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LiitoKala Lii-500 vs Opus BT-C3100
#1
Hi All,

thankyou for letting me post in your forum. I am a Bitcoin/Altcoin miner and have been for many years. Daily usage is around 140 kw/hours. I have decided to take my systems to a point where I can supply power at night to my rigs as well as solar during the day. I have been furiously studying up on powerwalls and have just bought my first batch of scrap batteries. I lashed out after watching Jehu Garcia review chargers and bought two LiitoKala Lii-500. Just wondering if I made the wrong decision but I wanted to measure internal resistance on my cells. Have I made a mistake and should I have gone with the OPus? of course I will need many more chargers and I wanted to keep them standardised. Many thanks for your advice.
dooogs likes this post
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#2
140kWh/d usage, scrap 18650s and just a pair of testers is going to be a challenge .... you might want to consider large format cells.
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#3
At this point I am going to salvage everything I can find big and small. Mining is pretty cruisy once you are set up its point and forget, so I have time. Some of my mini ASICs run on as little as 50 watts. I already have some 26650 cells as well and I can see the benifit of larger cells. Every cent that I dont give to the utility is money in my pocket. I intend to build chargers as I progress, I already have a heap of buck converters etc. Just want to find a starting point to get some experience of sorting cells. If the liitoKala perform they are a good half the price of the OPus here in Aus. 18650's are ubiqitous and easy to find, the large cells that I really like are a bit more rare. I like the 38120's for sure!
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#4
(04-20-2019, 09:49 AM)BitcoinBandit Wrote: 18650's are ubiqitous and easy to find ......

Have you secured a source of proven good cells yet ?
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#5
Only low volume at this stage but that was within 4 phone calls. Only started late last week. It is easter and everything is closed. I am tenacious. I also make biodiesel and have done for many years to power my diesels and I am toying with the idea of a diesel generator as well. I found if you are determined and knock on enough doors you will get waste vegetable oil. I will find cells. I am emailing will start ringing more next week. I am in HB Powerwalls general area and I am hoping he might give me some pointers as well. I am taking this very seriously it is my livelyhood to secure power. Mining profit is directly related to how much power I can source. Also once I am more confident and I can identify a reliable chinese source I will buy new large capacity cells.
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#6
Hi everyone

So what is the verdict on the liitokala vs the opus?
I have two opus bt-c3100 chargers but they seem to give variable results when testing the internal resistance.
Plus you have to take into account the offset.

Since the liitokala Lii-500 is only half the price I was wondering if it had the same issues or if it really is a better and cheaper device?

Thanks!
Kind regards
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#7
140kwh is HUGE! I have 29000 cells. A system of 16kwp solar and i cant even get close to sustain that you need... During summer perhaps 100kwh per day and during winter perhaps 2kwh per day. Average of 43kwh per day over the full year Smile

Internal resistance is not doable with any of them.

Lii is 0.5A discharge and the Opus is 1A. I vote for Opus since it can stress the cells better. If you want to test IR you need a proper 4 wire IR tester.

If you check my videos about the IR and all that you see that it can vary 200% easy by just pressing the battery harder on those testers Smile
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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#8
Liitokala vs Opus … just buy whatever is cost you less money.  For the most part, they both do the exact same thing.  These units should be used for nothing other than charge/discharge testing to get a capacity baseline.  Neither system is 100% accurate either.  Baseline being the key word, testing needs to be in a consistent manner with the same type of charger.  The capacity results are relative, with the end goal being to make packs which are balanced in capacity.

Internal resistance testing should be done using a separate 4 wire tester… I gravitate towards a good RC charger like the iCharger which can do a 4 wire, and a manually calculated DC load test using a resistor of known value or a CC load which is starting to turn into my preference because you can test cells at your actual real world load and get a more applicable IR value to your application.

Lastly, for that much capacity, don’t waste your time with salvaged or even new 18650 cells…  I would go straight for large format cells… prismatic, power backup modules, EV modules, or similar where you can obtain large amount of capacity preferably from a source which supplies you with some consistency, like a battery pack from an entire car.

I could not imagine doing 140 kWh using 18650 cells.  The time, cost, labor would be ridiculous.  I have 33 kWh or EV cells which I obtained in one run, and that is already enough work for me.  At an average capacity of 2000mAh, you would need approximately 19,500 cells to get 140kwh and we are not even talking about usable capacity... that's 100% DoD.  Its closer to 24k cells with 20% over provisioning which isn't even that aggressive.  I over provision by about 50% to reduce DoD / increase service live.
Ibiza likes this post
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#9
(11-15-2019, 11:44 PM)Crimp Daddy Wrote: i have seen this acronym a few times now... what is DoD?
if its already broke it is now an educational tool.... lets tear it apart now.
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#10
Depth of discharge
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
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