Re: [PSUBS-MAILIST] Batteries Bank

[MerlinSub@t-online.de]

Hi Cliff, 

my boat runs 25 sm (on the paper) underwater with lead acid batterys. 
If I replace them later with Lipos and use the same storage space 
the calculation shows that the boat runs 100 sm!

The only thing that stops me: 

- Complete unclear how to balance such a huge amount of big lipos.

- PRICE is far to high, but falls year by year - so have just to wait. 

- The Lipos in my cellular phone, my drilling machines and in the 
  camera lost clear a lot of capacitiy with in abt.2 years. 
  So I dont belive there liftime caclulations. 

It is clear that if you have four times more storage energy on the same volume 
in case of a fire it will be a much more powerful than on lead onces. 
But lead one can also explode if you short-securit them. 

Like to build first Lipos in the Sgt.Pepeprs outside battery storage tank 
I allready build for this purpose. But cooling this close space is unclear. 

vbr Carsten


"Cliff Redus" <cliffordredus@sbcglobal.net> schrieb:
> Based on the experience with my boat, I think AGM's are the way to go. If I 
built a new boat, I would use these.   As a point of comparison, I can give 
you my experience with AGM batteries for a psub application.  


I purchased 10 Lifeline Gp-2700T batteries about five years ago. These are 12V 
batteries rated at 100Ahr.  They weigh 63lbs each.  I operate my battery bank at 
120 VDC. During the build phase of the boat,  these were periodically top off 
with a dedicated 120 VDC battery charger that was setup for these particular 
batteries.  Over the  years, I have recharged these approximately 250 times.  
The initial cost of the batteries was $160 and the current cost is about $280 
each.  Over the five years, I have never, not one time smelled any off gassing 
during a charge cycle.  I have never had any leaked battery fluid.  I had to 
replace one of the batteries because I dropped it while removing it and riped a 
hole in the side.  Even  then, it still did not leak.  Now that I am in an 
operational mode on the boat, I noticed that the battery life was not as long as 
when they were new.  To analyze this, I built a poor mans battery tester which 
consisted of a 1200 Watt inverter that was connected to a bank of incandescent 
light bulbs with a light dimmer switch so that I could adjust load.  I tested 
each of the 10 batteries  against a 10 amp load and compared how long it took 
for them to  drop below 11 volts.   Compared to the data published by the 
manufacturer, these batteries tested between 40 and 70% of their initial 
capacity. The bottom line is it is time to replace the battery bank. 

To me, one of the major arguments for using lithium batteries is they have a 
better power density (power to weight ratio).  While this is important for a 
car, to me it is not as important for a psub as most of the time, we have to add 
ballast anyway to submerge.  So using a less expensive battery that provides 
both power a ballast makes more sense to me.  While they are inexpensive, 
conventional lead-acid car batteries leak acid and off gas while charging.  As 
such, to me a good compromise  is AGM.

Cliff


Cliff Redus
Redus Engineering
USA Office: 830-663-6445
USA mobile: 830-931-1280
cliffordredus@sbcglobal.com 




________________________________
From: Jon Wallace <jonw@psubs.org>
To: personal_submersibles@psubs.org
Sent: Sun, October 3, 2010 9:22:22 AM
Subject: Re: [PSUBS-MAILIST] Batteries Bank


The electrical requirements to fulfill the operating parameters of cars and subs 
are different enough I think, that the greater reserve capacity of Lithium is 
not enough to justify the added expense.  It would be interesting to hear how 
many psubbers have found that lead/acid does not adequately serve their needs 
and would move to lithium if they could.  Some time ago (in a different lead vs 
(?) battery discussion) Phil Nuytten advised that from his experience lead/acid 
provided the best "bang for the buck" for home-builders.  The US Battery Rep 
that we had as a guest in July talked about all battery types and seemed to 
confirm that for all its supposed weaknesses, the good ole lead/acid battery was 
the way to go.  That was my impression at least.

Jon




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