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Posted by mlw on June 12, 2005, 9:46 am
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The Artist Formerly Known as Kap'n Salty wrote:
> Mitch Berkson wrote:
>> mlw wrote:
>>
>>>As I posted in another thread, this isn't really true. A battery will
>>>naturally discharge over time. Constantly charging/discharging +- 1%
>>>will add up over time, and a battery left on a shelf and tricle
>>>charged one night a month will probably outlast a battery left on the
>>>charger 24x7
>>
>>
>> In keeping with your skepticism of hearsay, I'd be interested if you
>> could provide a reference which supports this.
>
> As would I, since this directly contradicts my experience with SLAs and
> decent chargers.
So you are saying a Gel, SLA (AGM) or simple lead acid will last longer on a
a good trickle charger 24x7 that it will being trickle charged once a
month?
All lead acid batteries degrade over time and have a finite life no matter
how they are handled, however, there are methods of handling that will make
them last longer. I think we agree on this.
So, I think we have the basis of a bet.
We need to acquire 2 identical SLA (gel or otherwise) made in the same
batch. Two identical tricle chargers. One connected to one battery 24x7,
and the other connected to the other battery one 24 hour period every
calendar month. At the end of a year, which of the two batteries will have
the greater capacity?
Are you up for the bet? I am, to me its a no brainer, I'll take the battery
charged once a month.
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Posted by The Artist Formerly Known as K on June 12, 2005, 8:19 pm
Please log in for more thread options
mlw wrote:
> The Artist Formerly Known as Kap'n Salty wrote:
>
>
>>Mitch Berkson wrote:
>>
>>>mlw wrote:
>>>
>>>
>>>>As I posted in another thread, this isn't really true. A battery will
>>>>naturally discharge over time. Constantly charging/discharging +- 1%
>>>>will add up over time, and a battery left on a shelf and tricle
>>>>charged one night a month will probably outlast a battery left on the
>>>>charger 24x7
>>>
>>>
>>>In keeping with your skepticism of hearsay, I'd be interested if you
>>>could provide a reference which supports this.
>>
>>As would I, since this directly contradicts my experience with SLAs and
>>decent chargers.
>
>
> So you are saying a Gel, SLA (AGM) or simple lead acid will last longer on a
> a good trickle charger 24x7 that it will being trickle charged once a
> month?
I said "a good charger". To give you an idea of exactly how well a good
charger works, REGIS has been using the same 5ah SLA (electronics) since
November 2000. For most of that time, the battery is in use around 12-14
hours a day, 7 days a week, and is on the charger nightly. The battery
has been frequently deep-discharged on more occasions than I care to
count. Only recently is this battery showing possible signs of fatigue,
and this is no special battery (Panasonic LCR1-125P1) . The same can be
said of the 7ah sla that powers the motor, although it is charged much
less frequently (and often deeply discharged).
So if I did nothing with the battery other than left it on a shelf and
charged it monthly would it last longer? Possibly -- I certainly
wouldn't take your bet. Even if you didn't win, I would have tied up a
$60.00 charger for a year. (Not to mention that, honestly, I don't know
you well enough to actually wager anything.)
Basically, if the battery is allowed to discharge, you'll end up with
some amount of sulfation on the negative plate (not good). But charging
the battery always carries some risk of erosion of the positive plate
(also not good). A good, temperature-compensated float charge algorithm
_should_ strike a reasonable compromise between the two, however, making
the real difference academic. In fact, some float charge algorithms
monitor the battery voltage and only apply a charge when the voltage
drops below a preset value, essentially mimicking your "charge it once a
month" approach -- the real difference between the two being that the
user isn't required to remember to charge the battery once a month.
--
(Replies: cleanse my address of the Mark of the Beast!)
Teleoperate a roving mobile robot from the web:
http://www.swampgas.com/robotics/rover.html
Coauthor with Dennis Clark of "Building Robot Drive Trains".
Buy several copies today!
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Posted by mlw on June 13, 2005, 5:07 am
Please log in for more thread options The Artist Formerly Known as Kap'n Salty wrote:
> mlw wrote:
>> The Artist Formerly Known as Kap'n Salty wrote:
>>
>>
>>>Mitch Berkson wrote:
>>>
>>>>mlw wrote:
>>>>
>>>>
>>>>>As I posted in another thread, this isn't really true. A battery will
>>>>>naturally discharge over time. Constantly charging/discharging +- 1%
>>>>>will add up over time, and a battery left on a shelf and tricle
>>>>>charged one night a month will probably outlast a battery left on the
>>>>>charger 24x7
>>>>
>>>>
>>>>In keeping with your skepticism of hearsay, I'd be interested if you
>>>>could provide a reference which supports this.
>>>
>>>As would I, since this directly contradicts my experience with SLAs and
>>>decent chargers.
>>
>>
>> So you are saying a Gel, SLA (AGM) or simple lead acid will last longer
>> on a a good trickle charger 24x7 that it will being trickle charged once
>> a month?
>
> I said "a good charger". To give you an idea of exactly how well a good
> charger works, REGIS has been using the same 5ah SLA (electronics) since
> November 2000.
You can choose the charger.
> For most of that time, the battery is in use around 12-14
> hours a day, 7 days a week, and is on the charger nightly. The battery
> has been frequently deep-discharged on more occasions than I care to
> count. Only recently is this battery showing possible signs of fatigue,
> and this is no special battery (Panasonic LCR1-125P1) . The same can be
> said of the 7ah sla that powers the motor, although it is charged much
> less frequently (and often deeply discharged).
I can't find the specs on that battery. I would be curious as to its
internal construction and plate materials, not to mention where it resides.
A 5 year life of a SLA battery is certainly not impossible, but difficult
to attain at room temperature, very difficult to attain in MA (where I
live) unless it is in an air conditioned or temperature controled room. The
North Eastern part of the country has very dramatic temperature swings both
in shorts spans of time and year 'round. We have regular yearly lows of 0F
(and lower) and regular yearly highs of 100F (and higher). We regularly (at
least a few times a year) have days which have, sometimes greater than, 40F
difference between the previous day.
>
> So if I did nothing with the battery other than left it on a shelf and
> charged it monthly would it last longer? Possibly -- I certainly
> wouldn't take your bet. Even if you didn't win, I would have tied up a
> $60.00 charger for a year. (Not to mention that, honestly, I don't know
> you well enough to actually wager anything.)
Well, I assure you I am honerable to a fault.
>
> Basically, if the battery is allowed to discharge, you'll end up with
> some amount of sulfation on the negative plate (not good). But charging
> the battery always carries some risk of erosion of the positive plate
> (also not good). A good, temperature-compensated float charge algorithm
> _should_ strike a reasonable compromise between the two, however, making
> the real difference academic. In fact, some float charge algorithms
> monitor the battery voltage and only apply a charge when the voltage
> drops below a preset value, essentially mimicking your "charge it once a
> month" approach -- the real difference between the two being that the
> user isn't required to remember to charge the battery once a month.
A simple 28 day timer would work, run a relay that connects and disconnects
the charger one a month. For the bet, I would absolutely implement such a
device, that way it wouldn't be forgotten.
Anyway, we have really run with the topic of batteries, I think if we can
conclude the original argument that I am, in fact, using a deep cycle
battery in my robot. :-)
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Posted by The Artist Formerly Known as K on June 13, 2005, 10:52 am
Please log in for more thread options mlw wrote:
>
>>For most of that time, the battery is in use around 12-14
>>hours a day, 7 days a week, and is on the charger nightly. The battery
>>has been frequently deep-discharged on more occasions than I care to
>>count. Only recently is this battery showing possible signs of fatigue,
>>and this is no special battery (Panasonic LCR1-125P1) . The same can be
>>said of the 7ah sla that powers the motor, although it is charged much
>>less frequently (and often deeply discharged).
>
>
> I can't find the specs on that battery. I would be curious as to its
> internal construction and plate materials, not to mention where it resides.
> A 5 year life of a SLA battery is certainly not impossible, but difficult
> to attain at room temperature, very difficult to attain in MA (where I
> live) unless it is in an air conditioned or temperature controled room. The
> North Eastern part of the country has very dramatic temperature swings both
> in shorts spans of time and year 'round. We have regular yearly lows of 0F
> (and lower) and regular yearly highs of 100F (and higher). We regularly (at
> least a few times a year) have days which have, sometimes greater than, 40F
> difference between the previous day.
>
The robot resides in my office, which is always room temperature.
Presumably room temperature is more or less the same in MA as it is here
(maybe a tad cooler -- South Louisiana winters aren't particularly
brutal). Both batteries were purchased from Herbach and Radelman, and
both look like they would be used in UPS and fire alarm applications.
The point of my little rant was that charger design is critical to
battery life. It's really common for folks to buy crappy chargers and
ultimately screw themselves on battery cost. Note that my application
really isn't the same as long term storage -- but this is a robotics
group, after all.
>
> A simple 28 day timer would work, run a relay that connects and disconnects
> the charger one a month. For the bet, I would absolutely implement such a
> device, that way it wouldn't be forgotten.
>
> Anyway, we have really run with the topic of batteries, I think if we can
> conclude the original argument that I am, in fact, using a deep cycle
> battery in my robot. :-)
I doubt you can know that without taking the battery apart -- but as I
imply above, I don't think it matters (at least for gel-cells) when a
good charger is used.
My guess is that a major factor in the poor performance of UPS batteries
(when installed in the UPS) is lousy charge circuitry, not the battery
itself. I've certainly abused the crap out of mine -- but it may be that
a prompt, 3-stage recharge staves off permanent sulfation. I have never,
ever, left these batteries for long in a discharged state, although I
have on occasion discharged them to the point that they show 8 and 1/2
volts or so connected to a load.
--
(Replies: cleanse my address of the Mark of the Beast!)
Teleoperate a roving mobile robot from the web:
http://www.swampgas.com/robotics/rover.html
Coauthor with Dennis Clark of "Building Robot Drive Trains".
Buy several copies today!
|
|
Posted by mlw on June 13, 2005, 7:10 am
Please log in for more thread options The Artist Formerly Known as Kap'n Salty wrote:
> mlw wrote:
>>
>>>For most of that time, the battery is in use around 12-14
>>>hours a day, 7 days a week, and is on the charger nightly. The battery
>>>has been frequently deep-discharged on more occasions than I care to
>>>count. Only recently is this battery showing possible signs of fatigue,
>>>and this is no special battery (Panasonic LCR1-125P1) . The same can be
>>>said of the 7ah sla that powers the motor, although it is charged much
>>>less frequently (and often deeply discharged).
>>
>>
>> I can't find the specs on that battery. I would be curious as to its
>> internal construction and plate materials, not to mention where it
>> resides. A 5 year life of a SLA battery is certainly not impossible, but
>> difficult to attain at room temperature, very difficult to attain in MA
>> (where I live) unless it is in an air conditioned or temperature
>> controled room. The North Eastern part of the country has very dramatic
>> temperature swings both in shorts spans of time and year 'round. We have
>> regular yearly lows of 0F (and lower) and regular yearly highs of 100F
>> (and higher). We regularly (at least a few times a year) have days which
>> have, sometimes greater than, 40F difference between the previous day.
>>
>
> The robot resides in my office, which is always room temperature.
> Presumably room temperature is more or less the same in MA as it is here
> (maybe a tad cooler -- South Louisiana winters aren't particularly
> brutal). Both batteries were purchased from Herbach and Radelman, and
> both look like they would be used in UPS and fire alarm applications.
> The point of my little rant was that charger design is critical to
> battery life. It's really common for folks to buy crappy chargers and
> ultimately screw themselves on battery cost. Note that my application
> really isn't the same as long term storage -- but this is a robotics
> group, after all.
>
>
>>
>> A simple 28 day timer would work, run a relay that connects and
>> disconnects the charger one a month. For the bet, I would absolutely
>> implement such a device, that way it wouldn't be forgotten.
>>
>> Anyway, we have really run with the topic of batteries, I think if we can
>> conclude the original argument that I am, in fact, using a deep cycle
>> battery in my robot. :-)
>
> I doubt you can know that without taking the battery apart -- but as I
> imply above, I don't think it matters (at least for gel-cells) when a
> good charger is used.
Sigh, this is where this whole sub-thread started. Have we not covered any
ground? There are three clasifications of lead acid batteries, starting,
marine, and deep cycle. Depending on the internal construction and
materials used, deep cycle lead-acid (sealed or otherwise) have variable
discharge depths, but they are classified as deep cycle.
We have discussed chargers, storage, internal construction, materials, etc.
already let us not do it again.
>
> My guess is that a major factor in the poor performance of UPS batteries
> (when installed in the UPS) is lousy charge circuitry, not the battery
> itself.
I 100% agree, but don't discount temperature and voltage spikes.
> I've certainly abused the crap out of mine -- but it may be that
> a prompt, 3-stage recharge staves off permanent sulfation. I have never,
> ever, left these batteries for long in a discharged state, although I
> have on occasion discharged them to the point that they show 8 and 1/2
> volts or so connected to a load.
Is that 8 1/2 volts under load? Why is it when the load is disconnected?
Most of the battery volt measurements assume no load.
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