FL, LiFePo4 and LiNMC comparison documentation

[HaldorEE]

I have been looking for discharge curves for the LG LiNMC batteries I am assembling into a battery pack and found this document (link and document attached).

https://www.batterypoweronline.com/wp-content/uploads/2012/07/Lead-acid-white-paper.pdf

I am still digesting the information in it, but it looks to have all the information I need to be able to intelligently use LiNMC batteries.

For example: Chart 10 on page 12 shows that a low voltage discharge cutoff voltage of 23 V corresponds well to the 10% SOC level I was planning on using for a 7S (25.9V nominal) LiNMC battery.

 

[gnubie]

It'd be interesting to see a document written today in regards to lifepo4 performance. We know things have improved quite a bit of the years so the gap between lead acid and lithium would be even greater than what is shown in the white paper.

 

[Ampster]

I agree, eight years is a long time in the evolution of Lithium chemistry. Besides I think there is bound to be bias in a white paper authored by any one comparing just LiNMC to Gel batteries. Changes in electrolyte and cathode and anode composition have been significant.

 

[Ampster]

For example: Chart 10 on page 12 shows that a low voltage discharge cutoff voltage of 23 V corresponds well to the 10% SOC level I was planning on using for a 7S (25.9V nominal) LiNMC battery.

Yes that is 3.29 volts per cell which is conservative for that voltage. What are you thinking for the top?

 

[HaldorEE]

Yes that is 3.29 volts per cell which is conservative for that voltage. What are you thinking for the top?

Haven't decided yet. 95% seems reasonable.

Full battery capacity is 3000 WH so reducing usage to 2700WH should be plenty for my needs. If I have plenty of reserve capacity, I could drop this to 90%. I won't be using this system daily, so while maximising the total number of use cycles is important, it is not my top priority.

 

[HaldorEE]

Make that 2250 WH (minimum discharge SOC = 20%, max charge SOC = 95%). Is 95% high enough for my BMS (Daly) to do top balancing? I have been considering adding an active balancer like this one that balances at any state of charge.

Amazon.com

 

[PerfectInsanity]

Thanks for starting this thread and that link. I'll add anything I find, as I ordered 56 from BatteryHookup, for a 480ah 48V setup (14s4p) and working on putting together the rest of the pieces I need. And a buddy added 8 to the order for a 200ah 12V setup (4s2p). Working through BMS decisions and testing/vetting process, so the build is solid, safe, and reliable. Nailing down the same info you're after is important.

 

[HaldorEE]

I went with a Dali 150A, 24V (3.7V 7S) BMS for my battery. 150A max discharge, 75A max charge. Perfect limits for these cells. Cost about $120 including shipping.

This is it.

Buy Products Online from China Wholesalers at Aliexpress.com

 

[PerfectInsanity]

Thanks for the suggestion and link. BMS-wise, I've been debating on a few avenues because of the cost involved. The 14s4p setup means 4 BMSes, or going with an Orion. I've been eyeing the Ant BMS, Tiny BMS, and Daly or Chargery, and it's escalating costs moving left to right there. Four Chargeries, I might as well just go to Orion and have it simplified to a single (more complex, though) device. Has Daly worked out the temp sensor cutoff yet?

I've been researching and found quite a bit on various LG cells, but not sure if it's going to get us any further than just using the settings Battery Hookup provides. I need more time to dedicate to digging into what I've found.

Finally got the cells, so I'm determining my physical structure/build components, and then need to find the optimal way to test the cells (might just multimeter check the voltages), then build them into actual batteries and proceed with charge/discharge testing via the actual inverter. (debating between Victron Quattro and Schneider ConextXW+/Pro ... not many high wattage 48V alternatives)

Found this on LiNMC you might be interested in.

 

[HaldorEE]

Finally got the cells, so I'm determining my physical structure/build components, and then need to find the optimal way to test the cells (might just multimeter check the voltages), then build them into actual batteries and proceed with charge/discharge testing via the actual inverter. (debating between Victron Quattro and Schneider ConextXW+/Pro ... not many high wattage 48V alternatives)

Thanks.

I have come up with a decent bus link concept for these cells. My portaband saw blade guides are worn out so after replacement parts get here I will be documenting them.

1.5" x 0.125" copper bar stock with bent ends for connection points. I will be tin plating them to prevent corrosion.

 

[HaldorEE]

Found this on LiNMC you might be interested in.

Thanks. From this document, it looks like 3.4V is a good number for 10% SOC discharging and 4.15V for 100% SOC charging.

That agrees well with Battery Hookup's numbers. That works out to 23.8V and 29.05V for my 7S pack. Good to get confirmation.

 

[HaldorEE]

So are these 3.6V or 3.7V cells? Battery Hookup uses both numbers in their web page. The paper you found showed both 3.6V and 3.65V.

 

[Ampster]

The 14s4p setup means 4 BMSes, or going with an Orion.

Are you sure that a single Orion can handle 14SP4?

 

[PerfectInsanity]

Thanks.

I have come up with a decent bus link concept for these cells. My portaband saw blade guides are worn out so after replacement parts get here I will be documenting them.

1.5" x 0.125" copper bar stock with bent ends for connection points. I will be tin plating them to prevent corrosion.

Curious to see your idea. I'm just planning to go with aluminum square tube/C-channel and bar stock similar to what David Poz used. Seemed to work well and shouldn't cause any issues, at least that I've found. Any specific reason you're going with copper?

 

[PerfectInsanity]

So are these 3.6V or 3.7V cells? Battery Hookup uses both numbers in their web page. The paper you found showed both 3.6V and 3.65V.

That's a question I still have, and part of why I kept digging for additional information. I found quite a few links discussing various LG Chem battery comps, and it sounds like it may depend on the year they're made, along with specific purpose (which also ties to C-rate variations). Haven't been able to dig through them enough yet to find out if there's info/labels in some of the threads indicating they're the same cells.

 

[PerfectInsanity]

Are you sure that a single Orion can handle 14SP4?

Thank you for making me double-check. No Orion for me. I'd misunderstood their wording on the product page, and just dug into the manual more. Single string per BMS, so that's a no go.

Likely going with an ANT BMS, if I can source them, or settle on the Daly at this point.

 

[HaldorEE]

Curious to see your idea. I'm just planning to go with aluminum square tube/C-channel and bar stock similar to what David Poz used. Seemed to work well and shouldn't cause any issues, at least that I've found. Any specific reason you're going with copper?

Flat copper stock bent into U shaped links with nuts and screws clamping the battery leads between the links and some pieces of flat stainless steel. I will be plating the copper with nickel to prevent oxidation or corrosion.

I bought a lovely piece of 2" x 1/4", silver flashed copper bar stock only to dicover that bending it takes a pretty serious press. The 1/8" stock I can bend in a vise.

You are correct. Aluminum stock should be fine electrically, but I got to be me.

 

[PerfectInsanity]

Flat copper stock bent into U shaped links with nuts and screws clamping the battery leads between the links and some pieces of flat stainless steel. I will be plating the copper with nickel to prevent oxidation or corrosion.

I bought a lovely piece of 2" x 1/4", silver flashed copper bar stock only to dicover that bending it takes a pretty serious press. The 1/8" stock I can bend in a vise.

I initially thought copper as well, but looking at costs, ease of access, and if I'd have any gains, I had to compromise. I wouldn't have thought 1/4" copper would be that bad, but I suppose anything at 1/4" is going to be rough to manipulate.

Something I'll mention, though it seems you've already considered this regarding the Cu bars at least. Stainless steel against the Al or Cu battery tabs could cause galvanic corrosion over time. The distance between Al and SS made the decision to resort to Zinc coated hardware for clamping everything together.

You are correct. Aluminum stock should be fine electrically, but I got to be me.

Haha, totally understand! That's how I am with my entire bus conversion / RV build I'm working on. (and why it's a balancing act deciding where to put time, such as digging into those battery links more) And thank you for your confirming thoughts regarding electrical adequacy of the Al.

 

[PerfectInsanity]

@HaldorEE I just went through a case of mine inspecting them more thoroughly alongside testing them and found an issue tied to how they cut the tabs. That process creates metal flecks/dust and it got in under the aluminum cover, creating a stippling pattern (indentations / impressions) on the pouch skin. All of the ones I've checked have it. This could definitely create a puncture if a big enough fleck got under there, or wedged at the wrong angle.

I'm not sure how I feel about these at this point. Even cleaning out the debris first (before compressing them), I don't know how resilient the skin is to know if this is going to cause an issue down the line after they've gone through heating/cooling associated with use. Further, thinking to David Poz's video and the assembly process using threaded rod to clamp them together... doing that without cleaning out these metal flecks is only going to cause them to make more of an impression or increase chance of puncture. I'm contacting him (as a heads up, for safety) along with BatteryHookup to see how they respond.

 

[HaldorEE]

@HaldorEE I just went through a case of mine inspecting them more thoroughly alongside testing them and found an issue tied to how they cut the tabs. That process creates metal flecks/dust and it got in under the aluminum cover, creating a stippling pattern (indentations / impressions) on the pouch skin. All of the ones I've checked have it. This could definitely create a puncture if a big enough fleck got under there, or wedged at the wrong angle.

I'm not sure how I feel about these at this point. Even cleaning out the debris first (before compressing them), I don't know how resilient the skin is to know if this is going to cause an issue down the line after they've gone through heating/cooling associated with use. Further, thinking to David Poz's video and the assembly process using threaded rod to clamp them together... doing that without cleaning out these metal flecks is only going to cause them to make more of an impression or increase chance of puncture. I'm contacting him (as a heads up, for safety) along with BatteryHookup to see how they respond.

Thanks for the heads up. I will definitely disassemble them and clean out any debris.