280a LifePO4 Battery (1 Viewer)

[Raul]

In my case I do have a tester, the zke 20. I won’t bother. I may use it to top up in parallel to 3.65v after first charge. It can charge with 5amps, and discharge with 20. I also have a resistance meter, and measured all cells to 0.016 mohms. The document from fogstar shows all my qr codes from the same batch no, and build date, with 291-292ah capacity, on al 32 cells. I have big hopes here.

 

[SeanF1]

Just taken the parallel connections off following top balance Thursday night and reconnected the BMS. Interestingly showing 99% remaining capacity 277ah. Is this normal?

 

[DavidCh]

Mine has never gone past 99%

 

[Raul]

Yes, that will be fine, it will reset itself after you start cycling the pack. At least that’s what I’ve seen on others experience. Also, take its accuracy on SOC with a pinch of salt, same goes for current calibration. Trust you victron bmv, reset the shunt to a know value as a reference point and follow that. When battery it’s full, re set the shunt to 100% soc and place the shunt after the bms.

 

[Raul]

Battery 2 it’s alive, I arranged the balance leads differently and re done battery 1 the same. Used to be a nest in the bms box. Not anymore, the bms and DC breaker is in the small box attached to the end of the big box.

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[Raul]

My next step it’s to connect this inverter to charge both banks. I have not done a top balance, I want to see the efficiency of the active balancer and batch matched cells as promised by fogstar. They may prove NO 1 provider of these cells in UK/Europe. If they prove to be as claimed, undoubtedly I will be wanting more of these.

 

[SeanF1]

My next step it’s to connect this inverter to charge both banks. I have not done a top balance, I want to see the efficiency of the active balancer and batch matched cells as promised by fogstar. They may prove NO 1 provider of these cells in UK/Europe. If they prove to be as claimed, undoubtedly I will be wanting more of these.

Looking good Raul.
My battery tester from ebay arrived yesterday. Ran it overnight with low voltage protection set at 2.55v and its saying I got 281ah. Well pleased with this

 

[SeanF1]

Yes, that will be fine, it will reset itself after you start cycling the pack. At least that’s what I’ve seen on others experience. Also, take its accuracy on SOC with a pinch of salt, same goes for current calibration. Trust you victron bmv, reset the shunt to a know value as a reference point and follow that. When battery it’s full, re set the shunt to 100% soc and place the shunt after the bms.

I notice that I have approximately a half a volt drop across the JK BMS. Is this correct or normal? In other words my cell pack measured from cell positive to cell negative terminals on the pack reads 13.2v (about 45% charged) and the BMS app is displaying 13.2 but measured from battery positive to BMS output side with a voltmeter reads 12.8v. Curious. Any other JK users seeing this? Many thanks

 

[DavidCh]

My JK bms is very wacky on its reported voltage. I have several times recalibrated it against my a couple of meters and my victron. However, it does report the voltage on the batteries as opposed to the voltage at the bms output so you do get odd results if you have a charger connected so the victron is reporting the output from the renogy solar charger but the bms is telling you the voltage on each cell, multiplied by the number of cells I think

 

[Raul]

I still think that’s a big difference 13.2-12.8v. Is this on free floating reading? Not under charge-discharge.

In a couple of days tops, I will be able to give more info on my packs. So far I only tested the inverter for charging, and the bms behaved fine With 50A charge. The voltages are very close to my multimeter, so I won’t calibrate nothing yet, until I get couple of cycles and observe the behaviour.

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[Raul]

Another think; did you had the discharge Disabled? Off? I remember swing in somewhere that JK does have a difference when blocking.

 

[SeanF1]

Another think; did you had the discharge Disabled? Off? I remember swing in somewhere that JK does have a difference when blocking.

No discharge is enabled and the reading was on a free float basis with no loads or charges. I noticed it yesterday when I was (I thought) finally putting the battery together. Thought it might be bad connections on the cables connecting to the BMS. (I am using 2x16mm cables from batt- to BMS and from BMS to -ve pole and 32mm cable on the batt positive. What are others using?) So today I took the BMS out and checked all the crimps and re-made the connections but it was still the same 0.5v drop.

 

[Raul]

Strange, I have my bms straight to the -ve first cell. I crimped two 16’s on the bms awg7 but added some strands to fill the lug. So bms -ve is on battery and bms -P will go to shunt. I’m using 2 16’s on +ve cell 16 to a DC breaker. From breaker will be 35mm2 to the buss bar.

 

[SeanF1]

Sorry, I should have said 35mm on the battery positive. I wondered if I should have crimped both 16s on the -ve side into a 35mm lug but didnt think it would make an adequate connection. Still could try that. Or indeed used 35mm on one of the two connection points on each side but I read that that was not a good idea. I wondered if the drop was exaggerated because the battery is only at 45% but I wanted to keep it at that level to test my solar set up. Tried today but too overcast to get much charge at all.
I have now done 2 capacity tests on the cells and got 281ah each time so very happy with that aspect.
Perhaps I have a badly crimped joint or something.
Cheers

 

[Raul]

That’s exactly what I did, two 16’s on one end, and one 35 on the other; like a Y branch. Works very well for small radius bends.

I can’t wait to test, I’m off grid and my house battery is down to 60 ish % after oven doing dinner. The EV I found it in the garage with 3% battery. So all solar coming in tomorrow, it’s greatly appreciated. I’m gonna test the JK to about 150 ish amps each.

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[SeanF1]

That’s exactly what I did, two 16’s on one end, and one 35 on the other; like a Y branch. Works very well for small radius bends.

Did you do this on both sides of the bms?

 

[Raul]

On B- two 16’s, on P- (blue) I did the same as I have different arrangement. But, you can stick a 35 on P-.

Where I did the Y with the two 16’s to one 35, it’s on +ve side. My cells are the eve with two bolt terminals, and makes sense to have 2 16’ for the surface area, instead one 35. I will post some photos and it will make sense.

 

[Raul]

Some progress with my built, battery two is full and balanced to 2-3mv just with the JK bms. No top balance. Battery one, I have two low cells that won’t come up past 3.4-3.45v. My tester is pants, I should of test it. It does discharge, but, won’t let me program it to charge. I was relaying on option two with the tester to top balance.
I set the bms to balance from 3.365v and 4mv trigger difference, then put the bank in float at 54v 16s. I have about 15mv difference with 0.4A float charge. I’m hoping they will catch up, they just empty/ less charged. Hope I don’t have a dud or two that have high self discharge.
I will update later, as I progress.

 

[SeanF1]

Maybe put them in parallel and charge to 3.65?

 

[Raul]

Yes that’s the idea, but my 3.65v source will not charge, as I mentioned. For some reason I can set it to discharge, but will not give me the option to run a charge. It’s a ZKE ebc 20. And I don’t have a alternative source of 3.65v.

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[SeanF1]

Yes that’s the idea, but my 3.65v source will not charge, as I mentioned. For some reason I can set it to discharge, but will not give me the option to run a charge. It’s a ZKE ebc 20. And I don’t have a alternative source of 3.65v

I have a simple 3.65v charger which I would happily send to you except that today we embarked on a month long trip to France and Spain so Im currently in the freezing north of France. If you want it I could try to arrange for one of the kids to send it to you. I haven't used it. Impulse purchase from Ali express but I used my bench top power supply instead.

 

[Raul]

I appreciate your offer. I’m in Romania. Back in UK I have access to a adjustable power supply. I have found something to borrow here, it’s just frustrating and takes time. The batteries are built to stay here.

 

[SeanF1]

I appreciate your offer. I’m in Romania. Back in UK I have access to a adjustable power supply. I have found something to borrow here, it’s just frustrating and takes time. The batteries are built to stay here.

 

[Two on Tour]

An interesting video by Andy of the Off-Grid Garage on compressing or not compressing battery cells.

 

[Tomass]

Well done,thank you!

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