Bow thuster batteries

[Mark and Karen]

I think we have tracked the bow thruster fault back to the pair of Exxide Maxxima 900dc batteries which seem to have lost their capacity (plenty of volts, no umph).Any idea of suitable alternatives as these have failed just outside of their two year warranty! Need to be able to deliver a very high current for a short period

[Jeff Shukis]

My thruster battery has the same symptoms. I find this odd given that the boat is just four years old and sits in the marina most weekdays, connected to shore power and charging whenever the charger decides that it needs to. When I do use the thruster, it's for a few seconds at a time, hardly using any battery capacity.

 

It turns out - I believe - that this low-usage scenario is exactly the problem. The charger is keeping the battery charged, but not quite fully charged and I don't cycle it deeply enough to trigger a really serious charge. I believe that the battery is simply losing capacity over time due to chronic undercharging.

 

I'm going to try an equalization charge to see if that fixes the problem. Later today I plan to poke the equalize button on the Xantrex charger to begin an eight hour equalization charge. My AGM house batteries are in good shape, so I'll disconnect these from the charger before equalizing. I'll let you know if it works.

 

By the way, my symptoms are these: I back out of the slip, using the thruster for maybe 20 seconds to spin the boat. After this, I get a low voltage alarm from the Beneteau panel. I've been doing this for four years, but the alarm just started happening. My diagnosis is the the thruster battery has lost much of its capacity. I assume that the starter battery is in a similar condition. The house batteries died last year, probably for similar reasons.

[Mark and Karen]

to my surprise the house batteries are not AGM, when they give up (which I hope is not soon) we will replace and increase capacity considerably.

Unfortunately the Dolphin charger we have fitted does not have an equalisation button on it, might need to review the charger

[Jeff Shukis]

We had absolutely fantastic weather this weekend - 28C and full sun - so we sailed instead of doing the equalizing charge that I promised. I'm still planning to do this, but it'll be a week or two.

 

Jeff

[Mike Brown]

Jeff, try cleaning all the terminals associated with the thruster. Any appreciable amount of build up on the surfaces can cause a voltage drop. Note that with the thruster in idle (on but not operating) you'll likely see full voltage, but with the thruster on you could see a significent drop if the terminals are dirty.

Mike

[Jeff Shukis]

Good advice, Mike.

I remove, clean, and coat with "Corrosion-X" spray the battery contacts annually - though they show no sign of corrosion. I also treat all of the other high amperage contacts as the same time, usually in January.

 

Jeff