T&T: Batteries

[Candy Chapman and Gary Bell]

Robin Brueckner wrote:

> "I also have read that some manufacturers use different mixes of acids 
> and acid concentrations so specific gravity can vary among brands...."
>
> REPLY:  Interesting.  Could you suggest where you found that?
>  
> I read it around 1998 or 1999. I don't remember.
>  
> When I bought my Hatteras in 1998 I read a LOT about batteries to see 
> if I could learn enough to actually make an informed choice among 
> battery brands. I was buying six or seven 8D's. I determined that for 
> the most part I could not because the technology, materials, 
> fabrication and chemicals involved were not only not readily available 
> for many brands but because even if I could determine them it would 
> not be possible to make an informed choice. In fact at
> the time I could not even figure out for sure which "deep cycle" 
> batteries really were deep cycle. Getting specs was tough; Inerpreting 
> them, even more so.
>  
> "Does the use of deep cycle batteries for starting result in shorter 
> life.."
>  
> It's possible but very unlikely. Just figure the power(amp hours)
> delivered to  an engine that starts promptly...it's insignificant.
> And besides, I have house batteries that are never used for
> engine starting and they weaken identically to those banks I
> use for starting. I believe the reverse is far more true: that 
> starting batteries do not serve well as dual purpose batteries.

REPLY:  You're probably right.  The deep cycle used just for starting 
would only fail if it couldn't provide enough current to start once and 
a while, while as long as the engine is running it is being recharged.   
Very light duty, it ought to last nearly forever.  Putting a thin plated 
starting battery though only a few really deep discharges would toast it 
for sure.  I should have suggested that the use of deep cycle batteries 
to provide both house bank and engine start duty will leave the boater 
soon enough trying to start with a depleted battery, a sticky wicket for 
sure.  There's the trouble.   I agree that there is likely no damage to 
the deep cycle battery when used only for starting.  Using a deep cycle 
just for starting jobs is particularly overkill however, why pay more 
for a special deep cycle battery when you only need  a  common 
automotive start battery to do the job?

>
>  
> The only thing I'm certain about is that (a) Rolls Surrette have a 
> great reputation for long life and cost a bundle, (b) AGM type
> according to the trade delivers the lowest cost per amp hour
> delivered...and they are high initial cost as well, (c) I have
> no idea whether (a) or (b) is the best value. (d) People seem to think 
> Sam's Club golf cart batteries are a good value.  

Yeah, right on.  One detail I caught when I first replaced my Canadian 
Tire golf cart batteries is that some marine models have envelopes 
around each plate to catch the lead that spalls off them when they have 
been through a bunch of discharge cycles -- preventing shorts that 
otherwise end the battery's life.   I bought West Marine's Sea Volt 
6volt GC2 sized batteries (made by West Penn, I believe) on the 
assurance that they had this feature.   Shortly thereafter my Prosine 2K 
Amp inv/charger went entirely gunnybag, and in the interim I have had a 
little 20 amp charger carrying the load.

MY CONCLUSION:  I agree all around.  Did you see my conversation with 
Arild?  He said he too had gotten that info from a manufacturer, and I 
asked if he could identify which lines/brands/manuracturers were 
involved, and some info about how far off the standard hydrometer curves 
would be with their 'new improved' designs.   So far, I am inclined to 
think the improvement is slight, not particularly significant, and more 
one-upmanship or as Arild put it specmanship.  Let's see if Arild can 
come up with more details, he might well be able to sort this out. 


Regards again from that old drone,
Mister Science (Gary's name when he is on his soap box)