Bow Thruster Battery

[Ventana]

When we purchased our boat it had (3) Optima blue top batteries in a separate bank for the bow thruster. Shortly after, one of the batteries died, and now a second one is gone. The thruster is basically useless with a single tired Optima, proven by a bad situation last week trying to leave the slip in high winds.
The boat also came with an almost new 8d starting battery, which is overkill. I can move the 8d up to the bow for the thruster and buy a cheap starting battery for the generator, which would be my cheapest fix. Any reason I don’t want to use the 8d for this?

 

[Comodave]

Most 8Ds are not deep cycle so it would probably do fine for the thruster if it is rated for the draw of your thruster. Make sure that it is.

 

[tiltrider1]

I never buy cheap batteries. They are never worth the money. Replace the thruster batteries with good quality batteries. There is nothing wrong with overkill when it comes to starting your boat in remote locations.

 

[catalinajack]

When we purchased our boat it had (3) Optima blue top batteries in a separate bank for the bow thruster. Shortly after, one of the batteries died, and now a second one is gone. The thruster is basically useless with a single tired Optima, proven by a bad situation last week trying to leave the slip in high winds.
The boat also came with an almost new 8d starting battery, which is overkill. I can move the 8d up to the bow for the thruster and buy a cheap starting battery for the generator, which would be my cheapest fix. Any reason I don’t want to use the 8d for this?

So, let's see, your thruster bank of three was reduced to one and you somehow thought that that one, puny, suspect, remaining battery was going to function and you attempted a diificult getaway in high winds. That is something most of us would not do. When the first and then the second battery failed, did you remove then from the bank? If not, know that a failed battery in any bank will drag the others down. As for moving that monster 8d up to the bow, hope you have a strong back and good medical insurance. Leave the 8d where it is and replace your thruster bank.

 

[Bacchus]

You dont mention 8D batty chemistry at all?
Nor what the bow batty location is like?

An 8D will satisfy most thruster needs but you really need to check specs for both and compare.
If 8D is a FLA and bow is not well vented you shouldn't even consider that. If you dont want to duplicate the 3 Optimas you might want to look at 3 - GP31 AGMs.

Same for start when it gets time... a pair of GP31 instead of the 8Ds. I'm starting to develop a plan for replacing my 3 - AGM 8Ds with something else and so far GP31s look good for thruster & start needs.

 

[O C Diver]

Unless you're planning to steer your boat with the bow thruster, it is used for very short bursts. This is similar to starting an engine. When refitting my boat, I installed the red top Optima batteries which are designed for starting versus deep cycle. I have 2 batteries that are in series as my boat has a 24 volt thruster. I'm on year 5 now with them and have been very pleased.

BTW, did you check the charging system for the batteries? Very important to recharge them after using them as opposed to plugging them in next time at the dock or when running the generator.

Ted

 

[ranger58sb]

When we purchased our boat it had (3) Optima blue top batteries in a separate bank for the bow thruster. Shortly after, one of the batteries died, and now a second one is gone. The thruster is basically useless with a single tired Optima, proven by a bad situation last week trying to leave the slip in high winds.
The boat also came with an almost new 8d starting battery, which is overkill. I can move the 8d up to the bow for the thruster and buy a cheap starting battery for the generator, which would be my cheapest fix. Any reason I don’t want to use the 8d for this?

I have read that several aftermarket bow thruster installers often recommend a pair of Odyssey 31M-PC2150 AGM batteries... ideally installed close to the thruster.

Our experience with 3x of those in two dual-purpose start/house banks has been very good. Not inexpensive.

If AGM fits in with your charging regime...

-Chris

 

[Arc]

The factory wired my thruster to a 8d that was located in the ER. It is new and works fine. I decided the put a 31 AGM right at the thruster 2’ away and isolated from the rest of the boat. The thruster works better with no fade at all. My stern thruster is set up the same way. Each has it’s own 10 amp charger . This way thrusters have nothing to do with house or engine batteries.

 

[mvweebles]

When we purchased our boat it had (3) Optima blue top batteries in a separate bank for the bow thruster. Shortly after, one of the batteries died, and now a second one is gone. The thruster is basically useless with a single tired Optima, proven by a bad situation last week trying to leave the slip in high winds.
The boat also came with an almost new 8d starting battery, which is overkill. I can move the 8d up to the bow for the thruster and buy a cheap starting battery for the generator, which would be my cheapest fix. Any reason I don’t want to use the 8d for this?

Lugging around an 8d battery is no small feat. But it is a 225ah battery and has more than enough ooomph for your thruster which takes around 400a. Theoretically, a single group 24 (small) has the CCA for this too, but cannot sustain the draw for very long. The 8D will be fine assuming in decent condition. Whether it makes sense to make the swap is a different question that only the installer can answer.

 

[Pete Meisinger]

Before I would drag an 8D from the bilge to the front of the boat I would drop it over the side. (Just kidding)

My bow thruster runs off the house bank. The draw is a lot but I have never run the thruster for more than a second or two at a time.

If you are killing batteries with your thruster use I suspect you are relying too much on it. Your next challenge will be replacing the thruster motor.

pete

 

[wwestman]

Have you thought of a single battery for your thruster with a charger connected to it. Connect charger to your inverter. Do you ever use the thruster when the mains are not running thus the inverter would be able to run the charger without a problem. Lowers the weight in the front of the boat, lessens the amount and size of the cables needed (battery can be right next to thruster). Much simpler.

 

[Codger2]

My thruster is a 10hp 24 volt thruster. The batteries are 4-6v Golf cart batteries with their own charger. It's been 4 years since the batts were installed and so far they are working just fine! The batts are secured in a tray that slides aft for easy batt removal and replacement. The batt cables are about 5 feet long and the panel & small SOC indicator is right beside the forward birth.

 

[Ski in NC]

My thruster runs off a cheap grp 24 12v starting batt mounted right next to the unit. No need to overthink this. Duty cycle for the batt is much like starting an engine. I get at least six years out of a $65 batt. No way was I going to run big a$$ cable all the way back to the ER and then deal with electronics blipping on the voltage dips. It is charged through a breaker to the house bank. The charge link is 12ga wire through a relay that opens when thruster motor is on. Use it a bunch and it takes a few hours to charge back up to house bank volts. No separate charger for thruster batt. Simple simple.

 

[Ventana]

So, let's see, your thruster bank of three was reduced to one and you somehow thought that that one, puny, suspect, remaining battery was going to function and you attempted a diificult getaway in high winds. That is something most of us would not do. When the first and then the second battery failed, did you remove then from the bank? If not, know that a failed battery in any bank will drag the others down. As for moving that monster 8d up to the bow, hope you have a strong back and good medical insurance. Leave the 8d where it is and replace your thruster bank.

I just want to clarify. When someone asks for an opinion on the forum, I should:
Find fault with as much of their life as I can think of.
Make some snarky comments about suggested solution.
Overall just come across as a jerk.

Got it.

 

[Ventana]

For the rest of you, thanks for the suggestions. We have been without income for several months now and money is very tight, that is my reasoning for trying to use what I have and avoid too much expense.
I’m not very familiar with these smaller (5 hp) electric thrusters so I wasn’t sure what they really pull for power. The battery box looks like it was probably built for an 8d, and because it was replaced with three Optimas instead of one I just wanted to make sure I wasn’t missing something.
A combination of poor connections, a poor charging setup, and age led to the death of the Optima batteries.

 

[catalinajack]

I apolgize, humbly.

I just want to clarify. When someone asks for an opinion on the forum, I should:
Find fault with as much of their life as I can think of.
Make some snarky comments about suggested solution.
Overall just come across as a jerk.

Got it.

 

[Ventana]

I apolgize, humbly.

No problem, I’ve been in a particularly shitty mood lately, can’t imagine why.

 

[JDCAVE]

If you think about it, the thruster is the most significant vessel system where battery health directly affects the performance of the unit. You can get by with a house bank at 75% state of health. You can probably still start your boat with a starter bank at 75% of its original CCA. But the performance of thruster with a battery bank at 75% of its original CCA may be severely affected, particularly units that are marginal to begin with.

When we bought our boat the 24 volt thruster was powered with two 12 volt Northstar Batteries at 1800 CCA a piece. After 10 years these were starting to be at the point where performance was affected. It was time.

I first did tests with the old batteries: voltages checked at the battery terminals and amperage leaving the batteries. I used 3 second bursts on the thruster (batteries combined in series with a Cole Hersee relay).

Old Northstar MS-210, Top battery: Volts: 9.0 Amps: 350
Old Northstar MS-210, Bottom battery: Volts: 9.9 Amps: 350
Average 3308 Watts.

New Northstar 190FT Red, Top battery: Volts: 11.4 Amps: 425
New Northstar 190FT Red, Bottom battery: Volts: 11.14 Amps: 428
Average 4790 Watts, or 45% more than the older ones.

So i suspect that for many thruster setups, the larger the battery bank the better.

This thread has a significant discussion on this topic:

https://www.trawlerforum.com/forums/s4/house-start-bank-design-issue-43989-4.html

Jim

 

[Ventana]

If you think about it, the thruster is the most significant vessel system where battery health directly affects the performance of the unit. You can get by with a house bank at 75% state of health. You can probably still start your boat with a starter bank at 75% of its original CCA. But the performance of thruster with a battery bank at 75% of its original CCA may be severely affected, particularly units that are marginal to begin with.

So i suspect that for many thruster setups, the larger the battery bank the better.

This thread has a significant discussion on this topic:

https://www.trawlerforum.com/forums/s4/house-start-bank-design-issue-43989-4.html

Jim

Thanks Jim.
It sounds like you have double the thruster for the same boat, probably a lot more effective when you want it.
Doing things the cheap way isn’t normal for me, especially for electrical work, but these are not normal times. If I can get the 8d out of the engine room it sounds like that should work for now, and I can revisit the issue when I have an income again.

 

[JDCAVE]

Yes, I think and 8D should certainly have the amps to power your thruster, depending on its state of health. Others have mentioned the issue with off-gassing in a living space which is a concern.

Jim

 

[FF]

Many thruster setups are time limited.

Starting batteries are also time limited as the plates with a high load become covered with bubbles.

Sounds like a good match.

Folks that need the ability to maneuver the boat should probably use hydraulics that are not time limited.

 

[Ralsy]

I just want to clarify. When someone asks for an opinion on the forum, I should:
Find fault with as much of their life as I can think of.
Make some snarky comments about suggested solution.
Overall just come across as a jerk.

Got it.

YES, you've finally grasped it!

I wish posters could stick to positive and constructive comments without having to be sarcastic and condescending.

 

[Ralsy]

Many thruster setups are time limited.

Starting batteries are also time limited as the plates with a high load become covered with bubbles.

Sounds like a good match.

Folks that need the ability to maneuver the boat should probably use hydraulics that are not time limited.

I have just gone through finding out about hydraulic thrusters which are great if you need to work the thrusters for long periods of time (wind, current conditions) but for me cost prohibitive, (DC approx $14,000 hydraulic double that)

 

[FF]

"DC approx ,,$14,000 hydraulic double that"

A hyd setup is far cheaper when a full SYSTEM is installed on a new build,

Thrusters , windlass (no white smoke on overloads) cruising AC generator and boat hoist ,autopilot are easy.

Other toys can easily be added , serious bilge/fire pump, radar arch lowering, eutetic refrigeration , scuba refill ,serious DC alt..(12v or 24V a 300A )

These can also be powered with the noise maker with hyd if desired

 

[JDCAVE]

FF: I agree. Hydraulics are definitely the way to go on larger vessels and new builds. However it may be prohibitively expensive for the budget conscious boater.

Jim