Replace genset with lithium batteries and a inverter...

[dtfeld]

This was the book I picked up to read up on the various battery chemistries and the design criteria for building them. Not a bad primer.

 

[ttmott]

Sorry for slow response but I cant do a long winded response using my thumbs, had to wait until I had time to get to my desk.
I agree completely with the assumptions about how boat power is utilized and how that does not lend itself to solar based charging. And a very detailed and well thought design obviously. However there are several choices you made that I believe complicate the solution and leads to the additional costs. And that is why I disagree that you need to make any changes to the boats current 12vdc systems.

The first choice was staying with a 12 volt inverter solution and charging using the standard 12v engine alternators.
Any automotive type alternator is not designed for continuous output. They are designed for flooded batteries, that discharge during statrup and then take a high charge for a short period of time and quickly taper off. Standard alternators have the diodes and regulator internal and as they heat up they cut back on output so even a 100A alternator rarely hits full output. This is why your design required Balmer externals to prevent over heating the alternators and burning them out when charging LifePo4 batteries. Also your main disconnect relays isolate the start, alternator & switched loads. This is appropriate for overcharging situations as that is the most damaging to the cells and highest risk of cell thermal runaway. You still have some "un-switched" loads that would not be disconnected on a low voltage disconnect. I assume those would be bilge pumps only. If you have a low or high voltage disconnect you lose all house functions, lights, radios, etc.

Each use case is slightly different as well, and that can drive choices. You have a generator, I never had one. So I am looking at the cost of adding a generator vs battery/inverter. I already changed my FLA battery banks. I have three separate batteries. two marine starting batteries, port independent, starboard engine & emergency bilge pumps, everything else is on a FLA deep cycle Duarcell trolling battery. I already had a three bank AC charger so that was no cost. I added a 1-both-2 battery switch for manual control and a Blue Seas ACR for normal underway charging. I will replace the ACR with a 48v to 12v DC-DC battery charger (Sterling) the manual switch will remain as a backup option if needed. So all my 12vdc systems will stay as they are and have redundant charge capabilities should I have any issues with the LifePo4 batteries/system.

Then as I already described above the inverter is a completely separate system, treated almost like a stand alone generator. The 48v split phase systems are readily available and reduce the size of so many components compared to the high amperage required at 12v. The inverters Mosfets & windings, cables, disconnect switches and relays are all significant smaller, and therefore usually less costly. Then the addition of the PMA/MPPT based charging system is akin to wind or hydro power solutions.

And finally I do plan on prismatic batteries. But have already planned the battery and box arrangement. It will be a bolted pack with separaters of aluminum plates. These plates will be wider than the cells on both sides (fins) The assembly will be inside an aluminum battery box. Ventilation will be included to dissipate heat during charging and to help isolate from engine heat.

Besides Nigel I have also gotten a great deal of marine lithium info form this firm.
http://nordkyndesign.com/category/marine-engineering/electrical/lithium-battery-systems/

In re-reading this I picked up that there is an assumption I don't have a BMS with this system (comment on over/under voltages on the batteries). Actually each battery in this baseline has it's own BMS. The current baseline is the Battle Born GC3 batteries (12V at 270AH) in which each have integral BMS. The down side of the Battle Born product is they have no external monitoring capability so should ABYC requirements for such become a reality these would be non-compliant. The primary reason for separate BMS is fault tolerance and redundancy. It is essential the charge systems maintain the battery banks within the BMS parameters; my selection of Balmar and Victron components considers their historical operational reliability and the consequential reduction in risk. I selected Battle Born simply because of their high current capability rendering my design with ample margin to these limitations.

 

[douglee25]

Our types of boats don't lend themselves to be without a generator; they are not misers' of electricity even sitting at the dock, including the SR mid sized boats.
I have been planning a conversion to lithium Iron Phosphate batteries for over a year. Below are the electrical sketches for the conversion; these drawings have been in review by a marine electrical engineering company for about a year (the pandemic has delayed progress) and there are some changes needed (save review and comment from @RollerCoastr) as well as the installation drawings to be done but the general configuration is correct. This system has over 1000 amp hours of battery storage with 800 amp hours useable for boat systems and a reserve of 100 amp hours for engine starting which establishes a maximum depth of discharge of 90 percent; this will keep battery life at around 5000 cycles which will yield a minimum 15 years of service. The primary intent is to size the battery bank and inverters to enable the boat's systems (AC and DC) including air conditioning to operate nominally without generator through the night. Even with this size of a system the generator will still be needed more frequently in specific load situations like AC running and making water or hot water heater heater operating; the battery bank will deplete faster than the over night requirement. As you can see the inverters can provide a continuous 10KW which is about what the generator or shorepower supplies nominally as a peak for this boat's summertime loads here in Florida. When the battery bank reaches a depth of discharge of 80 percent (that 100 amp hours still reserved for engine start) I have an Automatic Generator Start system that brings the generator on line to recharge the battery bank then the genset shuts back down. The great thing about the lithium batteries is they can be charged as fast as the charger can pump current to them plus they have virtually no absorption phase so the generator run time is reduced significantly. Typically on a 10 day trip on my boat the generator runs 18 hours per day so that is 180 hours which is about 360 gallons of diesel. Now with the batteries as the primary AC power provider then generator is pretty much there to charge the batteries and it's run time is reduced to provide the 800 amp hours to the batteries which if the boat's systems deplete three times a day that is 2400 amp hours needed from the generator. The system is designed to provide 300 amps of charge current during the charge cycle so consequently the generator needs only to run 8 hours instead of 18 hours and the boat's systems know no difference. That is a savings of 200 gallons of diesel for the 10 day trip not to mention the quite nights of sleep which is the main reason for the modifications. This doesn't include the contribution the boat's engine alternators provide to the charge cycles or when we are at a marina and plugged in; we typically don't stay in any one location for more than a day so the genset actually runs even much less over the 10 day trip.
You may ask how does this provide 240 volts that the AC systems require? These inverters can be setup to operate in split phase; they provide 120 volts 180 degrees out of phase so voltage across the two inverters is the desired 240 volts.
Regarding photo-voltaic solar panels - Our boats simply don't have enough unused acreage to install solar panels that would make a difference in comparison to the demand on the batteries from the boat's systems. The cost trade on my boat showed overwhelmingly no justifiable investment return on the solar panels. It was like peeing in the ocean....
Anyway, the investment and scope to change to a system like this is huge and pretty much every system in the boat requires modifications, large modifications. Just to give you an idea this modification will be between $25K and $30K with me doing the installation..... This is scalable for your boat so you can get an idea of the scope and investment.
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So 200 gallons on one 10 day trip/year is roughly $1000 bucks. That's a 30 year payback? 2 trips per year is a 15 year payback. How is that worth it?

 

[ttmott]

So 200 gallons on one 10 day trip/year is roughly $1000 bucks. That's a 30 year payback? 2 trips per year is a 15 year payback. How is that worth it?

It's not. Neither was the addition of an extensive NMEA 2000 network or sixteen inch MFDs or a watermaker, or Stidd helm seats or massive audio system or a hundred other things I've done..... It's more about the challenge to do something that crosses the line for me. Heck, I bought a sewing machine to learn upholstery and canvas. And this challenge is to operate the boat in the tropics through the night without a generator running... The fuel savings is an ah ha. This for the most part not about the investment.... It's a boat and It's play money right?

 

[douglee25]

It's not. Neither was the addition of an extensive NMEA 2000 network or sixteen inch MFDs or a watermaker, or Stidd helm seats or massive audio system..... It's more about the challenge to do something that crosses the line. And the challenge is to operate the boat in the tropics through the night without a generator running... The fuel savings is an ah ha this for the most part not about the investment.... It's a boat and It's play money right?

I suppose. On your size boat, is the generator sound even that noticeable?

 

[ttmott]

I suppose. On your size boat, is the generator sound even that noticeable?

It can definitely be heard but not annoying. It's just that mechanical engine running all night that I'd like to try and eliminate. If you have ever been on a boat anchored in the Abaco on a starry calm night you understand.

 

[douglee25]

If you have ever been on a boat anchored in the Abaco on a starry calm night you understand.

Well I can definitely say I haven't had that opportunity yet. I can see the draw.

 

[ttmott]

For my purposes, I have a stand alone inverter system that is not intended to be charged by the main propulsion engines. All current taken from and returned to the batteries would be via the inverter/charger using AC power from the generator or shore power. Also, this systems is not mission critical.

Here is the article from Battle Born. They used a MS2012 (2000 W) where mine is a 2812 (2800 W), but the general principles apply.

--> https://battlebornbatteries.com/can-use-magnum-ms2012-lifepo4-battery-bank/

I'd need 4 100Ah units to get full rated power out of the inverter and not exceed the BMS limits. The newer 270Ah versions are getting close at a 300A continuous load, but full power on this inverter is 373A. I'd still need 2.

Economics just don't work...yet.

Dave - can you adjust the bulk charge voltage on that Mangum? I remember when you installed that BTW. 14.4V is too high and leaves too little margin up against the BMS. You really need 14.1 or 14.2 max. Also the absorption phase needs to be changed to 10 minutes to get out from under the excessive time to float. In looking at your existing Inverter/charger I suspect it will need to be changed if going to Li in order to reduce risk and get the most out of the batteries.
Victron is the right path but be careful; take that step and you will get sucked in to their cool product lines, can't get enough... Garmin sucked me in and Maretron sucked me in.... And now Victron has me by the short hairs.

 

[hughespat57]

In re-reading this I picked up that there is an assumption I don't have a BMS with this system (comment on over/under voltages on the batteries). Actually each battery in this baseline has it's own BMS. The current baseline is the Battle Born GC3 batteries (12V at 270AH) in which each have integral BMS. The down side of the Battle Born product is they have no external monitoring capability so should ABYC requirements for such become a reality these would be non-compliant. The primary reason for separate BMS is fault tolerance and redundancy. It is essential the charge systems maintain the battery banks within the BMS parameters; my selection of Balmar and Victron components considers their historical operational reliability and the consequential reduction in risk. I selected Battle Born simply because of their high current capability rendering my design with ample margin to these limitations.

You posted more details while I was drafting my post...
But I was assuming somewhere in the Victron components the BMS/monitoring would control the master disconnect solenoids.
This whole thread shows how much detail is in a Lithium system, and the devil is in the details to getting a successful system.

 

[hughespat57]

Do not underestimate the 12 volt requirement. In my boat they do not make a marine DC to DC converter large enough to accommodate the loads especially when you factor in the windlass and hungry audio system; I would have to split up the systems and have multiple converters - not realistic for my baseline.... To convert my QSM11's to 24 volts isn't trivial either with Cummins spec DC to DC converters and the starters it became apparent early in the process to stick with 12 volts. So I did consider 24 volt and even 48 volt DC based systems but the trade landed me back on 12 volts. Secondly, there is a loss of redundancy at 24 and 48 volts when you install batteries in series; should one trip on a BMS fault then you loose everything in that serial chain. Where batteries are in parallel a BMS trip event only takes out that battery; this is important to me. So, in my case on this 52DB having larger wiring and components was far less expensive and intrusive than converting to voltages other than 12 volts. Now on a 58DB where the base system is 24 volts then it's a "no brainer".

Very true which is a reason I decided to keep a 12v FLA as the primary source for 12v DC power. The FLA deep cycle will act as the buffer for those high current/short duration loads like a windlass. The FLA can easily take those hits and go down to a Partial State Of Charge. Then the DC/DC charger at about 40A will bring it back up over the next hour or so.

 

[dtfeld]

Dave - can you adjust the bulk charge voltage on that Mangum? I remember when you installed that BTW. 14.4V is too high and leaves too little margin up against the BMS. You really need 14.1 or 14.2 max. Also the absorption phase needs to be changed to 10 minutes to get out from under the excessive time to float. In looking at your existing Inverter/charger I suspect it will need to be changed if going to Li in order to reduce risk and get the most out of the batteries.
Victron is the right path but be careful; take that step and you will get sucked in to their cool product lines, can't get enough... Garmin sucked me in and Maretron sucked me in.... And now Victron has me by the short hairs.

Yes, all of the charge parameters can be adjusted (along with a slew of other parameters, including a battery monitor and AGS system. You will need to install the advanced remote. It’s inexpensive, and gives you access to all sorts of parameters. There are a good number of advanced battery chemistry presets, (2 for AGM). Magnum added a lithium preset to these inverter chargers although I would assume you will still need to adjust tweak to match the recommendations of what ever battery you are using. Not sure I can update my old beast.

It’s a great inverter/charger. My only complaint is that the way I wired it, isn’t as clean or optimal os the Victron, but it is very functional. Price was right.

I’m going to add the Battery Monitor when I install the old AGMs as a separate battery source and see what functionality that add and if it will be useful for lithium.

 

[ttmott]

You posted more details while I was drafting my post...
But I was assuming somewhere in the Victron components the BMS/monitoring would control the master disconnect solenoids.
This whole thread shows how much detail is in a Lithium system, and the devil is in the details to getting a successful system.

The Victron components control source AC power including Generator start, stop, battery charge profile, and systems monitor/alarm; it does not support any battery protection (BMS) functions.
Yes you are exactly right - the devil is in the details.... Hence my year long trek on education, paying my electrical engineering staff for development and load analysis, and paying an outside marine engineering firm to support. This stuff is not for the weekend hack....

 

[dtfeld]

Tom, just curious why switching existing wiring/systems to lithium as opposed to just adding a large stand alone bank/system. Seems like a lot of work and expense compared to just a add on system.

I've thought about dumping the generator, and go with a 12/24v inverter system to run the coffee/ microwave, but swap out the Air Conditioning units to DC. Power consumption is a lot more reasonable using what I assume are variable speed compressors/fans.

Either way It's a lot of engineering, planning and above all...EXPENSE!

 

[ttmott]

Tom, just curious why switching existing wiring/systems to lithium as opposed to just adding a large stand alone bank/system. Seems like a lot of work and expense compared to just a add on system.

I've thought about dumping the generator, and go with a 12/24v inverter system to run the coffee/ microwave, but swap out the Air Conditioning units to DC. Power consumption is a lot more reasonable using what I assume are variable speed compressors/fans.

Either way It's a lot of engineering, planning and above all...EXPENSE!

First it's all about useable energy density over volume and weight. To get the amount of energy to fully operate the boat in the summer over a 6 or 8 hour period isn't insignificant. Secondly, to replenish that energy into the storage system within several hours at most is important. Only the lithium technology solves these two requirements. For example to get 1000 AH of useable energy from lead acid is over 1600 AH battery rated. That, for example, is eight 8D batteries at 120 pounds each vs. four of these at 81 pounds each - https://battlebornbatteries.com/product/270ah-12v-lifepo4-deep-cycle-gc3-battery/
To charge such a lead acid bank would be 10 plus hours vs the lithium bank less than 4 hours.
Yes it is a lot of effort and expense but it's a technology leap and a cool project that will make boating much more pleasant and comfortable. Another thing is it automates and integrates the boat's electrical systems so if on shore power the system automatically configures to shore power or if shore power is removed it configures to battery power while sheading unnecessary loads then automatically when the battery bank depletes to a given level the generator comes on line to recharge the bank then shuts back down.
Regarding DC HVAC units; energy is energy. BTU's to cool are Watts and Watts are amps; it doesn't matter wither AC or DC it's the same amount of energy..... Regardless if you have one inverter for all of the boat's systems or individual inverters like on a DC HVAC unit you will still have losses due to the inverting process so for the most part a wash. The big difference is the DC cabling going to the HVAC unit gets significantly larger...

 

[jmauld]

Amazon has some cheap lifepo4 options if anyone is brave enough to try them. I’m not there yet.
https://smile.amazon.com/gp/product/B0949CJ8VY?

 

[PlayDate]

I think you guys scared the OP off with the pros/cons of electrical science.

Perhaps we should have found out what was wrong with his generator?

 

[jmauld]

"Dark Event" - Let's say as in my design something in one of the inverters takes the battery bank out of specification and all of the BMS' shut down the entire battery bank. The boat will go dark which is bad, hugely bad. No Nav, no engines, no lights, no nothing.... In my configuration even the generator which is started by a lead acid battery will shut down. Can you imagine being in an inlet and loose all control of the boat? It is a significant risk in my design that needs to be addressed; the engineering firm helping me on the design wants an AGM battery in parallel with the Lithium batteries so should the BMS take out the lithium batteries from the circuit the AGM is still there to pick up the pace. The AGM will not be adversely affected with the lithium charge profile and at most the peak charge voltage needs to be lowered a bit in the lithium profile. What is interesting is the AGM if the system is operating nominally will never go through a discharge cycle because the lithium voltages are flat through most of discharge cycle and consequently when the lithiums require charge the AGM is never in the charge required range. The AGM if the system operates nominally through the lifecycle will be good for 10 to 15 years; it's never gone through a discharge cycle.... I'm still a bit "bullheaded" and challenging the engineers to find another solution to completely move away from lead acid but in reality I'll probably loose that battle....
Battling Alternators - When alternators in a duel engine configuration are combined to charge a single battery they tend to battle for charging and inevitably voltage and current becomes erratic. Individual charge controllers will not solve the situation. If voltage swings become increasing events then the chance to trip a lithium battery BMS increases and back to the Dark Event. To rectify this an alternator balancing device needs to be installed between the charge controllers. Balmar makes exactly that and is called a "Center Fielder". This will be added to my configuration.

Capacity Loss - Let's say one of the Lithium batteries in my system faults and goes off line, how would I know as the system is programmed for a given total capacity? Right now without BMS data output I don't know and this is a real risk situation. The only way I would know is the generator is cycling on and off more frequently. This requires visibility and a solution.

The message here is this is a path of discovery for me to do this right both for reliability and safety. I thought I would pass along some of the more relevant things needed to go down this great technology.

Have you made any updates to these schematics recently? Have you considered splitting your single 10 battery bank into two 5 battery banks? I think that would address some of the issues that you cover above, ie going completely dark, and the competing alternators. On your battery bank, you have +12 and -12. Is that a 24 V system, or should the -12 be 0 V? Also, I think you want to make the following change to your bank wiring, so that each individual battery pack is drained equally?

 

[jmauld]

One other question. What do you think about leaving each engine battery as a single AGM battery, and instead swap the generator battery to a large lithium bank that could be used to power all of your dc loads and your inverters.

DC - DC converters could be used to charge the large bank while the drive engines are running.

 

[ttmott]

Have you made any updates to these schematics recently? Have you considered splitting your single 10 battery bank into two 5 battery banks? I think that would address some of the issues that you cover above, ie going completely dark, and the competing alternators. On your battery bank, you have +12 and -12. Is that a 24 V system, or should the -12 be 0 V? Also, I think you want to make the following change to your bank wiring, so that each individual battery pack is drained equally?

Yes they have made quite a few changes.
The control system is now a Victron Cerbo GX
The batteries are now five Battle Born GC3's
The batteries are individually cabled with equal length wires to a positive battery buss and a negative battery buss.
The engine Alternators are now balanced using a Balmar Centerfielder in conjunction with Balmar regulators.
I still think the configuration is suitable for engine starting but the engineers think differently; more to follow on this.
A quick sketch of the revised battery config.

 

[jmauld]

Have they told you why they don’t think it’s suitable for engine starting? Is it because, even though you have redundancy, it’s not diverse. So if there is an event that activates one BMS, it will activate all of them. Since they are electronic, they are susceptible to more failures than a pure AGM starter system that has no electronics built into it. With electronics, you also have to consider failures such as an EMC (VHF, Radar, cell phone, microwave) signal taking out the BMS circuitry.

Did you see my follow-up question about leaving the drive engines as a lead-acid/AGM system and then building the alternator bank into a large capacity house bank?

Another thing that I’ve noticed is that not all of the 120 Vac powered Victron equipment carries US safety certification marks. They do meet European requirements, but those requirements don’t always carry over nicely to the US. And they aren’t recognized by US inspectors or during an insurance claim.