T&T: Batteries

[Candy Chapman and Gary Bell]

Arild Jensen wrote:

>  
>
>>From: GARY BELL  Let's see if Arild can
>>come up with more details, he might well be able to sort this out.
>>    
>>
>
>ARILD:
>Sorry Gary, its winter and I seem to have a serious case of CRS.
>The name of the person and the battery brand escapes me.
>
>  
>
GARY:  As a fellow sufferer I find it easy to forgive...  Forgive and 
forget....  What were we talking about?

> <>ARILD:  We were talking about boats and he mentioned selling 
> batteries in Vancouver.
> He claimed that his brand had better Amp hours capacity because they
> adjusted the SG to optimize it. 

GARY:  Apparently this is becoming common.  We have heard a couple of 
folks here suggest that they have heard the same story.  I like your 
term 'specmanship.'

> <>ARILD:  Vancouver is cool. I wonder how such a
> battery would do if it was installed on a boat that went to Baja Mexico. 

GARY:  I don't know, but I suspect the difference in battery performance 
would be subtle, rather than a major one.  Perhaps shorter lifetime, 
perhaps quicker sulphation...  all things hard to measure without lots 
of comparable results, which of course the battery owner wouldn't 
have.   I am a big believer in the notion that there is no free lunch -- 
you can't have an improvement in one aspect of flooded cell performance 
without diminishing something else.  Unhappily the owner would have 
trouble interpreting his hydrometer readings, if they had boosted the 
original SG very much.  He would see hydrometer readings that indicated 
more charge in the battery than was actually there.   Significantly 
more, I don't know until I know how much they goosed the original SG. 

> <>
> ARILD:  Another poster mentioned something I had forgotten from my 
> school days.
> Adjusting the SG for temperature range.

GARY:   Yeah, I already do that because the temperature compensation 
makes a significant difference in properly interpreting the results, and 
my key concern here is that the range of SG changes we are talking about 
in determining if a battery has a full charge is rather short.   Would a 
boater conclude that his system was Overcharging a battery because the 
maker (or the retailer who added the acid), tried to hotrod the battery? 

>ARILD:  I'm not sure if this is just within the range indicated on the thermometer
>scale in  the better grade of Hydrometers or if the acid is actually
>stronger for use in Northern areas.  
>  
>
GARY:  Might this be apples and oranges?  Shifts in initial SG and 
applying temperature compensation seem to me to be independent issues.  
It seems to be emerging that at least some batteries have hotter acid, 
whether it was the manufacturer, the distributor or the retailer who did 
that, we don't yet know.   If the manufacturers were innocent of this, 
they would continue to support the standard SG vs. charge relationship, 
which they seem to be doing.  Recalling that the retailers are the ones 
who add the acid, just at the time of sale usually, they seem the most 
likely source of any differences.  There are only a very few actual 
manufacturers of flooded cell batteries, and a fair number of sales 
folks for the distributors, but there are 'billions and billions' of 
folks who dump the acid into 'em at the retailers.  Lots and lots of 
folks may be involved in this, folks whose understanding of the details, 
or even the generalities of this technology vary widely. 

Regarding temperature compensation, since it ranges over such a short 
scale of SG differences, I suspect that factoring in the shift in 
initial SG would not change the temp. correction itself significantly.   
However, the range of SG changes involved in normal operations isn't all 
that large either, the difference in SG between a fully charged battery 
and a nearly exhausted one isn't all that large.  Same for resting 
voltage.  I can't tell if this issue is significant or not, for lack of 
specific information. 

>ARILD:  As the snow birds among you know, a frozen battery loses power compared to
>one that is at room temp.
>Increasing the SG would compensate for winter use and where the summer temp
>doesn't get excessive.
>
>  
>
GARY:  Yeah, that's probably right, but I can't tell for sure how much 
'compensation' is available, or what it implies regarding lifetime 
battery performance.   Without knowing how much the SG got boosted, and 
in which batteries, it is hard to sort out this stuff.  Recall that the 
initial information that sparked this thread looks more like second hand 
rumor and hearsay than technical bulletins from the manufacturers.   If 
there was a significant boost in initial SG, we could be giving 
ourselves misleading information with our hydrometer readings. 

Perhaps the really obsessive among us ought to completely charge our 
batteries when we first get them and carefully document the initial SG 
(temperature compensated of course), together with voltage and load cell 
performance for each.  Each successive time he tests his battery our 
truely obsessive boater should probably take corrected hydrometer 
readings on each battery in both its discharged and its fully charged 
condition, and correlate all of his readings with voltage and amp-hour 
data.  Then he could track the degradation of the battery by monitoring 
the diminishing fully charged SG  of each cell, which should diminish 
over the lifetime of the battery with the sulphation and other aging 
processes of a battery which is continually immobilizing sulfur in the 
form of sulphation, and where there is plate spalling and warping, 
together with oxidation and fatigue of the lead components, etc. etc. 
etc..  He could get out his slide rule and derive a family of 
algorithyms to precisely predict the performance and lifetime of each of 
his precious batteries.  Or perhaps not.  I wonder how many of us 
actually use our hydrometers (or even have a nice one)?   Surely (or 
Shirley), we jest.  I bet nearly all of us treat batteries as things 
that we can't completely understand or predict, and when they seem to 
have pooped out we replace 'em.   When our batteries seem to be 
misbehaving we get out that little floating bead hydrometer and use it 
to support the idea of going battery shopping.   Am I right guys?  I 
hope we are not beginning to count the angels that can dance on the tip 
of a 2 micron filter with this thread.

Nevertheless, when we go out today, I will see if I can talk the Admiral 
into allowing a quick visit with a big independent battery retailer for 
a couple of quick questions ... stay tuned.

Cheers!
Gary