Time for new Thruster Bank I'm afraid 😟

dhays · Sep 10, 2024

I think my thruster bank is toast. I am going to see if I can revive it but they are definitely on their last legs.

So I am am trying to figure out what route to take. Here is my current setup.
Thruster Bank - 2 x Lifeline 255AH 8d batteries for a nominal 510AH in the stern that control both bow and stern thrusters as well as windlass. These are at least 9 years old (been there since I bought the boat in 2016 I'll have to find a date on them.
House Bank - 4 x L16 6v AGM batteries for a nominal 760AH. July 2017
Starter Battery - 1 Lifeline 255AH AGM Same age and battery as the Thruster batteries
Genset - Group 27 West Marine AGM - 8 years old.

Eventually, I would like to switch the House bank to LiPro batteries. One option I was considering was to place the existing house bank in service as the Thruster bank, and then get new LiPro batteries for the House. One advantage of this would be that I would be getting more use out of those L16s. Another is that I would be decreasing weight in the stern by 120lbs and shifting the balance 336lbs to port of center, which would help the balance of my boat. A big advantage is that I would get a new house bank with a large increase in useable AHs.

One concern is using deep cycle batteries for the thrusters. I am not sure of what the amp draw is for my thrusters. I am trying to find that out now. Even so, 700AH is a lot of battery so maybe it won't be an issue.

The other option would be to replace the Thruster Bank with something similar to what was installed by the factory and then replaced by the PO, a pair of 8ds. I could then keep my current house bank which is still holding its own although it is 7 years old at this point but I don't know for how much longer. The downside the cost is pretty significant and it means installing 8ds. I don't really want to install 8ds as they are just a huge PITA to move. I could go with smaller AGM batteries in parallel. But then the question is what to get at what cost. I'm guessing it would need the mythical "dual-purpose" batteries as the windlass doesn't draw the same as the thrusters.

So as usual I'm looking for opinions from the TF brain trust.

O C Diver · Sep 10, 2024

I did a little research when looking at thruster batteries and came away with a better choice being normal engine batteries as the profile is relatively short, high amperage pulses, not long low amperage draw downs. I chose Optima red top batteries. The first set (2 batteries in series 24 VDC) lasted 8 years. I was very happy with that for all the locking and docking I did.

If you calculate the power consumption, the amperage is very high, but the watts are surprisingly small. A 15 second pulse at 200 amps 24 VDC equals 20 watts. That's about a 1.6 amp draw on 12 VDC for an hour. A 6 amp battery charger run off the inverter was all that was needed to recharge them.

Now the other thing to consider is how much you use the thruster (minutes per hour). If you're one who routinely trips the thermal overload, you may need more capacity.

Ted

dhays · Sep 10, 2024

O C Diver said:
I did a little research when looking at thruster batteries and came away with a better choice being normal engine batteries as the profile is relatively short, high amperage pulses, not long low amperage draw downs. I chose Optima red top batteries. The first set (2 batteries in series 24 VDC) lasted 8 years. I was very happy with that for all the locking and docking I did.

If you calculate the power consumption, the amperage is very high, but the watts are surprisingly small. A 15 second pulse at 200 amps 24 VDC equals 20 watts. That's about a 1.6 amp draw on 12 VDC for an hour. A 6 amp battery charger run off the inverter was all that was needed to recharge them.

Now the other thing to consider is how much you use the thruster (minutes per hour). If you're one who routinely trips the thermal overload, you may need more capacity.

I'm generally pretty sparing with the thrusters. I try to plan every evolution to not need to use the thrusters. Then we things don't go exactly as my feeble brain had planned, I fine tune with the thrusters. However, there have been a couple times when a game then a workout. Never have hit the thermal cut-out. I hope it actually works, lol.

How do you think they would do with the windlass demand? Raising 300ft of chain can take a while.

Edit: What about the Optima Blue Top?

SteveK · Sep 10, 2024

where is the thruster bank located. At the bow? Or with the house and starter banks

dhays · Sep 10, 2024

SteveK said:
where is the thruster bank located. At the bow? Or with the house and starter banks

In the stern, port of center. The bow thruster and windlass are connected to the battery with 4/0 cable.

Comodave · Sep 10, 2024

dhays said:
I'm generally pretty sparing with the thrusters. I try to plan every evolution to not need to use the thrusters. Then we things don't go exactly as my feeble brain had planned, I fine tune with the thrusters. However, there have been a couple times when a game then a workout. Never have hit the thermal cut-out. I hope it actually works, lol.

How do you think they would do with the windlass demand? Raising 300ft of chain can take a while.

Edit: What about the Optima Blue Top?

I have Optima Blue Tops for my thrusters. 2 in the bow and 2 in the stern for the 24 volt thrusters. Not real happy with them. 2 died the first year. I bought them through Amazon which apparently isn’t an authorized Optima dealer so the warranty wasn’t good, who would have guessed. I ended up buying one new one and returning the bad ones with that receipt since they were supposed to have a 2 year warranty. If I had it to do all over I wouldn’t go Optima.

O C Diver · Sep 10, 2024

dhays said:
I'm generally pretty sparing with the thrusters. I try to plan every evolution to not need to use the thrusters. Then we things don't go exactly as my feeble brain had planned, I fine tune with the thrusters. However, there have been a couple times when a game then a workout. Never have hit the thermal cut-out. I hope it actually works, lol.

How do you think they would do with the windlass demand? Raising 300ft of chain can take a while.

Edit: What about the Optima Blue Top?

IMO, Optima blue tops are a poor choice for a thruster or an engine. I have 4 Optima red tops on my boat. Two for the bow thruster, one for the engine start, and one for the generator. The bow thruster ones lasted 8 years, the engine one lasted 10 years (used when I put it in), and the generator is still going strong. Again, consider the profile, thrusters are the same as starting an engine. No need for deep cycle capacity.

If you're using it to power a windlass, you need to know actual amperage draw and duration.

BTW, is the 12 VDC or 24 VDC?

Ted

dhays · Sep 10, 2024

O C Diver said:
IMO, Optima blue tops are a poor choice for a thruster or an engine. I have 4 Optima red tops on my boat. Two for the bow thruster, one for the engine start, and one for the generator. The bow thruster ones lasted 8 years, the engine one lasted 10 years (used when I put it in), and the generator is still going strong. Again, consider the profile, thrusters are the same as starting an engine. No need for deep cycle capacity.

If you're using it to power a windlass, you need to know actual amperage draw and duration.

BTW, is the 12 VDC or 24 VDC?

Ted, 12v and you are right that I need to figure out the actual amp and power draw.

Comodave said:
I have Optima Blue Tops for my thrusters. 2 in the bow and 2 in the stern for the 24 volt thrusters. Not real happy with them. 2 died the first year. I bought them through Amazon which apparently isn’t an authorized Optima dealer so the warranty wasn’t good, who would have guessed. I ended up buying one new one and returning the bad ones with that receipt since they were supposed to have a 2 year warranty. If I had it to do all over I wouldn’t go Optima.

Thanks Dave. Good to get some solid feedback.

Bacchus · Sep 10, 2024

dhays said:
I think my thruster bank is toast. I am going to see if I can revive it but they are definitely on their last legs.

So I am am trying to figure out what route to take. Here is my current setup.
Thruster Bank - 2 x Lifeline 255AH 8d batteries for a nominal 510AH in the stern that control both bow and stern thrusters as well as windlass. These are at least 9 years old (been there since I bought the boat in 2016 I'll have to find a date on them.
House Bank - 4 x L16 6v AGM batteries for a nominal 760AH. July 2017
Starter Battery - 1 Lifeline 255AH AGM Same age and battery as the Thruster batteries
Genset - Group 27 West Marine AGM - 8 years old.

Eventually, I would like to switch the House bank to LiPro batteries. One option I was considering was to place the existing house bank in service as the Thruster bank, and then get new LiPro batteries for the House. One advantage of this would be that I would be getting more use out of those L16s. Another is that I would be decreasing weight in the stern by 120lbs and shifting the balance 336lbs to port of center, which would help the balance of my boat. A big advantage is that I would get a new house bank with a large increase in useable AHs.

One concern is using deep cycle batteries for the thrusters. I am not sure of what the amp draw is for my thrusters. I am trying to find that out now. Even so, 700AH is a lot of battery so maybe it won't be an issue.

The other option would be to replace the Thruster Bank with something similar to what was installed by the factory and then replaced by the PO, a pair of 8ds. I could then keep my current house bank which is still holding its own although it is 7 years old at this point but I don't know for how much longer. The downside the cost is pretty significant and it means installing 8ds. I don't really want to install 8ds as they are just a huge PITA to move. I could go with smaller AGM batteries in parallel. But then the question is what to get at what cost. I'm guessing it would need the mythical "dual-purpose" batteries as the windlass doesn't draw the same as the thrusters.

So as usual I'm looking for opinions from the TF brain trust.

Dave
If your current house was FLA deep cycle I'd think differently but AGMs perform well as both deep cycle and start/hi amp loads for shorter duration (confirmed by both East Penn and Trojan when I inquired)
I have an 8D AGM that serves my B & S thrusters. Last year I finally moved my single diesel start to the thruster batty and have been very happy. My thinking is starting hi A but brief and no thruster use (generally) until / unless eng is running and alt is assisting w/ hi amp draws. My house is 2 - 8D AGMs and now a pure house after start move.
Both banks have completed 11 season in NE and start / thruster still recovers quickly and appears strong. House bank shows some aging and quicker depletion (lost capacity) but no operational issues to date. I fully charge and disconnect in place for winter storage (no power available for charging). I monitor V every spring before reconnecting and charging and see typical V between 12.6 - 12.7 V.

I think your idea of switching current house to thrusters is a great idea.
I also think the windlass is closer to start / thruster use (hi amp short time) than typical house (lower amp longer duration - possibly with the exception of inverter use.

A large AGM bank can handle both applications very well... certainly worth a try IMO

SteveK · Sep 10, 2024

dhays said:
In the stern, port of center. The bow thruster and windlass are connected to the battery with 4/0 cable.

I was thinking what if you got the new Lithium starter batteries for engines and thrusters.

dhays · Sep 10, 2024

SteveK said:
I was thinking what if you got the new Lithium starter batteries for engines and thrusters.

I think they would well for a staring battery or windlass but I'm not convinced that I'm ready to trust them for the thrusters. Engine start is very quick, windlass doesn't have as much amo draw. So far I have not seen a thruster manufacturer recommends them for thrusters.

If I felt more comfortable with it, I would consider using a Lithium in the bow for both bow thruster and windlass and use a DC-DC charger to charge it.

dhays · Sep 10, 2024

Bacchus said:
I think your idea of switching current house to thrusters is a great idea.
I also think the windlass is closer to start / thruster use (hi amp short time) than typical house (lower amp longer duration - possibly with the exception of inverter use.

A large AGM bank can handle both applications very well... certainly worth a try IMO

My only reservation is that some consider the Lifeline more of a "dual purpose" battery. The 8ds have a pretty high CCA as published by Lifeline.

My house are true deep cycle L16s. They obviously to have a CCA rating, I just can't find it published. However, such a large bank is probably OK since even though it would have a relatively smaller CCA compared to its AHs, it has a LOT of AHs coming moated to a start battery. Hence my quandary.

The conservative move would be to just replace the current bank with something appropriate to the application and then change the house bank down the road when the the house bank dies.

Dawgfan · Sep 10, 2024

Dave, my NP45 is set up somewhat similar to your NP. I have 4 Rolls Surette AGM L16/6v (830Ah total rating when new) batteries for house, but they also serve the stern thruster. Those batteries are 8 years old and holding their voltage almost like new. The original design separated them into two banks, but I always keep them combined.

You probably have Vetus 95kgs for your thrusters. The rated draw is 600A. I have measured them and they are closer to 450-500A. Still a substantial draw.

My "house" bank serves the stern thruster very well since it is just a short distance to the thruster.
In short stern thruster operation, the Furuno plotters do not reboot. Extended stern thruster operation does drop house voltage down below 12v and my very voltage sensitive Furuno plotters will reboot even though I installed a Victron DC-DC converter.

I installed a 2000CCA battery under the forward berth to serve the bow thruster and the windlass. It is isolated from the house bank and has a separate charger. It works outstandingly well for the bow thruster and windlass which I use far more than the stern thruster.

All that to say, I would remove the 8D thruster batteries and connect your stern thruster to the L16 house bank for now. The batteries should handle the load just fine, mine of similar age and capacity, do. The actual Ah draw is very little, so your house bank capacity would not be materially impacted. Removing the old thruster batteries and utilizing the house bank for now buys you time to explore your battery and charging options at a future season.

We've been out for six weeks and going for another two to three weeks before returning home. A lot of that has been at anchor. In fact, we're at anchor in Reid Harbor right now after anchoring at Sucia for a couple of nights. I still get 325Ah at 60% SOC out of my L16s.

Maybe I'll switch to Lithium in the offseason, maybe I'll keep the existing bank another season or simply buy 4 new Rolls L16s and drop them in, which is much less expensive than switching to Lithium. For now, this setup gives me the performance I need to cruise now and time to explore options for the future.

Hope this helps.

Ron

dhays · Sep 10, 2024

Dawgfan said:
Dave, my NP45 is set up somewhat similar to your NP. I have 4 Rolls Surette AGM L16/6v (830Ah total rating when new) batteries for house, but they also serve the stern thruster. Those batteries are 8 years old and holding their voltage almost like new. The original design separated them into two banks, but I always keep them combined.

You probably have Vetus 95kgs for your thrusters. The rated draw is 600A. I have measured them and they are closer to 450-500A. Still a substantial draw.

My "house" bank serves the stern thruster very well since it is just a short distance to the thruster.
In short stern thruster operation, the Furuno plotters do not reboot. Extended stern thruster operation does drop house voltage down below 12v and my very voltage sensitive Furuno plotters will reboot even though I installed a Victron DC-DC converter.

I installed a 2000CCA battery under the forward berth to serve the bow thruster and the windlass. It is isolated from the house bank and has a separate charger. It works outstandingly well for the bow thruster and windlass which I use far more than the stern thruster.

All that to say, I would remove the 8D thruster batteries and connect your stern thruster to the L16 house bank for now. The batteries should handle the load just fine, mine of similar age and capacity, do. The actual Ah draw is very little, so your house bank capacity would not be materially impacted. Removing the old thruster batteries and utilizing the house bank for now buys you time to explore your battery and charging options at a future season.

We've been out for six weeks and going for another two to three weeks before returning home. A lot of that has been at anchor. In fact, we're at anchor in Reid Harbor right now after anchoring at Sucia for a couple of nights. I still get 325Ah at 60% SOC out of my L16s.

Maybe I'll switch to Lithium in the offseason, maybe I'll keep the existing bank another season or simply buy 4 new Rolls L16s and drop them in, which is much less expensive than switching to Lithium. For now, this setup gives me the performance I need to cruise now and time to explore options for the future.

Hope this helps.

Ron

Thanks Ron, that is great info.

I'd be curious to know what battery you decided to use for the Bow thruster/windlass.

Given your experience, it does support the idea of switching my current house bank for thruster duty and then upgrading the house to LiPo.

I have combined the two banks and found that thruster use would reset my plotters. Of course, the thruster bank was weak at the time.

Dawgfan · Sep 11, 2024

The bow thruster/windlass battery is a Northstar AGM-480. I selected it for both high short duration current output and for the vertical form size which fits at the very front of the storage compartment under the forward berth so as to not take up any storage space there.

Here's the spec sheet:

SMS-AGM480

www.northstarbattery.com

I should clarify that the battery is rated at 2400A "pulse", which is approx a 3s burst. That is similar to how we use high amperage thrusters. It also works extremely well for the windlass.

Ron

Comodave · Sep 11, 2024

Did you say the current bow thruster and windlass are powered by batteries in the stern? Or did I miss read the post? If they are truly in the stern then I would put a dedicated bank in the bow for the thruster and windlass. The voltage drop from the stern even with larger cables would be an issue for me. I would put the bank as close as possible and then use as large cable as possible. I always go larger than bare necessity for electrical wiring. I want as good a voltage as possible.

dhays · Sep 11, 2024

Comodave said:
Did you say the current bow thruster and windlass are powered by batteries in the stern? Or did I miss read the post? If they are truly in the stern then I would put a dedicated bank in the bow for the thruster and windlass. The voltage drop from the stern even with larger cables would be an issue for me. I would put the bank as close as possible and then use as large cable as possible. I always go larger than bare necessity for electrical wiring. I want as good a voltage as possible.

Yup. Having the thruster/windlass bank in the stern isn't ideal, but it is how the boat was setup 14 years ago. I have considered putting a battery in the bow for the bow thruster and windlass, but so far that hasn't risen high enough in the priority list. I don't think it would be too hard, but I haven't dug around it enough to be sure. Installing the battery and a DC-DC charger to it would be relatively easy. The harder issue would be moving/wiring the solenoids which connect them to the battery currently. I'd need to think about that.

dhays · Sep 11, 2024

Dawgfan said:
The bow thruster/windlass battery is a Northstar AGM-480. I selected it for both high short duration current output and for the vertical form size which fits at the very front of the storage compartment under the forward berth so as to not take up any storage space there.

Here's the spec sheet:

SMS-AGM480

www.northstarbattery.com

I should clarify that the battery is rated at 2400A "pulse", which is approx a 3s burst. That is similar to how we use high amperage thrusters. It also works extremely well for the windlass.

Nice looking battery, but that is a big puppy. I'd probably opt to try to find a pair of batteries I could parallel that would be easier to move.

Comodave · Sep 11, 2024

dhays said:
Yup. Having the thruster/windlass bank in the stern isn't ideal, but it is how the boat was setup 14 years ago. I have considered putting a battery in the bow for the bow thruster and windlass, but so far that hasn't risen high enough in the priority list. I don't think it would be too hard, but I haven't dug around it enough to be sure. Installing the battery and a DC-DC charger to it would be relatively easy. The harder issue would be moving/wiring the solenoids which connect them to the battery currently. I'd need to think about that.

Lots of times boat builders don’t do the best thing for a variety of reasons, usually because it is either cheaper or easier.

Insequent · Sep 11, 2024

I echo Comodave's points about having windlass/bow thruster battery in the bow. And points made by many posters that you need a "starter" type battery for that duty. High CCA. Thruster Ah draw is quite low, and windlass Ah draw is also small in my experience, and I have a Victron gauge to support this experience.

I'm using some Odyssey batteries for the purpose at present, and they are dual purpose AGM's that quote CCA. I'll likely use Full River HC series when I need to replace them. I use those for start batteries at present. If the battery you are thinking of using does not have a readily discoverable CCA rating then its very likely to be not suitable. At this point few, if any, LFP are suitable for high amp draw applications.

ranger58sb · Sep 11, 2024

SteveK said:
I was thinking what if you got the new Lithium starter batteries for engines and thrusters.

When I was shopping for thruster batteries with that in mind, I wasn't able to find much in the way of LiPo that would handle our thruster's current requirements (560A @ 24V for 4.5 mins)... and I checked against engine CCA requirements requirements too (1400 CCA, in our case)... no joy.

There's a thread on that...

-Chris

dhays said:
Eventually, I would like to switch the House bank to LiPro batteries. One option I was considering was to place the existing house bank in service as the Thruster bank, and then get new LiPro batteries for the House. One advantage of this would be that I would be getting more use out of those L16s. Another is that I would be decreasing weight in the stern by 120lbs and shifting the balance 336lbs to port of center, which would help the balance of my boat. A big advantage is that I would get a new house bank with a large increase in useable AHs.

The weight savings and balance shift sound good. Were it me, I think I'd replace your thruster Lifelines with Odyssey Extreme, bag the extra work it would take to get bow thruster/windlass batteries up forward, eventually replace the L16 house bank with LiPo, just take your weight/balance/capacity improvements when the time comes...

Yes, batteries forward would be technically better. IMO, not better enough to do the work required. Might think differently, if the bow thruster and windlass were having some sort of supply problem, but... if they're working, they're working.

We currently have 2x Lifeline 8D AGMs for our thruster bank (which also serves in inverter now), plus two more similar banks for engines/house, all 24V. Chose Lifelines for the thruster bank because it has slightly more capacity -- which I wanted for the inverter function -- otherwise, I'd have chosen Odyssey (higher CCA).

I'm happy enough with the Lifelines for our thruster usage -- which tends to be minimal -- and for our inverter loads when we have that going on, but I've only got about 2 whole seasons on them so far, not enough yet to report longevity stats.

-Chris

RCook · Sep 11, 2024

Our bow thruster / windlass bank, in the bow, is a paralleled pair of East Penn / Deka 12V g31 agm's. Another pair for starter bank. Still doing fine after eight summers cruising the Inside Passage. Stern thruster batt is a g31 Optima blue top which replaced a ten YO Optima yellow top with the same specs. House is four g31 Deka's, which replaced a 7 YO set of the same. G31 agm's sure work well for us, especially for thruster, windlass, and starting.

Bacchus · Sep 11, 2024

RCook said:
Our bow thruster / windlass bank, in the bow, is a paralleled pair of East Penn / Deka 12V g31 agm's. Another pair for starter bank. Still doing fine after eight summers cruising the Inside Passage. Stern thruster batt is a g31 Optima blue top which replaced a ten YO Optima yellow top with the same specs. House is four g31 Deka's, which replaced a 7 YO set of the same. G31 agm's sure work well for us, especially for thruster, windlass, and starting.

Richard
Thanks for confirming East Penn GP 31 AGM suitability.
My plan is to replace each of my EP AGM 8Ds w a pair of EP GP 31 AGMs. So far the 8Ds are performing OK but I'm anticipating the end is near at least for my house 8Ds.

dhays · Sep 11, 2024

Baring yet another unforeseen event, I plan on heading out on the boat on Friday for the weekend. Family commitments and emergencies have seemed to derail most of my plans for the past few years, so you never know.

I'll head out and anchor for a couple nights. One of the things I want to do is see how well the thruster and house bank do. The days are getting shorter now and the weather is cloudy, so solar is going to be minimal. I don't have any SOC meter on the thruster bank, but will interested to see what the resting voltage looks like and how deeply the voltage drops when using the Windlass and when I come back to the dock on Sunday.

BruceK · Sep 12, 2024

I query changing a system that has served well for a long period and produced long battery life. It suggests a well designed system, good quality suitable battery type selection, good charging maintenance, and sensible battery usage.
If as it seems it`s only the thruster/windlass bank that needs replacing (though others may not be far behind), for now just replace them. Fitting 4 more easily handled replacements to equal the 2 8Ds makes sense if you prefer. For selecting battery types, the demands of thrusters and windlass are similar and as a group, are more akin to start than deep cycle house technology. Staying with AGM, charging system changes don`t arise.

dhays · Sep 13, 2024

So because of todays little fiasco with how the boat was running, I wasn't able to get away for the weekend to test the viability of my current thruster bank. However, I had charged it really well using the shore charger earlier in the week. It then spent another 24 hours at float via a Balmar DC-DC charger, and then an additional 24 hours with no charge source at all. So when I got to the boat late morning today it had a resting charge of 12.8v. Better than I thought it would be. So it may still have some life left after being resurrected, we just don't know how long (just like Lazarus).

However, I'm a little more concerned with the House bank. I've noticed that the 4 x 6v L16s consistently have what I would consider to be an elevated temperature. In cool weather while just recieving a float charge, they are running around 26-27C°. The thruster bank, 2 Lifeline 8ds were running about 19-20C° in the same compartment. While I had diverted the shore charger to the Thruster bank, the only charge the house bank was getting was from the solar panel. There were no significant DC draws on the house bank as the refrigeration was coming from the shore 120v. In the morning the resting charge of the House was down close to 12v. I would expect it to be closer to 12.7v

I am not sure what the significance is of the higher temps when getting a charge. FWIW, the L16 AGM are configured as 2 sets of 2. Each set of two is in its own covered battery box and each set seems to have the same temp as checked with a heat gun that pretty well matches the Victron bluetooth battery sense that is on one of the 6v batteries.

Capt Ray · Sep 28, 2024

+1 Group 31 AGM by Interstate. About $400 ea. Good warrantee program.
2 or 3 of them to replace each 8D.

+1 for BatterycablesUSA.com for cables. I standardize on 2/0. Connect load from opposite ends of the bank.

My LiFePO4 vendor does not recommend that chemistry for starter / thruster type loads. Dakota makes a DL+ line of dual purpose LiFePO4, but generally the LA chemistry is more widely accepted for starter / thruster type loads.

Time for new Thruster Bank I'm afraid 😟

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