Wet Cell Charging Voltage

[kiltym]

Originally Posted by btrayfors

6. In my personal experience and testing, flooded golf-cart batteries which are kept fully charged (14.8V absorption level) but not often deep-cycled will begin to show significant (more than 20%) reduction in storage capacity after about five years. The deterioration in capacity begins much earlier. At six years you may have a battery with about 70% capacity remaining. These are very rough ball-park figures. Note that for many sailors, a battery with 70% remaining capacity is still "good". Therefore, I'd treat with extreme caution statements like, "my batteries lasted 8 years and are still good".
Bill

So, from this statement, if we have used our batteries constantly for 3 years, sometimes, but not every week, bringing them back up to 100% full charge, that's not too bad considering. I would say our batteries are on average about 75-80% full as a rough estimate. I would have liked to hope and get more like 5 years from a battery under heavy use, but I realize full time cruising is a heavy demand on batteries. We use a lot, but rarely bring them back up to full charge. Full time cruisers for the most part are not interested in running their engine 1-2 hours per day to do this, so we make do until we are at about 50% (maybe 4-5 days), and then run the engine. During those 4-5 days, the voltage increases a bit, and decreases a bit based on load and alternative energy sources, but at not time is if ever back to 100%, no way.

Your test is at optimal performance, basically 0 discharge. Although, it would seem one would want to keep the batteries at a float level (13.3V or so), not 14.8 for extremely long periods of times. By doing this, did you actually harm the batteries, or just fill them with water a lot?

We charge our batteries up to about 14.7V when charging by engine and solar (although solar rarely gets up that high because of loads). I figured 14.7 (before temp compensation) is high enough, but is certainly from from the recommendation of the manufacturer. I hate it when the manufacturer tells you something that seems out of whack with the general consensus, and what seems like common sense.

[capn_billl]

I would contact the manufacturer for more info. As stated above plate chemistries differ. 1 brand may have more resistance to sulfation. Another may have more alloys to better maintain plate integrity. You may want to visit electric car web sites. They have extensive experience and discussions about getting the most life, range from a variety of battery manufacturers, and charging styles, including solar.

[gonesail]

my charger charges at around 14.5 volts .. amps vary according to the charge level of the bank.

[conachair]

Originally Posted by capn_billl

I would contact the manufacturer for more info. As stated above plate chemistries differ. 1 brand may have more resistance to sulfation. Another may have more alloys to better maintain plate integrity. You may want to visit electric car web sites. They have extensive experience and discussions about getting the most life, range from a variety of battery manufacturers, and charging styles, including solar.

Some info on this thread, the poster spoke with US battery - see post 10

battery equalisation charge - Yachting and Boating World Forums

'Normal charging requires that the battery be brought up to 15.5 Volts (or the temperature corrected value) and held there for two to four hours. Mind you, this is not equalization.

[btrayfors]

kiltym,

Sorry, my phrasing wasn't good. I was talking about batteries kept pretty much fully charged using a 14.8V absorption level, then reducing to a 13.6 - 13.8V float level.

And, again, I'm talking about capacity which is distinct from state of charge (SOC). The statement usually seen by cruisers who typically run their batteries between 50% and 80% full (SOC) has almost NOTHING to do with the capacity of those batteries to store and deliver energy.

And, in a typical cruising scenario where batteries are cycled between about 50% and 80% SOC it's very difficult to recognize that capacity is slowly decreasing over time -- that is, until it becomes very obvious that the batteries can't deliver anywhere near as much energy as they used to.

BTW, flooded batteries at a 80% SOC WILL SULFATE. BADLY over time, thereby decreasing their capacity. That's why it's a good idea to bring your batteries to a fully charged state as often as you can, and if you can't then a stepped-up equalization regime would be indicated to help knock PbSO4 crystals off the plates.

Bill