LFP for thruster and inverter?

[ranger58sb]

This is going to ask for suggestions so I can better do some "what if?" shopping.

Last Summer we re-purposed our thruster bank to also service AC house loads via inverter. The bank is (now) two Lifeline 8D AGMs (1350CCA, 255Ah) in series to 24VDC. The inverter is actually an inverter/charger, Victron MultiPlus 24/3000/70-50/120V.

The goal was to be able to power our AC-only fridges/freezer while underway, make morning coffee or heat Happy Hour hors d'oeuvres, and while we're at it, power some light loads like cell phone chargers -- without the generator. Converting the thruster bank to also service inverter loads was the line of least resistance. Works nicely, although we don't have a long-term assessment yet.

We still anticipate generous genset usage, as when aircon is required and for electric cooking at anchor; I'm not trying to replace that.

The other two 24VDC battery banks on the boat each start an engine and service approximately half of the house/nav DC loads. They came to us with run-of-the-mill batteries (both wet, one bank sealed, one open for watering). I will need to replace those, as time goes on, perhaps even sooner than later... and my intention has been to replace with the same model of Lifeline 8D AGMs that we've put in service for the thruster bank.

I'm getting closer to the question...

IF there might be a LiFePO4 solution suitable for high current loads like a thruster, and IF there might be a suitable BMS to control all that, and IF such a change might not cost bazillions more than a couple of Lifeline 8Ds, and IF said system might fit in the same existing battery bank footprint, and IF said system wouldn't launch our insurance people into orbit, and IF the set-up might be relatively bullet-proof (well, OK, at least relatively reliable)...

I could imagine replacing the current Lifeline thruster batteries with said LFP solution... moving the existing Lifeline 8Ds to one of the other two banks whenever the time comes to replace...

And I'd end up (I think) with even more capacity in the thruster/inverter bank for house loads...

But there's that "high current versus LFP versus BMS" thing.

I've been reading this thread, as it's morphed, understanding maybe 1/4 of it:

https://www.trawlerforum.com/forums/s4/alternators-leave-them-alone-forget-about-them-66715.html

And I've also read Rod's treatise about drop-in LFPs here (understanding maybe 1/2 of it):

https://marinehowto.com/drop-in-lifepo4-be-an-educated-consumer/

(With thanks to Rod, and a plug for more donations to his site.)

I think I gather that an LFP solution for high current (thruster) loads is possible. I think I gather that it will depend on the quality of the system, and the quality of the BMS.

If that's close... I'd appreciate it if folks here could point out a few candidate systems that I might start learning about... to see if I really want to mess with the whole idea.

???

-Chris

 

[Jeff F]

But there's that "high current versus LFP versus BMS" thing.

There's the rub. Lithium does fine at short high current bursts. But building safe ways to manage that capability gets expensive.

 

[mvweebles]

Chris - I'm far from an expert here, but my sense is this all comes down to discharge capability and cable run distance. On my boat, I have a 12v thruster and if I remember, a 400 Amp T-fuse. My house bank (600ah) can support that type of discharge but the distance is unacceptably long. I considered going with LFP instead of AGM for a thruster/windlass battery, but would require a much larger/expensive LFP battery than necessary just to get adequate discharge.

I'm starting to see some specialized LFP batteries in the market that have high discharge capabilities but relatively shallow AH ratings used as starting batteries for performance cars and motorcycles and such. Since a thruster has a short usage cycle, I'd imagine there might be an acceptable use case. If my math is correct, the 60AH version of this Anti-Gravity battery would run a thruster for 5-10 mins at least. Weight is 18 lbs and it's tiny- 7"x7"x10" so could be mounted next to the thruster with very short cable runs.

https://antigravitybatteries.com/products/starter-batteries/automotive/ag-h6-rs/

I know I've drifted some from your original question, but I think there may be some barriers to LFP as thruster, at least using traditional thinking snd prevailing LFP formats that focus on high storage/slow discharge.

I'll eagerly await more informed comments. I learn a lot from the TF brain on topics like this.

Peter

 

[DavidM]

What are the current specs for your bow thruster?

David

 

[READY]

I think that possibly the easiest and most bullet proof solution these days is to add LFP just to power the inverter. Charge it from the inverter charger and via a DC-Dc connected to your alternator or of course from shore or genset. Set the DC-DC to limit the charge current so you don't fry your alternator. If you have solar also use this to charge the LFP.

Then use AGM or flooded LA to start and power house and for thruster as you have today. Add a moderate Victron 2 output charger to keep them topped off. It gets its powet from either shore, generator or LFP (via inverter). These are still charged from your alternators as originally designed.

This gives you a lot of flexibility and avoids major changes to the alternator or current battery setup.

Added benefit is you may find you can locate the LFP and inverter very close together so the DC runs are short.

There are one or more threads that discuss this approach.

 

[sunchaser]

Converting the thruster bank to also service inverter loads was the line of least resistance. Works nicely, although we don't have a long-term assessment yet. -Chris

So what you have is working good. Is this a case of wanting something vs needing something? I've no issues with your looking at another reconfiguration. Just be sure that what you need fits with what you want. You'll likely get about 8 years out of your newest setup and it is "working nicely" so -----

 

[ranger58sb]

What are the current specs for your bow thruster?

I think its a Vetus BOWA0902, 185mm tunnel, 24V, 250A, 5.7kW, 4150 RPM, 10 minute rating.

So what you have is working good. Is this a case of wanting something vs needing something? I've no issues with your looking at another reconfiguration. Just be sure that what you need fits with what you want. You'll likely get about 8 years out of your newest setup and it is "working nicely" so -----

Yep, everything now is working well.

So this idea his falls into the "maybe useful to consider" category. No need, not even necessarily want.

But I know I'll have to replace 8Ds in the other two 24V banks eventually (and eventually may be this season)... and could do that for one bank by moving the two new Lifelines on the thruster/inverter circuit... so I thought useful to see if there are alternatives I hadn't considered before.

-Chris

 

[ranger58sb]

I think that possibly the easiest and most bullet proof solution these days is to add LFP just to power the inverter.

Added benefit is you may find you can locate the LFP and inverter very close together so the DC runs are short.

The only easy place for the inverter bank, and the inverter/charger, is where the thruster bank and I/V live now.

If I split the functions, I think I'd need to relocate the thruster bank and then install another charger for it.

At that point, I think the whole idea begins to quickly fall into the "not worth the effort" category.

Which is, BTW, not necessarily a bad thing. I've got in place an improvement over what we started with... and if that's about as good as it gets without a lot of extra pain, so be it.

-Chris

 

[ranger58sb]

Chris - I'm far from an expert here, but my sense is this all comes down to discharge capability and cable run distance. On my boat, I have a 12v thruster and if I remember, a 400 Amp T-fuse. My house bank (600ah) can support that type of discharge but the distance is unacceptably long.

I'll eagerly await more informed comments. I learn a lot from the TF brain on topics like this.

Yep, this is my brain trust, too.

Our original physical architecture has the 24V thruster bank under the cockpit, and it's a bow thruster, so... of course the distance seems overly long, to me. And oddly (also to me), the 24V windlass is on one of the other banks even slightly further away, whereas it seems to me they both could have been serviced by one bank.

But it is what it is... and I've got so many other entries still on my punch list that this one falls into the "do a little light research, just in case" mode.

-Chris

 

[rslifkin]

Would it be possible to downsize the existing banks and split all of the house loads off to a big house/inverter/thruster bank? If you install an ability to start the engines from the house bank, I wouldn't be afraid of having the 2 engines normally share a single start bank (which would free up space to use for the larger house bank).


Depending on where the DC panel feeds are drawn from, it may be easy to move them to wherever you want.

 

[ranger58sb]

IF there might be a LiFePO4 solution suitable for high current loads like a thruster, and IF there might be a suitable BMS to control all that, and IF such a change might not cost bazillions more than a couple of Lifeline 8Ds, and IF said system might fit in the same existing battery bank footprint, and IF said system wouldn't launch our insurance people into orbit, and IF the set-up might be relatively bullet-proof (well, OK, at least relatively reliable)...

I could imagine replacing the current Lifeline thruster batteries with said LFP solution... moving the existing Lifeline 8Ds to one of the other two banks whenever the time comes to replace...

Expanding a bit, my definition of "worth the pain" would be something that satisfies all those IF conditions, isn't too difficult, provides a useful increase in capacity for house loads, and doesn't cost more than about 1.5x the cost of two Lifeline 8Ds. Maybe 2x if the capacity increase is more significant.

Since I don't have a lot of time with the new configuration, I don't really know yet how my (now) existing 255-Ah (or 50% thereof) will relate to our loads.

Remembering that if we need aircon underway, the generator is on. Remembering that if we're cooking, the generator is on... which mostly implies battery charging 2x/day anyway.

There's some guesswork and fiddle space involved...

-Chris

 

[DavidM]

I think its a Vetus BOWA0902, 185mm tunnel, 24V, 250A, 5.7kW, 4150 RPM, 10 minute rating.

-Chris

Battleborn has a 12v 8D with a continuous current rating of 300 amps, 500 for 30 seconds. A pair of these should run your thruster. But the price is $4,600 for the two.

A cheaper alternative, using Will Prowse’s recommended SOK’s is three of their 24v, 100 Ah batteries wired in parallel to get enough output current, since they are rated at 100A continuous each. Three of these are $3,033.

Sure sounds like a bunch of money for something that works ok with your existing batteries.

David

 

[ranger58sb]

Would it be possible to downsize the existing banks and split all of the house loads off to a big house/inverter/thruster bank? If you install an ability to start the engines from the house bank, I wouldn't be afraid of having the 2 engines normally share a single start bank (which would free up space to use for the larger house bank).

Depending on where the DC panel feeds are drawn from, it may be easy to move them to wherever you want.

It may be possible, but I don't think easy or straightfoward. And unfortunately, I haven't yet worked out the energy budget for draws on the other two existing 24V banks.

Also, our physical layout seems a little weird, to me, in a way that would make it more difficult to make many changes.

Imagine the cockpit hatch, entrance to the engine room. Bottom of the ladder, immediately to port, 24V thruster bank (two 8Ds), with inverter/charger above that and further to port. Relatively close to the AC/DC distribution panel, which is portside aft in the saloon. Any additional battery height would impede service access to the other stuff over there...

Bottom of the same ladder, immediately to starboard, 24V port (yep) engine bank (two 8Ds) that services house loads. Additional battery height, ditto.

WAY over to starboard and a bit further aft, yet another 24V engine bank that services the windlass and remaining house loads. (I'll probably be paying a crew of three men, two small boys, and maybe a mule or two, when it comes to replacing that starboard bank.)

Plus all the wiring. Plus the battery equalizers (apparently the name for the thing that provides 12V taps).

Anyway... not uncomplicated... and think significant architectural changes present too steep of an obstacle pile.

I think.

Battleborn has a 12v 8D with a continuous current rating of 300 amps, 500 for 30 seconds. A pair of these should run your thruster. But the price is $4,600 for the two.

A cheaper alternative, using Will Prowse’s recommended SOK’s is three of their 24v, 100 Ah batteries wired in parallel to get enough output current, since they are rated at 100A continuous each. Three of these are $3,033.

Sure sounds like a bunch of money for something that works ok with your existing batteries.

Ummm... yes, that's indeed significant money! And I don't think I'd see 300Ah as all that much of a capacity increase over the 255Ah the pair of Lifelines provides. The Lifelines were about $1600 (installation extra, of course).

Good factoids, very useful, thanks very much!

-Chris

 

[rslifkin]

Imagine the cockpit hatch, entrance to the engine room. Bottom of the ladder, immediately to port, 24V thruster bank (two 8Ds), with inverter/charger above that and further to port. Relatively close to the AC/DC distribution panel, which is portside aft in the saloon. Any additional battery height would impede service access to the other stuff over there...

Bottom of the same ladder, immediately to starboard, 24V port (yep) engine bank (two 8Ds) that services house loads. Additional battery height, ditto.

WAY over to starboard and a bit further aft, yet another 24V engine bank that services the windlass and remaining house loads. (I'll probably be paying a crew of three men, two small boys, and maybe a mule or two, when it comes to replacing that starboard bank.)

That doesn't sound too bad. If you dropped to 1 engine start bank and a bigger house/thruster/inverter bank you'd keep the starboard engine bank and then using the space on both sides of the ladder for the house bank. With no additional space that would give enough footprint to double the current inverter/thruster bank. I'm not sure if that would be enough battery capacity or not though.

 

[Wild Blue]

We run the stern thruster off the LFP Bank without issues. We run the bow thruster off the original two AGMs in the bow area.

We built the LFP bank in the lazarette area near the stern thruster. It seemed redundant to have 400+ lbs for 2 AGM batteries so near the LFP bank. We cabled the thrusters to the LFP bank via 500 amp fuse.

Our LFP bank is 24V 1100A split into 2 banks, controlled by 2 x 550A BMS units. We make sure there are no large draws on the LFP bank when we use the thruster.

We've operated this way for two years with no issues to date.

Alex on Wild Blue

 

[ranger58sb]

We run the stern thruster off the LFP Bank without issues.
We cabled the thrusters to the LFP bank via 500 amp fuse.

Our LFP bank is 24V 1100A split into 2 banks, controlled by 2 x 550A BMS units. We make sure there are no large draws on the LFP bank when we use the thruster.

Thanks. Can you say brands/models, costs?

-Chris

 

[CMS]

This is going to ask for suggestions so I can better do some "what if?" shopping.

Last Summer we re-purposed our thruster bank to also service AC house loads via inverter. The bank is (now) two Lifeline 8D AGMs (1350CCA, 255Ah) in series to 24VDC. The inverter is actually an inverter/charger, Victron MultiPlus 24/3000/70-50/120V.

The goal was to be able to power our AC-only fridges/freezer while underway, make morning coffee or heat Happy Hour hors d'oeuvres, and while we're at it, power some light loads like cell phone chargers -- without the generator. Converting the thruster bank to also service inverter loads was the line of least resistance. Works nicely, although we don't have a long-term assessment yet.

We still anticipate generous genset usage, as when aircon is required and for electric cooking at anchor; I'm not trying to replace that.

The other two 24VDC battery banks on the boat each start an engine and service approximately half of the house/nav DC loads. They came to us with run-of-the-mill batteries (both wet, one bank sealed, one open for watering). I will need to replace those, as time goes on, perhaps even sooner than later... and my intention has been to replace with the same model of Lifeline 8D AGMs that we've put in service for the thruster bank.

I'm getting closer to the question...

IF there might be a LiFePO4 solution suitable for high current loads like a thruster, and IF there might be a suitable BMS to control all that, and IF such a change might not cost bazillions more than a couple of Lifeline 8Ds, and IF said system might fit in the same existing battery bank footprint, and IF said system wouldn't launch our insurance people into orbit, and IF the set-up might be relatively bullet-proof (well, OK, at least relatively reliable)...

I could imagine replacing the current Lifeline thruster batteries with said LFP solution... moving the existing Lifeline 8Ds to one of the other two banks whenever the time comes to replace...

And I'd end up (I think) with even more capacity in the thruster/inverter bank for house loads...

But there's that "high current versus LFP versus BMS" thing.

I've been reading this thread, as it's morphed, understanding maybe 1/4 of it:

https://www.trawlerforum.com/forums/s4/alternators-leave-them-alone-forget-about-them-66715.html

And I've also read Rod's treatise about drop-in LFPs here (understanding maybe 1/2 of it):

https://marinehowto.com/drop-in-lifepo4-be-an-educated-consumer/

(With thanks to Rod, and a plug for more donations to his site.)

I think I gather that an LFP solution for high current (thruster) loads is possible. I think I gather that it will depend on the quality of the system, and the quality of the BMS.

If that's close... I'd appreciate it if folks here could point out a few candidate systems that I might start learning about... to see if I really want to mess with the whole idea.

???

-Chris

At this point you're likely looking at Mastervolt, Lithionics or DIY. For DIY I send all our readers to Current Connected. They sell Rec BMS and raw cells and the owner is not a sheister like far too many in this industry.......

 

[ranger58sb]

At this point you're likely looking at Mastervolt, Lithionics or DIY. For DIY I send all our readers to Current Connected. They sell Rec BMS and raw cells and the owner is not a sheister like far too many in this industry.......

Thanks, Rod. Your article I linked has been especially helpful, too.

That doesn't sound too bad. If you dropped to 1 engine start bank and a bigger house/thruster/inverter bank you'd keep the starboard engine bank and then using the space on both sides of the ladder for the house bank. With no additional space that would give enough footprint to double the current inverter/thruster bank.

Still thinking about this. First reaction is "too hard" (including bridging across the space between the two battery banks to connect them into one)...

But I'll keep chewing on this idea some more...

-Chris

 

[rslifkin]

Still thinking about this. First reaction is "too hard" (including bridging across the space between the two battery banks to connect them into one)...

But I'll keep chewing on this idea some more...

-Chris

You'd definitely have to run a few big cables between the 2 boxes. But it would give a simplicity advantage in using the system, as power (for non engine starting purposes) is then all in one bucket. So there's just the question of "how much power do we currently have available?" and no issues with having plenty of power available for X, but not enough for Y.

 

[Wild Blue]

Thanks. Can you say brands/models, costs?



-Chris

Chris:

House bank MG Energy LiFo 24v X 1120a in 2 banks, 2 X MG Energy BMS

2 X Victron Multiplus 24 v 3000w inverter charger in series

Victron Cerbo GX to monitor system.

Parts cost 2 years ago was $30,000.
DIY install working with ABYC Electrician was $5,000.

Alex

 

[ranger58sb]

Chris:

House bank MG Energy LiFo 24v X 1120a in 2 banks, 2 X MG Energy BMS

2 X Victron Multiplus 24 v 3000w inverter charger in series

Victron Cerbo GX to monitor system.

Parts cost 2 years ago was $30,000.
DIY install working with ABYC Electrician was $5,000.

Alex

Thanks! That cost is sobering...

-Chris

 

[38ark]

I am getting ready to switch over to lithium on my boat. Seriously considering Kilo Vault batteries. 300ah in a 8D sized enclosure. Saw a tear down review on the Panbo site. Looks like great quality at a good price.

 

[ranger58sb]

Thanks to everyone.

I think this idea is DOA for me, but it's been a useful exercise and it preps me nicely for whenever I need to replace another of the two remaining twin-8D 24VDC battery banks.

My thought was to learn in advance whether it'd be practical and cost-effective to replace our dual-purpose thruster/inverter bank with LFP... which could have meant first simply moving our new 8Ds to another bank.

So far, it looks like LFP costs aren't really low enough compared to any expected gain. The Kilo Vault "8D size" prices for example are $2145 (MSRP, so two wired to 24VDC would be in the neighborhood of $4K... for 300-Ah nominal capacity. Compared to approx $1500 for the Lifeline 8Ds and 255-Ah nominal capacity.

Even considering the 80% usable LFP (240-Ah) vs 50% usable AGM (~128-Ah)... the initial $$$ premium isn't all that attractive... given that I'll probably get decent enough life from the Lifelines.

Also, the KV max and continuous discharge limits of 200A doesn't seem to match our potential thruster use.

Then too... our inverter draw isn't really all that huge. Modified by generator ON when we need aircon ON.

My bottom line: when I next need to replace another twin-8D bank, I'll just get another pair of Lifelines and call it good.

-Chris

 

[Jeff F]

Also, the KV max and continuous discharge limits of 200A doesn't seem to match our potential thruster use.

Good conclusions. Lithium is great, but not general purpose in its current form. I'm using AGM starting batteries for thrusters and engine start. Can't imagine substituting LFP for that. Maybe some day, but not soon.

Of course with 48v it gets far easier

 

[ranger58sb]

Thanks to everyone.

I think this idea is DOA for me, but it's been a useful exercise and it preps me nicely for whenever I need to replace another of the two remaining twin-8D 24VDC battery banks.

My thought was to learn in advance whether it'd be practical and cost-effective to replace our dual-purpose thruster/inverter bank with LFP... which could have meant first simply moving our new 8Ds to another bank.

So far, it looks like LFP costs aren't really low enough compared to any expected gain. The Kilo Vault "8D size" prices for example are $2145 (MSRP, so two wired to 24VDC would be in the neighborhood of $4K... for 300-Ah nominal capacity. Compared to approx $1500 for the Lifeline 8Ds and 255-Ah nominal capacity.

Even considering the 80% usable LFP (240-Ah) vs 50% usable AGM (~128-Ah)... the initial $$$ premium isn't all that attractive... given that I'll probably get decent enough life from the Lifelines.

Also, the KV max and continuous discharge limits of 200A doesn't seem to match our potential thruster use.

Then too... our inverter draw isn't really all that huge. Modified by generator ON when we need aircon ON.

My bottom line: when I next need to replace another twin-8D bank, I'll just get another pair of Lifelines and call it good.

-Chris

This turned out to be sooner than I'd hoped. We fired up engines on 3/8... but had to parallel the start banks 'cause it turns out our starboard main bank (dual purpose, start and house) is toast.

Those batteries were Deka 908DTF HD Marine/Commercial 8Ds, sealed flooded lead acid. 1425 CCA, no capacity given. 127-lbs each vs. Lifeline's 156-lb 8Ds. Possibly "maintenance free calcium grid"? and I don't have a definite installation date. Maybe 2/2018. If that date is right, I guess they did OK.

-Chris

 

[ranger58sb]

What are the current specs for your bow thruster?

I think its a Vetus BOWA0902, 185mm tunnel, 24V, 250A, 5.7kW, 4150 RPM, 10 minute rating.

Correction, in case future readers benefit.

Our thruster is a Vetus BOW16024D, 160 kgf, 250mm tunnel.

24VDC, 560A current, 7 kW rated output, 3250 RPM, 4.5 min S2 rating.

The rating is "4.5 min. continuously or max 4.5 min. per hous at 560A (24 Volt.)"

Even higher max current than I'd earlier thought.

-Chris