Posts: 2754
Location: Mauston, Wisconsin | Bruce- Definitely get a second opinion/test. Connecting the battery charger to the post's is fine. The thing that concerns me is the the 90% state of charge when you had the battery tested. Did you put the battery on charge for 24 hours before getting it tested? If you are using the Vector 12A setting a fully discharged group 27 battery should be fully recharged in ~24 hrs. Does your Vector have an "equalize" setting" if so, set it to equalize and let it run through that cycle.
It is fairly easy to check the state of charge of a battery with a digital voltmeter, i.e., if the battery has just been recharged, and has been at "rest" for ~ 4 hours. By rest, I mean disconnect the charger or turn it off and do not put any load on the battery until you measure the voltage..Then measure the battery voltage.
State of Charge 12 Volt battery Volts per Cell
100% 12.7 2.12
90% 12.5 2.08
80% 12.42 2.07
70% 12.32 2.05
60% 12.20 2.03
50% 12.06 2.01
40% 11.9 1.98
30% 11.75 1.96
20% 11.58 1.93
10% 11.31 1.89
0 10.5 1.75
Guess what if the battery measures 12.4V using this "open circuit test" (thats what we call letting it rest for 4 hours after recharge without load and then meaasuring the voltage). You need a new battery!
Another possibility is your charger may have a problem- If the battery is connected and charging you should measure ~ 13.5V->13,8V in what we call float charge mode. If in equalize charge mode it should measure ~14.4V.
Re- Dual prpose batteries. They are a ballance between the two, i.e., a starting battery and a deep cycle. They are actually good for marine starting applications because of the amount of ancillary electronic loads that we connect to them. For your trolling motor you need to stick with a deep cycle battery, i.e., it will give you the best service life.
Have fun!
Al
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