Opinions welcome for Newbie Lifepo4 battery

[Shane_UK]

Hello All.

I've been reading many threads on this forum for some time now and learnt so much already so a big thankyou to the community.
This is my first post so please be gentle with me as I may have made some obvious mistakes or incorrect assumptions.

Here's the background. I live in the UK and I have a grid tie 4kw solar system since 2012 that's been providing reliable energy and a steady income that's long since passed the break even point. We've been driving purely EV's for the last several years and been making use of cheap overnight electricity to run our cars for a couple of pence per mile (Octopus Go). Now with energy prices approaching 40-50p/kWh during the day and no rest bite for the foreseeable future over the summer I decided it was finally time to invest in some lifepo4 cells.

My goal's / approach is as follows;
1 - In the summer be able to utilize 100% of current solar production (no more exporting surplus) by storing the excess generation.
2 - In the event of a power cut ensure my solar keeps on producing
3 - In the event of a power cut have enough stored energy to keep the lights on (figure of speech - I expect to run more than lights!)
4 - In the winter when solar yields are low (and let's face it most of the year in the UK) be able to top up battery's using cheap overnight electricity
5 - Eliminate purchasing of expensive daytime electricity.
6 - Allow expansion for potential future additional solar via Victron MPPT's
7 - Have 2 separate batteries to allow single battery operation to permit maintenance/fault resolution etc on the other.

To this aim I am proceeding with the following;
1 - Victron Multiplus II 48v 5000 inverter/charger
2 - 2x 16S EVE 280Ah lifepo4 batteries. (from Amy@Luayan - the one's with the factory report)
3 - 2x Victron Lynx distributors (1 for battery side and 1 for inverter side)
4 - Victron Lynx shunt (sandwiched between distributors)
5 - 2x JK 200A BMS
6 - 70mm cable (which I think is 2/0AWG equivalent) - Cable runs are expected to be short
7 - 500A 80v CNN Fuse (Littelfuse) in the shunt
8 - 3x 200A 70v (Littelfuse) MEGA Fuse's in the Lynx distributors (batteryA, batteryB and Inverter)
9 - 2x Class T 250A Fuse (BlueSea) as close to battery positive as possible
10 - 3x Unknown Isolators/Switches between batteries and inverter and the Lynx side.

My initial questions are;
1 - What do you all think so far, is this a good sound start
2 - Regarding points 8 and 9 above. My intention is that the cheaper MEGA fuse in the Lynx would sacrifice itself in most situations with the more expensive Class T fuse only coming into play for a dead short on the battery and to protect against the larger currents in this scenario to prevent ARCing.
3 - What type of precharge resistor should I buy for the initial connection to the inverter - I went for 50W/30ohm in the end
4 - I was planning on adding a small fuse on the BMS cables to the cells, given that the BMS also does 2A balancing would a 3amp 5x20mm fuse be correct for these - I went for 5A in the end

Many thanks to all that take the time to read and contribute.

 

[Shane_UK]

Hello, so I’ve received my cells and have some questions.

Firstly though the 32 cells arrived bang on 2 months after order date with no issues and where VERY well packaged.
The report supplied shows all cells in the range 289.4-292Ah.

1. Each cell has blue and black dots (from a marker pen) on the terminals. Is this normal for the premium (new terminal type with factory report) cells from Amy? (I think it might be as I've seen on some other photo's)

2. Some 'slight' bulging, again I thought these premium cells would arrive flat. Could this be because they are cold been sitting in warehouse etc?

3. I’m struggling to measure the same capacity as per the supplied report. using a EBC-A40L tester I’ve only managed 279Ah so far vs 291.7Ah for that cell on the factory report (which is 4.3% lower) My test is (I think my test matches that on the EVE spec sheet other than I am less than 0.2C?);
Step 1 - charge @ 40A to 3.65V
Step 2 - wait 30mins
Step 3 - discharge @ 40A to 2.5V
Step 4 - charge @ 40A for 150 mins to bring cell back to about 40% SOC

 

[Supervstech]

40Ah charge and discharge? You mean 40A charge and discharge.

How is your tester connected to the cells? What size are the leads?
Please post pictures of the connections to the tester and the battery.

 

[Shane_UK]

40Ah charge and discharge? You mean 40A charge and discharge.

How is your tester connected to the cells? What size are the leads?
Please post pictures of the connections to the tester and the battery.

Thanks for the interest, I’ve tidied up my post above to correct some of my sloppiness with the units etc.
I’m using the cables supplied with the tester.

You can also see the blue and black dots I mentioned on the terminal in the picture.

 

[Supervstech]

I dont know that I would trust 40A through those clamps.
I would get a cable with a lug on it and directly connect to the terminal.

 

[Substrate]

Don't forget the big automotive clamps either in other use. They look hefty, but have you ever inspected the wire-to-clamp connection? Sometimes really shady and high-resistance.

Oops - guess you were talking about those. Same advice.

Moving to the little tiny alligator clip - same deal. Ring terminals please.

 

[Shane_UK]

Thanks for the advice Substrate and Supervstech

I'm fitting a 10awg 6mm ring terminal to the large cables today and will re-test to see if this improves my results. Looking more closely at the existing clips and the contact area with the busbar, I can see it is quite small so a ring terminal will improve the contact area for sure. I really hope this resolves my missing 4-5% (or at least some of it). I'd like to see mid 280's given the supplied test sheets indicated 289-292Ah. It might not sound like much but I'm currently missing the equivalent of 1.5 of the 32cells I ordered.

The smaller cables are only measuring voltage and the readings I get match to the mV with 2 other meters I have so I'm not concerned about the crocodile clips on them.

In the meantime I did another test on another of my cells. This time I dropped the current to 28A (0.1C)
Step 1 - charge @ 28A to 3.65V
Step 2 - wait 30mins
Step 3 - discharge @ 28A to 2.5V
Step 4 - charge @ 28A until 100Ah to bring the cell back to approx. 36% SOC.
The result on this cell was 276Ah vs 289Ah on the supplied factory report, so about 4.5% down, consistent with the first cell I tested.

 

[Shane_UK]

having changed to ring terminals my capacity tests (2 since) are still yielding approx 4.5% lower than expected or 12Ah.

going to loop the same cell through the cycle a couple more times, I think there was a suggestion that it takes a few cycles to release the full capacity. Any merit to this or am I being too hopeful?

 

[Shane_UK]

Making progress elsewhere though..

 

[Substrate]

You are doing *fine* with only 4.5% less than stated capacity! Don't obsess over this.

In this game, one never cuts things so close to the edge anyway when they plan their system based on their power needs. You buy your capacity based on your calculated needs, and de-rate by at least 10-30% anyway. On every piece of gear in the chain. At least the smart ones do.

Don't do it backwards - buy some random capacity, and "see what I can run off it". Far too many do this.

Example - you don't see people jumping off the tops of buildings because their solar panels are putting out 5% less than rated do you? Even for those living on the equator at noon!

You are fine as long as the *de-rated* capacity meets your needs. Otherwise, I've got a bunch of testers, active balancers, and numerous other doo-dads to hang on the system to sell you. Believe it or not, that is a marketing demographic. Don't fall for it. De-rate and live easy.

 

[Just John]

I dont know that I would trust 40A through those clamps.
I would get a cable with a lug on it and directly connect to the terminal.

I don't disagree, however it has surprised me after running a few hundred tests, it works quite well. The 10 gauge wire does get warm, but not hot. Connected so you get the maximum bite on the busbars (maximum contact) it has surprised me.

 

[Just John]

having changed to ring terminals my capacity tests (2 since) are still yielding approx 4.5% lower than expected or 12Ah.

going to loop the same cell through the cycle a couple more times, I think there was a suggestion that it takes a few cycles to release the full capacity. Any merit to this or am I being too hopeful?

Apparently all the 280 cells test low. The 304AH cells all test high. I am not sure why, other than EVE supposedly optimized the chemistry of the 280s for cycle life rather than capacity. The size difference (aprox 2mm taller for the 304) should not make such a large difference, so I tend to believe the "cycle life" claim.

 

[Just John]

Thanks for the advice Substrate and Supervstech

I'm fitting a 10awg 6mm ring terminal to the large cables today and will re-test to see if this improves my results. Looking more closely at the existing clips and the contact area with the busbar, I can see it is quite small so a ring terminal will improve the contact area for sure. I really hope this resolves my missing 4-5% (or at least some of it). I'd like to see mid 280's given the supplied test sheets indicated 289-292Ah. It might not sound like much but I'm currently missing the equivalent of 1.5 of the 32cells I ordered.

The smaller cables are only measuring voltage and the readings I get match to the mV with 2 other meters I have so I'm not concerned about the crocodile clips on them.

In the meantime I did another test on another of my cells. This time I dropped the current to 28A (0.1C)
Step 1 - charge @ 28A to 3.65V
Step 2 - wait 30mins
Step 3 - discharge @ 28A to 2.5V
Step 4 - charge @ 28A until 100Ah to bring the cell back to approx. 36% SOC.
The result on this cell was 276Ah vs 289Ah on the supplied factory report, so about 4.5% down, consistent with the first cell I tested.

What is your tail current setting?
Every EVE cell I have tested came in below what EVE tested, but over their rated capacity. 304AH cells EVE said were 322 as their test results come in at 315, etc. I also don't have any of the 280s to test except some grade B cells almost 3 years old.

Use a tail current of 1 amp or less (3.65v, stop charging when current drops below 1 amp).

I will add that your test results match what others are getting for the 280 cells.

 

[Alkaline]

Hello, so I’ve received my cells and have some questions.

Firstly though the 32 cells arrived bang on 2 months after order date with no issues and where VERY well packaged.
The report supplied shows all cells in the range 289.4-292Ah.

1. Each cell has blue and black dots (from a marker pen) on the terminals. Is this normal for the premium (new terminal type with factory report) cells from Amy? (I think it might be as I've seen on some other photo's)

2. Some 'slight' bulging, again I thought these premium cells would arrive flat. Could this be because they are cold been sitting in warehouse etc?

3. I’m struggling to measure the same capacity as per the supplied report. using a EBC-A40L tester I’ve only managed 279Ah so far vs 291.7Ah for that cell on the factory report (which is 4.3% lower) My test is (I think my test matches that on the EVE spec sheet other than I am less than 0.2C?);
Step 1 - charge @ 40A to 3.65V
Step 2 - wait 30mins
Step 3 - discharge @ 40A to 2.5V
Step 4 - charge @ 40A for 150 mins to bring cell back to about 40% SOC

Sorry to hear welcome to the 280K is a DUD club, you are not alone:

What is going on here? Just got ZKE-40

Recently, I am thinking relying on AH is not enough to determine cell quality, so I finally ponied up the cash and bought a ZKE-40 tester and tested 1 of my Luyuan 280K cells, matched & batched genuine. As you can see it falls a bit short on the AH, but at the same time exceed the WH of the...

diysolarforum.com

 

[Alkaline]

Thanks for the advice Substrate and Supervstech

I'm fitting a 10awg 6mm ring terminal to the large cables today and will re-test to see if this improves my results. Looking more closely at the existing clips and the contact area with the busbar, I can see it is quite small so a ring terminal will improve the contact area for sure. I really hope this resolves my missing 4-5% (or at least some of it). I'd like to see mid 280's given the supplied test sheets indicated 289-292Ah. It might not sound like much but I'm currently missing the equivalent of 1.5 of the 32cells I ordered.

The smaller cables are only measuring voltage and the readings I get match to the mV with 2 other meters I have so I'm not concerned about the crocodile clips on them.

In the meantime I did another test on another of my cells. This time I dropped the current to 28A (0.1C)
Step 1 - charge @ 28A to 3.65V
Step 2 - wait 30mins
Step 3 - discharge @ 28A to 2.5V
Step 4 - charge @ 28A until 100Ah to bring the cell back to approx. 36% SOC.
The result on this cell was 276Ah vs 289Ah on the supplied factory report, so about 4.5% down, consistent with the first cell I tested.

Please connect the ZKE to your computer and save the screenshot , data and upload it, I would like to see what your WH ratings are. If they are over 896 WH then technically you met the WH rating.

 

[Substrate]

Unfortunately, there is a deragotary measuring term when things go too far.

And at some point, the effect has no measureable impact upon the manufacturer, but calling every owner a fool instead.

When in fact if you just used them, the small amount of de-rating (which is common and WONT be changed by hobbiest rants) makes for less gray-hairs.

 

[Alkaline]

Shane_uk any update? Did you contact Luyuan? The screenshot / data would be good if you can provide it.

 

[Alkaline]

You are doing *fine* with only 4.5% less than stated capacity! Don't obsess over this.

In this game, one never cuts things so close to the edge anyway when they plan their system based on their power needs. You buy your capacity based on your calculated needs, and de-rate by at least 10-30% anyway. On every piece of gear in the chain. At least the smart ones do.

Don't do it backwards - buy some random capacity, and "see what I can run off it". Far too many do this.

Example - you don't see people jumping off the tops of buildings because their solar panels are putting out 5% less than rated do you? Even for those living on the equator at noon!

You are fine as long as the *de-rated* capacity meets your needs. Otherwise, I've got a bunch of testers, active balancers, and numerous other doo-dads to hang on the system to sell you. Believe it or not, that is a marketing demographic. Don't fall for it. De-rate and live easy.

Sorry, not acceptable for GRADE A cells with the grade A price... we need to get to the bottom of this, Where is Lamparad LI? I know he is a member of the forum, certainly didn't take long when the packaging fiasco happened... was pretty quick to come here and chat away...