On Thu, 28 Jul 2005 22:48:01 GMT, John Horner <jthorner@yahoo.com>
wrote:

>flobert wrote:
>
>> Yes and no. The battery is designed to be chargable. using, and
>> draining and charging the battery doesn't 'damage it' per se. If it is
>> kept below 10V for an extended period of time (say 12 hours or more)
>> then it is irreperably damaged. using a trickle charger is the best
>> way to charge a low battery.
>
>Au contrar, cycling a battery, especially cycling it into a deep
>discharge mode, absolutely is a major factor in it's expected life time.
> Automotive lead-acid batteries do not recover well from deep
>discharge events. Take almost any new conventional battery and run it
>through twenty cycles of 90% discharge followed by full recharge. Most
>will be dead by the end of such a torture test.

a 90% discharge takes its voltage to somewhere in the 5-6V range,
obviously that damages plates. 10V is about 50%, and is aboutt he
minimum limit for successfull resotation.

>
>John

 

On Thu, 28 Jul 2005 22:48:01 GMT, John Horner <jthorner@yahoo.com>
wrote:

>flobert wrote:
>
>> Yes and no. The battery is designed to be chargable. using, and
>> draining and charging the battery doesn't 'damage it' per se. If it is
>> kept below 10V for an extended period of time (say 12 hours or more)
>> then it is irreperably damaged. using a trickle charger is the best
>> way to charge a low battery.
>
>Au contrar, cycling a battery, especially cycling it into a deep
>discharge mode, absolutely is a major factor in it's expected life time.
> Automotive lead-acid batteries do not recover well from deep
>discharge events. Take almost any new conventional battery and run it
>through twenty cycles of 90% discharge followed by full recharge. Most
>will be dead by the end of such a torture test.

a 90% discharge takes its voltage to somewhere in the 5-6V range,
obviously that damages plates. 10V is about 50%, and is aboutt he
minimum limit for successfull resotation.

>
>John

 

On Thu, 28 Jul 2005 15:53:20 -0700, "Michael Pardee"
<michaeltnull@cybertrails.com> wrote:

>"flobert" <nomail@here.com> wrote in message
>news:v01ie1hvmou7nejth7a0ruui64voajc0u1@4ax.com.. .
>> On Wed, 27 Jul 2005 05:49:38 -0700, "Michael Pardee"
>> <michaeltnull@cybertrails.com> wrote:
>>
>>>"ap" <corsica@ragingbull.com> wrote in message
>>>news:1122302819.747066.122750@z14g2000cwz.googl egroups.com...
>>>> Is it normal for the battery to fail load test
>>>> at only 36K?
>>
>> Batteries are not engine componants, they work by time, and not miles.
>> Was the battery topped up?
>>
>>>>
>>>
>>>That really depends on the climate. When I lived in Phoenix I never had a
>>>battery survive three summers - they would almost always give up early in
>>>the third summer (like around May, since summer there is pretty much
>>>May-September, and it's hit 100 degrees in March.) Now I live in Flagstaff
>>>and the only battery I've had to replace in 4 years was in a car we had
>>>recently bought.
>>
>> Did you let the car run for a little before turning the AC on, and
>> similarly turn the AC off a little bit before you turned the engine
>> off in Az? if not, thats what would have killed them.
>>
>My car didn't have A/C but had short battery life the same as my wife's. Two
>years, then replace (and that was with batteries advertised as being
>designed for hot climates). On hot afternoons the temp guage would already
>be off the bottom peg before I ever started the engine. The day it was 122,
>when I started my car the battery simply exploded.
>
>I also buy only full-service batteries. Sealed batteries in that heat are a
>bad idea, and I just carry on the tradition here.

Depends on the type of sealed battery. My preference is for a sealled
gas recombination based one, with gas vent - they don't explode at
all, don't even leak fluid. Used to run them all day long in a big
plastic greenhouse, lit by some 40KW of lighting, inside an old WW2
building, with the outside temp in the 110's - not a single
roble,.Course, at $300-ish a shot for a reletively small 30Ah one,
they're not cheap, but worth it - especially since they'll do about
2000A peak output, and will take the same input as charge.

>
>Mike
>

 

On Thu, 28 Jul 2005 15:53:20 -0700, "Michael Pardee"
<michaeltnull@cybertrails.com> wrote:

>"flobert" <nomail@here.com> wrote in message
>news:v01ie1hvmou7nejth7a0ruui64voajc0u1@4ax.com.. .
>> On Wed, 27 Jul 2005 05:49:38 -0700, "Michael Pardee"
>> <michaeltnull@cybertrails.com> wrote:
>>
>>>"ap" <corsica@ragingbull.com> wrote in message
>>>news:1122302819.747066.122750@z14g2000cwz.googl egroups.com...
>>>> Is it normal for the battery to fail load test
>>>> at only 36K?
>>
>> Batteries are not engine componants, they work by time, and not miles.
>> Was the battery topped up?
>>
>>>>
>>>
>>>That really depends on the climate. When I lived in Phoenix I never had a
>>>battery survive three summers - they would almost always give up early in
>>>the third summer (like around May, since summer there is pretty much
>>>May-September, and it's hit 100 degrees in March.) Now I live in Flagstaff
>>>and the only battery I've had to replace in 4 years was in a car we had
>>>recently bought.
>>
>> Did you let the car run for a little before turning the AC on, and
>> similarly turn the AC off a little bit before you turned the engine
>> off in Az? if not, thats what would have killed them.
>>
>My car didn't have A/C but had short battery life the same as my wife's. Two
>years, then replace (and that was with batteries advertised as being
>designed for hot climates). On hot afternoons the temp guage would already
>be off the bottom peg before I ever started the engine. The day it was 122,
>when I started my car the battery simply exploded.
>
>I also buy only full-service batteries. Sealed batteries in that heat are a
>bad idea, and I just carry on the tradition here.

Depends on the type of sealed battery. My preference is for a sealled
gas recombination based one, with gas vent - they don't explode at
all, don't even leak fluid. Used to run them all day long in a big
plastic greenhouse, lit by some 40KW of lighting, inside an old WW2
building, with the outside temp in the 110's - not a single
roble,.Course, at $300-ish a shot for a reletively small 30Ah one,
they're not cheap, but worth it - especially since they'll do about
2000A peak output, and will take the same input as charge.

>
>Mike
>

 

"flobert" <nomail@here.NOT> wrote in message
news:jooke1poj1eeh5ancrv1sdd4ej396thndl@4ax.com...
> On Thu, 28 Jul 2005 15:53:20 -0700, "Michael Pardee"
> Depends on the type of sealed battery. My preference is for a sealled
> gas recombination based one, with gas vent - they don't explode at
> all, don't even leak fluid. Used to run them all day long in a big
> plastic greenhouse, lit by some 40KW of lighting, inside an old WW2
> building, with the outside temp in the 110's - not a single
> roble,.Course, at $300-ish a shot for a reletively small 30Ah one,
> they're not cheap, but worth it - especially since they'll do about
> 2000A peak output, and will take the same input as charge.
>
Unless I'm mistaken, all sealed lead-acid batteries are recombination with
overpresure vents, also known as Valve Regulated Lead Acid (VRLA) batteries.

There are different grid chemistries, though. I assume the automotive types
are designed for higher temperatures and non-deep cycle. We use absorbed
electrolyte VRLAs where I work (communication sites) and they are spec'd at
15 or 20 years life, depending on the specific model. We started using them
because they have a smaller floor area for the capacity than flooded cells
and because they don't need venting to the outside or other safety
precautions. They have been very tempramental, though, and we have not had
one last ten years yet. They all die the same way, and the process was
described to me by a friend who worked for ABB selling the things. As they
age, the leakage current for a given temperature creeps up. At some point,
either because of A/C failure or just because the critical temperature
dropped to room temperature, the battery will go into thermal runaway. The
leakage current will rise, heating the battery and increasing the leakage
and further heating the battery. A couple weeks ago I caught one of our
banks at 120 degrees F and consuming 1500 watts... because somebody left the
room door open for a few hours. $20K will fix it up just fine, though. The
highest temperature we've recorded was 191F, and the tech felt the heat on
his face when he entered the room. Around 220F the polypropylene cases
soften and the batteries explode like small bombs - I've seen a picture of a
room full of equipment that was splattered with boiling acid that way.

The demise in automotive use should be different because a charger isn't on
it 24/7. Higher temperatures during charging cause the battery to vent,
losing the vented vapor forever. Eventually, the lost water causes the
battery to dry up and the output current and capacity to drop - the way gell
cells (and that's what all VRLA batteries are, after all) have died for
decades. A whole lot better than going supernova!

Mike

 

"flobert" <nomail@here.NOT> wrote in message
news:jooke1poj1eeh5ancrv1sdd4ej396thndl@4ax.com...
> On Thu, 28 Jul 2005 15:53:20 -0700, "Michael Pardee"
> Depends on the type of sealed battery. My preference is for a sealled
> gas recombination based one, with gas vent - they don't explode at
> all, don't even leak fluid. Used to run them all day long in a big
> plastic greenhouse, lit by some 40KW of lighting, inside an old WW2
> building, with the outside temp in the 110's - not a single
> roble,.Course, at $300-ish a shot for a reletively small 30Ah one,
> they're not cheap, but worth it - especially since they'll do about
> 2000A peak output, and will take the same input as charge.
>
Unless I'm mistaken, all sealed lead-acid batteries are recombination with
overpresure vents, also known as Valve Regulated Lead Acid (VRLA) batteries.

There are different grid chemistries, though. I assume the automotive types
are designed for higher temperatures and non-deep cycle. We use absorbed
electrolyte VRLAs where I work (communication sites) and they are spec'd at
15 or 20 years life, depending on the specific model. We started using them
because they have a smaller floor area for the capacity than flooded cells
and because they don't need venting to the outside or other safety
precautions. They have been very tempramental, though, and we have not had
one last ten years yet. They all die the same way, and the process was
described to me by a friend who worked for ABB selling the things. As they
age, the leakage current for a given temperature creeps up. At some point,
either because of A/C failure or just because the critical temperature
dropped to room temperature, the battery will go into thermal runaway. The
leakage current will rise, heating the battery and increasing the leakage
and further heating the battery. A couple weeks ago I caught one of our
banks at 120 degrees F and consuming 1500 watts... because somebody left the
room door open for a few hours. $20K will fix it up just fine, though. The
highest temperature we've recorded was 191F, and the tech felt the heat on
his face when he entered the room. Around 220F the polypropylene cases
soften and the batteries explode like small bombs - I've seen a picture of a
room full of equipment that was splattered with boiling acid that way.

The demise in automotive use should be different because a charger isn't on
it 24/7. Higher temperatures during charging cause the battery to vent,
losing the vented vapor forever. Eventually, the lost water causes the
battery to dry up and the output current and capacity to drop - the way gell
cells (and that's what all VRLA batteries are, after all) have died for
decades. A whole lot better than going supernova!

Mike

 

On Fri, 29 Jul 2005 16:32:21 -0700, "Michael Pardee"
<michaeltnull@cybertrails.com> wrote:

>"flobert" <nomail@here.NOT> wrote in message
>news:jooke1poj1eeh5ancrv1sdd4ej396thndl@4ax.com.. .
>> On Thu, 28 Jul 2005 15:53:20 -0700, "Michael Pardee"
>> Depends on the type of sealed battery. My preference is for a sealled
>> gas recombination based one, with gas vent - they don't explode at
>> all, don't even leak fluid. Used to run them all day long in a big
>> plastic greenhouse, lit by some 40KW of lighting, inside an old WW2
>> building, with the outside temp in the 110's - not a single
>> roble,.Course, at $300-ish a shot for a reletively small 30Ah one,
>> they're not cheap, but worth it - especially since they'll do about
>> 2000A peak output, and will take the same input as charge.
>>
>Unless I'm mistaken, all sealed lead-acid batteries are recombination with
>overpresure vents, also known as Valve Regulated Lead Acid (VRLA) batteries.
>
>There are different grid chemistries, though. I assume the automotive types
>are designed for higher temperatures and non-deep cycle. We use absorbed
>electrolyte VRLAs where I work (communication sites) and they are spec'd at
>15 or 20 years life, depending on the specific model. We started using them
>because they have a smaller floor area for the capacity than flooded cells
>and because they don't need venting to the outside or other safety
>precautions. They have been very tempramental, though, and we have not had
>one last ten years yet. They all die the same way, and the process was
>described to me by a friend who worked for ABB selling the things. As they
>age, the leakage current for a given temperature creeps up. At some point,
>either because of A/C failure or just because the critical temperature
>dropped to room temperature, the battery will go into thermal runaway. The
>leakage current will rise, heating the battery and increasing the leakage
>and further heating the battery. A couple weeks ago I caught one of our
>banks at 120 degrees F and consuming 1500 watts... because somebody left the
>room door open for a few hours. $20K will fix it up just fine, though. The
>highest temperature we've recorded was 191F, and the tech felt the heat on
>his face when he entered the room. Around 220F the polypropylene cases
>soften and the batteries explode like small bombs - I've seen a picture of a
>room full of equipment that was splattered with boiling acid that way.

sounds like you're using cheap ones. yuasa, powersonic, or similar?
those i'd expect, they're prety low quality ones. Personally, i'll
always use hawkers - never had a single runaway, explosion or other
problem. Had to deal with lots of the cheaper ones exploding, and
catching fire before, but in similar situations the hawkers have
swelled, and thats about it. There's a reason yuasas and such aren't
certified safe for air travel, and hawkers are.

>
>The demise in automotive use should be different because a charger isn't on
>it 24/7. Higher temperatures during charging cause the battery to vent,
>losing the vented vapor forever. Eventually, the lost water causes the
>battery to dry up and the output current and capacity to drop - the way gell
>cells (and that's what all VRLA batteries are, after all) have died for
>decades. A whole lot better than going supernova!
>
>Mike
>
>

 

On Fri, 29 Jul 2005 16:32:21 -0700, "Michael Pardee"
<michaeltnull@cybertrails.com> wrote:

>"flobert" <nomail@here.NOT> wrote in message
>news:jooke1poj1eeh5ancrv1sdd4ej396thndl@4ax.com.. .
>> On Thu, 28 Jul 2005 15:53:20 -0700, "Michael Pardee"
>> Depends on the type of sealed battery. My preference is for a sealled
>> gas recombination based one, with gas vent - they don't explode at
>> all, don't even leak fluid. Used to run them all day long in a big
>> plastic greenhouse, lit by some 40KW of lighting, inside an old WW2
>> building, with the outside temp in the 110's - not a single
>> roble,.Course, at $300-ish a shot for a reletively small 30Ah one,
>> they're not cheap, but worth it - especially since they'll do about
>> 2000A peak output, and will take the same input as charge.
>>
>Unless I'm mistaken, all sealed lead-acid batteries are recombination with
>overpresure vents, also known as Valve Regulated Lead Acid (VRLA) batteries.
>
>There are different grid chemistries, though. I assume the automotive types
>are designed for higher temperatures and non-deep cycle. We use absorbed
>electrolyte VRLAs where I work (communication sites) and they are spec'd at
>15 or 20 years life, depending on the specific model. We started using them
>because they have a smaller floor area for the capacity than flooded cells
>and because they don't need venting to the outside or other safety
>precautions. They have been very tempramental, though, and we have not had
>one last ten years yet. They all die the same way, and the process was
>described to me by a friend who worked for ABB selling the things. As they
>age, the leakage current for a given temperature creeps up. At some point,
>either because of A/C failure or just because the critical temperature
>dropped to room temperature, the battery will go into thermal runaway. The
>leakage current will rise, heating the battery and increasing the leakage
>and further heating the battery. A couple weeks ago I caught one of our
>banks at 120 degrees F and consuming 1500 watts... because somebody left the
>room door open for a few hours. $20K will fix it up just fine, though. The
>highest temperature we've recorded was 191F, and the tech felt the heat on
>his face when he entered the room. Around 220F the polypropylene cases
>soften and the batteries explode like small bombs - I've seen a picture of a
>room full of equipment that was splattered with boiling acid that way.

sounds like you're using cheap ones. yuasa, powersonic, or similar?
those i'd expect, they're prety low quality ones. Personally, i'll
always use hawkers - never had a single runaway, explosion or other
problem. Had to deal with lots of the cheaper ones exploding, and
catching fire before, but in similar situations the hawkers have
swelled, and thats about it. There's a reason yuasas and such aren't
certified safe for air travel, and hawkers are.

>
>The demise in automotive use should be different because a charger isn't on
>it 24/7. Higher temperatures during charging cause the battery to vent,
>losing the vented vapor forever. Eventually, the lost water causes the
>battery to dry up and the output current and capacity to drop - the way gell
>cells (and that's what all VRLA batteries are, after all) have died for
>decades. A whole lot better than going supernova!
>
>Mike
>
>

 

"flobert" <nomail@here.NOT> wrote in message
news:1s1me19bck33a9ssva6ogts63n7t9p08uf@4ax.com...
> On Fri, 29 Jul 2005 16:32:21 -0700, "Michael Pardee"
> <michaeltnull@cybertrails.com> wrote:
>>Unless I'm mistaken, all sealed lead-acid batteries are recombination with
>>overpresure vents, also known as Valve Regulated Lead Acid (VRLA)
>>batteries.
>>
>>There are different grid chemistries, though. I assume the automotive
>>types
>>are designed for higher temperatures and non-deep cycle. We use absorbed
>>electrolyte VRLAs where I work (communication sites) and they are spec'd
>>at
>>15 or 20 years life, depending on the specific model. We started using
>>them
>>because they have a smaller floor area for the capacity than flooded cells
>>and because they don't need venting to the outside or other safety
>>precautions. They have been very tempramental, though, and we have not had
>>one last ten years yet. They all die the same way, and the process was
>>described to me by a friend who worked for ABB selling the things. As they
>>age, the leakage current for a given temperature creeps up. At some point,
>>either because of A/C failure or just because the critical temperature
>>dropped to room temperature, the battery will go into thermal runaway. The
>>leakage current will rise, heating the battery and increasing the leakage
>>and further heating the battery. A couple weeks ago I caught one of our
>>banks at 120 degrees F and consuming 1500 watts... because somebody left
>>the
>>room door open for a few hours. $20K will fix it up just fine, though. The
>>highest temperature we've recorded was 191F, and the tech felt the heat on
>>his face when he entered the room. Around 220F the polypropylene cases
>>soften and the batteries explode like small bombs - I've seen a picture of
>>a
>>room full of equipment that was splattered with boiling acid that way.
>
> sounds like you're using cheap ones. yuasa, powersonic, or similar?
> those i'd expect, they're prety low quality ones. Personally, i'll
> always use hawkers - never had a single runaway, explosion or other
> problem. Had to deal with lots of the cheaper ones exploding, and
> catching fire before, but in similar situations the hawkers have
> swelled, and thats about it. There's a reason yuasas and such aren't
> certified safe for air travel, and hawkers are.
>
More expensive than the Hawkers, I suspect - they're GNB Absolyte batteries.
The small banks run $5000 US, while the larger banks are $20 thousand. The
large bank I mentioned was half a 3000 AH 48V bank. They look like
http://www.batterypowersystems.com/p...bsolyteIIP.htm .

The likely difference in failure modes is because of the type of service. In
communication service, the batteries are "floated" at 2.25 volts per cell by
fixed voltage, current limited chargers. In automotive use the charge is
more intermittent, so thermal runaway is rare. However, the batteries are
much smaller so the thermal mass is smaller. A battery that did fine on
in-town trips is really tested on long trips, where the charging is constant
enough to possibly trigger thermal runaway.

But I suspect the design is different enough that the car batteries fail
through dehydration most of the time. Our Toyota Prius has a sealed
lead-acid aux battery... reports from people who've had to replace them are
very familiar. They let it run down, charged it by jumping and letting the
car charge it, often in warm weather. Sealed batteries are still the old
gell cells with minor updates. As long as they aren't in the engine
compartment they aren't too bad.

Mike

 

"flobert" <nomail@here.NOT> wrote in message
news:1s1me19bck33a9ssva6ogts63n7t9p08uf@4ax.com...
> On Fri, 29 Jul 2005 16:32:21 -0700, "Michael Pardee"
> <michaeltnull@cybertrails.com> wrote:
>>Unless I'm mistaken, all sealed lead-acid batteries are recombination with
>>overpresure vents, also known as Valve Regulated Lead Acid (VRLA)
>>batteries.
>>
>>There are different grid chemistries, though. I assume the automotive
>>types
>>are designed for higher temperatures and non-deep cycle. We use absorbed
>>electrolyte VRLAs where I work (communication sites) and they are spec'd
>>at
>>15 or 20 years life, depending on the specific model. We started using
>>them
>>because they have a smaller floor area for the capacity than flooded cells
>>and because they don't need venting to the outside or other safety
>>precautions. They have been very tempramental, though, and we have not had
>>one last ten years yet. They all die the same way, and the process was
>>described to me by a friend who worked for ABB selling the things. As they
>>age, the leakage current for a given temperature creeps up. At some point,
>>either because of A/C failure or just because the critical temperature
>>dropped to room temperature, the battery will go into thermal runaway. The
>>leakage current will rise, heating the battery and increasing the leakage
>>and further heating the battery. A couple weeks ago I caught one of our
>>banks at 120 degrees F and consuming 1500 watts... because somebody left
>>the
>>room door open for a few hours. $20K will fix it up just fine, though. The
>>highest temperature we've recorded was 191F, and the tech felt the heat on
>>his face when he entered the room. Around 220F the polypropylene cases
>>soften and the batteries explode like small bombs - I've seen a picture of
>>a
>>room full of equipment that was splattered with boiling acid that way.
>
> sounds like you're using cheap ones. yuasa, powersonic, or similar?
> those i'd expect, they're prety low quality ones. Personally, i'll
> always use hawkers - never had a single runaway, explosion or other
> problem. Had to deal with lots of the cheaper ones exploding, and
> catching fire before, but in similar situations the hawkers have
> swelled, and thats about it. There's a reason yuasas and such aren't
> certified safe for air travel, and hawkers are.
>
More expensive than the Hawkers, I suspect - they're GNB Absolyte batteries.
The small banks run $5000 US, while the larger banks are $20 thousand. The
large bank I mentioned was half a 3000 AH 48V bank. They look like
http://www.batterypowersystems.com/p...bsolyteIIP.htm .

The likely difference in failure modes is because of the type of service. In
communication service, the batteries are "floated" at 2.25 volts per cell by
fixed voltage, current limited chargers. In automotive use the charge is
more intermittent, so thermal runaway is rare. However, the batteries are
much smaller so the thermal mass is smaller. A battery that did fine on
in-town trips is really tested on long trips, where the charging is constant
enough to possibly trigger thermal runaway.

But I suspect the design is different enough that the car batteries fail
through dehydration most of the time. Our Toyota Prius has a sealed
lead-acid aux battery... reports from people who've had to replace them are
very familiar. They let it run down, charged it by jumping and letting the
car charge it, often in warm weather. Sealed batteries are still the old
gell cells with minor updates. As long as they aren't in the engine
compartment they aren't too bad.

Mike

 

On Sat, 30 Jul 2005 05:49:21 -0700, "Michael Pardee"
<michaeltnull@cybertrails.com> wrote:


>>
>More expensive than the Hawkers, I suspect - they're GNB Absolyte batteries.
>The small banks run $5000 US, while the larger banks are $20 thousand. The
>large bank I mentioned was half a 3000 AH 48V bank. They look like
>http://www.batterypowersystems.com/p...bsolyteIIP.htm .
>
a 30Ah 12V hawker is about 200, maybe $250.
half a bank, of them is 100 for the capcity dobled for the voltage,
or, 200. 20,000/200 is about $100 a battery, which is the cheap side,
even taking into accont bulk-buying. thats only slightly more than the
low-end yuasa's, and then you have to build the bank, and transport
etc.

>The likely difference in failure modes is because of the type of service. In
>communication service, the batteries are "floated" at 2.25 volts per cell by
>fixed voltage, current limited chargers. In automotive use the charge is
>more intermittent, so thermal runaway is rare. However, the batteries are
>much smaller so the thermal mass is smaller. A battery that did fine on
>in-town trips is really tested on long trips, where the charging is constant
>enough to possibly trigger thermal runaway.

Actually, i use the hawkers mainly in electric vehicles. Part of my
job involves building and testing automotive-type electrical systems,
and i usea hawker till its flat, and charge, or at least untli i've
finished the day, then top up.

I know British telecom also use them for emergency power systems, and
for portable emergency power packs - and if you've ever seen BT's
infrastructure, you'll understand why they don't skimp on the
batteries.

>
>But I suspect the design is different enough that the car batteries fail
>through dehydration most of the time. Our Toyota Prius has a sealed
>lead-acid aux battery... reports from people who've had to replace them are
>very familiar. They let it run down, charged it by jumping and letting the
>car charge it, often in warm weather. Sealed batteries are still the old
>gell cells with minor updates. As long as they aren't in the engine
>compartment they aren't too bad.
>
>Mike
>

 

On Sat, 30 Jul 2005 05:49:21 -0700, "Michael Pardee"
<michaeltnull@cybertrails.com> wrote:


>>
>More expensive than the Hawkers, I suspect - they're GNB Absolyte batteries.
>The small banks run $5000 US, while the larger banks are $20 thousand. The
>large bank I mentioned was half a 3000 AH 48V bank. They look like
>http://www.batterypowersystems.com/p...bsolyteIIP.htm .
>
a 30Ah 12V hawker is about 200, maybe $250.
half a bank, of them is 100 for the capcity dobled for the voltage,
or, 200. 20,000/200 is about $100 a battery, which is the cheap side,
even taking into accont bulk-buying. thats only slightly more than the
low-end yuasa's, and then you have to build the bank, and transport
etc.

>The likely difference in failure modes is because of the type of service. In
>communication service, the batteries are "floated" at 2.25 volts per cell by
>fixed voltage, current limited chargers. In automotive use the charge is
>more intermittent, so thermal runaway is rare. However, the batteries are
>much smaller so the thermal mass is smaller. A battery that did fine on
>in-town trips is really tested on long trips, where the charging is constant
>enough to possibly trigger thermal runaway.

Actually, i use the hawkers mainly in electric vehicles. Part of my
job involves building and testing automotive-type electrical systems,
and i usea hawker till its flat, and charge, or at least untli i've
finished the day, then top up.

I know British telecom also use them for emergency power systems, and
for portable emergency power packs - and if you've ever seen BT's
infrastructure, you'll understand why they don't skimp on the
batteries.

>
>But I suspect the design is different enough that the car batteries fail
>through dehydration most of the time. Our Toyota Prius has a sealed
>lead-acid aux battery... reports from people who've had to replace them are
>very familiar. They let it run down, charged it by jumping and letting the
>car charge it, often in warm weather. Sealed batteries are still the old
>gell cells with minor updates. As long as they aren't in the engine
>compartment they aren't too bad.
>
>Mike
>