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

[john61ct]

Originally Posted by exMaggieDrum

There are some LFP monitors that have individual cell monitors that report back to either a BMS and or a cell logger. I actually am not sure how they get individual cell voltages but evidently they do.

If you think about it, they must be positioned between the cell "inside" and the external connections. The easier and more expensive Integrated Systems you can buy, that per cell monitoring and control is a routine part of what you're paying the extra money for.

[john61ct]

Originally Posted by PacificGreen

Yeah I have no doubt I can run a battery charger off an inverter to another battery bank. I've looked but I can only find power supply units and the odd 48v to 36v dc dc converter that would be acceptable to power the unit. The 36v battery charger is the same principle. I only need to match the input charge amps to the output amps of the motor for a gps anchor that can run all night. I already have a 12v battery charger that I have in the boat from a inverter, another 36v will be no different.

Sorry not my style, IMO inefficient kludge.

Why 48V again?

12 or maybe 24V DC should be your usage/conversion hub "Esperanto", not back and forth between AC and DC ya numnuts (with respect and affection!)

From there, this is one candidate
http://www.sterling-power-usa.com/Pr...lt-36volt.aspx

But you just need DC converter step-up/down (boost/buck) power supplies, no need for the extra intelligence of a battery charger. A ham radio geek could connect some much cheaper components together for you, but then marine conditions, better to talk to a marine electrical pro.

[PacificGreen]

My system is entirely solar electric. I have no starter battery. A dc 48v to dc 36v converter is difficult to source. There is one PBA1500F-36 - Cosel - TRC Electronics but why go that way when a simple battery charger will do the same thing.

I have 16 400ah cells running at 48v nominal. The system is charged by solar, generators and shore battery chargers. I have 6000 watts of inverter power between two 48v inverters that I use. It is trivial to run a battery charger and from a price point a battery charger is much easier to acquire.

I already have two dual 36v/48v generators but I'm not inclined to run a generator all night.

I'll refer you back to post #5514
This is where I started to contribute my experiences with this thread in regard to roetter's degraded cells and my goals for the remainder of my system. There is even a nice youtube link there for a pretty good idea of what my system is capable of. The aspect of the trolling motor is the final piece of outfitting my electronic autopilot. It is a backup to the outboard steer autopilot function and will also serve as a gps anchor. The particular trolling motor is a http://www.motorguide.com/store/product/xi5-saltwater of the 36v variety the biggest one available as my boat is 5600 lbs fully laden but it should still suffice to anchor and even move the vessel if necessary.

I've continued posting in regards to Joe's cells and arrived at some conclusions based on the age and usage patterns of his cells. I contemplate the condition of my smaller reserve bank of calb72ah lithium cells currently sitting in 48v configuration in storage. How many cells are required to make a 36v configuration? I've not worked with 36v systems yet so am unaware of the voltage range that I should be aiming for.

[senormechanico]

I put a small digital voltmeter on each cell in our home and on the boat as well.
Here's a shot of the "blinky blinky" codes and also of the home's bank.
Before anyone gets upset with the meters not reading exactly, they're in need of calibration. There's a pot on the back, and it's on my bucket list.

[PacificGreen]

Originally Posted by senormechanico

I put a small digital voltmeter on each cell in our home and on the boat as well.
Here's a shot of the "blinky blinky" codes and also of the home's bank.
Before anyone gets upset with the meters not reading exactly, they're in need of calibration. There's a pot on the back, and it's on my bucket list.

I really need to see this. The image did not come through.

[PacificGreen]

My other thought on an active BMS should my miniBMS ever fail is to simply create my own and now with the new X4 AC Pro AC/DC Four Port Multicharger | HITEC RCD USA this would seem to be possible. This would translate into an active BMS that could shunt and balance easily and provide information at the swipe of a finger. I've used an older model successfully to balance my smaller bank at times and certainly wanted 3 more of them but made due with one.

Essentially you would wire 4 of these to your 16 batteries and you would have a very capable BMS aside from any shutdown functions. I'm not sure the newer model is more capable than the older model at this time. Wiring four of these into a pack does give voltages for each cell and allows for balancing.

Never tried it only hypothetical especially on larger batteries but it is something that may work.

[PacificGreen]

This is what it is all about for me with the trolling motor:

https://www.youtube.com/watch?v=XOODe4sbvxc

Now having the ability to run that around the clock 24/7 priceless.

https://www.youtube.com/watch?v=Z5PNYUXa-eE&t=6s

[john61ct]

Originally Posted by PacificGreen

My system is entirely solar electric. I have no starter battery. A dc 48v to dc 36v converter is difficult to source.

Exactly my point. Why are you using an outlier voltage for your foundation? I really am asking, why, curious minds want to know?

Nothing about solar dictates 48V. Nor denying yourself a relatively cheap dedicated starter/reserve lead bank.

Store at 48V if you want (must?), but use 12V as I said as your "usage conversion Esperanto" and a whole world of cheap and easy options opens that is now closed to you except at great difficulty and expense.

I bet Andina could rig you up something like her Trollbridge, if you really do (think you) need to stick to that.

http://www.yandina.com/NewCatalog.htm

[PacificGreen]

Originally Posted by john61ct

Exactly my point. Why are you using an outlier voltage for your foundation? I really am asking, why, curious minds want to know?

From a marine systems integration standpoint 48v is the easiest for system integration with the choice of electric outboard motors that I decided on. Most if not all components for 48v are readily available unlike other voltages beyond that without even more sourcing. Anything above that and there are different ABYC suggestions for wiring.

Originally Posted by john61ct

Nothing about solar dictates 48V. Nor denying yourself a relatively cheap dedicated starter/reserve lead bank.

So for example, I built an array of 12 sheets of panels that weigh just 75 lbs and put out 2160watts - a truly useful amount of energy. You could actually charge an 20kWh pack in 10 hours - about two days in the sun.

I'm not clear on how a starter from an internal combustion motor and a heavy lead acid bank would even fit into my solution.

Originally Posted by john61ct

Store at 48V if you want (must?), but use 12V as I said as your "usage conversion Esperanto" and a whole world of cheap and easy options opens that is now closed to you except at great difficulty and expense.

I have 12v for most of the old electrical architecture and the newer electronics on the boat like the running lights and what not that is produced from an ac converter. It draws very little energy.

Originally Posted by john61ct

I bet Andina could rig you up something like her Trollbridge, if you really do (think you) need to stick to that.

Catalog Frame

Not sure how much clearer I can be on this. I don't have a internal combustion engine nor do I want one. It was never part of the system design and even integration with a gasoline outboard like my 9.9 yamaha for my tender is proving to be a waste of resources and time as opposed to simple electric.

[john61ct]

Originally Posted by PacificGreen

From a marine systems integration standpoint 48v is the easiest for system integration with the choice of electric outboard motors that I decided on.

Forgive my ignorance or misunderstanding, I'm sure it's frustrating. Now I understand much better, thanks.

But at least my link to the trollbridge has nothing to do with how you get propulsion.

It's about the fact that a 48V bank is 4x 12V banks. Not just in theory but can be concurrently, charge in at one voltage, output at another.

Apparently anyway, Andina knows the details.


And setting that aside for now, clean stepping down (DC buck conversion) from 48V to 12V is relatively cheap and easy. That circuit can now carry any 12V gadget loads you like, no need paying more for 48V stuff less you want to.

Stepping up from there (DC boost conversion) to 36V, you also have lots of choices, including that Sterling.

I have to believe it's worth at least looking at, since going DC-AC and then AC-DC again, when you only need DC-DC, seems (to me) very wasteful of your expensive electricity.

Maybe no big deal for your little legacy 12V stuff on your scale and budget, but

Running your 36V anchor motor 24x7 can't be an insignificant load, and if running it through inverter and then AC charger isn't wasting maybe half its final output I'd be surprised.

[PacificGreen]

Originally Posted by john61ct

Forgive my ignorance or misunderstanding, I'm sure it's frustrating. Now I understand much better, thanks.

Somewhat frustrating but it seems enlightenment is what your after here since January. What type of boat do you have? Are you using lithium batteries or have you ever had any?

Originally Posted by john61ct

But at least my link to the trollbridge has nothing to do with how you get propulsion.

Yes they seem from my brief look very ice engine alternator heavy.

Originally Posted by john61ct

It's about the fact that a 48V bank is 4x 12V banks. Not just in theory but can be concurrently, charge in at one voltage, output at another.

No and as I've mentioned before my lithium back is comprised of 16 cells in reality. Certainly I charge at 48v and from there I can do anything I like.

Originally Posted by john61ct

Apparently anyway, Andina knows the details.

I'm not clear on any details Andina knows?

Originally Posted by john61ct

And setting that aside for now, clean stepping down (DC buck conversion) from 48V to 12V is relatively cheap and easy. That circuit can now carry any 12V gadget loads you like, no need paying more for 48V stuff less you want to.

At his point if I choose to plug something or down convert really doesn't matter much. Yes there seems to be an abundance of cheap and easy 48v to 12v converters. Most of my 48v gear was had for very reasonable expenditures and is already acquired save for a few pieces if desired or wanted like the 48v to 36v dc dc converter.

Originally Posted by john61ct

Stepping up from there (DC boost conversion) to 36V, you also have lots of choices, including that Sterling.

I'm really not sure this would be any more efficient in terms of energy usage or system integration with what I have. Sterling from what I've seen offers nothing I can use.

Originally Posted by john61ct

I have to believe it's worth at least looking at, since going DC-AC and then AC-DC again, when you only need DC-DC, seems (to me) very wasteful of your expensive electricity.

John my electricity is free. It is a moot point really from an efficiency standpoint. The bulk of my system is dc to dc.

Originally Posted by john61ct

Maybe no big deal for your little legacy 12V stuff on your scale and budget, but

Exactly.

Originally Posted by john61ct

Running your 36V anchor motor 24x7 can't be an insignificant load, and if running it through inverter and then AC charger isn't wasting maybe half its final output I'd be surprised.

I believe it will be fairly insignificant and considering the data on the motor draw 40amps @36v max I hardly see this thing using 10 amps constantly. I can probably power it all night long from my 36v battery bank without a charger. You do get that I'll only have a charger running to another separate 36v battery lithium battery bank don't you and that the charger probably doesn't even need to run all day. From an integration standpoint it is just as easy to install another charger plug it in and run the leads to the battery and hook the motor to the battery. Doesn't get much simpler than that.

[exMaggieDrum]

Originally Posted by PacificGreen

Well it seem most modern BMS systems monitor cell voltages all the time. The aspect of placing the two probes on the top of terminals is the same. Not sure why you say you would have to disconnect all the batteries.

Clearly, I must not know what I am talking about. When I do what you are saying I get the average of the voltages of all the cells connected, whether they are in parallel or in series. I must be doing something wrong.

Good luck with your system.

[autumnbreeze27]

Originally Posted by Maine Sail

Joe,

The thing you need to focus on most is losing the lead acid mind set.

IDEAL LFP USE= Charge>Shut off All Charge Sources>Use Stored Energy>Charge>Shut off All Charge Sources>Use Stored Energy>Charge>Shut off All Charge Sources>Use Stored Energy>Repeat>Repeat

When at the dock isolate the LFP, discharge it to 50% SOC, and let it sit there. Use a lead acid reserve bank for dock side buffering.

When on shore power, I setup my charger so it only turns on when the SOC drops to 50% SOC. It brings the charge up to 80%. Solar can bring it up to 100% right around sunset. Then it takes several days before it gets to 50% again, because the solar charges the bank every day. I can't see how that would damage my battery?

If I'm running the engine for 8 hours and my alternator is set to charge to 13.6V, even if it goes to 100% for 4-5 hours and drops to 0A going to batteries, would you consider that damaging to the battery?

[PacificGreen]

Originally Posted by exMaggieDrum

Clearly, I must not know what I am talking about. When I do what you are saying I get the average of the voltages of all the cells connected, whether they are in parallel or in series. I must be doing something wrong.

Good luck with your system.

https://www.youtube.com/watch?v=1caNzXpoeas

Not that I'm advocating large battery banks comprised of small cells ever but this is a pretty standard procedure to measure individual cell voltages if you have a BMS or not.

I once had an option to purchase many small calb cells used very little for a antique truck project that worked well. From my experience with even 16 small cells I always found them problematic especially if one cell ever comes out of balance.

Thankfully I didn't go that route. Anyhow you must not be running individual cells and perhaps have some type of enclosed cell system. What type of lithium batteries do you have?

[PacificGreen]

Originally Posted by autumnbreeze27

When on shore power, I setup my charger so it only turns on when the SOC drops to 50% SOC. It brings the charge up to 80%. Solar can bring it up to 100% right around sunset. Then it takes several days before it gets to 50% again, because the solar charges the bank every day. I can't see how that would damage my battery?

Hope you don't mind if I give this answer a go. On shore power if your SOC usually based from coloumb counters is set to 50% SOC how can you be sure your coloumbs were counted correctly? A better indication would be to provide the volts of your bank and your individual cell voltages at what you believe is 50% state of charge. Coloumb counters if not accurately maintained are frequently wrong and frequent calibration is essential to accurate readings.

Isn't it nice how solar works to finish off charging. Again though what is 80% on your bank in terms of voltage and cell voltages? If your reading
13.48v and 3.37v on all your cells is this your 80%? If so what is your 100% state of charge around sunset in terms of voltages? If your 100% state of charge is oh say 13.8v with cell voltages of 3.45 and your holding your bank there slowly charging off solar for six hours then your keeping your bank hot and reacting the chemical in the upper knee for not much reason.

Originally Posted by autumnbreeze27

If I'm running the engine for 8 hours and my alternator is set to charge to 13.6V, even if it goes to 100% for 4-5 hours and drops to 0A going to batteries, would you consider that damaging to the battery?

Yes. You are floating your batteries at 100% or close to that upper knee for no good reason especially if you are not using that energy. How many amps does your alternator charge with and what is the acceptance rate of the batteries and how many are in your pack and your total amps?

In six months of normal usage on my pack It would seldom if ever be above in 12v speak 13.5v. If I were calibrating my coloumb counter, adjusting a potentiometer or simply charging it to specifically be completely full to conduct rudimentary baseline tests, then yes i would go beyond that mark. But then understand my automatic shore power chargers only ever dump 30amps total into the bank and usually terminate charge at 53.3 volts. If I want to go beyond that mark I have to physically reset the breaker to charge beyond.

In most cases the solar will bring it up past 13.325 towards the end of the day but seldom if ever past the 13.6 mark. I want to emphasize that on the occasions above that mark it was actually an arduous procedure to get the voltage up around 14.25v and 3.56v per cell. My upper knee acceptance kicks in around 54.4/4=13.6v and 3.4 volts per cell. After that my bank comes to full very quickly (10-15 mins) and it certainly does not like to sit there for long and wants to naturally come back to its resting voltage of 53.3. At which point having been there briefly one can say the bank is full and the coloumb counter is now correct for 100% state of charge.

But if in fact you are slamming the amps hard from an engine driven 100 amp alternator or otherwise and are continually pushing that current through to your batteries for very long expect to burn through your chemical more quickly. Hence with 12v systems 4x as many amps are carried and used by appliances, chargers etc., that are not always best for lithium based systems. With 12v it is important to limit the current both on charge and discharge when at all possible.

And I guess that is the reason they don't make 12v electric bikes or electric cars. Sure lithium can be used for 12v but some consideration must be given to the amount of charge source and discharge in these cases. For example I have 16 calb 72 ah cells I could arrange them any way I like. Would I choose one large 12v pack based on existing equipment and lead acid stereotypes or arrange for the starting point of electric vehicles at 48v. I would suggest the later as it naturally plays into the chemistry of the battery better.

Conversely if I have 500 watts of solar is it better to be set up at 12,24,36 or 48v? What is it charging and how many amps is it producing? The 12v order of magnitude in amps is usually double. Sure more amps always better right? Not so with 12v lithium. Reduce the amps increase the current for longevity of systems. Wires will be smaller as well.