LiFeYPo4 questions

[PNjunction]

Oh yeah, for an EV running 12v at 800a would be ridiculous, not to mention highly unsafe! Your point is well taken in the motive-power field.

However, in a 12v, low current solar storage housebank that draws about 1.2kw daily, with an 800ah bank that would last you about 6 days - assuming one really wanted to draw down to about 80% DOD. But no real big housebank setup should be running 12v anyway, so perhaps 24v at a minimum, ie an 8S battery string would do.

The major intent here was to help maintain a healthy balance among the cells by getting capacity first, and then series stringing them for voltage, rather than just thinking in terms of paralleling entire battery banks together at their end terminals. Housebanks voltages only, not EV's.

[Mike90250]

For the dump trailer, when dumping, it will always be attached to tow vehicle, and connected to the RV power feed. There are no parasitic loads. Battery is only needed to power electric brakes if it disconnects on the highway. I was thinking of a small 20ah size battery that has automotive style posts. But maybe a small AGM would be better.

[Sunking]

But maybe a small AGM would be better.

Yes Sir. Just put a 4 watt panel on the trailer to keep it charged up. No controller needed with a C/100 charge current. Or just take it inside and charge once every few months.

[Mike90250]

Yes Sir. Just put a 4 watt panel on the trailer to keep it charged up. No controller needed with a C/100 charge current. Or just take it inside and charge once every few months.

The small dashboard PV I had on it, got sunburn. really needed to be behind a sheet of glass indoors, the plastic frame and wire insulation is all toasted. And pulling the battery was too much pain. Easier to run an extension cord out to it 1x a month. If I remembered.

[Sunking]

The small dashboard PV I had on it, got sunburn. really needed to be behind a sheet of glass indoors, the plastic frame and wire insulation is all toasted.

Now that is some funny stuff, I don't care who you are. Your solar panel got sun burned.

[SunEagle]

Now that is some funny stuff, I don't care who you are. Your solar panel got sun burned.

More likely it was heat stroke.

[Hkalan]

Hello,

I am using CALB 3.2v 400Ah cells (8 in series) for a 25.6v House bank as I live totally off-grid on my Bertram 46.6 Flybridge Motor Yacht.

The Morningstar TS-60 MPPT is working wonderfully with four 300W panels (1,200w total). I have the custom settings on the Morningstar at 28v, and the cells are very happy.

I have the BMS protecting the cells, that incorporate 2 pole and single pole relays for the Warning HVC and LVC (28.4v and 23.2v), as well as the protection HVC at 28.8v. I have redundancy relays on the HVC to assure full isolation.

Even with the 24v alternator on the port engine, I have the emergency house bank (that drives the windlass) so the alternator will always be under a constant load. Attached is the diagram of my BMS and solar connections.

I have the Cell-Log-8 as well... I power the USB side from the generator 12v start battery. It is just an extra ($15 USD cost) monitor to assure the bank is good. When 150 miles offshore, redundancy is a good thing !

The Morningstar monitoring is fantastic, and adding the Network Hub has allowed me to connect their relay that will automatically start and stop the generator to energise the AC powered LifePO4 charger. The AC charger is set to 28.1v and never activates the BMS, thus keeping the cels very happy !

I keep the LifePO4 cells out of the engine room, as well as all other charge controllers (The AC charger is in the engine room), and there has never been a issue with the temperature sensor from the bank.

I have gone down to 90% DOD several times, and the LifePO4 are more then happy and will to give a bit more before the sun came up for the panels and Morningstar to get things topped off !

I have used AGM and FLA for too many years, and I am happy to be using the LifePO4.

Speaking from experience, the Morningstar TS-60 MPPT is an outstanding solar controller for LifePO4 banks !

Alan
LPF-BMS-Relays.jpg

[PNjunction]

The Morningstar TS-60 MPPT is working wonderfully with four 300W panels (1,200w total). I have the custom settings on the Morningstar at 28v, and the cells are very happy.

Nice - 3.5v per cell. Plenty of headroom, and still get rated 80% capacity overall before going well into the discharge knee. Now I just need to work on getting a vessel to house my cells properly.

I have the BMS protecting the cells, that incorporate 2 pole and single pole relays for the Warning HVC and LVC (28.4v and 23.2v), as well as the protection HVC at 28.8v. I have redundancy relays on the HVC to assure full isolation.

Sounds reasonable. Those voltages indicate to me that you are not driving them into an unnecessary balance routine, and the major safeguards are the high and low voltage disconnects. Personally, I'd change the LVD to 25v, but to each his own.

I have gone down to 90% DOD several times, and the LifePO4 are more then happy and will to give a bit more before the sun came up for the panels and Morningstar to get things topped off !

One thing that may be saving you here is that once you go below about 80% DOD, when you recharge, you should do so at a lower than normal charge current until about 3.2v per cell is reached, and then full current can be applied. Many people don't take this into consideration, but fortunately for solar, this is being performed prior to the start of the major solar-insolation hours, so it is doing this nicely behind your back.

I'm with ya' on the happiness factor!

[inetdog]

The small dashboard PV I had on it, got sunburn. really needed to be behind a sheet of glass indoors, the plastic frame and wire insulation is all toasted. And pulling the battery was too much pain. Easier to run an extension cord out to it 1x a month. If I remembered.

Almost anything will get fried sitting on the dash of a closed car.
The panel would, I suspect, have been perfectly happy sitting outside the car in the direct sun.

[Mike90250]

Almost anything will get fried sitting on the dash of a closed car.
The panel would, I suspect, have been perfectly happy sitting outside the car in the direct sun.

It's a coleman panel, sitting on top of the battery box of a dump trailer (outside, in the sun & dust). Battery is for the electric brakes if it breaks away from the tow vehicle.

[Spooner]

Not going to work. LFP batteries are not compatible with charge controllers made for lead acid.

Thank you for letting me know! that was one of my major concerns. what small light weight portable versatile powerful awesome charge controller would you suggest?

[PNjunction]

Actually that is wrong. As long as you know how LFP batteries charge, you can custom-set most of the higher quality controllers to very adequately charge an LFP pack. But you have to know what you are doing. I use a simple Schneider/ Xantrex C12 for my smaller stuff, but the voltages are tweaked properly. Others like just a few messages above, are successfully using Pb based controllers, and while they may not be exactly ideal, they can be made to work, again if you know how to properly set them.

Right now, I'd like to keep your project under one thread to make it easier to track your progress, rather than splitting up the details into this one - if that's ok.

[Spooner]

Actually that is wrong. As long as you know how LFP batteries charge, you can custom-set most of the higher quality controllers to very adequately charge an LFP pack. But you have to know what you are doing. I use a simple Schneider/ Xantrex C12 for my smaller stuff, but the voltages are tweaked properly. Others like just a few messages above, are successfully using Pb based controllers, and while they may not be exactly ideal, they can be made to work, again if you know how to properly set them.

Right now, I'd like to keep your project under one thread to make it easier to track your progress, rather than splitting up the details into this one - if that's ok.

ok I guess I'll only use the other one. I was just trying to drum up as much advice as I could get.

[asheville solar]

Acquiring LiFePo4 battery bank and need help

Hello,
I am new to this forum and my name is Chris. I do apologize if I should have started a new thread. I am currently acquiring all the components for a residential 10Kw solar array system. Most likely I will be using Outback's Radian "A" series hybrid inverters for a battery bank. I have contacted numerous chinese suppliers of LiFePo4 batteries and had a couple of questions on the specs one would want for a normal residential home LiFePo4 battery bank since they will build them to your specs.

After speaking to Outback, the Radian system I will be getting will need at least a 400ah battery bank system. Since I ultimately want a 48v system, I have decided to just start with that size and work my way up over the years with amp hour capacity.

Can anyone tell me what discharge rate I would want with a 48v 400ah battery bank? 20A (0.2C)?
max discharge rate?
Any other helpful info would be appreciated.

I am new to this world and trying to learn the language if you will.

Thanks for the help,
Chris

[inetdog]

Hi Chris and welcome to Solar Panel Talk!

At this point, your questions follow the general topic of this thread, but is it gets too far afield one of the moderators will help you spin it off into a new thread.
Starting your own thread (in ONE place please) is never going to be discouraged, although some of the answers you get may point to existing threads.

An LiFePO4 battery bank should be able to handle a discharge current much larger than .2C, although for a correspondingly limited time. Computer battery packs are often discharged at C/2 or higher (to the disappointment of their owners.) The serious restrictions will come on the charging rate, which will depend on the intelligence of the charger, but can be higher than C with the right algorithm and monitoring or .2C with a relatively dumb charger.