Bow thruster battery

CB-OTB

New Member
Joined
Mar 26, 2022
Messages
52
I’ve read the posts and have seen the concerns for using lifepo4 batteries to power a bow thruster. I have a smaller thruster that is rated at 200A cont. When I use it, it pulls my LA battery voltage down enough to stall the engine.

My plan is to build a 12v pack out of 8 EVE 280AH cells, which I‘m getting ready to order from Jenny Wu. I haven’t started looking at a BMS solution yet. I know some of the options could be one large BMS with external contactors, or maybe use two BMS and make two individual packs in order to split the current between each pack.

Have any of you had success powering the bow thruster and windlass from a lifepo4 pack and if so, do you have any pointers?

P.S. if this doesn’t work, I’ll have a large enough house battery that I can run without the generator for most of the day.
 

Don B. Cilly

Energetic energy padawan
Joined
Aug 24, 2021
Messages
950
Location
Mallorca ES
8 cells will let you build a 24V battery (which would halve the amps needed).
One way to charge it would be with a second alternator on the engine - with a regulator that can deal with lithium - so, considering you'll be using the thruster with the engine on... for much less than the price of that, two good starter batteries wired for 24 would deal with short high-amp draws better, probably :·)
-
-
 

CB-OTB

New Member
Joined
Mar 26, 2022
Messages
52
What is the cost to change my bow thruster and my windlass from 12v to 24v?

On a second tangent, can I use a solenoid to parallel the lithium batteries with the existing starter batteries? That way I could have both banks power the thruster and windlass? This would also let the lithium house bank act as Jump starter to a dead LA bank.
 
Last edited:

BobR

Solar Addict
Joined
Jan 4, 2021
Messages
186
What is the cost to change my bow thruster and my windlass from 12v to 24v?
$$$$ I would install a larger start battery, or add another battery in parallel, to run your bow thruster and winch. Also what size is your alternator?
 

CB-OTB

New Member
Joined
Mar 26, 2022
Messages
52
$$$$ I would install a larger start battery, or add another battery in parallel, to run your bow thruster and winch. Also what size is your alternator?
Yeah, I didnt think that was really a feasible option. Starter bank is already two group 31 LA batteries. When I bump the thruster it pulls that bank down to the 10v range which is barely enough to keep my fuel injected engine running. (It has stalled once.) Alternator is a 70A model. The starter bank is located about 34’ from the bow thruster and 38-40‘ to the windlass. My plan was to install a house bank closer to these two components.
 

Don B. Cilly

Energetic energy padawan
Joined
Aug 24, 2021
Messages
950
Location
Mallorca ES
You would only have to change or re-wind the motor(s). Maybe just a matter of switching (internal) wires to adjust series-parallel connections.
All the existing installation would remain in place.
Ask a local rewinding shop - or your mechanic will know one.
-
 

CB-OTB

New Member
Joined
Mar 26, 2022
Messages
52
I still don’t see the advantage of that switch.

In the best case, switching to 24V will drop my current consumption in half. Every individual cell in that pack would see the same current that it would see if I left it as a parallel 12 volt pack.

I would also need 24-12V converter(s) to run the rest of the house loads.
 

BobR

Solar Addict
Joined
Jan 4, 2021
Messages
186
You would only have to change or re-wind the motor(s). Maybe just a matter of switching (internal) wires to adjust series-parallel connections.
All the existing installation would remain in place.
Ask a local rewinding shop - or your mechanic will know one.
-
My only experience with having motors rewound is with large 3 phase motors '100hp +' that was around $2000.00. I don't know about rewinding small DC motors. I know that to change my 12v winch to 24 volt; the replacement motor was $750 from the supplier.
 

Don B. Cilly

Energetic energy padawan
Joined
Aug 24, 2021
Messages
950
Location
Mallorca ES
I would also need 24-12V converter(s) to run the rest of the house loads.

I was talking about a separate (dedicated) battery and a separate alternator.
As close to the bow as possible. The advantage being, halving the amps, packing more punch.
It was just an idea.
-
 

BobR

Solar Addict
Joined
Jan 4, 2021
Messages
186
I was talking about a separate (dedicated) battery and a separate alternator.
As close to the bow as possible. The advantage being, halving the amps, packing more punch.
It was just an idea.
-
I’ve read the posts and have seen the concerns for using lifepo4 batteries to power a bow thruster. I have a smaller thruster that is rated at 200A cont. When I use it, it pulls my LA battery voltage down enough to stall the engine.

My plan is to build a 12v pack out of 8 EVE 280AH cells, which I‘m getting ready to order from Jenny Wu. I haven’t started looking at a BMS solution yet. I know some of the options could be one large BMS with external contactors, or maybe use two BMS and make two individual packs in order to split the current between each pack.

Have any of you had success powering the bow thruster and windlass from a lifepo4 pack and if so, do you have any pointers?

P.S. if this doesn’t work, I’ll have a large enough house battery that I can run without the generator for most of the day.
What are the surge amps from your thruster?
 

CB-OTB

New Member
Joined
Mar 26, 2022
Messages
52
The specs don’t list surge current but states to use a battery with 665CCA.
 

CB-OTB

New Member
Joined
Mar 26, 2022
Messages
52
I was talking about a separate (dedicated) battery and a separate alternator.
As close to the bow as possible. The advantage being, halving the amps, packing more punch.
It was just an idea.
-
I don’t have a ton of space to carry extra batteries. Particularly in the bow area. I am trying to create one multi-purpose house bank to run all of my DC loads and get the bow thruster off of my starter bank.

I can easily run all of my DC for 10 hrs with a single 12v, 280ah pack. I figured adding the additional parallel pack would be enough to cover the surge overhead of the bow thruster.
 

gtstricky

New Member
Joined
Nov 2, 2020
Messages
8
Couple of random questions.... what is the engine? what is the current alternator? How do you plan to charge the lithium pack?
 

CB-OTB

New Member
Joined
Mar 26, 2022
Messages
52
Couple of random questions.... what is the engine? what is the current alternator? How do you plan to charge the lithium pack?
Engines are 8.1L mercruisers. lifepo4 charging would happen through two dc-dc converters (one from each engine) and via 120v charger, supplied from the generator or shore power.
 

gtstricky

New Member
Joined
Nov 2, 2020
Messages
8
I think you are going to find most people do not recommend LifePO4 for high amp draw. Even though they might be rated at 1c it would reduce life expectancy of the battery to be cycled at that rate. Many seem to choose .5C as the max draw. So 280ah would give you 140a to use, if you did 4s2p you could go 280a but now you are talking about a rather large BMS. Some ideas to investigate... would a higher amp alternator give you enough extra punch to fix the engine stall issue? Have your group 31 batteries run their useful life? If it was my boat I would try to keep things separate for backup/redundancy. If space is an issue you might be justified in buying a bigger boat. ;)
 

CB-OTB

New Member
Joined
Mar 26, 2022
Messages
52
The batteries are a year old, so they should be in good condition. I can‘t go with a bigger boat, because I already got a stern talking to about just slightly Overstepping my slip size. I rounded down, they wanted to round up.

I have ordered a set of 280ah batteries and will use them to get an idea of battery placement. I think if I double the load rating with 1C capable batteries that the cells should be fine. I can address the BMS by using one that’s capable of switching a solenoid.
 

BobR

Solar Addict
Joined
Jan 4, 2021
Messages
186
I would be interested in how your battery installation works for you. If you don't mind posting your results.
 
Top