Author Topic: Different voltages on similar batteries  (Read 4430 times)

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zmoz

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Different voltages on similar batteries
« on: July 09, 2005, 10:23:43 PM »
I have 3 Hawker AGM batteries that are new, but a few years old. I put them together on a float charge for about a week, and then let them rest for about a week. Hawker says a full charge is 12.84v. Two of the batteries now read 12.86v, while one reads 12.96v. I don't think that's much of a problem; however, I'm wondering what it might tell me about the condition of the batteries. What would cause the difference in voltage? Are some more sulphated than the others or something?
« Last Edit: July 09, 2005, 10:23:43 PM by (unknown) »

Norm

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Re: Different voltages on similar batteries
« Reply #1 on: July 09, 2005, 07:15:15 PM »
   5 yrs old? IMHO I think you ought to start using them...just light up some tail light bulbs or something

take them down about to maybe 95% full charge

especially the one that is reading low...could

be just one cell is weaker than the others and you

need to cycle it a couple of times then see if that gives you a higher reading.

   You mentioned that you float charge them a

week then give them a rest for a week?

   I must have missed the part where they were

working?LOL

                    ( :>) Norm

                 
« Last Edit: July 09, 2005, 07:15:15 PM by Norm »

zmoz

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Re: Different voltages on similar batteries
« Reply #2 on: July 09, 2005, 08:19:28 PM »
Who said anything about 5 years old? They're only about 2-3 years old, and designed to last a LONG time even under abusive conditions. Hawker claims 400 cycles at 100% discharge. I have cycled them to about 50% a couple of times...though I don't have any particular use for them at the moment.
« Last Edit: July 09, 2005, 08:19:28 PM by zmoz »

Norm

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Re: Different voltages on similar batteries
« Reply #3 on: July 10, 2005, 06:51:45 AM »
  Sorry about the gross misunderstanding...

you didn't say a couple of years you said a few

years (however enough with the semantics).

  It does sound pretty good that they could be

that close to having the same reading now if 2

batteries have exactly the same reading it could

hardly be possible that battery A had all its

cells would have different readings and average

out to tha same average as battery B...so maybe

we could conclude that maybe all the cells in battery C

would read the same except ONE!....

which would drag the total reading down....??

for that battery.

   I don't know that much about batteries ...

thanks for the information about Hawkers,

sounds like the kind of battery I might want to

use in an electric mower someday.


                ( :>) Norm.

« Last Edit: July 10, 2005, 06:51:45 AM by Norm »

Experimental

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Re: Different voltages on similar batteries
« Reply #4 on: July 10, 2005, 10:44:43 AM »
     Good morning,

    You are slightly over Hawkers fully charged voltage -- and you are talking about .1 volts !!!

    If all my batts, tested that close together -- I would Giggle and be happy as a lark !!


    Quit worrying, sounds really good to me -- but, you might exercise them, with just a small discharge regularly (10%)  and have a great weekend..  Bill H..

« Last Edit: July 10, 2005, 10:44:43 AM by Experimental »

TomW

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Re: Different voltages on similar batteries
« Reply #5 on: July 10, 2005, 11:24:52 AM »
Bill;


Yes, indeed, a difference of less than .1% is pretty negligible and could easily be from meter lead contact differences, etc.


Cheers.


TomW

« Last Edit: July 10, 2005, 11:24:52 AM by TomW »

TomW

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Oops....
« Reply #6 on: July 10, 2005, 11:36:45 AM »
Decimal error there it is less than 1%.


Sorry.


T

« Last Edit: July 10, 2005, 11:36:45 AM by TomW »

zmoz

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Re: Different voltages on similar batteries
« Reply #7 on: July 10, 2005, 01:24:11 PM »
Like I said, I'm not worried about any problems with the batteries, I'm just wondering what would cause one to be a higher voltage. It wouldn't surprise me if there was any error in the meter, (it's just a $3 DMM from harbor freight) but shouldn't the error be the same for every battery, comparatively?
« Last Edit: July 10, 2005, 01:24:11 PM by zmoz »

PaulJ

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Re: Different voltages on similar batteries
« Reply #8 on: July 10, 2005, 06:13:23 PM »
   Temperature has quite an effect on battery voltage, even a small variation due to the different positions of individual batteries within a battery bank can make a difference. Does the battery in the middle show the higher voltage ? Anyway, no two batteries are ever completely identical, manufacturing tolerances I guess, and the older they get the more apparent this becomes.


   I run my house off a bank of 40 used Sonnenschein wheelchair batteries in a 48V series/parallel configuration, if the battery voltages within each series string are within .2 or .3V of each other I'm pretty happy.


  Paul.


   Off grid 4 months and still married.


   

« Last Edit: July 10, 2005, 06:13:23 PM by PaulJ »

JWilliams354

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Re: Different voltages on similar batteries
« Reply #9 on: July 22, 2005, 01:07:42 PM »
Paul what area do you live in? Just curious.
« Last Edit: July 22, 2005, 01:07:42 PM by JWilliams354 »