Bow Thruster install Battery?

[mattnj]

Hi.
Having a Thruster installed over winter... Jeanneau Sun Fast 40, single hand a fair bit. Probably 65kg variable speed thruster. 300amps?

Currently has beefy cables up to bow for windlass...
What's the best solution... AGM battery up the front and connect windlass and thruster to that, and directly connected to existing house battery? (Lead not AGM)
Although I may change house to lithium at some point... So is a b2b better, and if so what current charger do I need?

Or any other better way....?

Thanks

 

[Boathook]

I would fit a b2b up towards the bow for the thruster and windlass. My b2b is about 4 amps for a 110ah battery that feeds my windlass and thruster. The battery is only about a meter away but the thruster cables are about 15mm diameter to take the 250amp load.

 

[Tranona]

Simplest way is to use a 30A B2B from the start battery using 16mm cables to the bow battery. 100Ah or so either good LA or AGM - I have a 105ah Numax that does both thruster and windlass. Previous boat had a 95Ah AGM for just the thruster. Really not critical so long as it has a good CCA. Then short run of heavy cable with an isolator to the thruster.

 

[Martin_J]

After many years of avoiding a thruster, I went for a Betus BowPro variable speed one a couple of years ago.. I am still impressed by the proportional control on it.

As you already have the cables run to the bow, you might as well use them to a new battery to battery charger, installed at the bow.
The other great thing I liked about the Victron Orion isolated B2B that I installed, was that it only took a couple of minutes to install their app on the phone and via Bluetooth, it's easy to see both the input and output voltages, as well as what the charger is doing.
(Other chargers may have similar apps. I liked this because it just worked straight out of the box).

 

[William_H]

I would advocate no bow battery but use the existing heavy cables to anchor winch to share with thruster. Run both directly off engine battery on the basis that engine will always be running when you use either winch or thruster. If cables are not heavy enough add additional cabling in parallel. ol'will

 

[Stemar]

How much power does the windlass draw? I'd guess no more than about half the 300 amps of the thruster, so I'd expect the cables to be undersized for the thruster.

OK, you don't run a thruster for minutes at a time, so they probably won't overheat, but voltage drop might well reduce the power available.

Battery and BTB charger for me. It doesn't need to have a huge output; I'd spend the money on a bigger battery rather than a higher output charger, as neither the windlass nor the thruster will run for long enough to run a good-sized battery down.

 

[Neeves]

How much power does the windlass draw? I'd guess no more than about half the 300 amps of the thruster, so I'd expect the cables to be undersized for the thruster.

OK, you don't run a thruster for minutes at a time, so they probably won't overheat, but voltage drop might well reduce the power available.

Battery and BTB charger for me. It doesn't need to have a huge output; I'd spend the money on a bigger battery rather than a higher output charger, as neither the windlass nor the thruster will run for long enough to run a good-sized battery down.

I've never had a bow thruster.

But surely if you are using a bow thruster, as you would with a windlass - you are also using the engine and the alternator is going to keep and battery topped up (maybe not to 100% - but enough).

Jonathan

 

[Blue Seas]

I looked into this a few months ago when refitting our battery banks. Our thruster is 15Hp (210kg) so we can rapidly use a lot of battery capacity even with short bursts.
I came to the following conclusions if it helps.
1. Spending money on extra battery capacity is sensible expenditure - AGM is best and 'Rolls' agm really do perform (2 x 230ah for us). Lithium not recommended by Sleipner.
2. There is a big difference in starting out 100% charged rather than 80-90% - so a decent 5 or 7 stage charger on your bank at all times is good - I run a 30a victron bluesmart either off shore power or the inverter at sea to keep the bank at 100%.
3. I also have a direct dc supply from the house bank which is normally isolated but can be x-connected if required (to supply either way).
HTH.

 

[Stemar]

I've never had a bow thruster.

But surely if you are using a bow thruster, as you would with a windlass - you are also using the engine and the alternator is going to keep and battery topped up (maybe not to 100% - but enough).

Jonathan

In the suggested setup - battery in the bow, and BTB charger, that's when the BTB will do its stuff. It would be a pretty special alternator that would keep up with, maybe, 150 amps for the windlass, let alone 300 amps from the thruster. My alternators have a 40 amp output, which means, in round figures, and allowing for losses, it's going to take 10 minutes to produce the power used by one minute of thruster. In practice, of course, with any variety of LA battery, it'll take significantly longer to get back to full charge, especially by a BTB charger

 

[PaulRainbow]

I'd suspect that the existing cables are too small to use for the thruster, but if they were big enough i'd connect them to the engine battery.

Assuming they are too small, fit an AGM battery at the bow and connect the cables to the engine battery. Fuse both ends of the cables, as close to the batteries as possible. If you decide to fit Lithium, that will not effect this arrangement.

This does assume that the cables are big enough to provide charging, but as they have been used for a windlass they should be. Would be useful if the OP can confirm the cable sizes.

 

[Tranona]

I looked into this a few months ago when refitting our battery banks. Our thruster is 15Hp (210kg) so we can rapidly use a lot of battery capacity even with short bursts.
I came to the following conclusions if it helps.
1. Spending money on extra battery capacity is sensible expenditure - AGM is best and 'Rolls' agm really do perform (2 x 230ah for us). Lithium not recommended by Sleipner.
2. There is a big difference in starting out 100% charged rather than 80-90% - so a decent 5 or 7 stage charger on your bank at all times is good - I run a 30a victron bluesmart either off shore power or the inverter at sea to keep the bank at 100%.
3. I also have a direct dc supply from the house bank which is normally isolated but can be x-connected if required (to supply either way).
HTH.

That is all of a completely different order from the OPO's modest 65kg thruster where the simple B2B charger from the start battery and 100Ah bow battery is more than adequate

 

[PaulRainbow]

That is all of a completely different order from the OPO's modest 65kg thruster where the simple B2B charger from the start battery and 100Ah bow battery is more than adequate

I wouldn't fit B2B to the engine battery. The charger will only work when the engine is running (or for a short time thereafter) and it's limited to 30a. Better to just connect in parallel to the engine battery IMO. If using a B2B i'd connect to the domestic bank.

16mm cables are almost certainly on the small side, 16mm cables on a 40ft boat will lead to a voltage drop of close to 1 volt. That said, i would expect the existing windlass cables to be bigger than 16mm.

 

[Blue Seas]

That is all of a completely different order from the OPO's modest 65kg thruster where the simple B2B charger from the start battery and 100Ah bow battery is more than adequate

I realise that (of course) - but the point I am making is that the starting point (a good battery, in good condition, and properly charged) is critical in the thruster use where near-instant 'Oomph' is required and where it is unlikely that any charging source can really affect the running period rather than playing catch-up afterwards. Even a B2B depends on the condition of the first 'B'! The economics work with a decent (upgraded) bow battery too.

 

[Tranona]

I wouldn't fit B2B to the engine battery. The charger will only work when the engine is running (or for a short time thereafter) and it's limited to 30a. Better to just connect in parallel to the engine battery IMO. If using a B2B i'd connect to the domestic bank.

16mm cables are almost certainly on the small side, 16mm cables on a 40ft boat will lead to a voltage drop of close to 1 volt. That said, i would expect the existing windlass cables to be bigger than 16mm.

Point taken about the cable size on a 40'boat - assuming the main batteries are aft. However that is what I used on my smaller boat where the batteries are only about 5m apart. can't see a problem with connecting to the start battery as normally the engine is running when the thruster is used.

 

[howardclark]

Don’t think I’m desperately different than others but for what it’s worth I have an upfront battery for bowthruster and windlass plus a separate domestics and engine start bank.
All are charged from the alternator and mains battery charger.
As others have said the bow thruster is nearly always used when the engine is on.
When my engine start battery has had a good life it is relegated to bow thruster battery!
This gives it a few more years of life and ensures my engine start battery is never old
Works for me.

 

[mattnj]

I'd suspect that the existing cables are too small to use for the thruster, but if they were big enough i'd connect them to the engine battery.

Assuming they are too small, fit an AGM battery at the bow and connect the cables to the engine battery. Fuse both ends of the cables, as close to the batteries as possible. If you decide to fit Lithium, that will not effect this arrangement.

This does assume that the cables are big enough to provide charging, but as they have been used for a windlass they should be. Would be useful if the OP can confirm the cable sizes.

Thanks... Yes cables are a decent size, Ive not checked size but they "normal" beefy starter cable size...
So can I connect an AGM directly to the lead acid engine start battery?

 

[geem]

I looked into this a few months ago when refitting our battery banks. Our thruster is 15Hp (210kg) so we can rapidly use a lot of battery capacity even with short bursts.
I came to the following conclusions if it helps.
1. Spending money on extra battery capacity is sensible expenditure - AGM is best and 'Rolls' agm really do perform (2 x 230ah for us). Lithium not recommended by Sleipner.
2. There is a big difference in starting out 100% charged rather than 80-90% - so a decent 5 or 7 stage charger on your bank at all times is good - I run a 30a victron bluesmart either off shore power or the inverter at sea to keep the bank at 100%.
3. I also have a direct dc supply from the house bank which is normally isolated but can be x-connected if required (to supply either way).
HTH.

I don't have a bow thruster but if I did I expect I would wire it from the engine batteries. I have 2x 100Ah in series as we are a 24v boat. I also have a Victron DC/DC charger keeping these batteries charged from my lithium house bank. An 80A alternator (@24v) would also be running whilst using the bow thruster.
I guess if you had a 12v system, you could add a second battery in parallel. This would double you capacity to drive the bowthruster.

 

[PaulRainbow]

Thanks... Yes cables are a decent size, Ive not checked size but they "normal" beefy starter cable size...
So can I connect an AGM directly to the lead acid engine start battery?

Yes, provided the cable is a suitable size and you fuse both ends. Post back with the cable size and i'll confirm for you.

 

[CJTurner]

I had your situation but just added a VSR(voltage sensitive relay) between the existing cables run to the bows and the new battery. So when on shore power or with engine running the battery is charged. I never had a problem with it and the VSR's are as cheap as chips.

 

[Baggywrinkle]

For some reason unknown to me, my house bank is 12v and consists of 4 x 130Ah Gel batteries wired in parallel. Two cables run to the bow (boat is 44ft) which are about an inch in diameter and they feed the bow thruster, anchor winch and genoa furler. It works, it is not what I would have expected, but I do like the fact that I don't have multiple batteries scattered around the boat. House bank is charged from alternator, as is the starter battery. I also have multiple electric sheet winches running off this battery bank, so that might be the reason.

Edit: Found the spec sheet for my thruster .... obviously, getting as close to 12/24V at the thruster as possible is better, but it seems a voltage drop doesn't cause much of a problem other than less thrust. The spec sheet goes down to 10,5V.