[TenTec] Hercules II battery arrangement

[Dr. Gerald N. Johnson]

On Fri, 2006-09-22 at 23:45 -0400, ARDUJENSKI at aol.com wrote:
> I have spend about a week milling thru the Ten Tec Archives reading the  
> posts regarding running the Hercules II on battery power. I have read the wide  
> range of suggestions from a couple of 6v golf cart batteries in series to using  
> 100 Ah deep cycle battery with recommendations for leaving charger attached 
> or  turning it off during operation. One large battery or two smaller capacity  
> batteries in parallel?
>  
> WHAT I WOULD LIKE TO KNOW is what is the preferred best method (good  
> engineering) for using battery power providing make and model of battery and  
> charger. Is something like the A&A Smart Charger a good choice for this  setup? Or a 
> standard RV charger?
> _http://www.a-aengineering.com/home.htm_ 
> (http://www.a-aengineering.com/home.htm) 
>  
> My Hercules is a few weeks off before delivery so I am not privy to any  
> information that may be in the manual but I am sure it would not be specific  
> other than the battery rating.
>  
> I would appreciate your feedback and any sketches for your system if  
> necessary. I do know about the use of an acid proof battery case and it will be  in a 
> well ventilated location
>  
> Thank you
>  
> Alan  KB7MBI
> Woodinville, WA
> FISTS 5702   CC: 1885
> SKCC 1988 NAQCC  058
> 
Like selecting a battery system for back up and for a RV, there are
arguments in all directions.

Sometimes one gets the most power for the buck going with 6 volt golf
car batteries. Two in series. The down side is that means four battery
connections to care for and if one cell gets weak (from loosing active
material or electrolyte), it prevents good charging to the other
battery. They should be replaced in pairs anyway. Trojan is a brand
often preferred in the solar energy applications.

More than a few diesel truck run two sturdy 12 volt batteries in
parallel. Fact is it also works, and still has four connections to
maintain. And a shorted cell in one battery will kill the other battery
from restricting the charge voltage and discharging that good battery.
Again they should be replaced in pairs.

In some theories, there can be a bit more energy stored in one
connection or the other, but since few makers actually fill the space in
the battery case with plates that's hard to prove.

Ultimately battery capacity depends on the plate area in a cell or cells
that are paralleled. With fewer separators in the battery case, there's
room for more plates (one or two at the most) in the pair of 6 volt
battery cases than in the 12 volt cases that are the same size. But if
the makers don't fill the space with plates, you can't tell which is
larger other than by reserve amps, or cranking amps, maybe cold cranking
amps. With two 6 volt batteries in series the amp ratings for the pair
are the ratings for one battery. With two 12 volt batteries in parallel,
the amp ratings for the system are the sums of the ratings for the two
batteries.

But without the golf cart battery vendor being close by, there are more
12 volt batteries to select from.

As for use while charging, the smart chargers like made for RVs seem to
get longer life and better load care than the dumb chargers and bring
the batteries back more rapidly. In RF power amplifiers, the power
available is greater at 13.8 volts than at 12.5 volts and you will only
see 13.8 volts while the charger is working. And even the deep cycler
battery lasts longer if not discharged but it makes a mighty fine filter
for the charger and does a good job of allowing a 10 or 20 amp charger
to run a 100 amp peak load like the Hercules.

Ventilation is important as is resistance of the battery surroundings
from acid. Getting a battery to full charge will lead to "boiling" where
bubbles of hydrogen and oxygen are liberated from electrolysis of the
water in the electrolyte. As this vents, it can take some acid with it.
And as it vents its in the optimum ratio for the best bang if ignited.
High load currents also cause some loss of electrolyte for the same
reason.

One good resource for safety, big batteries, and chargers is the Home
Power Magazine. Its available on line, and there are vendors advertising
replacement vents that capture the hydrogen and oxygen and return it to
the cells as water that can save much of the venting and acid spritz.


-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer