Replacement bow thruster batteries

[mlthomas]

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

 

[volvopaul]

" Plenty of volts and no umphhhh If you dont have volts you wont have power as a motor draws high amounts of amps, have you tested the battery voltage when you operate the thruster, if the volts drop rapidly yet the battery shows say 12.5 volts when nothing is applied its failing inside and requires renewing.

A simple cheap battery condition tester will appy a load and tell you its condition.

 

[mlthomas]

On load one battery dropped to 11.4 and the other to 9.8 As soon as the load was off they popped back to 14.4 (you have to be running the engine) then when the engine is stopped the voltage slowly drops back to 12.8 ish.
Took the pair round to the local ATS who put them on a Bosch tester and the result was 17% and 12% capacity but volts fine.

 

[volvopaul]

Id say the 9.8 volt battery is on its way out and dragging down the other with it, thats the problem with 2 batteries connected together the bad one draws from the good one to try and keep the cells level.

 

[pappaecho]

It i likely that only one has failed, specially as the bow thrusters have very limited use, so 2 year warranty period is not a great a deal of time.

I had a similar problem this year. Charged up both batteries, completely disconnected from the bow thruster circuit, and left them o self discharge

After a week of standing one was 12.76 volts and the other was 10.5. Bad one replaced. system now OK

 

[Assassin]

Traction batteries are worthwhile, lots of power and will stand a lot of abuse.

 

[DavidJ]

Simple test
Charge each battery fully and leave for 12 hours (to remove the surface charge) then read the voltage
12.7v or more 100% ok
12.4v 75% (on it's way out)
12.2v 50% (replace)
12.0v 25% (should have replaced it last season)

If it reads in the 10.5v range you have a shorted cell

My new batteries gave 12.83v a couple of weeks after fully charging.

 

[late-night-lochin]

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

Yeah, junk the separate bow thruster battery bank, buy some heavy cable (circa 120mm2) and connect your bow thruster to your (or one of your) engine start battery banks.

I know heavy cable is expensive but it lasts longer than batteries - so end of problem!