Bow thruster -weak altering watering 1-y/o battery

Hey. Put in a new bow thruster battery last year. Watered it and now it’s weak. Was fine before watering. Used distilled water. Watered to recommended fill level. Thoughts?

I'd guess it was also weak before watering and is toast. Adding water won't make a battery weak. If you had to add a lot of water maybe figure out why. Is the battery undersize? Do you tend to use the thruster for long periods? If so, maybe oversize the cables ad battery or learn new techniques.

Likely a defective cell. This caused the remaining cells to be over charged which boiled all the water out.

Also possible that you have a defective battery charger that just continuously cooks the battery.

Is the battery weak or is there a problem with the wiring or switches?

To troubleshoot, hook a voltmeter to the battery’s terminals and watch the voltage. If it starts at 12.5+ volts with no load and drops no lower than 11.5 volts under load, then the battery is ok. Then check the thruster motor terminals. If that voltage under load is more than a volt or so less than the battery voltage then there is excessive voltage drop in the switches/wiring between the battery and the thruster motor.

If the battery is bad, replace it with a G 31 AGM like this one. AGMs don’t require water addition.


David

What size cables and how long a run is it? Clean all connections and use something like Boeshield on them when you have them all clean and tight. What is the voltage at the thruster when it is on and when it is off.

IMO, the batteries boiled down to the plates and they were killed before adding water. Topping with distilled water would not do this.