curiouscarbon
Science Penguin
- Joined
- Jun 29, 2020
- Messages
- 3,024
for thermal camera and shiny metal, a piece of tape like painters/gaffer type has helped me before
Should I test every single Cell I received and other doubts/questions after Leaking Cell
- Thread starter silverstone
- Start date
Aridom82
Learning addict
Thank you for your advice. I have a flir and playing around with it i realised that things that reflect light you cannot measure with it, fortunately the jk case is black.
I did both the MOSFET calculations and the test, and the 200A version (at least the version at the time, should be same today) can handle 200A for at least an hour in my test.
silverstone
Solar Enthusiast
- Joined
- May 3, 2022
- Messages
- 1,041
But was it actually able to turn OFF charge / discharge at 200A after this "pre-hearing"?
Mosfet / igbt behaviors when hot tends to be (quite) different, especially regarding switching waveforms. I wouldn't expect to be able to handle this situation on a regular basis.
I think Andy from off grid garage had a mosfet end up in smoke. Cannot remember the exact circumstances though. The JK still worked afterwards though ?
SilverbackMP
Solar Addict
- Joined
- Apr 4, 2022
- Messages
- 928
There’s a reason why I own two of those and that’s the why. I had to do this completely off grid with inverter generator power for eight batteries. If I had to do it again, I’d buy something like a 48v chargeverter (which wasn’t out when I was messing with this), get them close in series and then finish with a ZKetech power supply. Either in parallel or each invidual cell. Be aware that the power supplies in these things are kinda shitty. I replaced one and bought a couple extras just in case. Sourced from Amazon.Now the question ... should I test every single of them ? They should be at around 50% SOC (3.26V - 3.29V) right now. With the EBC-A40L I can charge & discharge with 40A ... So theoretically that would be 280 Ah x (100% charge + 50% discharge) / 40 A = 10.5 hours / cell. Times 32 cells = 336 hours = 14 days full time ! More likely it's going to be 3 weeks. Not sure I'd like to wait that long to be honest.
View attachment 165906
Cells were bought from Docanpower if that matters. They have been in long term storage for a while and no, unfortunately I didn't cycle them yet. Couldn't even move in my garage in the meantime.
silverstone
Solar Enthusiast
- Joined
- May 3, 2022
- Messages
- 1,041
So you would test them before assembling the pack? Or just put them in series and measure the capacity thst way?
I'm not sure I want to wait 3 extra weeks, I'm already so late. Winter is almost here and Nu sun then ?
Daddy Tanuki
Solar Wizard
yep sounds like me last year, my last two sets of batteries came in after it was getting cold, so no time to test, I had to top balance and install without testing so that I could get the battery pack heater and box built in time for winter.
I fought with one pack for the entire winter while the other pack behaved for the most part. (the original two packs are champs with no issues.)
This summer I pulled the last two packs and tested them and low and behold out of 32 cells i had several that were seriously lagging in capacity compared to the others. rebuilt one pack with closely matched capacities and now have extra cells. thinking of waiting until next spring and ordering another 64 cells from whomever is the most trusted at that time.
silverstone
Solar Enthusiast
- Joined
- May 3, 2022
- Messages
- 1,041
I don't think I have the budget for ordering so many more right now...
But then again capacity of the pack will be dictated by the lowest capacity cell, so whichever will cause the whole pack to hit overvoltage or undervoltage limit. As long as you don't hit those you should be fine. Or are you throwing the lower capacity cell away?
My problem is that I'm not really saving a lot of money compared to off the shelf solution nowadays. And I already used several months on it
Yes
Andy went over spec in that test, and that was an early 4S version which was (still is?) underspecc'ed.
silverstone
Solar Enthusiast
- Joined
- May 3, 2022
- Messages
- 1,041
And do you actually use it at 200A ??Yes
Andy went over spec in that test, and that was an early 4S version which was (still is?) underspecc'ed.
On one hand I saw no need for it.. I have 30kW peak solar so unless it's full summer noon it's not going anywhere near that. Plus I'll habe some AC loads drawing current so that power won't flow into the batteries.
In my system design I was mainly limited by:
- Cables. 35 mm2 for 100A. Actually the cheap Schneider breaker only works up to 35mm2. Otherwise maybe 125A would be an option. 35mm2 for 125A is a bit of a stretch in my opinion. I think the tables state a limit of 115 ish for pvc insulated installation method B2 (?). True we might be installation method C but there is a whole bunch of these cables as well ?
- AR Fuse - 350A semiconductor fuse. Power dissipation was the limiting factor. Needed to oversize ~3x so that nominal power dissipation of fuse holder was within spec
- Breaker. Over 125A you go from a MCB to a MCCB. Much more expensive and bulky.
And since I planned for 8 battery packs, 8*5kW = 40kW is already much more than the actual power. Above 6 packs I would not be power limited even at summer noon.
Not sure how much I would waste due to not having enough POWER capability.
I will lose much more due to insufficient capacity I think.
If I were to do it all over again I would just do everyyhing inside batteries and outside batteries with 16mm2, then maybe take a 4p breaker. 2x63A in parallel per polarity. Much Cheaper cabling.
Just for the 50mm2 my box costed me 200 EUR in cables...
Generally, no. I use the 100A version and have 4 packs in parallel, so I'm at 20kW if I somehow max these out already...
silverstone
Solar Enthusiast
- Joined
- May 3, 2022
- Messages
- 1,041
So you built 2 extra packs ??
Yes, 4 now - maybe I make another two.
I care more about capacity than power output. I want to see if I can make a pack that can last me through e.g. December when I have 0 sunshine so I would only have to run a generator once a month in winter.
silverstone
Solar Enthusiast
- Joined
- May 3, 2022
- Messages
- 1,041
I think you need to build another 100 for that goal. Like a 40 foot container.
There is almost no sun in Denmark already during winter. Cannot imagine how it's like k Finland ?. Fully sunny during summer midnight (no sleep) , fully dark during day at winter (no power) ? It's similar here in Denmark but I don't think it's to *that* extent
RCinFLA
Solar Wizard
- Joined
- Jun 21, 2020
- Messages
- 3,565
A common trick by unscrupulous second hand LFP cell resellers, to relieve cell bloating, is to remove the blue plastic cover from overpressure vent then at the edge of vent, punch a small needle tip puncture to release bloating gas from cell. Then put blue plastic cover back on and you cannot see the pin prick hole without careful examination with a magnifying glass.
Another way is to peel back the black plastic top and drill a small hole in the top of metal housing to relieve pressure.
Another way is to peel back the black plastic top and drill a small hole in the top of metal housing to relieve pressure.
silverstone
Solar Enthusiast
- Joined
- May 3, 2022
- Messages
- 1,041
Docanpower just told me to remove the black plastic top and take pictures
Alkaline
Solar Wizard
I FINALLY managed to put all cells inside my battery box and ... well ... a few things went wrong (again).
View attachment 165907
I'm kinda disappointed with the result really. The cost was quite high, the quality so-so and of course, for all the extra features I wanted such as contactor, light signaling, extra signal cables for feedbacks & 5V/24V PSU etc, there is NO PLACE TO PROPERLY ROUTE the cables. And every device on the side DIN rail cannot have anything "output" in the lower hole because it's in contact with the cells / cover. An absolute nightmare.
Might as well have bought a ready-to-go battery. Learned something along the way, but I think this was NOT the result I wanted
Now at least the cells are in and squeezed lightly. More than handtight (couldn't even turn the nut by hand, would have left 20mm of gap ! - yeah 20 mm !), but "tightened" I'd say reasonably, then backed off a few nut-turns (M10 - pitch is ... 1.75 mm ?). Sometimes you can pull out the yellow spacer and sometimes you cannot, that kinda tight. But cells are NOT too loose by any means. So they may have maybe 2-5 mm gap ACROSS 8 cells at around 50% SOC.
Now the question ... should I test every single of them ? They should be at around 50% SOC (3.26V - 3.29V) right now. With the EBC-A40L I can charge & discharge with 40A ... So theoretically that would be 280 Ah x (100% charge + 50% discharge) / 40 A = 10.5 hours / cell. Times 32 cells = 336 hours = 14 days full time ! More likely it's going to be 3 weeks. Not sure I'd like to wait that long to be honest
View attachment 165906
Cells were bought from Docanpower if that matters. They have been in long term storage for a while and no, unfortunately I didn't cycle them yet. Couldn't even move in my garage in the meantime.
Actually I discovered yesterday that ***** ... one cell from the second batch that I got delivered from Docanpower had suffered an electrolyte leakage probably during transport (I only noticed it now several months later when I *could* open the packages).
View attachment 165908
I promply contacted Docanpower about it. Let's see how they react.
Thankfully I had one cell as spare and put that in instead, even though it was from the first batch, so a bit older ....
By the way, how do you evaluate the status of the pressure relief vent/seal?
Some look "clean & tidy" (just the gold dot in the middle with the 3 weak spots the blow over pressure), some have "slight" bleeding (black color) around the middle gold dot, .... They are all different
Peel the black cover off that cell, clean gently with rubbing alcohol see if the background of the QR code looks different than the other cell. If it does than you have been scammed by Docan.
silverstone
Solar Enthusiast
- Joined
- May 3, 2022
- Messages
- 1,041
Now you are scaring me. And here I thought they were a reliable supplier ?
Alkaline
Solar Wizard
Docan? No Docan is a big time scammer, just they had a lot of buyers who were in disbelief after the relasered QR codes started circulating in the market.
diysolarforum.com
diysolarforum.com
diysolarforum.com
diysolarforum.com
Lot of threads.
The only time you get lucky with Docan is if they send you cells from Ezeal which is a legit company that will sometimes ship out cells for Docan in there Houston warehouse. But never buy from Docan from China.
Docan Power bad experience, beware.
Hello! Having read here on this forum a lot of positive feedback about Docan Power decided to buy from them on Alibaba. Ordered 84pcs of Eve LF280K cells from Docan in January. Sales rep was Jenny Wu. Cells were sold as "brand new Grade A". I paid almost USD12K for them, USD141 per cell...
diysolarforum.com
Poor Docan Experience (Resolved)
Purchased 16 eve 280k from Docan over a month ago confirming the description had them as brand new, full capacity cells. Cells arrived bloated, more than 5mm out of spec at only 3.2v. No grade B QR and had the front labels that they had been "tested" at 280ah and matching IR .19. - Reached out...
diysolarforum.com
Disappointing EVE 280K Results
I wanted to share my recent (September 2022) disappointing experience buying prismatic cells to the forum. My plan was to buy a small group of prismatic cells (20 cells) and test them before committing to several larger purchases based on the results of the test. I first did a bit of research...
diysolarforum.com
Docan Power bad experience, beware.
On the subject of DDP. My experience is that they (alibaba sellers) do not actually pay the VAT on import. Instead they attach it to a different shipment eg food and presumably avoid it this way. So it’s basically smuggling. I confirm that. They call it DDP but actually it is not. I asked Jenny...
diysolarforum.com
Lot of threads.
The only time you get lucky with Docan is if they send you cells from Ezeal which is a legit company that will sometimes ship out cells for Docan in there Houston warehouse. But never buy from Docan from China.
Last edited:
silverstone
Solar Enthusiast
- Joined
- May 3, 2022
- Messages
- 1,041
Fuck ? ...Docan? No Docan is a big time scammer, just they had a lot of buyers who were in disbelief after the relasered QR codes started circulating in the market.
Docan Power bad experience, beware.
Hello! Having read here on this forum a lot of positive feedback about Docan Power decided to buy from them on Alibaba. Ordered 84pcs of Eve LF280K cells from Docan in January. Sales rep was Jenny Wu. Cells were sold as "brand new Grade A". I paid almost USD12K for them, USD141 per cell...
Poor Docan Experience (Resolved)
Purchased 16 eve 280k from Docan over a month ago confirming the description had them as brand new, full capacity cells. Cells arrived bloated, more than 5mm out of spec at only 3.2v. No grade B QR and had the front labels that they had been "tested" at 280ah and matching IR .19. - Reached out...
Disappointing EVE 280K Results
I wanted to share my recent (September 2022) disappointing experience buying prismatic cells to the forum. My plan was to buy a small group of prismatic cells (20 cells) and test them before committing to several larger purchases based on the results of the test. I first did a bit of research...
Docan Power bad experience, beware.
On the subject of DDP. My experience is that they (alibaba sellers) do not actually pay the VAT on import. Instead they attach it to a different shipment eg food and presumably avoid it this way. So it’s basically smuggling. I confirm that. They call it DDP but actually it is not. I asked Jenny...
Lot of threads.
The only time you get lucky with Docan is if they send you cells from Ezeal which is a legit company that will sometimes ship out cells for Docan in there Houston warehouse. But never buy from Docan from China.
I read a thread also here stating that Docanpower and Amy were reliable sellers.
I was in contact with Beki from Docanpower though.
Makes me really wish I went with an off the shelf solution now ??
Similar threads
