*Question preface: I'm having to lug my batteries to and fro boat b/c storage place won't let me charge it. Using a schumaker charger.*

Been charging my 2 month old otpima's this way ever since i bought them, charger would show gradual increase from its state say 70% to 100 (ie showing %s in between). Past weekend TM broke and in the process of installing a new one realized the female part of my electrical plug up front was melted replaced both (new fortrex is sweet) anyhow got to use my on board charger at the fish camp i was at this weekend, then brought them back to where i'm living and now when i charged both batteries they started at 80 showed no increase for hours, i unplugged and replugged and it immediately read 100...happened for both batteries.

Pretty much just trying to figure out if my batteries are indeed fully charged / why this is happening all of a sudden to both. sorry for the long question... Okeechobee was awesome this weekend. somewhat glad my tm broke gave me an excuse to buy me a new one

Many of the symptoms you describe correspond to batteries with a dead cell.  Take the batteries to a load testing place and get them tested. 

They fail to charge because the voltage is too low and the reading is unreliable.

They rapidly show full charge because with the dead cell the battery voltage rises very quickly when it won't accept a charge and it looks like it is 100% charged.

Many of the symptoms you describe correspond to batteries with a dead cell. Take the batteries to a load testing place and get them tested.

They fail to charge because the voltage is too low and the reading is unreliable.

They rapidly show full charge because with the dead cell the battery voltage rises very quickly when it won't accept a charge and it looks like it is 100% charged.

That's interesting.  I have experienced the same thing with a Shumacher charger 2/10 amp automatic.  And, my battery did not last very long, about four or five hours before it started to slow down.  This occurred on ponds where the motor is used only sporadically to move from one spot to another.

I suspected a problematic cell.  Did a hydrometer test, and all the cells were identical, showing a reading of 1150, which, according to the chart is about 25% charged.

Two voltmeters showed the battery to have a voltage of 13.20 plus or minus a couple of hundredths.

Batteries are branded Bass Pro Shop.  Took the battery, the charger, and my voltmeter to the local Interstate store to have it checked.

The battery is made by Exide.  Was manufactured last July.

They got the same results from all six cells on their hydrometer.  Did a load test, which indicated the battery is fine, but were still puzzled by the voltage reading and the specific gravity readings of the electrolyte in the cells.

The tech asked how I connected the battery to the charger.  Since the plastic caps were still on the large posts, I had been connecting the charger to the nuts on the steel studs which are used to secure the trolling motor terminals.

He felt this might be the problem since they do not conduct current as well as the lead posts, and thus giving the charger an inaccurate reading of the battery's condition.

I have tried charging it using the lead posts, but still end up with the same 13.2 volts when the battery charger is disconnected after the green indicator light shows it to be fully charged.

When near fully charged, and the charger connected and still charging, it will read as high as 14.5 volts or a bit higher.

Haven't used the battery since Interstate tested it, but the charged reading is the same as when I connected the charger clips to the metal nuts.

Still scratching my head.  Specific gravity readings still indicate it is not fully charged, but the charged percent does read a bit higher.

According to the Interstate fellow, my charger is functioning normally.

If he is correct, that leaves the trolling motor as the sole remaining factor in the equation.

Yet, I had just had a speed controller changed, and the motor was drawing the normal amount of amps on a test stand.  Of course, a test stand is not quite the same as being used in the water.

Any thoughts? 

I have a Shumacher 2/10/15 amp marine charger, and I experience the same thing from time to time.  Most times it will charge as normal all the way to 100%.  Never thought twice about it, batteries hasn't failed me...yet.