Absolute best 18650 (cycle life, DCIR)

[Corrida victim]

A couple years ago, after some extensive research, I went for the Sanyo GA cell for my 13s9p pack. While it held up okish, the capacity loss and dcir rise has been noticeable. Or at least more than I expected from the 4.0-3.4v cycles.
I clearly could have chosen far better cells.

I saw some very promising tests about the 'bulletproof' lg m36 or mj1.

But my question, what is the absolute best, bulletproof (100% DOD) cell available today. Price is irrelevant!

 

[john61ct]

To get a good answer, you need to formulate a better question.

There is no universal "best", only best for a given use case.

Energy density will always be opposed to high power density.

Cycle lifespan only relative to the usual C-rate, then held how long? peak vs continuous?

And none of those factors bring price into it!

LG m36/mj1 are fantastic for high energy density, along with VC7 and 35E

Same category as GA but more consistent.

But for good cycle lifespan, keep to discharge current well under 1C continuous

Maybe 2-3C for occasional very short bursts.

 

[john61ct]

100% DoD is crazy stupid abusive

if you mean literally down to 2.85V at rest as average stop discharge, every cycle.

Triple the lifespan between that and say 3.1V, then again to 3.3V, then again to 3.7V

And very little actual usable mAh energy down there anyway

 

[ZeroEm]

Corrida victim » Oct 15 2020 5:47am

A couple years ago, after some extensive research, I went for the Sanyo GA cell for my 13s9p pack. While it held up okish, the capacity loss and dcir rise has been noticeable. Or at least more than I expected from the 4.0-3.4v cycles.
I clearly could have chosen far better cells.

4.0V - 3.4V is a good range. You can charge higher 4.1 if you ride right after charge. Other things affect batteries, Heat, Cold, High charge rates, Fast discharges and when not in use best to keep them in the mid range of charge. Then there is just bad batteries. You can treat them the best you can and time will get them.

 

[electric_nz]

Have a read of this topic- some awesome persons actually tested a bunch of common cells. For my money the high power low IR ones are the best choice for ebikes - they can handle the abuse

https://endless-sphere.com/forums/viewtopic.php?f=14&t=103092&start=75

 

[jwunder]

Over the last two years, I've built equivalent packs from both mj1 and hg2 cells. The mj1 pack had a little more capacity at first, but has not held up over time. It's fading fast after only 100 cycles. But the hg2 pack is older and still going like new. I thought the mj1's we're supposed to have a longer lifespan. It may be that the hg2 pack can take a charge better, I don't know. Maybe I should have used a slower charger with mj1 pack.

 

[Dak77]

Over the last two years, I've built equivalent packs from both mj1 and hg2 cells. The mj1 pack had a little more capacity at first, but has not held up over time. It's fading fast after only 100 cycles. But the hg2 pack is older and still going like new. I thought the mj1's we're supposed to have a longer lifespan. It may be that the hg2 pack can take a charge better, I don't know. Maybe I should have used a slower charger with mj1 pack.

For 1C loads, MJ1 are normally among the best you can buy for cycle life. For anything over 4A per cell continuous, the HG2 is going to last longer . And yes in either case, .2C charge rate is your best bet if possible.

 

[jwunder]

For 1C loads, MJ1 are normally among the best you can buy for cycle life. For anything over 4A per cell continuous, the HG2 is going to last longer . And yes in either case, .2C charge rate is your best bet if possible.

Yeah, then the hg2 is better for me, for only a small loss in capacity. The quick charge is worth it, since I like to charge right before I use it. My understanding is that leaving a fully charged battery around for awhile is also bad for battery life.

 

[Dak77]

For 1C loads, MJ1 are normally among the best you can buy for cycle life. For anything over 4A per cell continuous, the HG2 is going to last longer . And yes in either case, .2C charge rate is your best bet if possible.

Yeah, then the hg2 is better for me, for only a small loss in capacity. The quick charge is worth it, since I like to charge right before I use it. My understanding is that leaving a fully charged battery around for awhile is also bad for battery life.

Yeh charging to "full" aka 4.2V per cell is fine if you're going to be discharging/riding within a few hours , but long periods at that level day after day will eat away at the life span. I have pack of Panasonic PF that are pretty hideous in most cases compared to most other modern Li-ion cells, but they're still trucking strong because I keep it at 3.8v per cell until Im almost ready to ride then I only charge to 4.1v . It's not the same story for every brand or model of cell, but it's a practice that shows good results with mine. Also , and I suspect the most important one, is I slow charge. As in 600mA per cell. It takes about 3 hours if I only used around 50% capacity , but I'll probably be using this until the next new tech comes out.

 

[jwunder]

I keep it at 3.8v per cell until Im almost ready to ride then I only charge to 4.1v .

Wish I'd thought of that. I read somewhere that if the pack doesn't get warm during charging, you're ok. Mine don't, but apparently that's still not true. I'm charging these 14s6p packs at 6 amps. I guess the hg2's can handle it, but the mj1's can't. Vtc6 would probably work well too.

 

[john61ct]

.2C charge rate is your best bet if possible.

Depends on ambient temperature.

Up to T-shirt weather 0.4C is gentle enough.

When it gets hot, or cells warm from use, 0.6C is OK.

But yes, if you aren't in a hurry, slow is better

 

[john61ct]

The quick charge is worth it, since I like to charge right before I use it. My understanding is that leaving a fully charged battery around for awhile is also bad for battery life.

charging at high C-rates is I think more stressful than sitting at 4.1V a few hours here and there, no problem.

That latter caution is more critical for those who think storing full while unused is OK.

But **all** these longevity factors get lost in the noise if the cells are routinely getting discharged to high DoD and high C-rates.

 

[john61ct]

if the pack doesn't get warm during charging, you're ok

Good goal, but temps can rise internally and be barely detectable from the outside. C-rate is the better measure

 

[john61ct]

For those googling / reading later, all the above suggestions as to make/model are excellent.

Pajda, docware threads well worth paying attention to, many expert members putting a lot of time into objective testing, new results posted regularly.

 

[ZeroEm]

by john61ct » Oct 19 2020 9:20am

For those googling / reading later, all the above suggestions as to make/model are excellent.

Pajda, docware threads well worth paying attention to, many expert members putting a lot of time into objective testing, new results posted regularly.

Information here is trustworthy!

 

[john61ct]

Not from all members, but over time you learn who to listen to.

 

[ZeroEm]

I'm trying to learn, want the best cycle life for myself too. And a money tree!

Don't think my batteries are top self but try not to stress them. They are big enough that I only charge "average" every three weeks.
That's an average, don't do two long rides (500-1300w) in a row without charging but most rides don't use 50-300w.
Have my rules I try to follow, 40-80 SOC don't draw amps above batteries recommended continuous discharge if even hitting that.

I like having more battery than needed and controlling the limits.

 

[Stealth_Chopper]

My conclusion after studying this data and Tesla production technology:

https://endless-sphere.com/forums/viewtopic.php?f=14&t=103092&start=75

Battery pack design and manufacturing process quality must be considered having greater effect than overall cell performance.

Home made ( "sometimes home rolled" eBay ) packs built with varying quality electrical connections,

Meh ! & nope

M.V.

 

[Hillhater]

Sure, pack design and build quality is critical....
.....but the OP’s question was specifically about CELL choice !

 

[john61ct]

And locating top quality cells at a decent delivered price

can be a lot harder than learning how to connect them together and create a top-notch packs.

If the best pack builder in the world lived local to me, and I could give them cells I want them to use, that would be ideal.

Assuming their labour rate was reasonable. . .

 

[ZeroEm]

by john61ct » Oct 19 2020 3:44pm

And locating top quality cells at a decent delivered price

can be a lot harder than learning how to connect them together and create a top-notch packs.

If the best pack builder in the world lived local to me, and I could give them cells I want them to use, that would be ideal.

Assuming their labour rate was reasonable. . .

I would too, it would feel like you know what is in there.

 

[Hillhater]

.

If the best pack builder in the world lived local to me, and I could give them cells I want them to use, that would be ideal.

Assuming their labour rate was reasonable. . .

Well that cannot happen for everyone,..or evem 99% of us i suspect !
So you have to put faith in guys like Paul at EM3ev who have good feedback and offer choice of genuine cells