LiFeYPo4 questions

[Sunking]

Ironically, most places to get these are EV sources, and accordingly are bms-centric if that's your thing, but you can get cells without them if you desire.

Not so sure that is Ironic or not because EV's are the only item you can justify the expense of using a large LFP battery, and you would for dang sure use a BMS to protect your investment. All the R&D in lithium is being driven by the EV market. RE applications will just be a secondary market that benefits from EV technology. Until there are controllers/BMS made for RE I do not see it going anywhere fast. Right now as it stands lithium cannot compete in the RE sector. I think that will change sometime in the future, but still a good ways off in the future.

With that said I would love to be on the ground floor or major investor of a company who comes up with a Lithium battery that has cycle life of 10,000 cycles, 5C charge/discharge rate, 300 to 400 wh/liter specific energy density,and $0.30/watt-hour cost. You would quickly become the biggest company in the world and can easily have a monopoly in the energy market. Heck you would not even need a factory or many employees, just license out the product to every battery manufacture out there and collect a royalty and make a few dollars off every human being on the planet many times over. Kind of scary of the kind of power that would give a company or group of individuals.

[PNjunction]

Actually nobody because I'm using GBS cells. but thanks for the info! Perhaps others might be interested!

If I had to get CALB, I'd probably prefer the newer gray versions, but then again, in a house-bank, the slightly older blue case ones would be fine I think.

At this stage, I really didn't care among GBS, CALB, or Winston - it is what they had at batteryspace. Ironically, most places to get these are EV sources, and accordingly are bms-centric if that's your thing, but you can get cells without them if you desire.

Since batteryspace isn't EV specific, they had a lot of the stuff I needed already put together, such as all the individual cell links, strapped (or just wrapped in a plastic box), hex keys, and assorted odds and ends like individual-cell 3.6v chargers yada yada. I made sure I was getting the blue prismatic cells, and not the higher powered cylindricals. Whatever you do, make sure you get all the proper cell-links AND possibly a set of end-terminal connectors. In other words, don't half-a** connections with speaker wire if you forgot to get these at the same time.

[Sunking]

PN who are you buying Calb cells from. You can PM me if you prefer. I gotta guy up in Oregon who is a licensed dealer with fair prices.

[PNjunction]

Hi Reed - looks like you are doing good so far. I've got some additional GBS cells headed my way, so your timing is good.

When you say you've reached float, I hope that your float voltage (which is unnecessary for lifepo4,) is not high, and low enough to be benign, although still active. If you could disable float, that would be even better.

In regards to your question - this brings up something I'm researching right now about "micro-cycle" life degradation of LFP. From what I've garnered so far, doing a micro-cycle repetetively leads to higher internal resistance and loss of capacity. But what exactly a micro-cycle is for LFP I'm still researching. Is it 10% DOD, 20%, 30% ?? Maybe Sunking can help us out here.

This is a different issue than overall charge voltage, which hopefully you've lowered to around 3.45 - 3.5v per cell. No need to go higher unless you need that for balancing purposes.

While I'm researching the micro-cycle DOD issue, I'm going to try and achieve at least 20-30% DOD per cycle to CYA. Perhaps it is less, I don't know yet. T1 Terry may have more info than I do about it. Heh, in your case with over-capacity, perhaps an even lower voltage would be advisable, like 3.4 volts so you cycle starting from 20% DOD right off the bat in a PSOC environment. Maybe just a weekly 3.5/3.6v higher voltage to check balance.

Interesting update: I found on some recent CALB spec sheets, in addition to the normal HVC and LVC damage points, along with "recommended" normal use voltages, suddenly there appeared a spec for "recommended DOD" cycling! Guess what - they list as 10-90% DOD, emphasizing the need to not always charge up to 100% SOC. Personally, I'm not going to go as low as 90% DOD, as I find that I'm well into the steep discharge knee at that point. (at least with my GBS cells).

[reed cundiff]

As noted above, we are full time RVers (caravaners) and are solar autonomous with LFP battery suite. The solar generally has the battery suite at float until near nightfall and they are almost always at 80 to 90% charged/10 to 20% DOD) at dawn. There were remarks earlier on this thread about problems in keeping LFP at to high a charge. Should we discharge them more fully.
Reed and Elaine

[Mike90250]

the fact that the TS-MPPT-60 can be set to a custom charge setting and will down convert my panel's 24 volts to the battery bank's 12 volts, but what charge settings would I program into the TS-MPPT-60 for a LiFeYPo4 battery bank?

Can indeed be programmed, I use the serial port and and usb translator to get to my laptop, along with MS View software to program.

[inetdog]

...Elaine thinks I am OCD with checking the instrument panel during the day, and perhaps she is correct.
Reed and Elaine Cundiff

Well, given the cost of the batteries and the risk to food, etc. I would have to say that you are not at all OCD. Maybe after some months of good performance I might cut back a little. But only if I were confident that the alarms, etc. work properly.
Unless you check at the exact same clock time each day. In that case I would say that you are actually CDO. (That's OCD but with the letters in alphabetical order like they should be.)

[reed cundiff]

Son Cary has stuck a card in the control panel cabinet where we can monitor the system that stated "49.6 V" turn-off. It is a nominal 48 V system but operates generally 52 to 54.6 V. This is four "12 V" battery packs in series. He generally designs and fabricates for commercial purposes and voltage loss is an important consideration. There is also supposed to be an audio alarm when it gets near that voltage. As I have noted in a previous post, we run the refrigerator on electric during the day. If we expect strong solar insolation the following day, we leave it on 110v overnight and get up with about a - 3kW-hour deficit. If it is a bright day, we are up to full charge by noon. We did have 1400 W to controller a few days ago when we let it drop to about -4500 W-hours and didn't get the snow off till 1 pm, aka full insolation on a right day. It was fully charged in about 4 hours. Elaine thinks I am OCD with checking the instrument panel during the day, and perhaps she is correct.
Reed and Elaine Cundiff

[PNjunction]

Wow - first of all I'm glad everyone is ok!

As a side note about crashing, if you smell a sweet-perfume like scent that is BAD. That means electrolyte is cooking, or perhaps one of the vents if they are covered has come off and is not immediately visible. Stop everything and be safe while inspecting. Lifepo4's are generally safe, but like any battery are a danger after an incident like that until inspected and verified for safety.

50% DOD - you'll have great cycle life. One thing to note is that although your bms should protect against this, but if you drop below 80% DOD for some reason, then do NOT apply a charge current larger than 0.1C to it until it comes back to the 80% DOD mark - once it does, THEN you can continue on with your normal current charge. Some small 12v-nominal lifepo4 specific chargers do this, like the little 5A Optimate TM-291 lithium.

[reed cundiff]

RV with LFP

The battery suites fabricated by Manzanita are apparently quite good for electric vehicle usage.l The BMS, controller and monitor are designed for electric vehicle usage (high drain rate) and not for RV (moderate to low drain rate).

We (our son with me watching at times) exercised system running both air conditioning and microwave simultaneously and the batteries were being drained at 3 kW. We have not run the batteries below 50%. The monitor gives the voltage of each of the 16 sub-cells as well as that of the total suite. It was below freezing last night and the forced air heater ran quite a bit and we are down -1600 kWh (down to 75% capacity) with suite voltage down to 52.4v and individual cells around 3.3V. Cut-off is 49.1V for suite and 3.1V for individual. Float is 54.4V for suite and 3.4V individual cell

This is the best answer I can give to your question of "...With the battery balanced, have you tried just running from an 80% to 10% DOD ratio without a bms - that is staying out of the extreme charge / discharge knees?"

I do not believe system has been exercised without BMS

When little sunlight is expected, we turn off the inverter at night which saves quite a few Wh (1.5 amps at 54V). We run the refrigerator on ac during the summer during daylight hours even though propane is much more efficient. We have changed to all LED lights except for the one below the microwave stove.

Our older system utilizing glass mat batteries was in wreck near Orizaba Mexico on March 15 of last year which totaled vehicle and trailer in 70 car pileup in heavy fog at 8500'. Mexican Insurance paid for truck (engine torn loose and frame bent to ground - no amount of Bondo would fix that) and finally agreed after one year (two days ago) that the trailer with bent, warped and cracked frame is totaled. The panels, batteries, and inverter were still attached. Son Cary and grand-daughter Sonya drove 1700 miles from Las Vegas, NM to haul our personal items back to US. We noticed that the brake breakaway was "broken-away" which dumps 10 amps (12 V) to hold the electro-magnetic brakes. Cary just clipped and isolated the wires and the system immediately began charging at 20 amps - and is probably still working great at some wrecking yard in Hidalgo, Mexico. The Onan generator was smashed and pushed back through the main baggage compartment - but the batteries, inverter and controllers were placed further back and were not damaged.
Reed

[PNjunction]

No worries about catching fire if those cells from Manzanito Micro are actually lifepo4 like the CALB's. Poor / insufficient wiring infrastructure, or bms failure perhaps, but the batteries themselves would have to be insanely abused since they are not the temperamental lithium-cobalt.

The yttrium versions of lifepo4, ie lifeYpo4 are similarly safe as they are still in the lithium-iron phosphate family.

With the battery balanced, have you tried just running from an 80% to 10% DOD ratio without a bms - that is staying out of the extreme charge / discharge knees? (In a nominal 12v system, that would be about 12.85v to 14.2v) In our fractional-C application, you may never need a balance unless the cells themselves are grossly mismatched to begin with.

[reed cundiff]

RV with LFP

Read every post on this thread and found them informative and interesting. We are full time RV'ers with four (4) Manzanita Micro 180 amp-hour (13.5 V) in series for a 180 amp-hour (54.5V) battery set. This is about 9.8 kWh total of which 80% should be usable. The batteries fit nicely into the forward baggage compartment. We have about 1.4 kW in solar. This was expensive but older son is in solar business and he wanted to see if he could design and fabricate a solar autonomous RV. The battery set allowed us to sit out a snow storm for four days with the forced air heater going almost full time (15 F). We have also been able to run the a/c for 3.5 hours as combination of solar and battery suite. We did not go below 60% energy storage in either case. This means dispersed camping in National Forest lands without a generator to annoy the birds and animals. We had two young Bull Moose "fighting' within 25 meters of the rig near Vedauwoo, Wyoming this last August. I slept late and missed most of it. The rest of the family was enthralled. We boondock as "dispersed camping" 90% of the time. The rest of the time we are "camped" in our kids backyards without using hookup.

Weight/cube is critical in a 5th wheel and equivalent usable energy storage with PbS would have probably been in excess of 750# as opposed to the 250# for the Mazanita batteries and BMS. 750# would have placed us in excess of rear axle loading of dualie 4x4. There would be no room to place such PbS batteries.

If we catch fire and burn to the ground, we shall report it, if possible.
Reed and Elaine

[inetdog]

G'day Mike, bought the gel 4 years ago before I knew anything about them and they were recommended for a solar set up in a bus. Had nothing but trouble, they seem to be at full charge, but lose it rapidly when used and haven't worked out why. Though it may e the controller, so have changed that a few times, or maybe the panels weren't providing the proper input, but they are working fine.

You're the first one to tell me gel isn't good for solar, but form using them would have to agree and don't even know why. Be interested to find out why, what they are good for and whether I can get better service from them until we can change over to lifepo4.

Found the answers in the battery forum, thanks. I've been battling these things for years and lucky they are still alive, can't wait to get my lifepo4 set up.

For those who are watching the thread and not doing their own research through the forums, the main drawback with GEL is that they cannot (with maybe one possible exception stated by one manufacturer) be charged at a high C/N rate.
Any substantial gassing inside a GEL battery can cause gas bubbles to form in the GEL and even though the gas may recombine back to water and not cause the cell to vent, the void in the gel at or near the surface of the electrode will cause a permanent loss in cell capacity (both current and AH) from which the cell cannot recover.

[tasman]

G'day Mike, bought the gel 4 years ago before I knew anything about them and they were recommended for a solar set up in a bus. Had nothing but trouble, they seem to be at full charge, but lose it rapidly when used and haven't worked out why. Though it may e the controller, so have changed that a few times, or maybe the panels weren't providing the proper input, but they are working fine.

You're the first one to tell me gel isn't good for solar, but form using them would have to agree and don't even know why. Be interested to find out why, what they are good for and whether I can get better service from them until we can change over to lifepo4.

Found the answers in the battery forum, thanks. I've been battling these things for years and lucky they are still alive, can't wait to get my lifepo4 set up.

[Mike90250]

.... We currently have a mix of AGM and gel, neither are satisfactory and gel seems very over rated....

GEL is not suited to solar, and I'm surprised someone sold you on it. (well, actually, not, but it never should have happened)