LiFePo4 House Bank Using SmartHousePower BMS

[Tinkerer007]

I think your math is off by a factor of 10x. So, should be $6.25 per AH. So you think lead acid batteries are ~$2 per AH?

And, if you don't like the price, you can shop for your own batteries. I got my 4 x 200 AH cells for just over $1000. There are sets of 8 x 100 AH cells on ebay for $999.

So, if you buy battery in a box without the batteries and buy your own batteries, ~$1600, then you pay ~$4 per AH, or only 2x lead acid.

For this 2 x premium, you get:

1. Half the weight
2. Charging at 1C (Capacity) or more
3 No peukerts effect (you don't have to put 1.3 amps in for every amp you get back).
4. No self discharge for months if left idle. Don't need to trickle charge.
5. 10x the lifetime (3000 to 5000 cycles vs 300 cycles for lead acid).

I agree that the premium for these batteries is hard to swallow, but if you shop around and work with it, you can reduce the premium.

The more I use my battery, the more I like it.

Originally Posted by Dockhead

Well, if we figure Lifepo batteries have twice the usable capacity of lead-acid, then these units cost $2500/200/2 or $62 per amp/h of lead-acid equivalent. That's not two or three times as expensive, it's 30x more expensive than a good deep cycle lead-acid.
{Snip}

[hellosailor]

Of course there's also a huge discrepancy between the "LiFePo4" costs themselves, on the one hand a vendor like Genasun insisting on a control system that doubles the final battery cost, on the other hand, a different vendor claiming that isn't necessary at all.

It is those little "It is! It isn't!" fights and cost discrepancies that make some of the rest of us wonder, which one might be right. At what price.

[Dockhead]

Originally Posted by Tinkerer007

I think your math is off by a factor of 10x. So, should be $6.25 per AH. So you think lead acid batteries are ~$2 per AH?

And, if you don't like the price, you can shop for your own batteries. I got my 4 x 200 AH cells for just over $1000. There are sets of 8 x 100 AH cells on ebay for $999.

So, if you buy battery in a box without the batteries and buy your own batteries, ~$1600, then you pay ~$4 per AH, or only 2x lead acid.

For this 2 x premium, you get:

1. Half the weight
2. Charging at 1C (Capacity) or more
3 No peukerts effect (you don't have to put 1.3 amps in for every amp you get back).
4. No self discharge for months if left idle. Don't need to trickle charge.
5. 10x the lifetime (3000 to 5000 cycles vs 300 cycles for lead acid).

I agree that the premium for these batteries is hard to swallow, but if you shop around and work with it, you can reduce the premium.

The more I use my battery, the more I like it.

Yes, you are right, my math was screwed up. Sorry for any disinformation. Should be:

Lifepo:
$2500/200 amp/hours = $12.50 per nominal amp/hour.

Lead-acid
$200/110 amp hours = $1.80 per nominal amp/hour.

Since lead-acid has only half the usable amps compared to nominal amps, let's double the cost of lead-acid -- $3.60 per usable amp/hour.

So the LifePo's are 3.5x as expensive as lead acid per usable amp/hour, 350% of the cost of lead acid.

That's starting to get interesting, I admit. If the price were to fall to double that of lead acid, then all of the advantages you mention would start to get really interesting for me.

So maybe by the time my present set of lead-acids need replacement (new last year; so maybe in 5 years), it will be time to switch. By then, LifePo's will be more developed, too, with battery chargers designed for them and so forth.

[hellosailor]

Dockhead, you missed one number: If the Li battery really has 10x the number of charges in the battery life--then paying twice the battery price is still pnly paying 1/5th the price for the same number of charge cycles.

If the charge cycles work out that way.

[goboatingnow]

I dont really see the point of BMS, in marine LiFepo4 systems. Firstly their isnt the thermal runaway issues of other Li technology, Secondly HVC events arnt possible with the voltages generated by onboard systems and LVC events are merely a low voltage disconnect, which there are already systems available for lead acid that will work fine on Li batteries. ALternator protection can be as simple as merely switching in another battery or just dumping into a high wattage resistor or field switching , which most smart alternators regulators offer today anyway, Again common alternators cannot generate HVC's anyway and given that there is no requirement to actually charge to 100% theres no incentive to have high final voltage chargnig setups anyway.

Balancing is not really an issue for 1-2C charging, which is all at best most marine charging sources can generate, in reality it could be fractions of C.

A lot of these systems are decended from EV's where the whole design paradigm is different.

Dave

[OceanPlanet]

Originally Posted by goboatingnow

I dont really see the point of BMS, in marine LiFepo4 systems. Firstly their isnt the thermal runaway issues of other Li technology, Secondly HVC events arnt possible with the voltages generated by onboard systems and LVC events are merely a low voltage disconnect, which there are already systems available for lead acid that will work fine on Li batteries. ALternator protection can be as simple as merely switching in another battery or just dumping into a high wattage resistor or field switching , which most smart alternators regulators offer today anyway, Again common alternators cannot generate HVC's anyway and given that there is no requirement to actually charge to 100% theres no incentive to have high final voltage chargnig setups anyway.

Balancing is not really an issue for 1-2C charging, which is all at best most marine charging sources can generate, in reality it could be fractions of C.

A lot of these systems are decended from EV's where the whole design paradigm is different.

Dave

If you are going to use an LiFePO4 bank "like" a lead bank, you are sort of correct (50% DOD, slow charging, etc.). However, if you are using the 80% DOD levels that you can do with lithium you are closer to the "bottom" and mistakes can and will be costly if they do get out of balance. If a particular cell is repeatedly run low (or high) you will shorten the cycle life (or worse). Just monitoring the overall pack voltage won't really let you know if a cell is low/high. I have personal experience with clients who didn't have a LVC, and said they would never run them too low...but did just that and killed off a pile of cells. A lot of $ wasted.

Also, if you take advantage of the faster charging capabilities then the risk factor is higher if you have a regulator issue. People can and do inadvertently overcharge lead banks, causing them to gas and create a dangerous situation. They could do the same with lithium. It's true that the thermal runaway isn't a problem with LiFePO4 but if you overcharge them with some high-output alternators, or even unregulated solar you will likely have made a costly mistake.

A good BMS is insurance so you don't have to worry about an expensive boo-boo.

[LiFeTech Energy]

Originally Posted by OceanPlanet

If you are going to use an LiFePO4 bank "like" a lead bank, you are sort of correct (50% DOD, slow charging, etc.). However, if you are using the 80% DOD levels that you can do with lithium you are closer to the "bottom" and mistakes can and will be costly if they do get out of balance. If a particular cell is repeatedly run low (or high) you will shorten the cycle life (or worse). Just monitoring the overall pack voltage won't really let you know if a cell is low/high. I have personal experience with clients who didn't have a LVC, and said they would never run them too low...but did just that and killed off a pile of cells. A lot of $ wasted.

Also, if you take advantage of the faster charging capabilities then the risk factor is higher if you have a regulator issue. People can and do inadvertently overcharge lead banks, causing them to gas and create a dangerous situation. They could do the same with lithium. It's true that the thermal runaway isn't a problem with LiFePO4 but if you overcharge them with some high-output alternators, or even unregulated solar you will likely have made a costly mistake.

A good BMS is insurance so you don't have to worry about an expensive boo-boo.

Wise words Ocean Planet. I totally agree with your comments.
Why would you not spend that little bit extra on a BMS which will protect your expensive lithium battery investment so it performs at its best and provides many years of reliable operation.
Of course you don't necessarily need a BMS to provide the LVC and HVC protection. The same effect as a BMS can be achieved by using a programmable battery capacity meter (Ah meter). The BMS does also give you the added benefit of the cell balancing function which the battery meter alone does not.

[olaf hart]

Practical application: You have a 36 foot sailboat boat with a v drive and a clapped out perkins, maybe 7 tons displacement. You want to put in a regenerative electric motor where the V drive goes, and a diesel generator where the motor goes, turned around so you can get to the service points.

Are we saying changing to a LFP battery setup means you only need 200Ah at 24V to make this thing workable for a cruiser?

The generator would be 24VDC, and use an inverter for AC power, so you could run 110v or 230v or 240v depending on where you are from.

[LiFeTech Energy]

Originally Posted by olaf hart

Practical application: You have a 36 foot sailboat boat with a v drive and a clapped out perkins, maybe 7 tons displacement. You want to put in a regenerative electric motor where the V drive goes, and a diesel generator where the motor goes, turned around so you can get to the service points.

Are we saying changing to a LFP battery setup means you only need 200Ah at 24V to make this thing workable for a cruiser?

The generator would be 24VDC, and use an inverter for AC power, so you could run 110v or 230v or 240v depending on where you are from.

A 200Ah LiFePO4 battery setup is roughly equivalent in useable capacity to a 400Ah lead acid setup. With the LiFePO4 bank you also have the added advantage of recharging the completely depleted battery bank in under 30 minutes.

Yes, as you say the 24VDC generator would be a perfect option since you could use inverters with different voltage ratings to suit the electrical requirements to run AC mains powered appliances from anywhere in the world.

[olaf hart]

I might have to go to 48V to use the right size motor, so I guess the battery cost is still an issue.
On the other hand, exchanging the motor and V drive gets close to $20,000, so the economic curves will intersect some time soon.

[LiFeTech Energy]

Yes I would tend to agree that the 48V option would be a better choice than 24V.
All of the electric boats I know of are running lithium batteries with 48V motors.
I have just ordered a 48VDC to 240VAC inverter for one of my customers.
The genset is set up with the alternators which have been adjusted for optimal charging of a 48V LiFePO4 battery bank (regulator cut off set to 58.4V).

[Dockhead]

Originally Posted by hellosailor

Dockhead, you missed one number: If the Li battery really has 10x the number of charges in the battery life--then paying twice the battery price is still pnly paying 1/5th the price for the same number of charge cycles.

If the charge cycles work out that way.

You assume:

(a) batteries economic life is limited only by the quantity of cycles; and

(b) money has no value through time -- that is, you simply add up the price of lead acid-batteries replaced periodically over time, and compare it to the large upfront expense of buying LifePO, without discounting the cost of future lead-acid batteries to present value.

Both are fallacious.


(a) For most cruisers, many years of cruising will not use up the charging cycle potential of lead-acid batteries. Batteries get replaced when they are ruined by some kind of mishandling or another, or they get sold on with the boat. Rarely are they replaced because the number of cycles has been exceeded; the exception might be people who live aboard AND at anchor for years at a time and cycle their batteries every day; this is a small minority. So fifty years of LifePO theoretical lifetime has no practical value if the average cruisers sells his boat every 10 years or burns up his batteries due to some fault or mistake, every 7 years, say.

(b) Your personal marginal cost of money is the highest interest rate you pay on any debts you have (do you run any credit card debt?), or the highest return on the best investment you have. So for most people, the marginal cost/value of money will be somewhere between 8% and 20% per annum. This greatly reduces any benefit of a greater number of cycles of Life PO batteries EVEN if you keep your boat for 50 years (and eliminates any benefit, if you keep your boat for less, or above a certain level of your personal cost of money). Even if your money costs you only 6% and even if you keep your boat for 20 years, it will be cheaper to buy lead-acid batteries every five years for twenty years, than to buy one LifePO bank which you use for twenty years. Theoretically, the LifePO becomes cheaper if you keep it for 40 or 50 years AND you have a low personal cost of money, but I'm not sure any of us around expects to even live so long, and if you're not earning at least 8% on your investments you need financial counseling.

So there is NO practical economic argument for LifePO so far unless MAYBE you are one of the 2% of cruisers who cycle your batteries every day, 365 days a year, so that you only get a year or two out of a set of lead-acid batteries. For all the rest of us, whose batteries last 5 years or even more, lead-acid is still much cheaper.

But as I said -- I think Lithium is the wave of the future. I can't wait for them to come down in price so I can try them on my own boat.

[hellosailor]

"You assume:"
No, I didn't assume any of that. I simply ignored those points since I'm not trying to do a complete financial breakdown. Rather, I'm just looking at the ballpark numbers involved. You gave a ballpark number for some costs, I pointed out there's a rather large cost factor you left out. The cost of money is widely variable and right now, ho-ho, try to guess it from day to day when the financial markets are behaving like a bull gone berserk in a china shop, worldwide.
Most cruisers....well, better to say most "boaters" seem to get 4-5 years from their battery banks, despite the few who get better than twice that from premium systems and using them wisely.

"So there is NO practical economic argument for LifePO" Ah, but you can't have an argument without premises to build it on. And so far, there are essentially zero premised about Li-anything that are not in debate. The depth of discharge, the number of charge cycles, the need for a BMS (Genasun says must, LT says not really) which literally DOUBLES the up-front cost...the ability to recharge in a fraction of the time, using a fraction of the genset fuel...

All we've really seen, is that there's a tremendous variation in claims. No offense to anyone but "unsubstantiated claims" would seem to be the proper term, as everyone cites some results but there's no large or objective set of installations to look at, and no ironclad warranty to rely on.

Of course that's not all that different from conventional lead batteries, where some makers claim 300 50% duty cycles and others claim a thousand, for the same technology. Or the folks who claim AGM lasts much longer. Or, not long at all.

Proper financial comparisons? Well, first give me a dozen boats and battery systems then give me five years to cycle them and let you know what really happens.<VBG>

[Dockhead]

Originally Posted by hellosailor

"You assume:"
No, I didn't assume any of that. I simply ignored those points since I'm not trying to do a complete financial breakdown. Rather, I'm just looking at the ballpark numbers involved. You gave a ballpark number for some costs, I pointed out there's a rather large cost factor you left out. The cost of money is widely variable and right now, ho-ho, try to guess it from day to day when the financial markets are behaving like a bull gone berserk in a china shop, worldwide.
Most cruisers....well, better to say most "boaters" seem to get 4-5 years from their battery banks, despite the few who get better than twice that from premium systems and using them wisely.

"So there is NO practical economic argument for LifePO" Ah, but you can't have an argument without premises to build it on. And so far, there are essentially zero premised about Li-anything that are not in debate. The depth of discharge, the number of charge cycles, the need for a BMS (Genasun says must, LT says not really) which literally DOUBLES the up-front cost...the ability to recharge in a fraction of the time, using a fraction of the genset fuel...

All we've really seen, is that there's a tremendous variation in claims. No offense to anyone but "unsubstantiated claims" would seem to be the proper term, as everyone cites some results but there's no large or objective set of installations to look at, and no ironclad warranty to rely on.

Of course that's not all that different from conventional lead batteries, where some makers claim 300 50% duty cycles and others claim a thousand, for the same technology. Or the folks who claim AGM lasts much longer. Or, not long at all.

Proper financial comparisons? Well, first give me a dozen boats and battery systems then give me five years to cycle them and let you know what really happens.<VBG>

Exactly, and a good point. The long-term cost of LifePO is entirely hypothetical, and is likely to be much worse than the theory holds.

It means smiply that the financial case has not been made for the much higher expense of LifePo batteries. Yes, it's complicated, and nothing good, particularly, has been shown.

In the absence of a reasonable economic case, lead-acid is the way to go for the time being, at least, for anyone who does not have unlimited money to throw at such things.

[goboatingnow]

I still remain to be convinced as to the need for BMS systems in LifePo technology. There's a bit of an " industry" being generated here ,rather then dealing with the electronics.

I'm not arguing against bms in general most lead-acid based boats have some form of bms even if it's an amp hour meter and you average smart charger is in essence a bms. I can't see the justification for some very expensive Li bms that are being proposed though.

Let's look at typical marine systems let's take a big capacity boat ( to justiy Li tech in the first place) so 400 amp/ hours at 12v ( nominal). This isn't a particular big system
typical uses are likely to be charging at between 0.1C ( solar) to say 0.25C ( large alternator) , discharge rates probably typically 0.1C with some intermittant loads to 0.75C ( thrusters and the like) though most high loads are performed with the engine running and the alternator taking most of the load. The other possibly of high C loads might be an invertor but most invertors spend a lot of time at very low power outputs.

Technical evidence has shown that cell balancing in this environment is very unlikely and even then top balancing is easily done ( I have a design that costs about 50$ to build in one offs. Again there's no real evidence that it's needed in practice once you don't exced the HV limits per cell the cells can remain partially out of balance indefinitely.

Let's look at HVC potential events. There are three types of charging sources on a well equipped cruising boat. Engine alternator ( main or engine dc generator), mains battery chargers ( either shore or ac gen driven) and solar via a controller ( which is really an equivalance to mains battery chargers) wind gens etc are treated similarly.

Firstly unlike lead acid there is no need to 100 % charge lifepo technology with no detremental effects. Almost all the problems and the need for high tech solutions in lead acid charging are due to the need to 100% charge in lead acid this leads to high absorbsion voltages gassing loss of capacity etc or more commonly premature death due to terminally undercharged batteries ( often as a result of inadaquate capacity recharging sources in the first place)

So with lifeo we can actually use simple constant current charging with a safety cutoff at 90 % ie we can never generate HVC events. Talk of regulator faiure is misplaced alternator failure generates no output not high p
output and in fact Lifepo can tolerate faults for a while better then lead acid

battery chargers are already smart and hence for lifepo systems they can be set never to get near a HVC

Let's look at the other end. Today in most boats there is no LV monitoring ( except by the humans looking at the lights going dim) most LV events are often flagged by one piece of electronics or another complaining low voltages. In lead acid systems at this point damage is already being done and most people have far less capacity in their lead acid banks than they expect mainly as a result of LV events ( and poor charging as mentioned)

using li tech without LV monitoring is no worse then current systems with the addec benefit that the characteristics of lifepo mean that LV events Re actually detected before damage is done ( voltage is more an indication of state of charge then in LA systems)

hence LV risks are if anything less of an issue in boats. ( especially since the humans watch for LV all the time anyway). From a technology point of view LVC is easy to handle a simple disconnect system ( widely available today) will do anyway.

As I said before cell balancing is really not an issue especially with high capacity individual li cells as opposed to the use of large numbers of small li cells ( a process that will disappear with time anyway and is a throwback to other Li technologies)

even that said cheap top of charge cell balencing is easy any cheap to do .

Hence in reality complex Bms system for LiFepo4 systems is unneccessary it has arrived on the back of other Li technologies that have thermal runaway issues or multiple of C discharge and charge rates such as Evs ( which ate still really at the NiMH stage anyway), laptops model RC use etc. Boats are far less stressful electrically.

Let's return to the cost argument. Firstly comparing the costs directly of Lifepo and lead acid is disingenuous. Lead acid is probably the worst solution to a boats electrical storage requirements. We use it because that's all we really have available. But all the issues such as depth of discharge, weight , 100 charge requirements, absorbsion cycle time, premature failures due to sulphation etc are actually cured by LiFepo4. I really don't think
people realise this. Hence the cost comparison is more like why do you nit buy 4 Honda generators rather then one expensive marine diesel generator ( why becUse the solution is technically better and that's worth a Premium)

it's suprising in this day and age that the Dc systems on most boats out of the wrappers is apalling. Clients will spend literally tens of thousands on sails or deck gear ( most of which add fractional improvements) yet below is a Dc system out of the dark ages.