Friday, January 1, 2010

Re: [Electric Boats] AGM Battery: To Float Or Not To Float

 

Steve:

IMO I don't think you need to go that far in maintaining the battery bank. Don't forget you  will be adding extra weight with the battery. I've found the combination of solar and wind generator keeps things pretty topped up in the battery bank. Many times the wind generator cranks up and then shunts down because the battery voltage has reached the set point. During the day in sunshine it is also often shutdown  because the solar panel is keeping the bank charged. When I do connect my Zivan NG-1 charger to either the Honda generator or dock power it immediately drops out of bulk charge mode and goes to the pulse charge phase and finishes to green in short time. Perhaps an hour or two. I have not been keeping accurate records but, usually when I get on board the 48 volt bank is reading somewhere around 52 to 53 volts. There is some load on the bank from the wind generator control electronics and XBM battery monitor. Yes, I suppose there could be times when there would be minimal sun and no wind but, those times won't last long. For cruising sailboats on moorings or at anchor like mine that is the reality we sail in. The more options for charging you have the better. So far I've found the solar/wind generator/Honda 2000/shorepower situation is working for me. The charge and discharge cycles are what they are. Since my boat is rarely at a dock full time float charging is not an option. The great unkown at this point is how long the battery bank will last. I'll start my third season using electric propulsion in a few months and will continue to monitor and do more testing on the system. In between sails of course.<g>  I'll also be learning from the experience and knowledge of others here on the list.  Nothings perfect but, the goal is always to make it better and avoid making it worse.
 
Capt. Mike
 

--- On Fri, 1/1/10, Steve Bull <steve.bull@gmail.com> wrote:

From: Steve Bull <steve.bull@gmail.com>
Subject: Re: [Electric Boats] AGM Battery: To Float Or Not To Float
To: electricboats@yahoogroups.com
Date: Friday, January 1, 2010, 9:36 PM

 
To continue this thread:

Imagine trying to maintain battery longevity of a boat at anchor with no one aboard and dealing with the irregularities of sunshine on PVs and/or a wind generator to top off the batteries.

Is it possible or advisable to use a 'sacrifice' battery in conjunction with a voltage booster to continue to maintain the topping off charge on the main group of batteries and another small task like bilge pumps? The 'sacrifice' battery would of course go through many more charge cycles while effectively maintaining the  longevity of the battery mains.

- Steve

On Fri, Jan 1, 2010 at 3:06 PM, Joe Siudzinski <siudzinski@telis. org> wrote:
 
The Question:

"For battery LONGEVITY, is it preferable to have the battery absorb every
last bit of energy and sit there fully charged with an external float
charger (set to, e.g., 13.2v at 70degF), or is simply turning off everything
when float current gets below a certain point preferable?"

> From: James Graham <osirissail@yahoo. com>

>
> Battery life is measured in "cycles" not hours, days or years. Each time the
> battery is allowed to discharge and then a battery charger kicks in to
> re-charge the battery that is a cycle...

> - - Constantly "on" charge battery charges not only keep the battery topped
> off but they will provide the electricity to run the other equipment

Thank you for emphasizing that the measure of longevity is "number of
cycles", even if those cycles are extremely shallow DOD and last only a few
seconds. I should have pointed out that my series strings (156v EV, 48v
boat) are strictly separate motor-energy suppliers, isolated from the
vehicle/boat's normal 12v system.

 

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