Bow thruster batteries - what type?

[West Coast]

My new (to me) boat has a Max Power CT 100 bow thruster. There are 2 batteries powering it, both AGM type. Presumably due to bad connections, the battery posts are damaged (melted) so going to replace them.

Question is - do I need to replace them with AGMs? I don’t know why originals were AGMs, perhaps as they are located in the bow so thrown about a bit more?

Thanks

 

[Tranona]

Not sure whether it is essential (or even preferable) to have AGMs but mine came from the factory with a 95AH AGM. Probably standardisation of production as the other 4 batteries (engine start and 3 domestic) are all the same.

 

[Mistroma]

My new (to me) boat has a Max Power CT 100 bow thruster. There are 2 batteries powering it, both AGM type. Presumably due to bad connections, the battery posts are damaged (melted) so going to replace them.

Question is - do I need to replace them with AGMs? I don’t know why originals were AGMs, perhaps as they are located in the bow so thrown about a bit more?

Thanks

I have the same unit but rarely use it nowadays. They benefit from a battery able to provide a large current, withstand being thrown up and down bashing into waves and preferable spill-proof. A spiral wound AGM battery fits the bill (large plate area, robust and non-spill). Unfortunately, they are pretty expensive.

A good low maintenance engine start battery will be a lot cheaper and probably acceptable.

I think my Max Power unit failed part way through 2nd season because the battery wasn't charging. Connections looked perfect on the outside but lots of arcing on inside of the clamps. I think neither clamps nor posts had been cleaned prior to assembly. Lots of arcing and heat generated out of sight. It probably only lasted as long because the bowthruster was used sparingly and in short bursts.

I replaced the clamps, cleaned everything prior to assembly and they are still prefect after about 7 years.

Get a battery with high CCA rating (my Optima one is 815A) as that will give some indication of performance. I know CCA isn't same as hot performance mid. summer but it's a pretty widely available figure and a reasonable method of comparing suitability.

 

[West Coast]

I have the same unit but rarely use it nowadays. They benefit from a battery able to provide a large current, withstand being thrown up and down bashing into waves and preferable spill-proof. A spiral wound AGM battery fits the bill (large plate area, robust and non-spill). Unfortunately, they are pretty expensive.

A good low maintenance engine start battery will be a lot cheaper and probably acceptable.

I think my Max Power unit failed part way through 2nd season because the battery wasn't charging. Connections looked perfect on the outside but lots of arcing on inside of the clamps. I think neither clamps nor posts had been cleaned prior to assembly. Lots of arcing and heat generated out of sight. It probably only lasted as long because the bowthruster was used sparingly and in short bursts.

I replaced the clamps, cleaned everything prior to assembly and they are still prefect after about 7 years.

Get a battery with high CCA rating (my Optima one is 815A) as that will give some indication of performance. I know CCA isn't same as hot performance mid. summer but it's a pretty widely available figure and a reasonable method of comparing suitability.

Thanks, saw you had mentioned the bad connection issue before when searching the forum on this topic. The AGM type battery makes sense, But any issues with having a mix of AGM (for bowthruster)and wet cell type for engine and house, thinking of charging systems?

 

[Mistroma]

Thanks, saw you had mentioned the bad connection issue before when searching the forum on this topic. The AGM type battery makes sense, But any issues with having a mix of AGM (for bowthruster)and wet cell type for engine and house, thinking of charging systems?

Lots of people will tell you it isn't a good idea and there are obvious reasons. I ended up with 2 spiral wound AGMs and 4 T105s but not by design. I won't bore you with the details but also ended up with upgraded charging via heavier cables and a Smartbank system. This means that domestic, start and bow thruster are all connected by relays during charging. I didn't upgrade the long cable to bows so that battery does get a slightly lower voltage (approx. 0.2V, I think).

I charge the T105s up to around 14.7V because an alarm trips at 14.8 and display starts to misbehave. The start battery also gets 14.7V and bow thruster a bit less at 14.5V. Not ideal for AGMs but Optima's technical data seemed to indicate that it would be fine.

Optima RedTop charging directions for Type: 34 & 34R - 34/78 - 78 - 25 & 35 - 75/25
Alternator:13.3 to 15.0 volts, no amperage limit.

Battery Charger:
13.8 to 15.0 volts, 10 amps maximum, 6-12 hours approximate.

Rapid Recharge:
Maximum voltage 15.6 volts (regulated), no current limit as long as battery temperature remains below 125°F (51.7°C). Charge until current drops below 1 amp.

Float Charge:
13.2 to 13.8 volts, 1 amp maximum current, time indefinite (at lower voltage).

I have had this setup since 2012 and keep expecting the Start battery (formerly the dud bow thruster battery) to fail. No sign of a problem yet though I don't always get to 14.7V at anchor during summer.

 

[West Coast]

Lots of people will tell you it isn't a good idea and there are obvious reasons. I ended up with 2 spiral wound AGMs and 4 T105s but not by design. I won't bore you with the details but also ended up with upgraded charging via heavier cables and a Smartbank system. This means that domestic, start and bow thruster are all connected by relays during charging. I didn't upgrade the long cable to bows so that battery does get a slightly lower voltage (approx. 0.2V, I think).

I charge the T105s up to around 14.7V because an alarm trips at 14.8 and display starts to misbehave. The start battery also gets 14.7V and bow thruster a bit less at 14.5V. Not ideal for AGMs but Optima's technical data seemed to indicate that it would be fine.

Optima RedTop charging directions for Type: 34 & 34R - 34/78 - 78 - 25 & 35 - 75/25
Alternator:13.3 to 15.0 volts, no amperage limit.

Battery Charger:
13.8 to 15.0 volts, 10 amps maximum, 6-12 hours approximate.

Rapid Recharge:
Maximum voltage 15.6 volts (regulated), no current limit as long as battery temperature remains below 125°F (51.7°C). Charge until current drops below 1 amp.

Float Charge:
13.2 to 13.8 volts, 1 amp maximum current, time indefinite (at lower voltage).

I have had this setup since 2012 and keep expecting the Start battery (formerly the dud bow thruster battery) to fail. No sign of a problem yet though I don't always get to 14.7V at anchor during summer.

Thanks, my questions relate to a Jeanneau 439 from 2012, so I suspect our electrical systems are very similar. Still familiarising myself with the setup, as only had the boat for a few weeks.