You have to buy a charger specifically made for "float
charging", like the BatteryTender

http://www.batterytender.com/

If in doubt, connect your charger to a battery for 6 to 12
hours. Use an accurate digital voltmeter to measure the voltage
between the battery terminals with the charger still charging.
If the measured battery voltage after a few hours exceeds 13.6V,
the charger is not suitable for long term float charging.

In summary, if all you own is the typical Sears 10A charger with
the time clock, then while the aircraft/motor home/boat is not
being used, hook the charger to the battery with the time clock
set to 6 hours. Go back and do it each month. That is the best
you can do to prevent the battery from loosing capacity while
inactive. During the six hours, the charger will put back the
self discharge, and then it will bubble the battery just enough
to stir the acid. This regemin is way better than just letting
the battery sit idle for six months.

MikeM (PhdEE)
Pacer '00Z
Skylane '1MM

 

[Seaace]

Try looking at this site http://www.uuhome.de/william.darden/

John

"mikem" <mladejov@CharlieEchoDelta.utah.edu> wrote in message
news:bptbhh$fth$1@coward.ks.cc.utah.edu...

Johan Wagener wrote:
Lead Acid batteries die when they discharge completely right? What do I
need
to keep my battery alive? Will a simple 12V DC power supply do? Is there
a
more advanced circuit that can be used to charge the battery and to keep
it
charged?

Johan,

here is something I recently posted on one of the aviation
newsgroups: I think it is relevant to your question:

---------- Forwarded message ----------
Date: Fri, 7 Nov 2003 12:12:26 -0700 (Mountain Standard Time)
From: MikeM <...
To: Pacer15P@...
Cc: Short Wing Piper Maillist <swpc@shortwing.org>,
aeroelectric-list@matronics.com
Subject: Re: Battery Chargers

On Thu, 6 Nov 2003 Pacer15P@... wrote:

Mike,

Read your response about chargers and snake oil and agree with your
comments.
I would appreciate your help with my questions.

Hi Dick,

hope you dont mind if I also forward my reply back to the list.

What charger, amp size, etc., would you recommend to slightly
charge or maintain a std lead acid 35 series aircraft battery?

By "maintain", I assume you are concerned about what happens to
the typical G35 aircraft battery during times when the aircraft
is not flown regularly (say bi-weekly).

The answer is complicated. As long as the aircraft is flown
once every couple of weeks, assuming that the generating
capacity in the aircraft exceeds the current being drawn by the
instruments, avionics and lights, (meaning that the reserve capacity
is available for charging the battery), and that the voltage
regulator gets the battery voltage up to 14.2+ Volts for the
duration of a flight, then you dont need to do anything
involving external chargers.

If the aircraft generation capacity or regulation is suspect,
then instead of tinkering with chargers, you really should fix
the root cause (which is install enough generating capacity,
adjust the voltage regulator to produce said 14.2+ V, fly the
airplane an hour or two every two weeks, etc.)

The reason for the "every two weeks" statements above are based
on the physics of flooded-cell batteries. There are two parts to
prevent degradation of a battery which is sitting unused for
periods of weeks to months. Lets call this "battery
maintenance". Note that "maintenence" only needs to be done when
the aircraft is not regularly flown, as in the winter months.

First, you need to keep the battery from discharging itself even
after disconnecting anything that draws current, which should be
the case if you turn off your Master. Second, you need to
periodically stir the acid in battery to prevent the acid from
stratifying with the lowest specific gravity on top.

All lead acid batteries loose charge just by sitting around. at
100 deg F, a G35 will loose 10%-20% of its capacity per month.
In cold weather, the self discharge rate is much lower. So if
you want to maintain a battery near full capacity, you have to
replace the charge lost due to self discharge. It requires only
~ 0.25A to make up for the leakage.

Preventing self discharge is usually accomplished by "floating"
the battery using a voltage-limited charger, which puts out 13.5
+-0.1 V open-circuit. Most commercial automotive chargers such
as you would get at Sears or Checker are not voltage limited
accurately enough to leave them connected to a battery for more
than 24 hours!!! They are suitable for recharging a run-down
battery, but they must be manually disconnected after a few
hours.

The better models of the automotive chargers have a time clock
shutoff which means you dont have to drive back to the airport
to shut off the charger. If you have the disipline, you can
"maintain" an unused battery through the winter months by giving
it an 4-6 hour charge every 30 days or so, relying on the clock
in the charger to shut it off, otherwise you have to drive back
to airport to disconnect the charger.

One of the primary causes of loss of capacity of batteries is
sulfation of the lead plates; Sulfation happens when the battery
is allowed to sit around in a partially or totally discharged
state for long periods; sulfation is minimised by keeping the
Specific Gravity of the acid high (fully charged) see:

http://www.sierrasolar.com/design/b_leadbattery.htm

The acid in a stationary battery (not being sloshed around in a
car, boat, motorhome, airplane) will stratify, meaning that the
Specific gravity at the top of the battery will be much less
that at the bottom. Due to low SG at the top, the top parts of
the plates will sulfate first, reducing the capacity and cold
cranking amperage of the battery.

The solution to stratification is to mechanically stir the acid,
which happens normally if you take your battery for a ride in
the car, or for a flight in the airplane. However, if the
airplane/car is parked for six months, what then?

A good substitute for mechanical agitation is to periodically
(once every two weeks or so) connect the battery to a charger
whose voltage is set to 14.4+ V for a few hours. In the industry
this is sometimes called "equalization", but the primary benefit
comes from charging the battery hard enough to evolve gas
(hydrogen at one plate, oxygen at the other). The bubbles rise
through the acid, stirring it as they go, mixing the weaker acid
with the stronger.

So, for total automatic unattended maintenance of batteries, the
charger has to float at 13.5V continuously, and every two weeks
or so, it needs to bump up the voltage to about 14.4V while
delivering a few amps for a few hours, and then revert back to
the float mode. If the aircraft is flown regularly, then you
dont have to bother with equalization.

Is it feasible to leave the master switch "on" to activate the
solenoid and charge/maintain the battery thru the cigar
lighter circuit?
Do you think this might create any unforeseen
problems such as overheating the solenoid if left unattended
for several days at a time etc. Or is this just a plain bad
idea?

Its just a bad idea. Overheating of the solenoid shouldn't be a
problem, because the solenoid is rated for it. However, your
charger has to deliver approximately 1.5A to the coil in the
solenoid, plus whatever unswitched loads there are in the aircraft (like
the fuel gauges)

Suppose someone unplugs your charger? Now the solenoid/gauges
will kill your battery. Its not hard to wire in a fused
connector which will allow direct access to the battery with the
master off.

Is it possible to overcharge a battery with today's low
amp chargers?

Yes.

You have to buy a charger specifically made for "float
charging", like the BatteryTender

http://www.batterytender.com/

If in doubt, connect your charger to a battery for 6 to 12
hours. Use an accurate digital voltmeter to measure the voltage
between the battery terminals with the charger still charging.
If the measured battery voltage after a few hours exceeds 13.6V,
the charger is not suitable for long term float charging.

In summary, if all you own is the typical Sears 10A charger with
the time clock, then while the aircraft/motor home/boat is not
being used, hook the charger to the battery with the time clock
set to 6 hours. Go back and do it each month. That is the best
you can do to prevent the battery from loosing capacity while
inactive. During the six hours, the charger will put back the
self discharge, and then it will bubble the battery just enough
to stir the acid. This regemin is way better than just letting
the battery sit idle for six months.

MikeM (PhdEE)
Pacer '00Z
Skylane '1MM

 

[CWatters]

Look for a battery charger with a normal/float mode switch. Charge on
"Normal" setting then leave it on the "float setting" all the time. Avoid
storing the battery where it can get cold and damp. Put it on wooden blocks
rather than direct on the the concrete garahge floor etc.

Lead acid batteries are usually charged by a constant voltage source (backed
by a current limit). The voltage for a 100% full charge is too high to leave
it on that setting constantly. If you do leave it on an ordinary charger the
battery acid will "boil" off. The voltage for "Float charging" is lower and
is designed to keep the battery as full as possible without excess
evaporation/"boiling".


"Johan Wagener" <pil(nospam)@webmail.co.za> wrote in message
news:5rudnTBz2pvmv1yiU-KYgw@is.co.za...

Lead Acid batteries die when they discharge completely right? What do I
need
to keep my battery alive? Will a simple 12V DC power supply do? Is there a
more advanced circuit that can be used to charge the battery and to keep
it
charged?

 

[mikem]

CWatters wrote:

Avoid
storing the battery where it can get cold and damp.
Put it on wooden blocks
rather than direct on the the concrete garahge floor etc.

OWT!! The bit about concrete floors has been debunked ad nauseum

Just keep the top of the battery clear of acid residue.

MikeM

 

[Keith R. Williams]

In article <bpubl8$psh$1@coward.ks.cc.utah.edu>,
mladejov@CharlieEchoDelta.utah.edu says...

CWatters wrote:


Avoid
storing the battery where it can get cold and damp.
Put it on wooden blocks
rather than direct on the the concrete garahge floor etc.

OWT!! The bit about concrete floors has been debunked ad nauseum

IIRC, there was reason behind this OWT with the old rubber cases.
They did leak thought the case. With today's plastic cases, not.

Just keep the top of the battery clear of acid residue.

Keeping a lead-acid cell on a float charge is crucial for it's
longevity. A properly maintained lead-acid will last eight years
or perhaps more (where "last" is defined as 80% capacity). They
do *not* like to be discharged and they *will* self-discharge.

--
Keith

 

[Jeff Wiseman]

mikem wrote:

CWatters wrote:

Avoid
storing the battery where it can get cold and damp.
Put it on wooden blocks
rather than direct on the the concrete garahge floor etc.

OWT!! The bit about concrete floors has been debunked ad nauseum

MikeM

No it hasn't.

Due to the concrete's thermal mass, setting a battery on concrete
can result in there being a temperature differential between the
top of the battery and the bottom during changing air
temperatures. This can produce a small electrical differential
within each of the cells resulting in a slow discharge. Storage
of a battery should allow for a constant temperature across the
entire battery to reduce this problem.

- Jeff

 

[Jeff]

"Jeff Wiseman" <wisemanja@earthlink.net> wrote in message
news:3FC37E0B.8528D0E7@earthlink.net...

mikem wrote:

CWatters wrote:

Avoid
storing the battery where it can get cold and damp.
Put it on wooden blocks
rather than direct on the the concrete garahge floor etc.

OWT!! The bit about concrete floors has been debunked ad nauseum

MikeM


No it hasn't.

Due to the concrete's thermal mass, setting a battery on concrete
can result in there being a temperature differential between the
top of the battery and the bottom during changing air
temperatures. This can produce a small electrical differential
within each of the cells resulting in a slow discharge. Storage
of a battery should allow for a constant temperature across the
entire battery to reduce this problem.

Yes, this is the real underlying problem. Battery powered submarines must
use bubblers in the batteries which are in close proximity of the hull to
keep the electrolite circulating so thermal gradiants do not cause
electrolite density differnces, and thus electrical gradiants that discharge
the batteries.

Also Jeff

- Jeff

 

[mikem]

Jeff Wiseman wrote:

No it hasn't.

Due to the concrete's thermal mass, setting a battery on concrete
can result in there being a temperature differential between the
top of the battery and the bottom during changing air
temperatures. This can produce a small electrical differential
within each of the cells resulting in a slow discharge. Storage
of a battery should allow for a constant temperature across the
entire battery to reduce this problem.

- Jeff

So if your battery is already being "floated" with the appropriate float
charger to keep it from self discharging, why does it matter if it is
sitting on concrete?

If its occasionally charged hard enough to evolve gas to stir and
destratify the electroyte, why does it mattery if it is sitting on concrete?

MikeM

 

[Sofie]

mikem:
I don't see that there is a problem with you leaving it set on the concrete
floor.......
...... all the right things are being done..... trickle charging.... and an
occasional "hard" charge to stir things up.
--
Best Regards,
Daniel Sofie
Electronics Supply & Repair
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -



"mikem" <mladejov@CharlieEchoDelta.utah.edu> wrote in message news:bq0fa6>

So if your battery is already being "floated" with the appropriate float
charger to keep it from self discharging, why does it matter if it is
sitting on concrete?

If its occasionally charged hard enough to evolve gas to stir and
destratify the electroyte, why does it mattery if it is sitting on
concrete?

MikeM

 

[Asimov]

"Jeff" bravely wrote to "All" (25 Nov 03 17:12:04)
--- on the heady topic of "Re: lead acid battery maintenance."

Je> From: "Jeff" <levy_jeff@hotmail.com>

Je> "Jeff Wiseman" <wisemanja@earthlink.net> wrote in message
Je> news:3FC37E0B.8528D0E7@earthlink.net...

mikem wrote:

CWatters wrote:

Avoid
storing the battery where it can get cold and damp.
Put it on wooden blocks
rather than direct on the the concrete garahge floor etc.

OWT!! The bit about concrete floors has been debunked ad nauseum

MikeM


No it hasn't.

Due to the concrete's thermal mass, setting a battery on concrete
can result in there being a temperature differential between the
top of the battery and the bottom during changing air
temperatures. This can produce a small electrical differential
within each of the cells resulting in a slow discharge. Storage
of a battery should allow for a constant temperature across the
entire battery to reduce this problem.

Je> Yes, this is the real underlying problem. Battery powered submarines
Je> must use bubblers in the batteries which are in close proximity of the
Je> hull to keep the electrolite circulating so thermal gradiants do not
Je> cause electrolite density differnces, and thus electrical gradiants
Je> that discharge the batteries.

I think a fix for the temperature gradient aka electrolyte density
difference on the garage concrete floor in cold weather is in how the
black case tends to radiate heat. I'm guessing that one way to overcome
this is to cover the terminals with a plastic bag and then wrapping the
whole battery in aluminium foil to equalize the case temperature by
conduction. I've never heard of this being tried before but I think it
might work.

.... A fail-safe circuit will destroy others.

 

[Animesh Maurya]

"Tweetldee" <dgmason99@att99.net> wrote in message news:<jiawb.318281$0v4.18462528@bgtnsc04-news.ops.worldnet.att.net>...

Lead-acid batteries will become permanently damaged if completely discharged
and left in that condition for a long period of time.

How much long period of time? Just want to get an initial idea about it.

Thanks

Animesh Maurya

 

[mikem]

Animesh Maurya wrote:

How much long period of time? Just want to get an initial idea about it.

Thanks

Animesh Maurya

Read the entire thread!

 

[CWatters]

I use a deep discharge lead acid battery to charge nicad and nimh cells for
electric aircraft. When I started out I was killing two lead acid batteries
a year by leaving them partly discharged between use. Typically I would
charge them on a friday night and use them on the weekend then leave them
until the next friday before charging them again. I never discharged them
more than say 50% but that routine was enough to kill them over a 6 month
period. Typically the capacity fell until the battery didn't have enough
capacity to do a days work.

After about my 4th battery in two years I got a new charger with a float
setting and switched to a new routine - I fully charge them overnight after
use (typically Sunday night) then switch the charger to float mode
permanantly. My latest battery is now 6 years old. It's survived several
winters where it got no use and was on float charge for the 4-6 months
between full charges.

That charger (with full/float switch) cost Ł28 (about $40) from a
caravan/car accessory shop and has probably saved me Ł600 to Ł800 over those
6 years.



"Animesh Maurya" <animesh_m@eudoramail.com> wrote in message
news:9f6c9f5d.0311260426.29325e6e@posting.google.com...

"Tweetldee" <dgmason99@att99.net> wrote in message
news:<jiawb.318281$0v4.18462528@bgtnsc04-news.ops.worldnet.att.net>...
Lead-acid batteries will become permanently damaged if completely
discharged
and left in that condition for a long period of time.

How much long period of time? Just want to get an initial idea about it.

Thanks

Animesh Maurya

 

[Keith R. Williams]

In article <E4kxb.45947$cn5.1252393@phobos.telenet-ops.be>,
colin.watters@pandoraBOX.be says...

I use a deep discharge lead acid battery to charge nicad and nimh cells for
electric aircraft. When I started out I was killing two lead acid batteries
a year by leaving them partly discharged between use. Typically I would
charge them on a friday night and use them on the weekend then leave them
until the next friday before charging them again. I never discharged them
more than say 50% but that routine was enough to kill them over a 6 month
period. Typically the capacity fell until the battery didn't have enough
capacity to do a days work.

After about my 4th battery in two years I got a new charger with a float
setting and switched to a new routine - I fully charge them overnight after
use (typically Sunday night) then switch the charger to float mode
permanantly. My latest battery is now 6 years old. It's survived several
winters where it got no use and was on float charge for the 4-6 months
between full charges.

That charger (with full/float switch) cost Ł28 (about $40) from a
caravan/car accessory shop and has probably saved me Ł600 to Ł800 over those
6 years.

Sounds about right. The lead-acid batteries I used were rated for
an eight-ten year life if treated well.

I was responsible[1] for a battery and charger where the designer
was so concerned with proper float charging that that's all he
designed. It worked wonders, as long as the battery was never
discharged. Since this battery was in a mainframe system (used
for crypto key retention and hardware tamper alarms) it was
decided[2] that this was a good scheme. After all, who powers
off a >$20M mainframe? The system and batteries were designed for
an eight-year life with up to a two-week power outage before the
keys were "zeroized" (reset because tamper alarms were no longer
reliable).

All was fine in systems test. After a couple of months in the
field we stated getting field reports with keys being zeroized,
and random tamper alarms. We found that the Japaneese are
required to shut down systems that aren't in actual production (a
surprise to everyone in mainframe-city). Each night the banks
powered down the systems for eight hours. The float charge
wasn't enough to *ever* fully charge the batteries, and wasn't
keeping up with the 2/3s duty cycle.

Moral: Always treat batteries as their manufacturer recommends.


[1] Design wasn't mine, but on my card and the designer retired
before TSHTF.

[2] The battery's manufacturer (Gates Energy) didn't like the
scheme at all, so I rather sided with them. I tried to fight city
hall....

--
Keith

 

[Neil Preston]

"Johan Wagener" <pil(nospam)@webmail.co.za> wrote in message
news:5rudnTBz2pvmv1yiU-KYgw@is.co.za...

Lead Acid batteries die when they discharge completely right? What do I
need
to keep my battery alive? Will a simple 12V DC power supply do? Is there a
more advanced circuit that can be used to charge the battery and to keep
it
charged?

Keeping a garden tractor battery alive over the winter has in the past
proved to be a challenge.

Float chargers on for 24/7 tend to 'evaporate' the electrolyte.

I've found the most effective solution to be to use an appliance timer set
to turn on a standard battery charger for its minimum time (about 15
minutes) every day. The charge is 'hot' enough to generate some hydrogen
bubbles to agitate the electrolyte, but short enough not to evaporate any
significant amount.

To eliminate sulfation, I use a Solargizer, which applies a high-frequency,
high voltage pulsating current to bust up the sulfate molecules.

The system seems to work well for car batteries, too. And it's inexpensive.

 

[CWatters]

"Neil Preston" <npreston@no.spam.swbell.net> wrote in message
news:m_Axb.3092$to5.635@newssvr24.news.prodigy.com...

Float chargers on for 24/7 tend to 'evaporate' the electrolyte

That sounds like the float voltage is slightly too high. Mine works just
fine with virtually no loss over 9 month. Some float chargers have an
adjustment so you can fine tune it. The main problem is that the adjustment
is usually inside the case and the case is not intended to opened by the
user because there are hazardous voltages. You need to make very small
adjustments with the battery connected and then wait a day or two to allow
the battery to adjust to the new voltage setting - then repeat until it's
right.