I have 4 Optimas in my boat, two for the trolling motor and two for the engine, and I fish maybe once a month, sometimes longer due to work. One of my Optimas went bad due to it not being maintained. I have an onboard charger and it charges all 4 at one time before I go fishing. Will the Optimas be fine if I charge it once a week or every two weeks with the onboard charger or do i need a trickle charger? I was about a month and a half or two before I checked those batteries and found one went bad.
If a trickle charger is the way to go instead of my onboard charger, is there one that will charge all 4 Optimas at one time?

Go get a load test on that battery if it bad there is nothing you can do except get a new battery.

what charger is in the boat? most will go to a maintain mode when fully charged.

you can also use a timer, I put one on mine due to now having li ion. runs for 2 hrs. a day

https://www.homedepot.com/p/Interma...eavy-Duty-Timer-Black-HB11KD89/205478787

A Minn Kota onboard charger

Larry, Optimas do not go bad after 9 months, the staff at the battery depot says to use a maintainer / trickler when not fishing on the boat. Batteries do drain when not using them, especially after 1 and a half months, its when it went bad.

I don’t read many postive reviews on optimas in deep cycle applications, they say they are good for cars/trucks. Make sure your charger is meeting the voltage needed to keep the optimas in good condition, many chargers don’t put out enough voltage. Same goes with lithiums now, they need more voltage than what a regular lead acid charger provides.


Obviously 4 batteries should not be dead in a month or two from just sitting. Maybe something is drawing power, TM’s are known to pull voltage when plugged in and not being used.

if that is a digital or the newer precision charger it should go to maintenance mode once full charge is reached.

just leave it plugged in and on and you will be fine, check water in batteries about once a month (just use distilled water to refill).

Just one battery which has access to the water pump in the hull which is connected, only that went bad, other 3 was disconnected with a switch. My guess was it drained the battery.

The batteries coming in from China are very poor quality. There is only one battery mfg left in the us and even they have offshored some of their products. If a battery will not hold a charge then testing it with a load test is the only way to determine if its bad. Battery chargers of today will have charge profiles for ea battery and when they are full the charger goes into maintenance mode. So charge it up and do the load test. It the only way you will know if its good and it can be 1 week old and go bad with todays china quality. Even if Edwin likes the 6 pack batteries. IF you just leave your battery charger plugged in it will do the same thing as a trickle charger If you are going a long time between boat uses then leave it plugged.