24 volt thruster with 12 volt system

[jdrakeford]

I'm planning an upgrade of my Max Power thrusters. My idea was to upgrade from the existing 12v CT80s to 24v CT125s. The 24v model offers the main advantage of lighter cabling due to the much lower current flow. It also looks like the batteries will last longer due to less power losses.

The CT125 is 24 volt so I need to overcome the charging issues that arise. The thruster battery banks are independent and currently use 2 x 50ah batteries.

My plan for charging is as follows:
Install a 12v dc - 24v dc charger to allow charging from the alternator while at sea. Using something like a victron 16 amp charger.
For shore power charging, connect a 24v charger of around 16 amp.

Existing Ct80 thruster: 4.8kw, 369 amp max
Ct 125 thruster: 8.5kw, 330 amp max

The other option is a CT100 but requires much bigger cables with a max current draw of 660 amps.

Any advice on the 24v option and possible pit falls I may be missing?

Thanks

 

[kashurst]

Why are you upgrading? What boat is it?

 

[jdrakeford]

Beneteau swift trawler 34. More thrust needed for days when it's fairly windy, especially the stern thruster is pretty feeble.

 

[BB1]

I'm planning an upgrade of my Max Power thrusters. My idea was to upgrade from the existing 12v CT80s to 24v CT125s. The 24v model offers the main advantage of lighter cabling due to the much lower current flow. It also looks like the batteries will last longer due to less power losses.

The CT125 is 24 volt so I need to overcome the charging issues that arise. The thruster battery banks are independent and currently use 2 x 50ah batteries.

My plan for charging is as follows:
Install a 12v dc - 24v dc charger to allow charging from the alternator while at sea. Using something like a victron 16 amp charger.
For shore power charging, connect a 24v charger of around 16 amp.

Existing Ct80 thruster: 4.8kw, 369 amp max
Ct 125 thruster: 8.5kw, 330 amp max

The other option is a CT100 but requires much bigger cables with a max current draw of 660 amps.

Any advice on the 24v option and possible pit falls I may be missing?

Thanks

Is it possible to leave the batteries as 12volt but have a relay that links them in series when the thruster is operated, I believe that Brooms used to do this.

 

[rogerthebodger]

I have a 12Vdc boat that I am fitting 24Vdc winches and simply fitting a second battery adding it in series to the existing 12 Vdc batter and charging the second 12 Vdc battery using an isolated 12 Vdc charger.

either from a solar setup of an isolated 12Vdc 12 V dc battery to battery charger

 

[jdrakeford]

I have a 12Vdc boat that I am fitting 24Vdc winches and simply fitting a second battery adding it in series to the existing 12 Vdc batter and charging the second 12 Vdc battery using an isolated 12 Vdc charger.

either from a solar setup of an isolated 12Vdc 12 V dc battery to battery charger

So it would work to charge one battery from the existing 12v system without any issues with the 2 battery's being connected in series making 24v?
That way I only need to charge one of the batteries from another charger?

 

[jdrakeford]

Is it possible to leave the batteries as 12volt but have a relay that links them in series when the thruster is operated, I believe that Brooms used to do this.

Yes, I think that would be possible but the setup may end up more expensive than buying chargers to charge them independently.

 

[PaulRainbow]

So it would work to charge one battery from the existing 12v system without any issues with the 2 battery's being connected in series making 24v?
That way I only need to charge one of the batteries from another charger?

It would work, but can cause imbalances between the batteries, shortening their life.

An alternative would be a series/parallel switch/relay. You can get manual or automatic versions. For instance Vetus Series parallel switch for 24 volt thruster with 12 vo (Vetus BPSPE)

Another option would be to fit a pair of batteries in series, just for the thruster and charge them with a 12v - 24v DC-DC charger. Similar cost to buying a second charger Victron Energy Orion-Tr Smart 12/24V 15A (360W) Non-isolated DC-DC Charger - ORI122436140

 

[jdrakeford]

It would work, but can cause imbalances between the batteries, shortening their life.

An alternative would be a series/parallel switch/relay. You can get manual or automatic versions. For instance Vetus Series parallel switch for 24 volt thruster with 12 vo (Vetus BPSPE)

Another option would be to fit a pair of batteries in series, just for the thruster and charge them with a 12v - 24v DC-DC charger. Similar cost to buying a second charger Victron Energy Orion-Tr Smart 12/24V 15A (360W) Non-isolated DC-DC Charger - ORI122436140

Excellent advice thank you.
I already have separate thruster batteries so the 2nd option with the victron charger would be most economical. In addition I would need a mains 24v charger for when I'm alongside on shore power.

 

[jdrakeford]

Excellent advice thank you.
I already have separate thruster batteries so the 2nd option with the victron charger would be most economical. In addition I would need a mains 24v charger for when I'm alongside on shore power.

Or can the 12v dc to 24v dc charger do both jobs?

 

[PaulRainbow]

Or can the 12v dc to 24v dc charger do both jobs?

If the 12V input battery is on charge by the shore charger, then yes, the DC-DC charger will charge the thruster bank. It doesn't care if the 12V source battery is being charged by shore charger, alternator or solar.

 

[jdrakeford]

OK great, then it simplifies things and saves the cost of a 2nd battery charger.

 

[z16]

I've recently upgraded my 12v CT100 to 24v CT125. Lots of lessons learned. Happy to share if not too late. Let me know.

 

[jdrakeford]

I've recently upgraded my 12v CT100 to 24v CT125. Lots of lessons learned. Happy to share if not too late. Let me know.

No not too late, nothing has been ordered yet! Any advice would be greatly appreciated

 

[z16]

IMO you are right to go for the 24v CT125 rather than the 12v CT100. The CT125 delivers 20% more thrust than the CT100 and the challenges of delivering the required current (680A at 11v) to the CT100 are considerable.

I had a look at the CT80’s parts list to see if you could get away with just changing the motor and relay assembly but I’m fairly sure you will need a complete CT125. However, the drive leg and propellers are the same so, provided the CT125’s upper motor support (p/n 313714) attaches to your current motor support (p/n 313715) which it should, you’ll be able to do the upgrade with the boat in the water (as I did) and keep the new drive leg and props for spares. The coupling between the CT125’s motor and the drive leg is more complex and longer than on the CT80 hence the need for p/n 313714; it also means the CT125 will sit higher than the CT80 so make sure you have room.

As you probably already know, the installation instructions recommend not running the thruster’s control circuitry from the same battery bank as the thruster motor. This makes good sense because the motor will generate electrical noise (especially when it turns on and off) that could interfere with the control circuitry. There are therefore two versions of the CT125. p/n 42535 is if you are running the control circuity from a 24v supply (which would include the thruster battery bank if you are ignoring the Max Power recommendation). p/n 317601 is for situations where the control circuitry has a 12v supply.

My CT100 was installed using 70mm2 cable. There’s no doubt this contributed to its poor performance. Max Power’s minimum cable size for the CT100 is 95mm2 and, given the round trip distance from my thruster battery to the thruster via the motorised switches, the wiring should have been 150mm2. But the good news is the 70mm2 was ideal for the CT125 (and by rerouting it I was able to reduce the round trip by almost 2m).

I replaced the original Optima Blue Top 34M 50Ah 800CCA with two Optima Blue Top D31Ms, 75Ah 900 CCA each. With these and the 70mm2 cable I had expected to see Max Power’s minimum 22v (under load) at the motor terminals. But no; it is close (I can’t recall the exact figure) and is certainly much better than the 8v I was seeing with the 12v CT100. I know that on the Garcia Exploration 45 the boatyard installed CT125 is powered by four D31Ms in series / parallel. I’m not planning to go that extra step as the performance I’m getting is a significant step up from the CT100.

With the CT100, the 12v battery to 12v battery charger was in the bow, close to the thruster & windlass battery. I replaced this with a Victron Energy Orion-Tr Smart 12/24V 15A Non-isolated Charger (as mentioned by PaulRainbow) but located this close to the house / service bank as it is better to do the long run to the bow at 24v rather than 12v. This charger’s 15A output is a good match for the D31M optimum charging profile.

The installation manual specifies a 225A ANL fuse. This makes no sense when the CT125 will draw 430A at 22v. I did give it a try with 250A fuse but it blew the first time I used the thruster in anger. I’m using a 500A temporarily but have some 400A on order to try. (The fusing needs to be consistent with the cable size.)

I did consider continuing to run my 12v windlass from the original bow battery but decided against and upgraded my windlass to 24v as well (a change of motor, switching relays and circuit breaker). I had expected I might see some improvement in performance due to less of a voltage drop by running 24v through cabling that had been sized for the 12v current. But any improvement is minor.

Hope that helps. Ask away if you have any questions.

 

[jdrakeford]

Thank you for the detailed reply, it helps a lot.
As far as I can see, and as you suggest, it makes sense cost wise to buy the complete thruster assembly including drive leg, rather than buying all the individual parts (motor, coupling, relay etc), at least then I'll have a spare drive leg. Anyway, I want to install the newer type 6 blade propellers instead of the existing 3 blade so I'll be able to use them too.
The electronic controller appears to have the same part number p/n 315308 for the CT80, 100 &125 so should be reusable with the new CT125. You also mentioned about the CT125 having a 12v and 24v control circuitry option, when I look on the Jimmy green website they show a 12v or a 24v relay option. But the relay would be supplied from the 24v battery bank rather than than the "separate" battery for the control wiring avoiding electrical noise when operating the thruster? So my thinking is i need the 24v option?

I tested my existing CT80 thruster and was getting 10.3v at the motor terminals and 400 amps current flow. Most of the voltage drop seemed to be directly from the 2 x 50ah exide batteries due to the high current draw. I think the fuse installed is 300 amps and the manual states 225 amps.

The 15 amp victron charger with 2 x 75 ah batteries sounds good. The only observation I had when testing my ct80 was that with the engine running and alternator charging around ~15amps was being supplied to the batteries (probably as they only needed topping up) and when operating the thruster, close to 100 amps (only for a few seconds of course). So with the 24v thruster with b2b charger there would only ever be 15 amps charging rate.

What about the electric battery isolator? Max power recommend to use their one part number 318401 24v version. Currently my ct80 has a 12V sodrep ecans (i think it is) so would need changed as well.

 

[z16]

At some point after my CT100 was installed in 2019, Max Power changed the method of securing the propellers from a small grub screw on the side of the prop to a nyloc nut on the actual prop shaft. (Reports of missing propellers abound.) This meant a change of prop part number, from 35031 to 636576. However, as far as I can tell, the drive leg part number didn’t change. It is and always has been 35035, the same as on the CT80. So you may be able to get away with fitting the new six blade props to your existing drive leg.

The relay assembly bolts to the motor and houses an Ametek JCM46 series contactor (a big relay). A contactor has two voltage parameters: the voltage the contacts are able to handle (at least 48v in the case of the JCM46s) and the voltage required to activate the coil that causes the contacts to close. The coil is activated directly by the electronic controller (p/n 315308) so the contactor’s coil voltage needs to be consistent with the supply to the controller, in your case 12v. This means you need CT125 317601 (24v motor and contacts / 12v control circuitry).

I learned this the hard way. CT125 317601 is a well kept secret. It isn’t even listed on the Max Power web site and searching for it results in a Not Found error. Unsurprisingly, the dealer I ordered from (in Malta) wasn’t aware there were two versions of the 24v CT125 and ordered for me CT125 42535 (24v motor and contacts / 24v control circuitry). It installed ok but when I tried to activate the thruster all I got was a click …. the 12v from my control circuitry was insufficient to activate the 24v coils. I got round the problem by removing the 12v relay assembly (315328) from my CT100 and fitting it to the CT125. The dealer I bought it from is now in a tussle with Max Power to get the 24v relay assembly (315329) that came with the CT125 swapped for a new 12v relay assembly.

A couple of related points. The electronic controller 315308 seems to be common to all CT 12v and 24v thrusters and will function with either a 12v or 24v supply. The thruster is an inductive load and the continuous duty inductive load rating of the JCM46 series contactors is 300 amps. The CT100 draws 680 amps at 11v. That’s quite a mismatch. I assume the engineering justification for it being ok is that thrusters are only ever operated in short bursts and not continuously. But, for me at least, another reason not to persist with the 12v CT100.

You are correct that by going to a 24v thruster you will limit the benefit of having the engine running to the 15 amps the Victron charger can deliver. There may well be a way of inserting a 12v:24v converter between the alternator and the thruster to harness the power of the alternator but the control wiring would need to ensure that it only ever came on when the thruster motor was running. Much easier to just size the batteries appropriately.

I think you are also correct that your battery isolator will also need to be replaced with a 24v version. (Bow battery isolation on my set up is via two motorised switches rated to 48v.) The Max Power isolators are designed to be controlled by the electronic control unit (I’m guessing the isolator de-isolates the batteries when the control unit is switched on at the helm station). So the contactor coil voltage questions comes into play again: if your control circuitry is 12v, do you need the 12v or the 24v isolator? Probably simpler and cheaper to get the 24v version of what you have.

 

[jdrakeford]

At some point after my CT100 was installed in 2019, Max Power changed the method of securing the propellers from a small grub screw on the side of the prop to a nyloc nut on the actual prop shaft. (Reports of missing propellers abound.) This meant a change of prop part number, from 35031 to 636576. However, as far as I can tell, the drive leg part number didn’t change. It is and always has been 35035, the same as on the CT80. So you may be able to get away with fitting the new six blade props to your existing drive leg.

The relay assembly bolts to the motor and houses an Ametek JCM46 series contactor (a big relay). A contactor has two voltage parameters: the voltage the contacts are able to handle (at least 48v in the case of the JCM46s) and the voltage required to activate the coil that causes the contacts to close. The coil is activated directly by the electronic controller (p/n 315308) so the contactor’s coil voltage needs to be consistent with the supply to the controller, in your case 12v. This means you need CT125 317601 (24v motor and contacts / 12v control circuitry).

I learned this the hard way. CT125 317601 is a well kept secret. It isn’t even listed on the Max Power web site and searching for it results in a Not Found error. Unsurprisingly, the dealer I ordered from (in Malta) wasn’t aware there were two versions of the 24v CT125 and ordered for me CT125 42535 (24v motor and contacts / 24v control circuitry). It installed ok but when I tried to activate the thruster all I got was a click …. the 12v from my control circuitry was insufficient to activate the 24v coils. I got round the problem by removing the 12v relay assembly (315328) from my CT100 and fitting it to the CT125. The dealer I bought it from is now in a tussle with Max Power to get the 24v relay assembly (315329) that came with the CT125 swapped for a new 12v relay assembly.

A couple of related points. The electronic controller 315308 seems to be common to all CT 12v and 24v thrusters and will function with either a 12v or 24v supply. The thruster is an inductive load and the continuous duty inductive load rating of the JCM46 series contactors is 300 amps. The CT100 draws 680 amps at 11v. That’s quite a mismatch. I assume the engineering justification for it being ok is that thrusters are only ever operated in short bursts and not continuously. But, for me at least, another reason not to persist with the 12v CT100.

You are correct that by going to a 24v thruster you will limit the benefit of having the engine running to the 15 amps the Victron charger can deliver. There may well be a way of inserting a 12v:24v converter between the alternator and the thruster to harness the power of the alternator but the control wiring would need to ensure that it only ever came on when the thruster motor was running. Much easier to just size the batteries appropriately.

I think you are also correct that your battery isolator will also need to be replaced with a 24v version. (Bow battery isolation on my set up is via two motorised switches rated to 48v.) The Max Power isolators are designed to be controlled by the electronic control unit (I’m guessing the isolator de-isolates the batteries when the control unit is switched on at the helm station). So the contactor coil voltage questions comes into play again: if your control circuitry is 12v, do you need the 12v or the 24v isolator? Probably simpler and cheaper to get the 24v version of what you have.

Hi z16,
Apologies for the delay replying on this one. Many thanks for the comprehensive reply which is really helping me

Regarding the battery isolator, you are correct that it's activated by 12v from the electronic control unit, via a 12v relay when switching on from the joystick panel. So I'm thinking that maybe the existing 12v isolator is more suitable as the 24v version likely requires 24v supply to operate and de-isolate the battery's. The isolator would also be handling less current through it with the 24v setup?

The fact that the 24v CT125 requires the 12v contactor relay is an excellent point and one I would have overlooked myself!! I also searched for the CT125 p/n 317601 online with only a few hits abroad. I contacted a place called Brit boat parts and they can supply the CT125 p/n 317601 but it's at least £600 more than the 12v version which is quite significant.

I wonder if I could install the regular thruster p/n 42535, then use the contactor relay from my existing CT80 thruster, as you did with yours (I know yours was a CT100)? The 24v setup will mean less current flow but maybe there are other issues associated with using my CT80 contactor relay?

A bit if a minefield but would rather explore all options before splashing out!