Bow Thruster & Battery Question

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Bay Retriever

Senior Member
Joined
Oct 13, 2019
Messages
154
Location
USA
Vessel Name
Bay Retriever
Vessel Make
2004 Mainship 400
I recently experienced loss of my GPS electronics when using my bow thrusters to maneuver my 2004 Mainship 400 when leaving a boatyard and then upon entering my slip at my home marina. Each time I used the bow thruster, the GPS would cut off and automatically restart on its own.

I have not yet tested the main two large batteries that seemingly run everything onboard. I do have a small battery in the lazarette for the generator. Question. Is there another battery just for the bow thruster or is it wired directly to the main two large batteries?

Let me know your thoughts and steps to take. I purchased the boat in September of 2019 and I am not sure how old the batteries are.
 
The bow thruster is probably wired to the two main batteries. They are old and use of the bow thruster pulls the voltage down and trips your electronics.

This can be confirmed with a voltmeter on the batteries terminals while you use the bow thruster. If the voltage drops to 11.0 volts or lower, that is your problem.

Replace the batteries.

David
 
I have a similar problem on my 2001 Mainship 390. Replacing the batteries could be a solution, but there could be other issues.

I have all new batteries as of last season, and this did not solve my problem, nor did I think it would.

My Mainship has a 1-2-all switch. Bank one (Start) is 2x Group 31 AGM's and bank 2 is 2x group 31 AGM's and a 4D AGM. Even when I have the switch on "All", I still have the issue. In my case, it is not the batteries.

This has not been a huge issue for me, but definitely one I want to track down. I do not see a large voltage drop to 11 or lower when I use my thrusters, but have the same behavior on the lower helm Raymarine MFD. It's on my list to fix, but new batteries did not address the issue.

Once I get down the list of more urgent fixes, I'll post if I solve my issue.

Thanks
 
I concur with David M on our 390 that is how the thruster was wired, and did the same - if you do not know how old the batteries are I would Suggest they are Pooched
 
I recently experienced loss of my GPS electronics when using my bow thrusters to maneuver my 2004 Mainship 400 when leaving a boatyard and then upon entering my slip at my home marina. Each time I used the bow thruster, the GPS would cut off and automatically restart on its own.

I have not yet tested the main two large batteries that seemingly run everything onboard. I do have a small battery in the lazarette for the generator. Question. Is there another battery just for the bow thruster or is it wired directly to the main two large batteries?

Let me know your thoughts and steps to take. I purchased the boat in September of 2019 and I am not sure how old the batteries are.
It could also be the alternator is not keeping up with battery load, keep an eye on the tach's when the GPS Goes out, if they die also it is probably the alternator is getting weak
 
Our 350 has a separate battery located at the thruster with a builtin dedicated charger on a breaker on the AC power panel. This reduces the severe drag on the house batteries. Running the thruster is like running your engine starter and really puts a drain on the main batteries especially with a long cable run that further puts a big drain when wired to the main battery bank. Best way to eliminate this is with a separate battery at the thruster.
 
The draw from the thruster is similar to the starter on the engine. The results you are getting therefore is not a surprise. Electronics and lights should be on the house bank. Thrusters & winches like starters should be on batteries that exist for short term heavy draw loads. Problem solved.
 
if you do replace batteries, "start" bank (starting, thruster) should be batteries with high cranking amps. "house" bank should batteries with high rating on total amp/hr capacity.
 
When my electronics were installed the installer insisted that they be on their own separate battery. Never have a problem. They are isolated from any voltage spikes that might occur.
 
Have not had any issues using house bank for electronics while other items are operated as there are no high suden draws.
Even the gauges on the dash react to a starter.
 
My MS 34HT had 2 8Ds that factory set up as combined house / start. With av1-2all selector sw. I had situations wherebrlcttonics dropped out / reset when eng started on one 8D - never with both. I never liked the combined set up.
I also had a dedicated thruster 8D for B & S thrusters.,in addition to other changes I moved engbstart to the thruster bank and now use the 2 8Ds combined as a pure house bank.
I was able so eliminate/ repurpose a 4/0 cable for starting and the run from thruster bank was half the previous 2/0 cable length. I have a batty monitor on house that also displays thruster/ start bank V for monitoring.
Seems like a win-win all around.
 
The draw from the thruster is similar to the starter on the engine. The results you are getting therefore is not a surprise. Electronics and lights should be on the house bank. Thrusters & winches like starters should be on batteries that exist for short term heavy draw loads. Problem solved.
For that reason I have my two Group 31 AGM start batteries wired in series for 28 volts to drive my 28 volt thruster and 28 volt windlass. I'm not sure if there will ever be a time where both are used back to back, so the batteries have ample time to recover. I located these batteries within 8 feet of the windlass and 3 feet of the thruster to minimize line loss.
 
I like dedicated thruster batteries. I have 2 AGM start batteries forward and 2 aft for the thrusters, 24 volt. Each thruster bank has it’s own charger. That way they don’t reboot your electronics. Also your house batteries should be a deep cycle and the thrusters want start batteries. By having the batteries next to the thrusters you also limit cable length so you get good voltage at the thrusters.
 
On my 2004 Pilot II 30 I have 2 T-165 Trojan 6V's for the house, with 2 Renogy Flex 175W panels and a 40 amp MPPT. Bow and Stern Thrusters, both powered by 2 6V batt's, and a Group 31 for the start, all flooded. Inverter charges the house, when plugged in, and a seperate charger for the Start and Thruster banks. This is the set up that came with the boat when I bought it, with the exception of me adding the T-165's and the Renogy Solar, but the system works well.
 
The draw from the thruster is similar to the starter on the engine. The results you are getting therefore is not a surprise. Electronics and lights should be on the house bank. Thrusters & winches like starters should be on batteries that exist for short term heavy draw loads. Problem solved.
Depending on the thruster and engine, the draw from the thruster could be double the starting load. My 95kgf 12v thruster draws ~600 amps, much more than a mid-size diesel starter.

Expecting good performance with a long cable run to deep discharge house batteries is unrealistic IMO. The alternator @100a doesn't provide a big contribution in supporting those loads, and voltage sag from the batteries and voltage loss from the cabling exacerbate the issue.

I'll second the recommendation to install a dedicated battery bank for the thruster, with its own charger. You'll get stronger more robust thruster performance and protect your house bank from the high draw/low voltage issue.
 
I recently experienced loss of my GPS electronics when using my bow thrusters to maneuver my 2004 Mainship 400 when leaving a boatyard and then upon entering my slip at my home marina. Each time I used the bow thruster, the GPS would cut off and automatically restart on its own.

I have not yet tested the main two large batteries that seemingly run everything onboard. I do have a small battery in the lazarette for the generator. Question. Is there another battery just for the bow thruster or is it wired directly to the main two large batteries?

Let me know your thoughts and steps to take. I purchased the boat in September of 2019 and I am not sure how old the batteries are
I recently experienced loss of my GPS electronics when using my bow thrusters to maneuver my 2004 Mainship 400 when leaving a boatyard and then upon entering my slip at my home marina. Each time I used the bow thruster, the GPS would cut off and automatically restart on its own.

I have not yet tested the main two large batteries that seemingly run everything onboard. I do have a small battery in the lazarette for the generator. Question. Is there another battery just for the bow thruster or is it wired directly to the main two large batteries?

Let me know your thoughts and steps to take. I purchased the boat in September of 2019 and I am not sure how old the batteries are.
Hi Their are really 2 problems here. 1st== You never add enough Battery Capacity to run the Thruster without causing a sag on the Battery Voltage. The starting current, for the thruster is at least 5 times the running current & only lasts for a few seconds. As for instruments dropping out during starting, Forget it, this is common due to the inrush. Just make sure that U have enough ampacity to run everything during thruster operation. As to the wiring configuration, as it is now. If the previous owner did not leave U a wiring diagram or schematic, hire someone locally to make U a New Wiring Diagram. U Need this!...ken Ongemach BSEE, Tampa
 
The bow thruster is using so much current it is pulling down the voltage to below 11.5 volts and your electronics go tango uniform.
You can add a dedicated thruster battery or do what I do.
I dont turn on my electronics until I leave the harbor and I am finished with needing the thruster.
When returning to a docking situation where I conceivably might need a thruster, I turn off the electronics before I get there. I dont need electronics to dock.
 
I recently experienced loss of my GPS electronics when using my bow thrusters to maneuver my 2004 Mainship 400 when leaving a boatyard and then upon entering my slip at my home marina. Each time I used the bow thruster, the GPS would cut off and automatically restart on its own.

I have not yet tested the main two large batteries that seemingly run everything onboard. I do have a small battery in the lazarette for the generator. Question. Is there another battery just for the bow thruster or is it wired directly to the main two large batteries?

Let me know your thoughts and steps to take. I purchased the boat in September of 2019 and I am not sure how old the batteries are.
In my 400 from 2005 I measured 950A on the stern thruster and only 9,5V at the thruster and 650A and 10,5 V at the bow. Mainships electical design is bad, just half the size of cables according to the manufactor. When an belectrical motor go slow it needs much more current and less speed gives less power out. Sleipner calculate nominal power, (95kp in my case) at 11,5V, if you can increase the voltage the motor will give out more power. And 1500A for stern and bow at the same time. As you see the help from an 80A alternator as give maybe 50 A at low revs is not much of a help.
I solved the bad installation with AGM-batteries at the stern and bow by connecting them together with the startbattery all of the same kind. And in order to get red of the cavitation(as can take like 30-40% off) I changed the propellers to more powerful and also rebuilt the tunnel for the bowthruster. And finally i installed speedcontrol witch is very nice. Normally you only need quite small power to correct your boat in the marina and at low revs the thruster is complete guite.
 
In my 400 from 2005 I measured 950A on the stern thruster and only 9,5V at the thruster and 650A and 10,5 V at the bow. Mainships electical design is bad, just half the size of cables according to the manufactor. When an belectrical motor go slow it needs much more current and less speed gives less power out. Sleipner calculate nominal power, (95kp in my case) at 11,5V, if you can increase the voltage the motor will give out more power. And 1500A for stern and bow at the same time. As you see the help from an 80A alternator as give maybe 50 A at low revs is not much of a help.
I solved the bad installation with AGM-batteries at the stern and bow by connecting them together with the startbattery all of the same kind. And in order to get red of the cavitation(as can take like 30-40% off) I changed the propellers to more powerful and also rebuilt the tunnel for the bowthruster. And finally i installed speedcontrol witch is very nice. Normally you only need quite small power to correct your boat in the marina and at low revs the thruster is complete guite.
I do want to ad that my thrusters are much more poweful than they ever have been before and gives out more power than nominal.
 
In my 400 from 2005 I measured 950A on the stern thruster and only 9,5V at the thruster and 650A and 10,5 V at the bow. Mainships electical design is bad, just half the size of cables according to the manufactor. When an belectrical motor go slow it needs much more current and less speed gives less power out. Sleipner calculate nominal power, (95kp in my case) at 11,5V, if you can increase the voltage the motor will give out more power. And 1500A for stern and bow at the same time. As you see the help from an 80A alternator as give maybe 50 A at low revs is not much of a help.
I solved the bad installation with AGM-batteries at the stern and bow by connecting them together with the startbattery all of the same kind. And in order to get red of the cavitation(as can take like 30-40% off) I changed the propellers to more powerful and also rebuilt the tunnel for the bowthruster. And finally i installed speedcontrol witch is very nice. Normally you only need quite small power to correct your boat in the marina and at low revs the thruster is complete guite.
I do want to correct and also add, it was only the tunnelends that I rebuilt. (check YT-film from Sleipner and you will understand) and then I disconnected the thrusters from the house battery, so no longer voltagedrop with my house battery. B.t.w I have connected Lithium battey together with the Lead battery with a bypolar relay inbetween, and keeping all the same chargers for lead batteries, only with some changed settings were it’s possible.
 
Our 350 has a separate battery located at the thruster with a builtin dedicated charger on a breaker on the AC power panel. This reduces the severe drag on the house batteries. Running the thruster is like running your engine starter and really puts a drain on the main batteries especially with a long cable run that further puts a big drain when wired to the main battery bank. Best way to eliminate this is with a separate battery at the thruster.
My 2003 390 also has a separate group 31 located at the thruster to assist during use. It is actually wired in parallel with my group d start battery.
 
My 2003 390 also has a separate group 31 located at the thruster to assist during use. It is actually wired in parallel with my group d start battery.
How did they mount the battery? Is it in the cavity with the thruster? I was just poking around up there and noticed there was a lot of room. For charging, it just charges with the start batteries? Definitely sounds like not stock. I'm finding a lot of stock things on my 01 390 were just for ease of assembly, not the right thing to do.
 
I recently experienced loss of my GPS electronics when using my bow thrusters to maneuver my 2004 Mainship 400 when leaving a boatyard and then upon entering my slip at my home marina. Each time I used the bow thruster, the GPS would cut off and automatically restart on its own.

I have not yet tested the main two large batteries that seemingly run everything onboard. I do have a small battery in the lazarette for the generator. Question. Is there another battery just for the bow thruster or is it wired directly to the main two large batteries?

Let me know your thoughts and steps to take. I purchased the boat in September of 2019 and I am not sure how old the batteries are.
The Vetus 130 PRO bow thruster that I have installed on my boat has its own set of batteries 2 x 180Ah, which in turn are connected to the charger. This specific model comes with a built-in charger for it draws a lot of power when in use. When turned off, I keep the thruster batteries on low charge.
 
We had everything connected to a large house bank (1100 amps - 10 Trojan golf cart batteries) and never had a problem. The thruster only operates when the engine/alternator is charging the bank (you do have a modern 110A alternator, don't you?) and adequately sized wiring throughout the boat. Frequently, would operate the thruster and the windlass at the same time - never a problem with electronics. Additional banks of any kind are just a complication and really unnecessary.
 
How did they mount the battery? Is it in the cavity with the thruster? I was just poking around up there and noticed there was a lot of room. For charging, it just charges with the start batteries? Definitely sounds like not stock. I'm finding a lot of stock things on my 01 390 were just for ease of assembly, not the right thing to do.
If the battery is under the berth don’t use a lead acid battery. Use an AGM, or similar, that doesn’t off gas.
 
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