battery charge level- whats appropriate

[jtm]

I've got a 24M 12v standard battery that is about 3 yrs old.
In season, I keep it maintained via 5W solar panel during the week and top off/condition it on weekends with a Promariner 12 charger while running shore power to the boat.

In the winter I take it home and every 4-5 weeks put it on my car charger box @ 2A setting for 1-2 days. I also connect a "nanopulser"( to blow off the plate salts) to the posts during this charging period. Thru-out its life I often check the water level and ensure it's got the plates covered. It has not "drank" much of any distilled water over time.

It seems fully charged (per the meter gauge) but has plateaued at 12.56v when measured from post to post on the battery. At that reading, it is said to be "90% charged" per my readings. I thought I should get to 12.75-ish

I know this may be niggling but "inquiring minds want to know"- Is this the best charging level I can hope for ? Might these readings be much different for a 27M similarly cared for?

 

[Warren Milberg]

Jim:
I, too, have 2 Grp 24 batteries for my H28.5. Both are just about to begin their 3rd year of service when I launch next month. I also keep them in my coolish basement over the winter and take a reading of their charge about monthly. I use a trickle charger once in a while to keep the charge up. They tend to lose no more than .1vdc per month when sitting idle and currently (no pun there....) read between 12.82 and 12.84vdc, which I believe is "fully charged."

In your case, the first thing I would do is use another DVOM to test them. I have two: one is an expensive one and one is relatively cheap. They show a variance of .2vdc between the two when reading the same batteries. Secondly, if in fact, your batteries are only able to hold 12.56 v after sitting for 24 hrs after being charged, my guess is that they are on their way to failure. You may want to take them to a West Marine or local auto service station that can test them under load to get a better sense of where they are in their life cycle before reinstalling them on your boat in month or so. FYI, I just replaced the 6 yr old Grp 24 battery in my car when it began showing a charge of 12.45 vdc after sitting overnight. I've found that these kind of batteries can experience a pretty sudden faillure. Not a problem (usually) with a car, but not one you want out on the water in your boat...

 

[jtm]

Say it aint so Warren- but I'll try measure them with another meter.

 

[chp]

I find that unless you have a very expensive meter, they all read a little different. I always check mine with a battery hydrometer. I've had my batteries for 3 years, keep them charged on the boat with solar and occasionally boost with a charger and they still take and hold a full charge.

 

[Maine Sail]

I've got a 24M 12v standard battery that is about 3 yrs old.
In season, I keep it maintained via 5W solar panel during the week and top off/condition it on weekends with a Promariner 12 charger while running shore power to the boat.

What are your actual absorption charging voltages? Do you see 14.4V+/-..?

In the winter I take it home and every 4-5 weeks put it on my car charger box @ 2A setting for 1-2 days.

What are the specs for this charger? What is the absorption voltage? Is this a constant current trickle charger, a multi-stage "smart charger" or a constant voltage charger? If constant voltage or multi-stage what are the voltages?

I also connect a "nanopulser"( to blow off the plate salts) to the posts during this charging period.

Better to use that as a paper weight because these are basically pure snake oil.

Thru-out its life I often check the water level and ensure it's got the plates covered. It has not "drank" much of any distilled water over time.

This can indicate your charge voltages are pretty low and not being charged for long enough at those voltages.

It seems fully charged (per the meter gauge) but has plateaued at 12.56v when measured from post to post on the battery. At that reading, it is said to be "90% charged" per my readings. I thought I should get to 12.75-ish

Did you A/B this to voltage readings when the batteries were new? What does your battery manufacturer call "full" in terms of open circuit resting voltage? Some batteries are "full" at 12.6V and others are full at 12.72 - 12.74V this all depends upon brand.

I know this may be niggling but "inquiring minds want to know"- Is this the best charging level I can hope for ? Might these readings be much different for a 27M similarly cared for?

The simple test is to "equalize" the batteries at 15.5V for two to 4 hours. After this let them rest for about 24-36 hours at about 70F. If the voltage is still the same, 12.56V, then that is the best you can hope for. If it rises to 12.72V or so then you've been under charging them.

 

[jtm]

thanks Mainsail & CHP-

I went back after about 6-7 hrs to test again with the original sears digital Ohm meter - it was up to 12.62v.

As for you other questions- on battery mfr spec- (Autozone Marine)- I don't know.
I have tried a cheap trickler but I assume its a "single stage" So I use the home auto charger that i believe is multistage & multi amp 2-10.

What I am most sure of is the Promariner12 which Is a multi-stage charger. Using that charger early in the sailing season/on commissioning I find that the Promariner tends to run rather warm to the touch the first couple times I use it- I suspect that it was
"conditioning" the battery to bring it up as high as possible. After that initial period i find it runs cool for the rest of the summer/fall. Perhaps this early conditioning is really when the salting is being cooked off the plate and full charging is achieved..

When the promariner is charging(dual batteries) I can see (IIRC) ~13.75 on the meter gauge at the nav table.

I'm gonna find another meter and see if Warren's .2v difference can be found

 

[thinwater]

Also temperature. Room temperature or near freezing? That could account for ~ 0.4V.