Small Boat Electrical for Sail

[rgleason]

After some reading and figuring, it appears likely that a Lifepo bank of 250-300ah will cost at least $3K plus the cost of the BMS, monitoring, switches and other devices.

This is almost the same cost as methane fuel cell, Efoy140ah, but the batteries with a new Alternator (not included in the cost) will charge faster. Also the lifepo batteries are a better match with solar than FPA because they are more efficient and not wasting sunpower, across the entire state of charge, unlike FPA above 80%SoC.

This 3-5 year update is a good case example for Lithium Batteries. The battery temperature and BMS temperature all make a difference. If you are going to charge Lithium fast (too fast is not good for longevity) pay attention to heat as well.

I've been looking into various lithium battery systems, some with BMS and some without,my conclusion is that lithium definitely not inexpensive and the evaluation must account for some loss of capacity greater than the optimistic projections.

[john61ct]

Originally Posted by rgleason

After some reading and figuring, it appears likely that a Lifepo bank of 250-300ah will cost at least $3K plus the cost of the BMS, monitoring, switches and other devices.

Absolutely, was that not plain from the beginning?

But perhaps lower outside the NA market, where lead is also a lot pricier.

> This is almost the same cost as methane fuel cell, Efoy140ah

I didn't realize their fuel was methane. Have you found readily available sources where you plan to sail? Easy enough you won't need a whole 'nother redundant system to back it up?

> but the batteries with a new Alternator (not included in the cost) will charge faster

I'm confused. The Efoy dies not get charged does it? It is a charge source you have to buy fuel for like a genset right?

> Also the lifepo batteries are a better match with solar than FPA because they are more efficient and not wasting sunpower, across the entire state of charge, unlike FPA above 80%SoC.

Sorry what the heck is FPA now?

If you mean FLA (wet cell, needs watering) are you just comparing to LFP as we've done so much recently in other threads? Any relationship between that and the fuel cell approach? Comparing the fuel cell to an alternator?

> I've been looking into various lithium battery systems, some with BMS and some without,my conclusion is that lithium definitely not inexpensive and the evaluation must account for some loss of capacity greater than the optimistic projections.

Not sure about the last part. You mean the extra- speculative estimates greater than (what I call lowball) vendor ratings? Or do you think the vendor ratings at say 2000 cycles are in themselves optimistic?

[john61ct]

I hope you don't take Technomadia as a technical resource.

The huge impact high temps have on longevity were very well documented in the very "mother thread" he cites, as well as the importance of No Float and avoiding the shoulders.

> We’ve spent the past year using 14.2V bulk charging, and a 13.55V float. I’ll probably soon change to even lower – 14.0V bulk and 13.4V or even 13.2V float

Closing the barn doors after the horse got out.

[rgleason]

Absolutely, was that not plain from the beginning?

• Yes, but there are some budget limits here. It is just 32'

> This is almost the same cost as methane fuel cell, Efoy140ah

I didn't realize their fuel was methane. Have you found readily available sources where you plan to sail? Easy enough you won't need a whole 'nother redundant system to back it up?

• It is available, and you can stow enough of it for distances.

> but the batteries with a new Alternator (not included in the cost) will charge faster

• - I was considering the various options and total cost.
• Relocate batteries to cabin, rewire, change to Lithium $3500 anyway
• New Alternator and Serpentine $1200
• Efoy 140 $4200

I'm confused. The Efoy dies not get charged does it? No it does not get charged. It does need a little electricity. It is a charge source you have to buy fuel for like a genset right? Yes.

> Also the lifepo batteries are a better match with solar than FPA because they are more efficient and not wasting sunpower, across the entire state of charge, unlike FPA (Yes FLA, typing to fast I guess) above 80%SoC.

Sorry what the heck is FPA now?

• (FLA, sorry)

If you mean FLA (wet cell, needs watering) are you just comparing to LFP as we've done so much recently in other threads? Any relationship between that and the fuel cell approach? Comparing the fuel cell to an alternator?

• --Well that might be a very good point. What is the efficiency of FLA from 85%-%100? Those amps are going to be created by the Efoy. How many amps are really required to get to 100%, that are just being wasted as heat? You guys would have a better handle on that than me, but it's going to take the Efoy longer and use more fuel!

> I've been looking into various lithium battery systems, some with BMS and some without,my conclusion is that lithium definitely not inexpensive and the evaluation must account for some loss of capacity greater than the optimistic projections.

Not sure about the last part. You mean the extra- speculative estimates greater than (what I call lowball) vendor ratings? Or do you think the vendor ratings at say 2000 cycles are in themselves optimistic?

• --I think the location, conditions and user are factors which may affect the longevity of this high initial cost power storage, so keep your expectations in check!

[rgleason]

@ John61ct
What manuf & size Lifepo batteries?
What BMS? Does it do Top balencing? Bottom Balancing?
Your use:

• Bulk Charge 14.2v (3.55v/cell)
• Float 13.55v (3.39v/cell) -To cover active house loads? how long?
• "Case C. bring it up to 13.75V and Just Stop (no Absorb) -Daily use 98%Soc.
• "Case D. bring it up to 13.8V & Absorb until endAmps 12A reached"

Saw the above from another thread (I hope you were speaking of lifepo!).
Low Voltage warning?
Low Voltage disconnect?
Charge source when floating? Solar?
Would you prefer not to float?
What is your normal alternator charge amperage? or %C?
Does your alternator charge into an FLA and then combine to lifepo to charge and avoid issues with LVD frying alt diodes? or is the field wire disconnected by the BMS?
Comment - Lithionics setpoints: not below 2.4v and not above 3.65v.

Over-discharge thread

• Total Ah drawn is a a good metric, instead of # cycles, relative to depth of discharge/charge.
• Bottom balanced series strings - avoid creating dead cells, downtime.
• Top balanced series strings - avoid cell overcharge, charge weaker cells.
• Cell monitoring -voltage differential, etc.
• Active balancing at all SOC stages - ABMS from REC.

Practical (Catnewbee)
Stay between 3.0V (~4% SOC at 0.2C), and 3.45V or 3.50V (~89-92% SOC at 0.2C) may be close to optimal for having 80%C left in 7-10 years.
- So useful capacity is about 86% of manufacturers label and declines over 7-10 years.

It appears many are de-rating lifepo capacity to get longer use. What is the anticipated total ah drawn, or cycles or years of use expected past the manufacturer's stated cycles?

Mainesail is interested studies for charging to 4.0v/cell or 3.8v/cell (without using float), which tends to reduce lifepo capacity particularly as the setpoints move away from the shoulders.

[rgleason]

Comment - Lithionics setpoints: not below 2.4v or damage.
Start charging at 3.2v and do not go above 3.65v.

[john61ct]

Sorry rg but I am just lost here.

I can't distinguish between what you are stating you believe to be true, what you are just summarizing from others' posts, seem to be claiming I said thing I know I didn't, using terminology in not standard ways,

all mixed up.

So maybe ask one question at a time?

[rgleason]

Victronics BMS setpoints
HVC >=3.9v high voltage cutoff
AGR 3.1v trigger to run generator which must start within 20 sec.
RVC 3.0v per cell or 90% discharge. The battery will shutoff
LVC <=2.55v low voltage cutoff

Lithionics
Do not go above 3.65v.
Start charging at 3.2v
Not below 2.4v or damage.

Catnewbee
BMS ABMS
Batteries Manuf, Type, Capacity?
HVC 3.45v or 3.50v (~89-92% SOC at 0.2C)
LVC 3.0v (~4% SOC at 0.2C)

@John61ct
Do you have Lifepo4 batteries or not? If so,
What manuf & size Lifepo batteries?
What BMS? Does it do Top balancing? Bottom Balancing?
HVC?
- "Case C. bring it up to 13.75v (no Absorb) -Daily use
- "Case D. bring it up to 13.8v & Absorb until endAmps 12A reached"
- Float 13.55v (3.39v/cell)
AGR?
RVC?
LVC?
Is your field wire disconnected by the BMS or do you use a FLA battery?

[rgleason]

VSR Alternator Regulator Al Thompson has a post about Lifepo settings.
Revised default CPE #8, better optimized for LiFePO4 batteries
"LiFePO4 batteries share a lot in common, but there seems to be some slight variances with some manufactures... charge them to 95% and stopping makes them happiest " (Well, he adjusted it down to 90% below)

With that, here is the new default CPE #8 for LiFePO4 batteries. Remember, these are for a 'normalized' 12v / 500Ah battery.

• Bulk / Acceptance Vmax: 14.0v (3.5v per cell)
• Acceptance Termination: 14.0v & Amps < 50a (C/10, Stops at about 90% SOC))
• Float: Max VBat: 13.36v (3.34v per cell)
• Float: Max Amps: 0A (This is new, see below)
• Resume Charge at: 13.3v (Resume when battery reaches SOC 10% based on Vbat or .... ) (3.25v per cell)
• Resume Charge at: -50Ah (Resume when 10% of battery capacity has been removed)

Charging will stop at a very conservative 14.0v.

Not only is this withing the range that may give good battery life, it is well below most HVC limits for BMS systems, reducing the risk of a battery disconnect happening in a non-integrated system. How to handle the hold, or 'float' state is a bit different. Two new capabilites have been added:

1. The ability to regulate Amps into the battery during Float.
2. An exit float criteria based on Ahs that have been removed from the battery.

First, to allow house loads to be carries by the Alternator we can not shut it down when the battery is fully charged. However, there is little know about doing slow trickle charges into a LiFePO4 battery during traditional voltage based 'floats', so a new capability has been enabled: managing the number of Amps placed into the battery during Float. By setting this parameter = 0 for LiFePO4 batters we assure that no additional energy is pushed into a 'fully charged' battery, but at the same time allow the alternator to carry house loads. The Float Voltage of 13.36 is actually a backup, and it may need to be adjusted if in your installation it is to restrictive and you see current flowing out of your battery.

Another new capability that has been enabled is a mini SOC meter: Once we decide the battery is fully charged, the regulator will monitor any amperage draw from the battery - counting the total number of Ahs.

This regulator seems to be much more flexible than Balmar's
It also is getting a phone App.

[rgleason]

Demo Lithium Battery System Comparison to AGM

"If you go for the compact Lithium system and discharge them 80% they end up being 37% more expensive. If you go for long life and discharge them 50% they end up being only 2.5% more expensive. In each case of course the Lithium batteries have a higher up front cost."
"Performance: The weight will be from 50-75% of a comparable AGM bank and the Volume reduction is comparable also. Speed of charge and discharge is vastly increased, the voltage output of Lithium when used as described will always be 12.5 volts or above."
----

These characteristics also work efficiently and well with various charge sources like alternators, solar PV and the quiet Efoy cell fuel charger.

Performance characteristics is why a non-liveaboard, moored or anchored boat without frequent access to shorepower, would use Lifepo. These batteries could be the answer to life without a shorepower charger or engine running all day.

The voltage stays quite constant over the range of state of charge compared to FLA, for this reason it is more difficult to determine state of charge from voltage. However voltage drops quickly and noticeably as the SoC gets to the end. These characteristics are good for motors and nav equipment operation.
Additionally, they can be charged quickly and efficiently at .5C, (double the FLP rate), reducing engine hours and fuel costs and they provide higher discharge rates, if needed. Compare that to a .25C charge rate for FLA. They do not have the long (4-8 hr) charging tail like FLA, which is bad for engines. Indeed they prefer not being fully charged to 100%, and resting not fully charged, which is compatible with most cruiser's use.
Victron on efficiency:

• The round trip energy efficiency (discharge from 100% to 0% and back to 100% charged) of the average leadacid battery is 80%.
• The round trip energy efficiency of a LFP battery is 92%.
• The charge process of lead-acid batteries becomes particularly inefficient when the 80% state of charge has been reached, resulting in efficiencies of 50% or even less in solar systems where several days of reserve energy is required (battery operating in 70% to 100% charged state).
• In contrast, a LFP battery will still achieve 90% efficiency under shallow discharge conditions.
• Additionally they save up to 70% in space Saves up to 70% in weight

However, Lifepo need a special Battery Management Systems to protect them from damage:

• LVD -Low Voltage Disconnect - Shut down the load whenever the voltage of a battery cell decreases to less than 2,5V.
• HVD- High Voltage Disconnect (make sure the alternator diodes are protected) - Stop the charging process whenever the voltage of a battery cell increases to more than 4,2V.
• Maintain the balance of each cell (Top & bottom balancing are being discussed)
• Shut down the system whenever the temperature of a cell exceeds 50°C.
• Some BMS will disconnect the field wire to the alternator to prevent diodes from failing, before shutting down the load.

There are a number of BMS available at a reasonable price, but the entire electrical system should be designed to work together properly, this is often a hurdle for the DIY.
When to use which battery type?

https://www.victronenergy.com/blog/2...um-ion-vs-agm/
...it is reasonable to say that an AGM battery will need to be twice the Ah rating of a Lithium one.
High rate charging will.. not substantially reduce the charging time of a lead-acid technology battery. Charging the last 20% (and 25%) of a lead acid technology battery is always slow and inefficient compared to Lithium. Increased fuel costs (whatever charge source), charge times, engine hours.
Lithium batteries can be charged at 0.5C until almost full. Simple. Lithium costs about 3.5x more than AGM, and they last considerably longer with proper care. They are 1/4 of the weight of AGM and are well suited for high loads. They will charge faster and more efficiently.

Sizing your Lithium Ion Bank

What is the biggest load and how much discharge is acceptable?
Battery Max. continuous discharge rating must be greater than the boats max continuous loads.

For our boat, max continuous load is 13.2a or 158watts. This is easily met.
Refrigerator 5.5a + Autopilot 3a + Chartplotter .8a + radar 1.67a + instruments 0.5a + ais 0.6a + vhf 1a + navlights 0.13a

80%DoD=2500 cycles
70%DoD=3000 cycles
50%DoD =5000 cycles

How many cycles a year does your battery see, assuming good care, 1 day's capacity & 80%DoD?
Weekend cruiser= 40 days --> 62 years
Summer liveaboard = 3 months = 90 cycles --> 27 years
Yearly liveaboard= 365 cycles --> 6.85 years

Lifepo makes more sense for year round Liveaboards, but the good discharge and charge characteristics may be very meaningful to others who are on board less frequently.

For our boat:

• For discharge cycle, we will select 80%DoD 2500 cycles.
• Daily load at sea 140ah/day and cruise-anchor 85ah/day (see previous post)
  
• Capacity: We need about two days at Cruise-Anchor or 170ah, so considering cycling from 0.2SoC to .95SoC, we would need 170ah/.75 = 227ah of Lifepo.
• Charging at .4C x 170 = 90 amps with a new 120amp Balmar
• Charging 170ah at 90awill take 2 hours, or 1hr/day.
  
• At sea, bump charge rate to .5C (recommended) or 112 amps to charge in 1.5 hrs
• It might be a good idea to get a slightly bigger alternator perhaps..
  
• Adding 100 watts of solar on the dodger will add 33 amps/day
  

Two 100ah batteries would work or even three 75ah (225ah) would work.

The height under the port cabin seat is limited. Allowing for a 12" wide battery, we would need less than 9" height. This is in the bay closest to the battery. The next bay is 24" further away from the engine, but it will have a little more height.

[rgleason]

For a 3P4S (I think it is labeled wrong in the image!!) LiFePo4 cells is this the correct wiring pattern?
Two alternatives shown, one is just 7"x 24" and the other is 14" x 12" and both are 7" high.

[rgleason]

Suggested LiFePo charge routines gathered from discussion. Per 3.2v cell.

Max charge voltage 3.65v
Range of "knee wall" Max 3.45v
Range of "knee wall" Min 2.9v
Voltage drop after charging 0.1v
Float voltage 3.2v. -note some say don't float. Some liveaboards float at 3.3v-3.32v at the terminals.
Discharge cutoff voltage 2.5v
For greater than 2500 cycles charge to only 3.45v

This is my understanding so far.
When the LiFePo4 curve is so flat and you are defining upper and lower limits with very small differences in voltage measurements it becomes very very important to have good connections and measuring equipment or you will damage the batteries. AH counters are also used by charging to the upper voltage 3.45v/cell resetting counter and counting down.

This is not a set it and forget it system. Nor are FLA either.

[rgleason]

Why LiFePo4 batteries? Sizing an alternator for LiFePo.

• Do not require recharge at 50% State of Charge like FLA lead acid.
• Do not have a very very long (3-5 hour) tail charge to get to 100%SoC like lead acid.
• Do not require frequent charge to 100% State of Charge to prevent sulfation and dramatically reduced capacity and cycles (very difficult & impractical with FLA charging wiith Alternator/Engine with no shore power).
• Do not sulfate like lead acid, and thus do not require equalization, time and energy to recover lost capacity (equalize FLA is almost impossible without shore power charging).
• Usable capacity is about 100- 95% of manufacturer capacity, unlike lead acid.
• LiFePo4 bank can be approximately 1/2 the size & weight with same capacity or you can get almost double the capacity of your current Lead Acid bank.
• The voltage stays nearly constant across the full state of charge at about 13.6-13.7v, not 12.8 and below as with lead acid, so equipment runs better.
• 2000-2500 cycles, far better than lead acid.
• Low charge and discharge resistance, so they charge very easily and quickly, with no long tail charge and increasing resistance and reduced efficiency (CEF).
• The acceptance ratings vary a little by manufacturer but 1C is perfectly ok, some say 3C and 0.4C is good
• Best to have them somewhat discharged (during storage .3C-.6C) which is how we use batteries anyway
• Best not to "float charge" to prevent easy overcharging and damage. For example: Once charged to 100%SoC, shut off the charger or alternator or set float voltage quite low (eg. 13.2a, verify with manuf.)
• Do not charge above their capacity or they are damaged (LA is more forgiving about this).
• Do not fully discharge them or they will be damaged.
• Use a BMS Battery Management System to control charging and loads. Victron appears to the be the most comprehensive and commercially engineered BMS.
• LiFePo4 system requires rethinking the entire system and some rewiring and better controls for charging and loads.
• LiFePo4 system installation is more expensive, but with good care will perform better and last longer, and considering the # of cycles will be less expensive. With a long use period these batteries are not a frequent maintenance replacement.
• Particularly good for liveaboards, cruising off a mooring with no shore power, solar works well as a charge source, but is not necessary as in FLA.
• DIYer's are installing, I am trying to learn about it.

So if you were to change to LifePo4 later, I think you'd want to install a bigger Alternator with a serpentine belt.

• For example: 200ah x .4C charge rate = 80a and 300ah x .4C charge rate= 120a
• Both of these configurations will charge to 100%SoC in 2-2.5 hours and provide about double the ah as compared to lead.
• Best to get a bigger alternator and drop the top output amps down with Belt load Manager, so it will run cooler and last longer.
• Best to fit a large case alternator, rather than the Series 6, as they run big loads cooler with better air flow.
• Best to use Balmar MC614 Regulator with sense leads wired properly at the batteries and specially user programmed for the batteries in accord with the battery manufacturer settings. Or VSR Alternator Regulator
• Best to include alt and batt temp sensors for protection.
• Balmar compact Series 6 is has dual fans front and back which vent in the middle. It is well built, but is more compact and thus is medium duty compared to the large case Balmar. Other marine manufacturers are similar.
• See MaineSail's LiFePo4 chart attached.

This change to the alternator is pretty expensive, but would prepare for the next generation of batteries. So as long as you are installing the serpentine, I'd seriously consider a Large Case Alternator on belt manager to reduce output.
Battery x Accptance with Belt Manager
200ah x .4C = 80ah ---> 100-120ah
300ah x .4C = 120ah ---> 140-160ah
400ah x .4C = 160ah ---> 180-200ah
600ah x .4C = 240ah ---> 260-280ah Not available. Drop down to .3C charging.
600ah x .3C = 180ah ---> 200-220ah
For usable Ah, LiFePo4 capacity can be almost half and have the same capacity.

Note that AGM batteries and FireFly have midpoint characteristics between FLA and LiFePo4.


MaineSail LiFePo4 on Boats

[john61ct]

Getting there, some nit picks

Originally Posted by rgleason

Do not require recharge at 50% State of Charge like FLA lead acid.

Actually same sort of DoD vs cycles curve. 50% is arbitrary. LFP just is so pricey and can last so long, people don't leave as much reserve is all.

> Usable capacity is about 100- 95% of manufacturer capacity, unlike lead acid.
Maybe in theory, overstating IMO. Sizing for some Reserve is a good idea, plus going **that** low regularly, drastically shortens cycle lifespan.

> Do not have a very very long (3-5 hour) tail charge to get to 100%SoC like lead acid.
None at all in fact no need to even have an Absorb stage unless you want to, e.g. precise calibration.

> Do not require frequent charge to 100%
In fact need never go there, sitting Full is harmful

> The voltage stays nearly constant across the full state of charge at about 13.6-13.7v

No that's a charging surface V maybe, Resting and under load more like ~12.8V 3.2Vpc. Big loads don't sag as much as lead is all.



> Use a BMS Battery Management System to control charging and loads. Victron appears to the be the most comprehensive and commercially engineered BMS.

Not sold except as part of a system with their cells.


> Note that AGM batteries and FireFly have midpoint characteristics between FLA and LiFePo4.

Firefly is a type of AGM. Other AGM do not withstand PSOC cycling, nor such deep discharging.

Firefly still has long tail charging, needs capacity recovery maintenance run regularly if PSOC.

[Stu Jackson]

Nice to see you learning, along with the rest us.


Keep up the good work, rg.