Matronics Email Lists :: View topic - What Causes Battery to Go Bad

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

What Causes Battery to Go Bad

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

billhuntersemail(at)gmail
Guest

Posted: Fri Oct 28, 2016 3:56 pm Post subject: What Causes Battery to Go Bad

My car battery died after 9 months. In the last 20 years I seem to have very bad luck with batteries in various vehicles. These vehicles are classic cars used rarely (I disconnect the negative terminal when not in use) and some are often used daily drivers (stock cars with stock electric systems).  

It seems back in the day "maintenance free" batteries seemed to last longer.  

Is there something different now a days?  

Bill Hunter

chaskuss(at)yahoo.com
Guest

Posted: Sat Oct 29, 2016 12:42 am Post subject: What Causes Battery to Go Bad

Bill,

 Simply disconnecting the batteries does not prevent them from discharging while sitting. It merely slows down the rate of discharge [not having to supply power to those electrical circuits which run even with the ignition switch off] It's best to keep a "trickle" charger on batteries that sit, unused for long periods of time. 

 I would suggest that you have your alternator(s) tested for shorted diode(s) in the rectifier bridge. A diode is the electrical equivalent to a check valve in a hydraulic system. It allows current to flow in one direction only. The rectifier's purpose is to change the AC current the alternator makes into DC current that your car's battery needs. Diodes can fail two ways. Fail Open [most common] - the diode no longer allows any current to pass. This causes the alternator to lose a portion of it's output capacity. Fail Shorted - this allows the alternator to pass a portion of it's output as AC current. No drop in the alternator's capacity will be noted. However, pumping AC current into a DC battery will kill the battery in a matter of months, hence the premature battery failures. Why do alternator diodes fail? Generally, because the battery is low and when the engine starts, the alternator has to generate a LOT of current to charge the battery. You can NOT test for shorted diodes with an ammeter. You need proper testing equipment to find this condition. So, if you find that you have shorted alternator diodes, repair the alternator(s). Then make sure that each battery is fully charged BEFORE you start each engine. That way, you don't over tax the alternator right after start up.



Charlie



--------------------------------------------

On Fri, 10/28/16, William Hunter <billhuntersemail(at)gmail.com> wrote:



 Subject: What Causes Battery to Go Bad

 To: aeroelectric-list(at)matronics.com

 Date: Friday, October 28, 2016, 7:54 PM

 

 My car battery died

 after 9 months. In the last 20 years I seem to have very bad

 luck with batteries in various vehicles. These vehicles are

 classic cars used rarely (I disconnect the negative terminal

 when not in use) and some are often used daily drivers

 (stock cars with stock electric systems). 

 It seems back in the day "maintenance

 free" batteries seemed to last longer. 

 Is there something different now a days? 

 Bill Hunter

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Oct 29, 2016 2:22 am Post subject: What Causes Battery to Go Bad

My car battery died after 9 months. In the last 20 years I seem to have very bad luck with batteries in various vehicles. These vehicles are classic cars used rarely (I disconnect the negative terminal when not in use) and some are often used daily drivers (stock cars with stock electric systems).



  The 'classics' did not load the battery  in the normal 'parked' condition. Disconnecting the  battery in such vehicles for long term storage was  seldom, if ever, a useful thing to do. I think the  electric clock was the biggest load with very small  energy requirements.



  Modern vehicles MAY have small battery demands  while parked. I think my wife's Saturn has a battery  load on the order of 0.02 amps when parked. This  is greater than the normal and expected self-discharge  current characteristic of flooded batteries. If her  car is not driven for a long period of time, the battery  will be discharged. Further, a battery stored in a  discharged condition self-destructs. 



 It seems back in the day "maintenance free" batteries seemed to last longer. 

 Is there something different now a days?



  I don't think so. Modern cars may have some very  small persistent loads even when parked . . . the  older cars will not. Batteries that sit for long  periods of time will benefit from use of a 'maintainer'  . . . not a 'trickle charger' the maintainer simply  holds a battery's terminal voltage just above that at  which self-discharging takes place. A maintainer holds  a nominally 12.9v battery up to about 13.2 to 13.5 volts. Not high enough to do any charging but higher than  normal open circuit volts. Hence, the ac mains become  a source of energy to offset self-discharging. I used  to have a stable of laboratory batteries that were  stored on a single maintainer all connected in parallel.  Some of them were service-ready after more than ten years.



  A 'trickle charger' puts a small but constant  charge into a battery . . . which can be  greater than the self-discharge current . . . and  is ultimately deleterious to a battery on long term  storage. I still have a couple of Battery Tenders  I keep attached to my battery inventory. There's  a host of products out there.



   http://tinyurl.com/zzjhalk



  The Battery Tender and the Schumacher SEM1562 are  used in my shop. Walmart stocks the Schumacher  product for about $25.     =================



 Simply disconnecting the batteries does not prevent them from discharging while sitting. It merely slows down the rate of discharge [not having to supply power to those electrical circuits which run even with the ignition switch off] It's best to keep a "trickle" charger on batteries that sit, unused for long periods of time.



  Generally true . . . with additions. The lead-acid  battery also has a self-discharge characteristic  that is a function of dissolved oxygen in the electrolyte.  Flooded batteries of bygone times would run down in  90-120 days just sitting unload. Maintenance free  batteries were a step up for controlling self discharge  with the sealed battery being the present king  of long term storage. An SVLA battery should retain  70-80% of capacity after a year of storage as long  as the temperatures are not really high.  I would suggest that you have your alternator(s) tested for shorted diode(s) in the rectifier bridge.



 <snip>



 Then make sure that each battery is fully charged BEFORE you start each engine. That way, you don't over tax the alternator right after start up.



  I've never encountered such a failure. The power  diodes used in alternators are exceedingly robust  devices and their reverse leakage at battery voltage  is measured in nanoamps. Unlike generators (with  brushes and commutators that carry output current),  the alternator has no such weak-link. Alternators  are inherently current limited. Normal operations   . . . even starting an engine with jumpers with  the alternator grunting the load of a fully discharge  battery does no 'over tax' an alternator in any  serious way. I've seen that admonition for making  sure your battery is fully charged before firing  up the engine with a new alternator . .  and I'm  mystified by it.

  These things are explained in more detail in The AeroElectric Connection. You can download a copy here



    http://www.aeroelectric.com/Book/AEC_R12A.pdf



  or acquire a paper-copy here



   http://tinyurl.com/cgr42l5



  Your unexplained short term failure may be a one-of event. But as a general observation, today's battery products are as good as they ever have been. Persistent failures have an explanation that should and can be identified.

    Bob . . .

billhuntersemail(at)gmail
Guest

Posted: Sat Oct 29, 2016 6:12 am Post subject: What Causes Battery to Go Bad

Thanks All!!!

 

This is very good information.  My 87 year old father and I have had this conversation numerous times over the decades and I will share this email thread with him.

 

BTW…the most recent victim was a Saturn.

 

..

 

Cheers!!!

 

Bill  Hunter

 

 

 

 



 

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III

Sent: Saturday, October 29, 2016 3:21 AM

To: aeroelectric-list(at)matronics.com

Subject: Re: What Causes Battery to Go Bad

 

My car battery died after 9 months. In the last 20 years I seem to have very bad luck with batteries in various vehicles. These vehicles are classic cars used rarely (I disconnect the negative terminal when not in use) and some are often used daily drivers (stock cars with stock electric systems).

The 'classics' did not load the battery 

in the normal 'parked' condition. Disconnecting the 

battery in such vehicles for long term storage was 

seldom, if ever, a useful thing to do. I think the 

electric clock was the biggest load with very small 

energy requirements.

Modern vehicles MAY have small battery demands 

while parked. I think my wife's Saturn has a battery 

load on the order of 0.02 amps when parked. This 

is greater than the normal and expected self-discharge 

current characteristic of flooded batteries. If her 

car is not driven for a long period of time, the battery 

will be discharged. Further, a battery stored in a 

discharged condition self-destructs. 

It seems back in the day "maintenance free" batteries seemed to last longer. 

Is there something different now a days?

I don't think so. Modern cars may have some very 

small persistent loads even when parked . . . the 

older cars will not. Batteries that sit for long 

periods of time will benefit from use of a 'maintainer' 

. . . not a 'trickle charger' the maintainer simply 

holds a battery's terminal voltage just above that at 

which self-discharging takes place. A maintainer holds 

a nominally 12.9v battery up to about 13.2 to 13.5 volts. 

Not high enough to do any charging but higher than 

normal open circuit volts. Hence, the ac mains become 

a source of energy to offset self-discharging. I used 

to have a stable of laboratory batteries that were 

stored on a single maintainer all connected in parallel. 

Some of them were service-ready after more than ten years.

A 'trickle charger' puts a small but constant 

charge into a battery . . . which can be 

greater than the self-discharge current . . . and 

is ultimately deleterious to a battery on long term 

storage. I still have a couple of Battery Tenders 

I keep attached to my battery inventory. There's 

a host of products out there.

http://tinyurl.com/zzjhalk





The Battery Tender and the Schumacher SEM1562 are 

used in my shop. Walmart stocks the Schumacher 

product for about $25. 

  

=================



Simply disconnecting the batteries does not prevent them from discharging while sitting. It merely slows down the rate of discharge [not having to supply power to those electrical circuits which run even with the ignition switch off] It's best to keep a "trickle" charger on batteries that sit, unused for long periods of time.

Generally true . . . with additions. The lead-acid 

battery also has a self-discharge characteristic 

that is a function of dissolved oxygen in the electrolyte. 

Flooded batteries of bygone times would run down in 

90-120 days just sitting unload. Maintenance free 

batteries were a step up for controlling self discharge 

with the sealed battery being the present king 

of long term storage. An SVLA battery should retain 

70-80% of capacity after a year of storage as long 

as the temperatures are not really high. 

I would suggest that you have your alternator(s) tested for shorted diode(s) in the rectifier bridge.



<snip>



Then make sure that each battery is fully charged BEFORE you start each engine. That way, you don't over tax the alternator right after start up.

I've never encountered such a failure. The power 

diodes used in alternators are exceedingly robust 

devices and their reverse leakage at battery voltage 

is measured in nanoamps. Unlike generators (with 

brushes and commutators that carry output current), 

the alternator has no such weak-link. Alternators 

are inherently current limited. Normal operations 

 . . . even starting an engine with jumpers with 

the alternator grunting the load of a fully discharge 

battery does no 'over tax' an alternator in any 

serious way. I've seen that admonition for making 

sure your battery is fully charged before firing 

up the engine with a new alternator . .  and I'm 

mystified by it.

These things are explained in more detail in 

The AeroElectric Connection. You can download 

a copy here

http://www.aeroelectric.com/Book/AEC_R12A.pdf





or acquire a paper-copy here

http://tinyurl.com/cgr42l5

Your unexplained short term failure may be a 

one-of event. But as a general observation, today's 

battery products are as good as they ever have been. 

Persistent failures have an explanation that 

should and can be identified.

  Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Oct 29, 2016 6:27 am Post subject: What Causes Battery to Go Bad

At 09:11 AM 10/29/2016, you wrote:

  	  Quote: 	
		   Thanks All!!!

  

 This is very good information.  My 87 year old father and I have had this conversation numerous times over the decades and I will share this email thread with him.

  

 BTW…the most recent victim was a Saturn. 	


   I will suggest an experiment. . .



   Acquire a multimeter . . . nothing

   fancy. One of those $5 Harbor Freight

   things will work.



   Put it into the current measurement

   mode. Remove one wire from the

   Saturn's battery and put the multi-

   meter in the gap.



   I'll do the same on my wife's car . . .

   it was about 15 years ago that

   I made the discovery and my memory

   of exact value is fuzzy . . .

   but tomorrow.



   Right now I'm packing up our Cotton

   Candy concession into another 'classic'.

   My father willed his '87 GMC Sierra

   Classic 1500 to Dr. Dee . . . with

   only 37K miles on it.



   I've been honing my mechanics skills

   re-furbing the things that succumb to

   age and use.  But it's very road-worthy and

   we're participating in a fund raiser for

   my grandchildren's grade school in

   Wichita this evening.



   Hmmm . . . the Sierra has TBI and

   some other 'electro whizzies . . .

   I'll check all the cars for parasitic

   parked loads and report back. If

   anyone else on the List is so inclined,

   it would be interesting to get some

   data on a variety of vehicles.



 

 

   Bob . . .

billhuntersemail(at)gmail
Guest

Posted: Sat Oct 29, 2016 6:39 am Post subject: What Causes Battery to Go Bad

Good idea Bob... I'm on a trip right now but will participate in this clinical study when I get home. I'll see if my dad will join in on the fun and contribute as well.  

I hope your skills at setting the digital clock have not deteriated...  

Bill Hunter 

  

On Oct 29, 2016 9:33 AM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote: 	  Quote: 	
		    At 09:11 AM 10/29/2016, you wrote:

  	  Quote: 	
		   Thanks All!!!

 Â 

 This is very good information.Â  My 87 year old father and I have had this conversation numerous times over the decades and I will share this email thread with him.

 Â 

 BTWâ€¦the most recent victim was a Saturn. 	


 Â  I will suggest an experiment. . .



 Â  Acquire a multimeter . . . nothing

 Â  fancy. One of those $5 Harbor Freight

 Â  things will work.



 Â  Put it into the current measurement

 Â  mode. Remove one wire from the

 Â  Saturn's battery and put the multi-

 Â  meter in the gap.



 Â  I'll do the same on my wife's car . . .

 Â  it was about 15 years ago that

 Â  I made the discovery and my memory

 Â  of exact value is fuzzy . . .

 Â  but tomorrow.



 Â  Right now I'm packing up our Cotton

 Â  Candy concession into another 'classic'.

 Â  My father willed his '87 GMC Sierra

 Â  Classic 1500 to Dr. Dee . . . with

 Â  only 37K miles on it.



 Â  I've been honing my mechanics skills

 Â  re-furbing the things that succumb to

 Â  age and use.Â  But it's very road-worthy and

 Â  we're participating in a fund raiser for

 Â  my grandchildren's grade school in

 Â  Wichita this evening.



 Â  Hmmm . . . the Sierra has TBI and

 Â  some other 'electro whizzies . . .

 Â  I'll check all the cars for parasitic

 Â  parked loads and report back. If

 Â  anyone else on the List is so inclined,

 Â  it would be interesting to get some

 Â  data on a variety of vehicles.



 

 

 Â  Bob . . .

yellowduckduo(at)gmail.co
Guest

Posted: Sat Oct 29, 2016 8:01 am Post subject: What Causes Battery to Go Bad

Won't matter too much on an 87 but especially for newer vehicles I'd 

suggest putting the ammeter in the circuit before disconnecting the 

battery so that you don't lose momentary power with resultant loss of 

accumulated "learning" in the ecu as well as things like radio settings. 

I understand that it can even require a return to the dealer to 

re-instate radios that have anti-theft security features. Even better 

might be a 9 volt battery temporarily plugged into a cigarette lighter 

which should also keep the memories intact.

Ken



On 29/10/2016 10:26 AM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   At 09:11 AM 10/29/2016, you wrote:

> Thanks All!!!

>

> This is very good information.  My 87 year old father and I have had 

> this conversation numerous times over the decades and I will share 

> this email thread with him.

>

> BTW…the most recent victim was a Saturn.



   I will suggest an experiment. . .



   Acquire a multimeter . . . nothing

   fancy. One of those $5 Harbor Freight

   things will work.



   Put it into the current measurement

   mode. Remove one wire from the

   Saturn's battery and put the multi-

   meter in the gap.



   I'll do the same on my wife's car . . .

   it was about 15 years ago that

   I made the discovery and my memory

   of exact value is fuzzy . . .

   but tomorrow.



   Right now I'm packing up our Cotton

   Candy concession into another 'classic'.

   My father willed his '87 GMC Sierra

   Classic 1500 to Dr. Dee . . . with

   only 37K miles on it.



   I've been honing my mechanics skills

   re-furbing the things that succumb to

   age and use.  But it's very road-worthy and

   we're participating in a fund raiser for

   my grandchildren's grade school in

   Wichita this evening.



   Hmmm . . . the Sierra has TBI and

   some other 'electro whizzies . . .

   I'll check all the cars for parasitic

   parked loads and report back. If

   anyone else on the List is so inclined,

   it would be interesting to get some

   data on a variety of vehicles.

   Bob . . .

ashleysc(at)broadstripe.n
Guest

Posted: Sat Oct 29, 2016 8:52 am Post subject: What Causes Battery to Go Bad

Hi Bob;



Hi All;

Further to the SLVA battery success stories:

When we were living 7 months in Anchorage and 5 months in Costa Rica each year, we had a 1982 Nissan King Cab pickup that sat outdoors in Alaska's winter, Every April first we would arrive back in Alaska, shovel the snow away from the pickup, turn the switch, and it never failed to start up. The sealed lead acid battery never let us dawn, even though we abused it unmercifully.

Cheers!   Stu.

From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>

To: aeroelectric-list(at)matronics.com

Sent: Saturday, October 29, 2016 3:21:26 AM

Subject: Re: What Causes Battery to Go Bad

  My car battery died after 9 months. In the last 20 years I seem to have very bad luck with batteries in various vehicles. These vehicles are classic cars used rarely (I disconnect the negative terminal when not in use) and some are often used daily drivers (stock cars with stock electric systems).

  The 'classics' did not load the battery  in the normal 'parked' condition. Disconnecting the  battery in such vehicles for long term storage was  seldom, if ever, a useful thing to do. I think the  electric clock was the biggest load with very small  energy requirements.

  Modern vehicles MAY have small battery demands  while parked. I think my wife's Saturn has a battery  load on the order of 0.02 amps when parked. This  is greater than the normal and expected self-discharge  current characteristic of flooded batteries. If her  car is not driven for a long period of time, the battery  will be discharged. Further, a battery stored in a  discharged condition self-destructs. 

 It seems back in the day "maintenance free" batteries seemed to last longer. 

 Is there something different now a days?

  I don't think so. Modern cars may have some very  small persistent loads even when parked . . . the  older cars will not. Batteries that sit for long  periods of time will benefit from use of a 'maintainer'  . . . not a 'trickle charger' the maintainer simply  holds a battery's terminal voltage just above that at  which self-discharging takes place. A maintainer holds  a nominally 12.9v battery up to about 13.2 to 13.5 volts. Not high enough to do any charging but higher than  normal open circuit volts. Hence, the ac mains become  a source of energy to offset self-discharging. I used  to have a stable of laboratory batteries that were  stored on a single maintainer all connected in parallel.  Some of them were service-ready after more than ten years.

  A 'trickle charger' puts a small but constant  charge into a battery . . . which can be  greater than the self-discharge current . . . and  is ultimately deleterious to a battery on long term  storage. I still have a couple of Battery Tenders  I keep attached to my battery inventory. There's  a host of products out there.

   http://tinyurl.com/zzjhalk

  The Battery Tender and the Schumacher SEM1562 are  used in my shop. Walmart stocks the Schumacher  product for about $25.     =================

 Simply disconnecting the batteries does not prevent them from discharging while sitting. It merely slows down the rate of discharge [not having to supply power to those electrical circuits which run even with the ignition switch off] It's best to keep a "trickle" charger on batteries that sit, unused for long periods of time.

  Generally true . . . with additions. The lead-acid  battery also has a self-discharge characteristic  that is a function of dissolved oxygen in the electrolyte.  Flooded batteries of bygone times would run down in  90-120 days just sitting unload. Maintenance free  batteries were a step up for controlling self discharge  with the sealed battery being the present king  of long term storage. An SVLA battery should retain  70-80% of capacity after a year of storage as long  as the temperatures are not really high.  I would suggest that you have your alternator(s) tested for shorted diode(s) in the rectifier bridge.

 <snip>

 Then make sure that each battery is fully charged BEFORE you start each engine. That way, you don't over tax the alternator right after start up.

  I've never encountered such a failure. The power  diodes used in alternators are exceedingly robust  devices and their reverse leakage at battery voltage  is measured in nanoamps. Unlike generators (with  brushes and commutators that carry output current),  the alternator has no such weak-link. Alternators  are inherently current limited. Normal operations   . . . even starting an engine with jumpers with  the alternator grunting the load of a fully discharge  battery does no 'over tax' an alternator in any  serious way. I've seen that admonition for making  sure your battery is fully charged before firing  up the engine with a new alternator . .  and I'm  mystified by it.

  These things are explained in more detail in The AeroElectric Connection. You can download a copy here

    http://www.aeroelectric.com/Book/AEC_R12A.pdf

  or acquire a paper-copy here

   http://tinyurl.com/cgr42l5

  Your unexplained short term failure may be a one-of event. But as a general observation, today's battery products are as good as they ever have been. Persistent failures have an explanation that should and can be identified.

    Bob . . .

skywagon

Joined: 11 Feb 2006
Posts: 184

Posted: Sat Oct 29, 2016 11:27 am Post subject: What Causes Battery to Go Bad

Just some suggestions about auto battery failure. . .  .

  

 From a simplified view point, batteries usually fail  because. . .

  

 1. Being over-charged in the vehicle or on a charger or  both. . 

 2. Being constantly under-charged in vehicle or charger or  both. . 

 3. Bad environment; vibration, etc.

  

 My personal opinion is your problem is #2.

 Just disconnecting the negative lead is not  enough for a lead-acid based battery.  It will self discharge  thru a variety of "paths"; internally and externally.

 Hooking up a small (low amperage) charger also leads  mostly to a disaster as it eventually goes to an over-voltage state, thus  gassing the cells dry.

  

 A good solution is to connect a "Battery Maintainer" to  the battery and leave it connected.  If it is set to the correct  float voltage, it will charge essentially to that voltage and then "sit"  adding a little bit as is needed.  These units are cheap.  Even Harbor  Freight has models that on sale or under $10.

 However, many of the units may come out of the box not  calibrated exactly correct for float voltage.  The float voltage should be  in the region of 13.2 - 13.4 volts in my opinion.

 One can buy a fairly good DVM, digital volt meter, for  under $20.  I suggest buying a Maintainer from a close by local  store.  Also pick up the DVM.  Hook it up to one of your batteries  that is "good" and let it run for a couple of days until it is stabilized and  check the battery voltage; this will be the stabilized float  voltage.  If it is too high or low, box it up and return it for another  unit.  The factory QC in many cases is not very good at final V settings of  these units.

  

 Personally, I take mine apart, carefully, locate the  adjustment "pot", drill a small hole for a tiny screwdriver in the case and  reassemble it.

 And, carefully, adjust the voltage control pot over  several days until I like the final float voltage.......

 Dave

 PS; be careful of using a small solar panel to maintain  charge.  Many "12 volt" types can go to 18v or higher in bright sun.   The panel must have a voltage control within it.  Low amp units can be  controlled simply with a Zener type diode. . .. 

  

   

  

  

  

 ---

Tundra10

Joined: 14 Jun 2010
Posts: 102
Location: Scarborough, Ontario

Posted: Sun Oct 30, 2016 4:40 am Post subject: What Causes Battery to Go Bad

 	  Quote: 	
		   I used

 to have a stable of laboratory batteries that were

 stored on a single maintainer all connected in parallel.

 Some of them were service-ready after more than ten years.


	


Beware putting multiple batteries in parallel on a single maintainer.

I had a cell die in one battery.  The maintainer was unable to hold  

the float voltage.

After a month or two the other batteries had sat completely discharged  

for a while

and none were serviceable.  Now I use a separate maintainer for each.



Perhaps a low voltage alarm would suffice instead.



Jeff Page

Dream Aircraft Tundra #10

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Oct 30, 2016 6:26 am Post subject: What Causes Battery to Go Bad

 	  Quote: 	
		  

 Beware putting multiple batteries in parallel on a single maintainer.

 I had a cell die in one battery.  The maintainer was unable to hold  

 the float voltage.

 After a month or two the other batteries had sat completely discharged  

 for a while

 and none were serviceable.  Now I use a separate maintainer for each.



 Perhaps a low voltage alarm would suffice instead. 	


   My maintainers have lights on the front that

   annunciate status of battery(ies). While

   a shorted cell in one battery would indeed

   upset the universe of batteries on storage,

   it's a very rare event in the SVLA world . . .

   occurring mostly in batteries that probably

   shouldn't be on the maintainer in the first

   place . . . capacity badly compromised. 



   Active and obnoxious notification of

   low voltage would be helpful in this situation.

   A 5 cell battery's open terminal voltage drops

   to (12.8/6)*5 = 10.7 volts. The same battery's

   'charge voltage' drops to (14.2/6)*5 = 11.8

   volts which would indeed draw down the remaining

   batteries as they 'charged' the compromised

   battery.



   I think it prudent to know that all batteries

   in an array of 'maintained' batteries are

   worthy of being maintained . . . i.e. not

   less than 75% of nameplate capacity. A substantial

   drop in capacity precedes cell degradation

   which precedes mechanical compromise

   of insulators that produces the shorted

   cell.



   My instrument batteries were used as stand

   alone power for data acquisition equipment,

   portable power for hand tools and occasionally

   as cranking batteries for vehicles. They

   were periodically cap-checked (you don't want

   the DAS to go down in the middle of a flight

   test!).



   Keeping an eye on your maintainer(s) annunciator

   lights is a useful thing to do . . . and yes, separate

   maintainers is the ultimate firewall against suffering

   a similar inconvenience.



 

   Bob . . .

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum