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Bow thruster battery replacement.


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Our BT installed in 2014 is a Sleipner twin blade 6hp 12V SE80/185 with/connected to a 240V marine charger operating from our onboard system. We need a new battery.

We would greatly appreciate any advice as to what heavy duty battery to purchase. Thanks.

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My 2007 boat still has its original BT, domestic and starter batteries. The domedtic batteries are down to about 50% of their capacity now, but are still OK for my needs.

 

All are Lifeline AGM's, expensive but extremely long lasting when looked after properly.

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Less than a week ago  I had to replace my bow thruster battery. It had lasted 7 years almost to the day .  It was a Sunday so Halfords was open. Halfords are not cheap but the chief officer felt an urgent need to fix the fault.  

 

I don't believe you necessarily need a huge Ah capacity since the bow thruster is used only when the engine is running so it should be  quickly recharged . However a battery capable of engine starting is required as it needs to quickly deliver a high current.  I dare say the bigger the battery the less work it will do and the  longer it will last .

If fitted in an unventilated space  a sealed type battery should be used to satisfy BSS requirements. 

 

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20 minutes ago, MartynG said:

Less than a week ago  I had to replace my bow thruster battery. It had lasted 7 years almost to the day .  It was a Sunday so Halfords was open. Halfords are not cheap but the chief officer felt an urgent need to fix the fault.  

 

I don't believe you necessarily need a huge Ah capacity since the bow thruster is used only when the engine is running so it should be  quickly recharged . However a battery capable of engine starting is required as it needs to quickly deliver a high current.  I dare say the bigger the battery the less work it will do and the  longer it will last .

If fitted in an unventilated space  a sealed type battery should be used to satisfy BSS requirements. 

 

 

So for the OP, comparing the Cold Cranking Amps (CCA) figure with the existing battery would be the thing to do when selecting a replacement, rather than Ahr capacity. Size would also be important, so it fits in the mounting point and can be secured without movement to meet Boat Safety Scheme requirements. Post terminals of the same sort and on the same side as the existing one so that the cables fit!

Jen

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10 hours ago, MartynG said:

Less than a week ago  I had to replace my bow thruster battery. It had lasted 7 years almost to the day .  It was a Sunday so Halfords was open. Halfords are not cheap but the chief officer felt an urgent need to fix the fault.  

 

I don't believe you necessarily need a huge Ah capacity since the bow thruster is used only when the engine is running so it should be  quickly recharged . However a battery capable of engine starting is required as it needs to quickly deliver a high current.  I dare say the bigger the battery the less work it will do and the  longer it will last .

If fitted in an unventilated space  a sealed type battery should be used to satisfy BSS requirements. 

 

When I see some mooring up with large use of the bow thruster and then turning the engine off I expect some bow thruster batteries sit in a depleted state.

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29 minutes ago, Rob-M said:

When I see some mooring up with large use of the bow thruster and then turning the engine off I expect some bow thruster batteries sit in a depleted state.

Solar panel small one sorts that fully charged in a few days at most more often hours as it is short bursts of high current so not massive Amp hours used.

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Very many thanks for all replies. Much appreciated.

We haven't seen our boat since October 2019 due lockdown etc. The battery label is on the side of the battery and not visible until the big lump is lifted out, something we've never done. Fingers crossed we will see our boat next week and after clearing the cobwebs we'll lift the big truck starter battery out, take some photos then find the nearest Halfords after a cuppa.

Thanks again folks!

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21 hours ago, Rob-M said:

When I see some mooring up with large use of the bow thruster and then turning the engine off I expect some bow thruster batteries sit in a depleted state.

Same here, that is after they have negotiated the turn into the marina and down to their pontoon 

Edited by ditchcrawler
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When I first fitted out Lyra 15 years ago I used high-Ah AGM batteries for the bow batteries (which for us do BT & domestic, at 24v). These constantly charge from the main 48v propulsion battery, and when I came to replace them last year realised that I didn’t need high Ah, just high enough cranking amps for the bow thruster. After a bit of research I went with Optima spiral batteries, which are particularly good for high cold cranking amps. They were much easier to lift in and take up less space, and for us do the job well. You obviously need to consider all the factors that are important for your system, but I’d give Optima spirals a look along with other options (including replacing like for like). 

Edited by Thames Bhaji
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  • 3 weeks later...

Evening all, once again thanks for all the replies. We now have a new bt battery fitted. The original, installed on building during 2014 had no labels. Etched into the casing was 661210_ and that was all, which was difficult to see. It took about 18 hours of online searching to find an equivalent replacement/supplier which has a maker’s name and various bits of info.

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