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

[Jd1]

Originally Posted by Maine Sail

Why did you go to 2.6V? Was that just the lowest cell? Winston told me not to go below 2.8V even though the manual says 2.7V. For an accurate bottom balance 2.65V is okay in order to achieve a 2.75V resting voltage but this is carefully monitored and done with low "C" rate loads.

All my capacity tests have been cut off with the lowest cell reading 2.8V and no inverter shut down because this is 11.2V or better.....

Current should have actually gone up as the voltage dropped unless it was your inverters losing efficiency. I prefer to run the inverter at less than full bore so my current stays steady, though it will rise slightly as the voltage drops....

My capacity tests from 550 cycles forward will be done with a lab grade DC load device for better accuracy. I will establish a new baseline...

A full Winston cell will rest at about 3.38V - 3.40V. They won't stay at 3.6V for very long...

The figure of 2.6V was based on the Balqon documentation on their web site. The voltage quickly recovered (didn't watch the actual voltage though) when the load was taken off the batteries.
My inverter shuts down at about 10.8V or so and I had a fairly long cable going and was losing some voltage there. It was a 3 kW inverter but I was only pulling 2 kW.
I don't recall what the current was doing exactly but I do remember that I had to reduce the total load to avoid (or correct) the inverter shutdown due to low voltage.
I will probably run this test again once all the control electronics are installed which will be some time yet ... today I managed to get a whopping 30 AHr worth of capacity into the batteries so it will take another 20 boat days at that rate

[SV THIRD DAY]

Originally Posted by Jd1

I finally was (sort of) able to do a capacity test today.

I would guess that I am pretty close to 700 A hr total capacity but will not be able to verify this for at least another week or two until everything is hooked up. .

Just so I can wrap my head about your thinking, what's your rationale for the 2K draw tests down to 10.4v Bank/2.6v cell voltage? I guess this is the difference between data type testing for "data" compared to more real life testing where you don't see those huge types of loads. In a way is the BS of the batteries being rated at a 0.5C discharge rate because what real world cruising boat ever sees a 0.5C load? I know you want to verify that you got what you paid for...but what most cruisers want to know is how long these expensive LiFePO4 banks will last and hold up under real life cruising type loads.

[Jd1]

Originally Posted by SV THIRD DAY

Just so I can wrap my head about your thinking, what's your rationale for the 2K draw tests down to 10.4v Bank/2.6v cell voltage? I guess this is the difference between data type testing for "data" compared to more real life testing where you don't see those huge types of loads. In a way is the BS of the batteries being rated at a 0.5C discharge rate because what real world cruising boat ever sees a 0.5C load? I know you want to verify that you got what you paid for...but what most cruisers want to know is how long these expensive LiFePO4 banks will last and hold up under real life cruising type loads.

Pretty simple actually - 2 kW draw because that was the biggest load I had (1600W load plus the inverter took the rest apparently). The 2.6V was based on the Balqon documentation (the graph showing cell voltage vs capacity with a big red line at 2.6V meeting the various discharge curves.
http://www.balqon.com/wp-content/upl...ttery_2013.pdf on page 5 shows 2.6V intersecting with the 1C discharge curve with 0% charge remaining.
I used the biggest load I had because I had to be present and I wanted the time to be reasonable but at 175A or thereabouts it is nowhere near 1C anyway.
In case I didn't mention it, the A Hr count was generated by a Victron BMV700 SOC meter.
Oh yes, I wanted to verify that I got the capacity I paid for, especially with the one cell that was suspected of being a used cell.

[SV THIRD DAY]

Got it.
The question I have then is what data/info do we have showing the relationship between these large discharge rates and the more typical discharge rates seen on a real life boat? I'm just trying to figure out if this test is good for the real world...or just for testing. What AH capacity would you get at a 20A or 15A draw? More...less or do we know?

[Jd1]

Originally Posted by SV THIRD DAY

Got it.
The question I have then is what data/info do we have showing the relationship between these large discharge rates and the more typical discharge rates seen on a real life boat? I'm just trying to figure out if this test is good for the real world...or just for testing. What AH capacity would you get at a 20A or 15A draw? More...less or do we know?

Going back to the graph I referenced above, from Balqon, the rated capacity of the batteries is rated at a 1C load. There is a 0.5C curve showing that you get additional capacity with a lower draw. I do not know how much additional available capacity you might see if you went to a really low discharge rate (I suspect it will be yet a bit more).
As far as I am concerned this test is only good to establish a baseline and to make sure you got what you paid for.

[Dashby]

Originally Posted by Dashby

Hi
Second lot of batteries were US$1276 for 320Ah (256 at 80% DOD)
Shore power charger, wiring and Votronic BMS: $1147 (replaced some cabling which was undersized)
BMS from ClenaPowerAutoLLC: $300 (including second relay for cut off)

Cost per usable AH USD10.63 per usable AH

Its higher than I initially budgeted for but we have a much more stable electrical system on board now and it has better safety features than we ever had on the LA system. Which was regularly abused with batteries taken down to 10%, meant we only got 5 years from the LA bank which was 240Ah and not sufficient to run systems for 24hrs with no charging.

Batteries now in use for a year.
They have been drained to 50% several times and once to the relay cut off at 40%. Users have all reported it takes several days to get to this point.
The big advantage is that after 2 to 3 hours of engine running the batteries are back to 90%.
The biggest issue is the alternator heating up and having to cool down. Not an issue for most people as motor sailing for 3 hours with engine at 1800rpm is easy.
Happy with the system.

[Maine Sail]

Originally Posted by Jd1

Going back to the graph I referenced above, from Balqon, the rated capacity of the batteries is rated at a 1C load. There is a 0.5C curve showing that you get additional capacity with a lower draw. I do not know how much additional available capacity you might see if you went to a really low discharge rate (I suspect it will be yet a bit more).
As far as I am concerned this test is only good to establish a baseline and to make sure you got what you paid for.

Your batteries are rated for 700Ah at .5C not 1C....

[Jd1]

Originally Posted by Maine Sail

Your batteries are rated for 700Ah at .5C not 1C....

I was not able to find anything on capacity on their web page other than the graph referenced above which shows 100% capacity is used up at 2.6V at a 1C discharge.
This is a general curve, not specifically geared to the 700Ah cells.
Do you have a link to specs stat are more specific to the 700Ahr cells?

[ebaugh]

For spec curves on the Winston 700Ah cells...See:

http://en.winston-battery.com/index....ategory_id=176


Sent from my iPad using Cruisers Sailing Forum

[lestef]

Hy all,
I read a lot of discussions about LFP and I have noticed that many prefer the new gray Calbs instead of other brands, but also I found that the Winston lifepo4 will extend its life cycle by using yttrium in their chemical composition.
For my storage system I don't need big discharge currents where Calbs have better results (evtv tests), the only parameter that I consider is the life of the cells...
What you think abou these ?
I want to go with 16 x 200 Ah battery bank, but I can't decide which mahufacturer...
For the BMS I think I will go with this model: MiniBMS Cell Module - CleanPowerAuto LLC

[ColdEH]

My version of the the "Flux Gate Capacitor" .

With separate charge and load bus bars in place , house BMS in the center and the Tyco EV 200 above .

Regards

[lestef]

Originally Posted by lestef

Hy all,
I read a lot of discussions about LFP and I have noticed that many prefer the new gray Calbs instead of other brands, but also I found that the Winston lifepo4 will extend its life cycle by using yttrium in their chemical composition.
For my storage system I don't need big discharge currents where Calbs have better results (evtv tests), the only parameter that I consider is the life of the cells...
What you think abou these ?
I want to go with 16 x 200 Ah battery bank, but I can't decide which mahufacturer...
For the BMS I think I will go with this model: MiniBMS Cell Module - CleanPowerAuto LLC

Any help for my decision ? Until now I really don't know what to choose between Calb and Winston...

[mcarling]

Originally Posted by lestef

Hy all,
I read a lot of discussions about LFP and I have noticed that many prefer the new gray Calbs instead of other brands, but also I found that the Winston lifepo4 will extend its life cycle by using yttrium in their chemical composition.
For my storage system I don't need big discharge currents where Calbs have better results (evtv tests), the only parameter that I consider is the life of the cells...
What you think abou these ?
I want to go with 16 x 200 Ah battery bank, but I can't decide which mahufacturer...
For the BMS I think I will go with this model: MiniBMS Cell Module - CleanPowerAuto LLC

The new CALB CAM72FI cells are much lighter and more compact than previous generations of LiFePO4 cells. They weigh only about 10kg per KWh. A 4S12P arrangement would give you 4x216AH and would weigh only 91kg or 200lbs.
Energy storage battery_CALB

Others will disagree but, in my opinion and experience, a BMS is a complete waste of money at best and an additional point of failure at worst. LiFePO4 cells do not go out of balance if not overcharged or overdischarged. Balance them once (either top or bottom balance should be fine) and ensure that the charging voltage never ever exceeds 3.50V (14.0V for a nominal 12V system). 3.45V is almost certainly adequate. Don't keep charging them after they are fully charged. Separate load and charge buses with separate HV and LV cut-offs are, in my opinion, a wise investment, but the BMS market appears to me to be a snake oil scam.

[hellosailor]

les-
If you go back and read over the whole four thousand odd messages, I think you'll find that Winston have repeatedly perplexed customers by shipping "in stock" three or four months later. Little issues like that, which I don't think Calb has had. I can't speak for the product being better or worse, just that we hear of Winston acting more like a kid with a lemonade stand than a real business. Along with not-so-impressive news about the company's financials, which could affect whether they'd be around if you needed warranty service in the future.

[lestef]

I like the Winston datasheets, but many say they are little bit superficial... 0.5C optimal charge/ discharge current, 5000 cycles at 70% DOD - this is the best on the market!
I think I will go with 16 x 180 Ah CALB (CA180FI)