You are Correct -Sir! Nicads are a totaly different breed of battery, which I also did research work on a gillion years ago. They have up til now had problems with a memory of the discharge floor, and then never charging up beyond that floor. That reportedly has now been cured, just in time for Nicads to be outlawed due to the mercury content.
Wet cells are different. They suffer when not used much, then are recharged, but it is not a life threatening problem..as in nicads. They just lose their lives faster due to part of the plate getting eaten up heavily and the rest not getting much use at all. The cell is not fully working..only part of it is.
Enter the equalization charge. This has at least two effects that are of immediate interest here. It shakes up the electrolyte with bubbles and currents, and this tends to distribute the electrolyte evenly through the cell, so that the whole cell can be utilized.
The second benefit is what happens to the battery as a whole. Consider this situation: Battery is in use for several years, and over time, one cell has a better production rate of current than the others. This is fine as it is But now add in a cell that lags the rest in production, which there certainly will be if there is one that is higher..right? 'Sointenly! So ok, now the battery is "Unbalanced", with the cells all producing more or less than the rest, with one clear loser. This situation will now escalate due to other processes. The low guy gets progressively lower in output. Trouble is..this then increases the self-discharge rate of the cell..how long it holds a charge sitting idle. The darn thing will self discharge faster now as the rest of the cells try to pick up their lagging friend and get him to their voltage levels.
The whole battery voltage should have been say 12.8v open circuit. Now with this low cell, it has dropped to 12.2v and next month to 11.8v etc. You will notice a definite current loss also..or throttling effect due to the low cell..they are in series, and a higher resistance to current flow in that low cell will drop voltage and waste energy thru excessive heat, which causes excessive gassing, which dries out the cell faster, increasing the SPG until the electrolyte is so concentrated that it forms little stalagmites to grow between cells, shorting them out..now that battery is worth $5.00 as trade in at WalMart.
In your case, if you have access to a 120vac 15A supply, go get yourself a small Guest or Statpower or ?? 3 stage charger. Make sure you can do this equalization charge with that charger..it should brag in the specs about this ability. Charge as often as you like to do it, and a few times during the summer, give the battery the EQ charge for 30 minutes or whatever the charger recommends for your bank size. This will tend to even out the individual cell voltages, and to redistribute the electrolyte.
You will find a marked increase in battery life, a marked decrease in the gassing you noted (gassing is overcharging, plain and simple. During EQ, we do it intentionally and in a controlled way. During charging, it is just a waste of water, and can damage the battery long term).
I realize how much you enjoy the simplest system you can get by with..and I have actually practiced this myself with my former boat, and 20+ years of backpacking and canoe camping where you were either a minimalist or a chiropractors best patient. Now with DLM, we have asperations of going farther than our horizons presently allow..repeatedly. Maybe we will get to the Med someday even. I know that my heart is set on seeing the Azores in my own boat...
...so we have been quietly upgrading our home as money allows and before money is worthless (kidding..?). My system is more involved compared to a bare-bones system, no doubt, and I do not advocate going as far as I did unless you have a need for 400+aH of total capacity (225aH to the 50% point), and total independence for long periods of time (>1 Month).
While the boiling..really just gassing, will certainly mix the elctrolyte..it also damages the cells over time through overheating them, causing the cell separators to buckle, moving the whole cell structure, sometimes shorting them to each other internally. So simply overcharging a bunch then replacing the water gaurantees a three year battery life.
Hope all this helps..;^)
Cheers Cap't.
Larry DeMers
s/v DeLaMer
........D. Stump, Hanalei wrote: Captain,
Do you mean to say that I don't need to discharge the batteries to about 50% and then recharge them to maintain the full "depth" of charge. All I need to do is to hit them with an "equalization" charge to restore the full "depth" of charge or shall we rightly call that "capacity"? So, flooded batteries are not like ni-cads, that will take a set if only discharged a little and then recharged. This then would make a ni-cad show full charge when in fact the charge is very "shallow".
When I recently pulled the batteries and took them home to charge them, I noted that the electrolyte level was down a little in each cell. Plates weren't exposed, but level was definately down. Did it just evaporate, or is this an indication that in fact the batts. had been brought to an "off gassing" state and boiled off some electrolyte when charged by the alternator?
I don't remember what top voltage is when the alternator is charging, but I seem to remember about 13.5 to 13.8 volts. Wouldn't that cause the electrolyte to "boil" and remove the stratification p>
D. Stump, Hanalei wrote: Dave Stump
demers@sgi.com