What mods to accommodate lithium battery bank?

[SVArcturus]

Teak varnishing hell: 12#, Stainless cheap look: 15#, Aluminum corrosion mess: 12#, Carbon...?

What! You are varnishing teak handrails?  Just makes them slippery.  I just replace them every 20 or 25 years and leave them natural.  Plus, look at how much weight you'd save without all that shine glinting all about and blinding you at critical moments. 

 

[Raz'r]

What! You are varnishing teak handrails?  Just makes them slippery.  I just replace them every 20 or 25 years and leave them natural.  Plus, look at how much weight you'd save without all that shine glinting all about and blinding you at critical moments. 

The wife wanted handrails. We're going teak.will wash. Maybe oil.

 

[kru]

might be worth a look...

https://marinehowto.com/

https://marinehowto.com/lifepo4-batteries-on-boats/

https://marinehowto.com/category/electrical/batteries/

 

[longy]

Oh yeah baby!

Come on, pay attention. Panope has a whole thread, with VIDEO, of him testing all the anchors available

 

[IStream]

How are you driving the right charge profile?

All my chargers are programmable, which is critical. I didn't see a need to upgrade them for higher charging current but if they weren't already programmable, I would've gotten ones that were. If you're shopping for chargers, another very useful (though arguably not essential) feature is separate battery voltage sense wires. Unlike the main charger output cables, the sense wires carry almost no current so they can give the charger a very accurate measurement of battery voltage. You don't need or want battery temperature sensing but as mentioned upthread, you absolutely do want your voltage regulator to have an alternator temperature sensor so it can throttle the alt down before it burns up trying to charge your bank at full output for hours on end.

The "standard" charging profile recommended by Valence for my lithiums is a constant current / constant voltage (CC/CV) profile with the CC current limit set to C/2 (212A in the case of my 424A bank) at a voltage not to exceed 14.6VDC. The 14.6V should be held for about 30 minutes after the current drops to less than 20A to allow for top-balancing. The recommended CV stage after that is a constant voltage of 13.8VDC.

Valence's primary markets are medical devices and other high-availability contexts where the batteries need to be at 100% SOC all the time. They're designed to tolerate that better than most but the chemistry's the chemistry and lithium doesn't like to sit at 100% SOC. Because of this, I prefer to hold the batteries at 13.28V, which corresponds to about 70% SOC. If I tried to do that using a CC/CV program, the charger would periodically kick back into the CC phase to top them up and needlessly cycle them. Hence, I deliberately use a standard three phase lead acid charge cycle with the bulk-to-absorbance transition voltage set to 14.6V and an absorbance duration of 1.5 hours, which I determined empirically is long enough to reach 100% SOC plus a ~30 minute top-balance period. After that, it goes into float at 13.28V. When I want to take the boat out, the first thing I do is manually kick off a recharge which gets them back up to 100% SOC in under an hour.

 

[SVArcturus]

The wife wanted handrails. We're going teak.will wash. Maybe oil.

Ah.  Aesthetics.  Will get you every time.   

 A lovely gray patina is possible.  Might be an acquired taste.

 

[SVArcturus]

After that, it goes into float at 13.28V.

Just curious, what is the nominal operational voltage for your batteries?  Mine are 13.8V, and they call for floating at that same voltage, (charging at 14.0V-14.6V)

 

[El Borracho]

 A lovely gray patina is possible.  Might be an acquired taste.

Yes, it is lovely. The neighbor has an old barn finished in that style.

 

[Raz'r]

Come on, pay attention. Panope has a whole thread, with VIDEO, of him testing all the anchors available

I know...

 

[IStream]

Just curious, what is the nominal operational voltage for your batteries?  Mine are 13.8V, and they call for floating at that same voltage, (charging at 14.0V-14.6V)

Here's some data I took from my ~400Ah bank at 10 degrees C operating temp. The red line is slow discharging (<5A) while the green line is charging at 125A nominal.

The discharge curve starts at about 13.3V and drops to about 12.5V at 10% SOC. The discharge curve will shift down about 0.1V at an 80A (C/5) discharge rate, 0.2V at a 160A (C/3) discharge, and 0.5V at a 400A (1C) discharge rate.

For each 10C increase in temperature, the curves will shift upward by roughly 0.1VDC.

 

[Not My Real Name]

I keep hearing this discharge myth promulgated on this site.... This is completely untrue about maximum discharge rates. This LiFePO4 cell can do a continuous 540 amps and safe at short durration at 1,800 amps. See this spec sheet here: http://media3.ev-tv.me/batterybrochure.pdf. And my picture attached

View attachment 379025

That's exactly what I built my house bank from - 32 of those cells in 4P8S configuration for 24V.

 

[Not My Real Name]

Did you buy and use these or are you posting a screenshot of an ad

I have 32 of those in my boat.

They are rated for 3C.

In theory I could output 2000A, but in practice (well, theoretically in practice, I've not tested that much current and have noway to do so) that would trip my BMS and kill the draw before the giant fuses blow.

 

[jack_sparrow]

If you have no BMS then you are the BMS. I have yet to meet a human being who doesn't forget something. How many award winning chefs have been known to burn something? 

No, I am not the BMS.   

Correct are not the Battery Management System. You are a human Battery Monitoring System.

LFP requires "Management" not just "Monitoring" to maximise it's survival and longevity to get the return on the investment with the additional capital investment entailed.

You don't appear to read that well, so I will explain more for the benefit of others on account your advice is dangerously misleading.

All the equipment in the 'system' is Lithium compatible. It has a charge profile that shuts down and does not trickle charge. It has a Lithium charge profile on it's voltage/current curve for all devices installed. Just like the other 800 or so lead-acid systems that I have installed that date back as far as 1984. Not a single electrical failure in hundreds of installs used in some cases by relatively inexperienced  users.

Your LA experience clearly is an impediment by the nature of your response and as I pointed out that would probably be the case. 

You may have charge sources that are LFP compatible, but ONLY in so far as pack voltage is concerned. Fine for LA, not for LFP. That is why your LA experience produced little/no system issues. BTW LA is not necessarily immune. Modern high C rate LA chemistry has cooked many a charge source, particularly small case auto style alternators. 

Those charge sources of yours DO NOT monitor cell voltage. Cell drift voltage at the low and high voltage ends is where irrepairable damage easily occurs. It occurs with either no or a very small variance in pack voltage, depending on what pack voltage those charge devices are set to STOP charging at.

Similiarly your load devices ONLY measure pack voltage NOT cell voltage when discharging. For instance an inverter the most common device that can be programmed to STOP. For the balance of load my guess you have a simple shunt style Battery Monitor, again only pack voltage and with an alarm. Your ARE the human battery monitor listening for that alarm (unless it has a integrated relay set to up to high load contactor to disconnect batteries from their load. 

So damage to one cell. If a sealed pack it is an expensive doorstop. If not sealed then out of action until until that cell is replaced if it can be purchased. This is far from ideal as it will be the odd man out in terms balanced voltage/age with the original cells. At best that will reduce available capacity working within a narrower voltage range to avoid cell voltage drift.

That is a lot of money down the drain.

I never cease to be amazed by comments and advice this subject generates, many from people who have no idea what they are talking about. I know many people who have LFP, ownership doesn't necessarily guarantee knowledge.

A BMS is just as likely to fail as anything else and my experience. In fact - in practice -  the BMS fails more often that the rest of the gear.

LFP is a "system" not a battery.

Drop in style LFP batteries are NOT a system. Most are an abomination.

I respect that you are now working with Lithium chemistry for others and that a BMS is nessesary when you design for the general public.

You say you have no experience using LFP with a BMS, but you say;  

"A BMS is just as likely to fail as anything else and my experience. In fact - in practice -  the BMS fails more often that the rest of the gear." 

Experience with failing more often than what?

I rest my case.

Failures are extremely rare, I have only seen two in all the other cruising boats we have encountered between North America and New Zealand on our cruise thus far.

You have only seen two LFP systems without a BMS fail? Out of how many total? Less than 5 or 40%? I guarantee those failures are listed below. 

I have seen very few failures in properly engineered and set up LFP systems that have done serious miles and had very serious use. LFP loves to work. Offshore race boats are one.

The most failures I have seen roughly in order are:

- "Drop in" systems, with or without a self styled integrated BMS with limited features. The vast majority due to operator ignorance to their limitations not being spelt out by manufacturers and resellers, many on-line with questionable business practises. Some of the recommended charge voltages are insane, guaranteeing failure.

The proliferation of sailing Vlogs where promoters secure a complementary or heavilly discounted drop in package has helped push a lot of rubbish product to the LFP ignorant.

They are doing LFP chemistry a great disservice. The people impacted very pissed off.

A similiar thing occured when Sealed LA became the norm over Flooded LA. Gel chemistry when first introduced and marketed as a drop in without any regard to changing charge voltage. They got a very bad name because of that, despite it being first class chemistry. When AGM was introduced, no emphasis to longevity issues when discharging below 50% SOC and not regularly returning it to 100% SOC another example.

Not all LFP drop in systems are the same. There are a small number produced by reputable manufacturers and resellers with integrated BUT featured BMS's. Examination of the caveats applied to their warranty is a good sign to the limitations they highlight, not hide a good sign. Lithiomics is a good example.

- Small case auto style engine alternators turning to toast and or constant belt failures/dust with high LFP loads not tapering off like LA when short bulk period is over. Lack of any BMS alternator control or a LA load dump provision to protect diodes in the event of LFP shutdown another costly/very inconvenient experience. Ignoring the critical system approach for LFP is a recipe for issues.

- Cell damage by incorrect set up of programmable charge pack voltage being too high and or if not turning off (preferable) going to high float voltages. Cell drift takes off particularly if low load, cell buggered.

- Cell damage by incorrect set up/use from discharging too low where cell drift quickly takes off. Inverters with high loads the most common culprit.

- Expensive integrated systems are not immune to the above.

- Inexpensive DYI self assembled LFP packs being "dropped in" with no BMS are even less immune. Better cell quality than drop in and cheaper than some drop in. This setup seems to have been propagated by difficulty in sourcing DIY external BMS and cell boards plus high cost of a full system approach. A largely DYI cruiser crowd just left BMS out!! You are obviously one.

- The occasional cell board failure particularly in DYI, but mainly moisture ingress caused by inadequate protection having regard to location. Easily remedied by replacing cell board.

- Removing an uninsulated spanner that dead shorted LP was an interesting job. LFP certainly doesn't have the energy density of other lithium chemistries, but that proved it had enough to cause serious damage if good installation practises aren't followed.

There will be exceptions to the above where users preach no issues .....until it happens to them of course. In my experience it always does. 

I respect that you are now working with Lithium chemistry for others and that a BMS is nessesary when you design for the general public.

LiFePO4 without a BMS, can be used with the same dedication  and experience that we devote to many aspects of sailing... 

...It is not essential  to have a BMS ..

My clients would be horrified if I regarded them as the "general public"   :lol:

The bottom line is you are advocating an approach not supported by the industry and AS IF every user is like you, aware/not aware there is a substantive investment risk and you are prepared to accept that risk. However you are/were not spelling that risk out.

Hence my objection to your posts promoting it in the manner you have. 

PS. I am a big fan of LFP but probably talk just as people out of it. For instance cheaper, more forgiving advanced LA chemistry that addresses partly charge/capacity issues like carbon Firefly's or even humble dirt cheap flooded LA for some applications.  

If you are not prepared to take advantage of the chemistry and introduce lots of charge capacity why bother? Have constraints like limited fuel tankage/fuel supply issues in remote locations, solar capacity restrictions on many monos etc makes LFP brilliant. Conversely lots of deep centre line bilge space is ideal for flooded LA if usage matches it. Horses for courses.

 

[2flit]

Jack,

 I have asked this question, could you please answer:

"  I’m trying to understand, Have you ever actually bottom balance these  cells yourself (not top-balancing, which I have actually tried) .  If you have done Bottom Balancing, why did it not work for you with these cells? What went wrong and how bad di it get? I’m really interested. What set up did you use to individually discharge all the cells to the same level?"

 

[jack_sparrow]

LFP cells for fractional C use as in a sailboat should be "top" NOT "bottom" balanced to max capacity. EV's is not fractional.

Jack,

 I have asked this question, could you please answer:

I’m trying to understand, Have you ever actually bottom balance these  cells yourself (not top-balancing, which I have actually tried) .  If you have done Bottom Balancing, why did it not work for you with these cells? What went wrong and how bad di it get? I’m really interested. What set up did you use to individually discharge all the cells to the same level?"

Both...cells from same build batch and each cell voltage individually logged. Inverter/AC load then light globe individual cells bottom. Variable DC benchtop power supply for top. Rest both overnight using individual cell boards to get final balance to 2nd/3rd decimal point. 

With charge and discharge voltages outside the cliff shouldn't have to do it again for years for LFP with decent BMS getting max capacity voltage range and no issues. Check cell log occasionally to be sure all good. 

Sailboat fractional C use top best. High C use like an EV bottom best.

Your batteries are crashing because they were never bottom balanced. Never having done had this, they just get more out of equilibrium as time goes on. You are dependant on your BMS because of how the batteries were assembled without individual bottom balancing.  

 

[Oceanconcepts]

Cost vs. weight basis: This weight fanatic says not worth it.

Reliability and ease of repair...okay if close to home..incipient disaster if long range cruising.

Charge efficiency benefits hard to quantify. If racing with shorepower everyday or two then no advantage. If mostly solar and sunny when moored then little advantage. More advantage underway but actually small percentage of time is spent underway.

Some unquantifiable advantage to not having to know anything about bottom balancing and a myriad of controller functions vs. remembering to top up with water.

My opinions based on my usage. 

Weight is not much of a consideration for me, but a couple of other things are making me very thoughtful about switching to lithium.

• I have 4 older golf cart batteries that won’t last a lot longer. They take-up prime space that could be much better used. Smaller, lighter Li batteries could fit into currently unused space. 
  
• I have an old pressurized alcohol stove that needs to go, and the prospect of switching to an induction cooktop in the space-challenged galley is appealing. Ditto having a small microwave or combo oven. I’m not thrilled about introducing propane, and the cost of doing so would be subtracted from the cost of a Lithium system & a bigger inverter.
  

I understand the charging/ energy system would need to be upgraded as a whole. It’s kind of an interesting project.

On the plus side, I’m married to an electrical engineer/ instrumentation designer, and whatever technical issues I have trouble with, I can (probably) get help… 

 

[jack_sparrow]

Jack,

 I have asked this question, could you please answer:....

Both...cells from same build batch and each cell voltage individually logged. Inverter/AC load then light globe individual cells bottom. Variable DC benchtop power supply for top. Rest both overnight using individual cell boards to get final balance to 2nd/3rd decimal point... 

...Sailboat fractional C use top best. High C use  like an EV bottom best.

2flit now my two questions to you that are unanswered.

1. You say; "A BMS is just as likely to fail as anything else and my experience. In fact - in practice -  the BMS fails more often that the rest of the gear."

Q. In practise then, approximately how many from each category with a BMS have you seen fail;

Q(a) Number of "Drop Ins" with an internal BMS fail?

Q(b) Number of "Integrated Systems" with an external BMS fail?

2. You say of those with no BMS like yours; "Failures are extremely rare, I have only seen two in all the other crusing boats.." 

Q(a) That number of boats approximately you saw that had no BMS and no failures, how many boats, including yours was that? 

Q(b) Then complete the calculation.

@2flit No BMS Failure Rate % = 2 Failures ÷ (2 Failures + Number No Failures) 

...A BMS is just as likely to fail as anything else and my experience. In fact - in practice -  the BMS fails more often that the rest of the gear...

.. Failures are extremely rare, I have only seen two in all the other cruising boats we have encountered between North America and New Zealand on our cruise thus far...

Experience with failing more often than what?

You have only seen two LFP systems without a BMS fail? Out of how many total? Less than 5 or 40%? I guarantee those failures are listed below..... 

And one question that I didn't ask, what are the "set" voltages on each of your charge sources incl voltage regulators for those that have them?

 

[Hitchhiker]

To the OP.  There are a number of posters on this thread who make claims that they cannot back up with proof.  Carcrash and BJ porter not included.  

I am certainly no expert.  But, I did find several very useful sources to help guide me in the design of the system we installed in the 51 ft race boat I nav on.  The big difference for us is that we have a very strict discharge and re-charge discipline based on our usage and rarely go below 60% discharge. But, given we are in 24/7 mode we optimized around a twice daily recharge cycle. 

I digress.  This article is very useful. http://honeynav.com/lfp-battery/

 

[jack_sparrow]

Cost vs. weight basis: This weight fanatic says not worth it.

Reliability and ease of repair...okay if close to home..incipient disaster if long range cruising.

Charge efficiency benefits hard to quantify. If racing with shorepower everyday or two then no advantage. If mostly solar and sunny when moored then little advantage. More advantage underway but actually small percentage of time is spent underway.

Some unquantifiable advantage to not having to know anything about bottom balancing and a myriad of controller functions vs. remembering to top up with water.

My opinions based on my usage. 

Weight is not much of a consideration for me, but a couple of other things are making me very thoughtful about switching to lithium.

• I have 4 older golf cart batteries that won’t last a lot longer. They take-up prime space that could be much better used. Smaller, lighter Li batteries could fit into currently unused space. 
  
• I have an old pressurized alcohol stove that needs to go, and the prospect of switching to an induction cooktop in the space-challenged galley is appealing. Ditto having a small microwave or combo oven. I’m not thrilled about introducing propane, and the cost of doing so would be subtracted from the cost of a Lithium system & a bigger inverter.
  

I understand the charging/ energy system would need to be upgraded as a whole. It’s kind of an interesting project.

On the plus side, I’m married to an electrical engineer/ instrumentation designer, and whatever technical issues I have trouble with, I can (probably) get help… 

My posts above with PS from last one copied below seems to fit both your posts.

PS. I am a big fan of LFP but probably talk just as people out of it. For instance cheaper, more forgiving advanced LA chemistry that addresses partly charge/capacity issues like carbon Firefly's or even humble dirt cheap flooded LA for some applications.  

If you are not prepared to take advantage of the chemistry and introduce lots of charge capacity why bother? Have constraints like limited fuel tankage/fuel supply issues in remote locations, solar capacity restrictions on many monos etc makes LFP brilliant. Conversely lots of deep centre line bilge space is ideal for flooded LA if usage matches it. Horses for courses.

El Boracho you are the "LFP knocker."   An LFP "Integrated System" with external BMS is tailor made for long distances/cruising, set up properly use and forget.

Reliability and ease of repair not an issue. I recommend seperate bank design for larger boats for redundancy regardless of chemistry. Incl a LA start that can act as an emergency service supply I recommend but does come at a cost of a DCDC variable voltage power supply to charge it or something like Balmars Duo Charge.

Charge efficiency benefits are piss easy, not hard to quantify when assessing application. Small engine run time yes, but with high charge capacity going into LFP that can use all of it for the full curve which LA can't. If renewables your prime charge source and don't need engine then forget about LFP. Waste of $ unless space poor.

Oceanconcepts you are the "more energy chaser" (for inverted AC) currently with golf cart LA. LFP is the only solution. I would think long and hard about that extra energy as it comes at a large cost as your current set up is a LA ideal without it. In my own boat I have a massive 1,400 Ahrs of LFP, have a microwave but would never give up my propane oven/cooktop. :lol:

If you do decide to jump remember it is a "system" not a "battery" and this about LFP  "Drop Ins".

I have seen very few failures in properly engineered and set up LFP systems that have done serious miles and had very serious use. LFP loves to work. 

The most failures I have seen roughly   in order are:

"Drop in" systems, with or without a self styled integrated BMS with limited features. The vast majority due to operator ignorance to their limitations not being spelt out by manufacturers and resellers, many on-line with questionable business practises. Some of the recommended voltages are insane, guaranteeing failure.....

 

[jack_sparrow]

To the OP.  There are a number of posters on this thread who make claims that they cannot back up with proof. ....

I digress.  This article is very useful. http://honeynav.com/lfp-battery/

Hitch so I'm chopped liver  :lol:

Stans DIY project excellent article. Only trouble is the availability of anologue BMS's has got harder for pack builders since then. The excellent one he has the guy stopped production and joined Lithionics a US system provider.