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Old 05-06-2015, 11:13   #4546
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by cll2 View Post
Is there a maximum number of posts allowed in a given thread and are we getting close to it yet?
I hope there's room for one, or two more questions.

I am planning on a 30 kwh house bank.

I also drive a Chevrolet Volt. The Volt has a 16kwh lithium (I don't know the precise chemistry) battery pack. The Volt only uses about 10 kwh of the pack. Chevrolet never lets the pack be completely charged, or discharged.

Question 1: is it surprising that the Volt, by design, never completely charges the pack?

My daily commute uses all of the 10 kwh available. My last 15 miles or so is using the gasoline generator. I plug the Volt in every night to recharge it. I use a 120v device to plug it in. Once in a while I may use a public charger, this is usually 240v. Note that while driving, the Volt uses regeneration; every time I step on the brakes, energy goes to the battery. I have had the Volt for more than 3 years. I figure I am approaching 1,000 complete charge cycles and literally millions of partial charges. As far as I can tell, the pack has suffered no loss of its ability to provide 10kwh of energy, without any effort on my part.

Question 2: Is there something different about having a pack on a boat? The Volt is so easy. This thread (I apologize, I have not read it all) makes me wonder if I need a PhD in battery charging to avoid problems (fire, premature battery failure, etc) on the boat. Will one of the established vendors take care of me, or do I still need to worry that this technology is not ready for prime time on a boat (I guess that is three questions)?

Thanks for any advice.
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Old 05-06-2015, 11:28   #4547
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by Cottontop View Post
I hope there's room for one, or two more questions.

Question 2: Is there something different about having a pack on a boat? The Volt is so easy. This thread (I apologize, I have not read it all) makes me wonder if I need a PhD in battery charging to avoid problems (fire, premature battery failure, etc) on the boat. Will one of the established vendors take care of me, or do I still need to worry that this technology is not ready for prime time on a boat (I guess that is three questions)?

Thanks for any advice.
I will take on this portion..

Unlike your Volt, marine Li batteries have not had the benefit of millions of dollars of engineering to make them prime time ready. Chevy spent years and a boat load of money to ensure the battery pack in the volt would meet the requirements. They also have the luxury of completely controlling the charge circuit. They don't have to worry about someone feeding 4.6V into a single cell. The user simply plugs the car in to a wall outlet and the circuitry takes care of the rest. When the battery is depleted to the level that the Chevy engineers are comfortable with, then the gas motor kicks in. They insure the battery is never over discharged.

The current state of marine Li batteries is just that, JUST BATTERIES. No manufacturer has wrapped the intelligent circuitry around the bare cells yet. Without that circuitry it is very easy to overcharge of over dischage a cell or multiple cells. Overcharge or over discharge just once will effectively kill a cell.

A few people in this thread (Mainsail) have built the circuitry themselves and spent the hours to figure out the proper charging and discharging rates. For those inclined, the information is here if you want to build your own. Its quite involved and would require a basic understanding of electrical and electronics.
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Old 05-06-2015, 12:10   #4548

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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Cottontop-
From what you are saying the Volt is set up to never use more than 60% of the battery capacity, leaving it with 40% unused before it starts recharging. With pretty much any marine deep cycle battery, you can get ~10x more charge cycles from it by using it that way, to a 40-50% discharge instead of letting it go down to 20% or possibly even 10%. The harder you discharge them, the fewer charge cycles they get.
As traveler said, Chevy designed a whole *system* that ensures when and how much charge will be applied. If a boat operator was smart enough to do that manually, or to put in the equipment to do it automatically, they'd also get radically better life from the batteries. Laptop computers and cell phones have also been doing this for years, often invisible to the user. But the better ones "never" charge the battery to 100% or discharge it past a certain depth (if possible).
The problem is that technology costs money, and it isn't visible or particularly sexy, and the mass market doesn't want to be bothered with details. On the marine market it is even worse, after all, who wants to design a charge controller for those few sailors who are willing to drop a couple of grand on fancy batteries? The boat manufacturers can't even get their customers to buy external regulators, they're still cheaping out with "automotive" ones in most cases.
The few that do offer solutions? Will charge you a "concierge service" price. And, that still leaves you to question how reliable and durable they'll be, as they continue to disagree about everything with each other.
But if you can (and prefer) to drive a manual shift in your car, you can certainly manage batteries on your boat.
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Old 05-06-2015, 12:42   #4549
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Travellerw and Hellosailor, thanks.

Your comments, while disappointing, were not entirely unexpected.

Hellosailor, just to clear one thing up, although it may not matter much on this thread, I think the Volt uses the 60% of capacity out of the "middle," that is, it will discharge to 20%, but never charges beyond 80%.

I guess if my intended system didn't work so well and I had to replace what are currently very expensive batteries in 4 years instead of 8, I would be disappointed, but not life-changing.

On the other hand, if a wire to a solar panel chafes through and shorts, setting in motion some sort of cascading event that results in a battery fire, well, that could be unacceptably life-changing.
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Old 05-06-2015, 14:23   #4550
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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No manufacturer has wrapped the intelligent circuitry around the bare cells yet.
SuperB, Victron Energy and Mastervolt have done it, and I could come up with more.
Not everyone will like the price tag, but then - what is the price of an replacement battery for a Volt vor Tesla?


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Old 05-06-2015, 14:40   #4551
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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SuperB, Victron Energy and Mastervolt have done it, and I could come up with more.
Not everyone will like the price tag, but then - what is the price of an replacement battery for a Volt vor Tesla?


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Alright I should have said. "Done it affordably or done it well!"
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Old 05-06-2015, 14:41   #4552
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by woodenboats View Post
SuperB, Victron Energy and Mastervolt have done it, and I could come up with more.
Not everyone will like the price tag, but then - what is the price of an replacement battery for a Volt vor Tesla?


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No they haven't even "done it". They just provided protection with some balancing capability. They routinely overcharge if you don't keep using the power and while you get a functional and safe system, you won't get the battery life you should for this reason.
Since they also sell the batteries it is hardly a problem from their angle.

Not overcharging LFPs (and not leaving LFPs charged too high) is the main challenge on marine installations, because if you keep at it long enough, they overcharge at just 13.6V. Voltage control is not good enough, there is no magic charging voltage.
Some of us managed to work their way around the issue, but only as long as the bank keeps getting used hard enough in relation with the charging regime in place.
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Old 05-06-2015, 14:49   #4553
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

All three provide a "do not charge" and a "do not discharge" signal from their bms and/or solenoid. To my best knowledge that prevents the battery from overvoltage, overcharge and deep discharge. Or am I mistaken?

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Old 05-06-2015, 23:06   #4554
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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All three provide a "do not charge" and a "do not discharge" signal from their bms and/or solenoid.
...
If you look closely at some of their diagrams, you will see that it doesn't appear to be the case at all. The Victron system for example is a common positive installation (yeah nice) that switches the lithium bank in and out of parallel with the charging battery. It doesn't rely on external disconnects and the alternator spike gets absorbed by the start battery.

There will be another part bundled with the battery however.

Some DIY setups were designed and built here doing almost exactly that without having a common positive for a fraction of the cost.

And all this doesn't do much about the cells getting stuffed from being left near-fully charged, which will happen as soon as you stop using the boat. Ah, but of course you can "manually" address this, but then it is not "all taken care of" anymore.

Along the same lines there are some (other) "brand name" lithium MPPT solar controllers that just regulate at 14.2V indefinitely. Walk away from the boat and see what happens with battery life when they get floated that high.
You can buy that kind of gear and it solves many issues, but I wouldn't say that it results in a fully engineered solution like what is found in a production EV. It just works and is safe enough to be sold.
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Old 06-06-2015, 00:48   #4555
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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And all this doesn't do much about the cells getting stuffed from being left near-fully charged, which will happen as soon as you stop using the boat. Ah, but of course you can "manually" address this, but then it is not "all taken care of" anymore.

Along the same lines there are some (other) "brand name" lithium MPPT solar controllers that just regulate at 14.2V indefinitely. Walk away from the boat and see what happens with battery life when they get floated that high.
Here's a thought. How about using the relay control in the battery monitor to only allow charging when in a specified range of state of charge? For example, the solar panels could be turned on anytime SOC is below 95% and turn off at 99%. As a result you would never cook the cells with unnecessary voltage when they're full.

I've already got relays in place to stop charging sources (solar and alternator) in the event the BMS senses an overvoltage. I could have the battery monitor trip these same relays.
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Old 06-06-2015, 04:07   #4556
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Here's a thought. How about using the relay control in the battery monitor to only allow charging when in a specified range of state of charge? For example, the solar panels could be turned on anytime SOC is below 95% and turn off at 99%. As a result you would never cook the cells with unnecessary voltage when they're full.

I've already got relays in place to stop charging sources (solar and alternator) in the event the BMS senses an overvoltage. I could have the battery monitor trip these same relays.
Yes, it is bit more complicated but the idea is there. The issue is that BMS solutions don't track SOC like in production EVs, they just operate based on voltage. They just offer protection, they don't do anything for battery life. I firmly believe that all of the battery management needs to be packaged into one. Charging should be a BMS function and it should adapt to the energy usage made on board.

I have run my bank in the 40-60% range at times when demand was low, the challenge is packaging everything. The system needs more information than just voltage. I am working on something, but it is some time away.

Charging to a target voltage and cutting off is a definite way of avoiding charging to 100%, but with higher C-rates like when using alternators, it tends to undercharge quite significantly. With solar panels, it tends to be very effective because I only get 0.1C and often even less. I have no more solar charge controller, the BMS is doing it.
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Old 07-06-2015, 09:32   #4557
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Yes, it is bit more complicated but the idea is there. The issue is that BMS solutions don't track SOC like in production EVs, they just operate based on voltage. They just offer protection, they don't do anything for battery life. I firmly believe that all of the battery management needs to be packaged into one. Charging should be a BMS function and it should adapt to the energy usage made on board.

I have run my bank in the 40-60% range at times when demand was low, the challenge is packaging everything. The system needs more information than just voltage. I am working on something, but it is some time away.

Charging to a target voltage and cutting off is a definite way of avoiding charging to 100%, but with higher C-rates like when using alternators, it tends to undercharge quite significantly. With solar panels, it tends to be very effective because I only get 0.1C and often even less. I have no more solar charge controller, the BMS is doing it.

I guess a bit more complicated. >
It is true that Voltage is not enougth , but also conflicts between current source are more difficult to handle w/o communication through the various monitor.
For my view, the bank BMS HV can cut either the alternator field. This is Ok with a single bank set up.
OR the charge relay for a multiple bank set up. but then cut the solar source.

For the solar panel I used the HV alarm from the Victron battery monitor, but with an extra (small) charge relay to keep the bank voltage at max.
Also, eack bank has it own solar MPPT.

This introduces a bit more of complexity....
Today, I personally I dnt mind with these batteries to be 90 or 95 or 100%... the MPPT's are directly connected to their bank and I rely on Victron sound alarm.
When I leave the boat, I switch off all banks, but I have a very good isolation for fridge and freeze. As said Keepling, this is an other story.

cheers
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Old 07-06-2015, 16:08   #4558
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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I guess a bit more complicated. >
It is true that Voltage is not enougth , but also conflicts between current source are more difficult to handle w/o communication through the various monitor.
For my view, the bank BMS HV can cut either the alternator field. This is Ok with a single bank set up.
OR the charge relay for a multiple bank set up. but then cut the solar source.

For the solar panel I used the HV alarm from the Victron battery monitor, but with an extra (small) charge relay to keep the bank voltage at max.
Also, eack bank has it own solar MPPT.

This introduces a bit more of complexity....
Today, I personally I dnt mind with these batteries to be 90 or 95 or 100%... the MPPT's are directly connected to their bank and I rely on Victron sound alarm.
When I leave the boat, I switch off all banks, but I have a very good isolation for fridge and freeze. As said Keepling, this is an other story.

cheers
gael
Yes, cutting the alternator field is a bit of a disaster prevention measure, but it is critically important. You can "regulate" it this way too by cutting at a target voltage, but it is rather crude.

HV disconnect comes with its own set of challenges anyway. Some sources like MPPTs and wind generators can spike (sometimes fail) when simply disconnected under load or go to quite high voltages afterwards. A wind generator free-wheeling could put a fairly outrageous voltage on the disconnected charge bus frying the other devices. Some kind of early shutdown is always better than a HV disconnect.
There are a lot of engineering challenges when you go through all the possible situations and ask "what could happen here?"

As long as charging and discharging keep happening regularly and the system was tuned properly, there shouldn't be battery life problems - there are some remarkable examples of that here. If the bank charges to full and mostly stays there, I don't know if lithium will prove much of an investment in the end, other than for the performance. How would it look after 3 or 5 years? This is what happens with most if not all commercial solutions however.
Conversions are quite costly, so I always worry a lot about the bank losing capacity the way laptop batteries do when they are not used much, or seeing some "battery protection event" causing unexpected and expensive damage elsewhere. Explaining afterwards that it is "normal, of course" is a bit steep.

The problem is not so much the bank itself and protecting it, it is dealing with all the gizmos that were never designed to operate with a lithium system and aren't in fact suitable: bad voltage, bad regulation, no charge termination, can't disable, can't disconnect safely, load and charger combined together... the list is quite long.

What is the best pathway forward? Toss them overboard at the start? Maybe. At least this is simple. My boat is dead simple and I hate marine electrogadgets. I don't have most of these problems.
I don't see fully-engineered lithium becoming mainstream any time soon for all these reasons and I am not sure about what it would look like.
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Old 07-06-2015, 16:51   #4559
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[QUOTE=OceanSeaSpray;184296
I don't see fully-engineered lithium becoming mainstream any time soon for all these reasons and I am not sure about what it would look like.[/QUOTE]

If Tesla is going to put batteries in lots of houses, don't you suppose they will have to also supply a fully engineered system? And why wouldn't that system be readily adaptable to a boat?
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Old 07-06-2015, 17:15   #4560
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

I think they will indeed supply a fully engineered system and it will be high voltage. What I know is that I won't be scratching my head about hooking up to it 14VDC alternators and bloody wind generators.
Lithium comes with integration issues. I don't think solving the integration with grid-tied systems and AC mains voltage is going to help much on small yachts.

The question with boats is about the pathway forward. It is a bit hard to claim integrating every gizmo available for lead-acid systems...

A proper BMS truly taking care of the bank? A few well-engineered solutions/schematics to integrate selected or typical gear? A few specialised components to solve specific problems? Which ones?
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