which battery type is best?

[jimmyhackers]

i got myself into a youtube spat with a yank who i think has many misconceptions about ebikes....one appears to be about batteries

his argument is 18650 and 21700 are better than lipos now........for undisclosed reasons :s (probably group bias, or solely safety fears)

my arguments is good old lipo pouch cells are best as, they take up less space (better form factors), weigh less, provide higher current.

i think the industry shift to round 18650s/21700s is partly the elon musk hype train, and partly safety concerns as they just pop/vent instead of puff up.

seeing as i visually inspect all my cells after each ride and charge i can tell if a cell is bad/going puffy, whereas if i was using 18650's i couldn't really.

so to simplify if a lipo pouch battery is properly maintained, are there still better battery technologies out there?

id imagine if there was, all the quadcopter/rc car/rc plane pilots would use it????? but they dont

 

[billvon]

i think the industry shift to round 18650s/21700s is partly the elon musk hype train, and partly safety concerns as they just pop/vent instead of puff up.

And because they are dirt cheap - and readily available on the used market. And they are relatively tolerant of mechanical abuse.

I've used two pouch cell batteries over the years. One worked fine. The other started leaking almost immediately and died after six months. OTOH I've never had an 18650 leak.

Nowadays I'd have no problem using pouch cells as long as they were well protected. A 16S Pacifica pack in original housing? No problem. A 13S pouch battery in a nylon bag? No thanks.

id imagine if there was, all the quadcopter/rc car/rc plane pilots would use it????? but they dont

I think the reason they use it is because 1) to them, weight is everything, and lipo cells are a little lighter and 2) lipo can be cut into shapes more compatible with small vehicles.

 

[john61ct]

Yes, LiPo literally just a packaging difference.

Safety is not a trivial concern.

But your rig, your choice.

Could you link to good sources for the pouch cells you like?

Actual chemistry differences are greater, energy density vs power discharge C-rates, longevity vs acquisition cost per kWh, temperature issues

There is no one "best" solution, and certainly not a "tribal identity" issue, each use case and buyer preferences vary.

 

[999zip999]

What are you using it for ? A flying drone or energy storage ?

 

[jimmyhackers]

i use pouch cells for my ebike...but 18650s for other things.

the whole reason for this post this person on youtube said i was usuing old tech (lipos) and i was merely curious asto wether i was spouting nonsense in response. hence asking on here

my opinion was, lipo pouch is the best, 18650's and 21700s are potentially "safer" but a lesser option in almost every other respect.

i think most people have had a few pouch cells puff on them (me included)...which is why they get scared, most the time i find they only go bad from misuse rather than regular use. if it is manufacturer defect.....it usually shows its head withing the first few uses.

as for a cheaper option....im pretty sure i could buy a 6s 6ah lipo pouch cell with a 50-100C (probably a lie/exageration) rating for cheaper (about £60) than i could build an equivalent out of 18650's. i could match the capacity but nowhere near the discharge rate.

 

[LeftieBiker]

As already noted, you seem to be confusing chemistry with packaging. Many (but not all) of the pouch cells are LiFePo4, which is very stable and long-lived but has a low energy density. Most (but not all) of the 18650 cells are various variations of LiPo, and have more energy density but less stability and longevity. Still, talking about the packaging type as if it were the chemistry is wrong.

 

[billvon]

As already noted, you seem to be confusing chemistry with packaging. Many (but not all) of the pouch cells are LiFePo4, which is very stable and long-lived but has a low energy density.

Hmm, I've used pouch cells a lot, from 1.3 amp hour to 13 amp hour. I've never seen a LiFePO4 pouch cell, nor have I seen any RC battery pouch cells that are LiFePO4. I am sure they exist though.

 

[spinningmagnets]

If I was building a battery pack for an electric motorcycle, I am certain my top three cell choices would be flat pouch cells. (Chevy Volt would be high on the list)

However, ebikes have severe size and shape restrictions, so I would likely choose 18650's...and my current favorite is the 30Q, factory rated for 15A 3000-mAh each

 

[dustNbone]

Hmm, I've used pouch cells a lot, from 1.3 amp hour to 13 amp hour. I've never seen a LiFePO4 pouch cell, nor have I seen any RC battery pouch cells that are LiFePO4. I am sure they exist though.

A123 20Ah pouches have been around for a long time, a few people here use them on their bikes. Plus whatever pouches Ping uses in their batteries. I think those ones are 5Ah.

On the RC side, LiFePo4 is more common for smaller transmitter and receiver batteries. Their lower energy density makes them less practical for powering motors in flying models, but I've seen them used as traction batteries in RC cars and boats where weight is less critical.

 

[LeftieBiker]

As already noted, you seem to be confusing chemistry with packaging. Many (but not all) of the pouch cells are LiFePo4, which is very stable and long-lived but has a low energy density.

Hmm, I've used pouch cells a lot, from 1.3 amp hour to 13 amp hour. I've never seen a LiFePO4 pouch cell, nor have I seen any RC battery pouch cells that are LiFePO4. I am sure they exist though.

Ping Packs use them, and since I use mostly those on bicycles, I probably haven't noticed their decline in the market. It's a shame, because I have a 4 year old Ping pack that performs almost like new, after literally thousands on miles.

 

[john61ct]

Looking for links to known-good sources of pouch style cells, not pre-made packs.

LFP would be fine, as well as other LI chemistries.

 

[jimmyhackers]

yeah i was on about lipo RC pouch cells (pre builts)

i havnt seen any llifepo4 ouch cells.

seem slike i was still right in my initial inklings.

a lipo pouch cells is better than a lifepo4 pouch cell.
and a lipo pouch cell is better than a 18650 lipo cell.


i can wait till they fix zinc oxide batteries........make them more rechargeable.....they are already nearly double energy density of lipo etc

 

[billvon]

i can wait till they fix zinc oxide batteries........make them more rechargeable.....they are already nearly double energy density of lipo etc

Li-S is already available, the cycle life and temperature range just suck. But as they improve them they have the potential to be far lighter per kwhr than li-ion.

 

[sleepy_tired]

When comparing to 18650 you have to take into account that 18650 comes in lots of different chemistries. Some come in just regular Lithium-Colbalt like Lipos, but others come in different chemistries with different properties. So you have to look at specific cells, the ratings, and what chemistry they use to get a good idea about what is going on.

Also it's the competitive market that companies are spending money on.

In my eyes there are 4 major concerns when comparing battery type:

* Safety

* Power density, both in weight and volume. How much sustained amperage the battery can generate.

* Energy density, both in weight and volume. How much watt-hours capacity.

* Lifespan


I haven't done the math in a while, but it looks like:

LiFeP04 -- Wins in safety. The thermal runaway for this style is over 250C. The trade off is lack of power/energy density. It takes roughly twice the weight and volume to equal Lipos or 18650s. They MAY win in lifespan, but it's hard to tell.

18650s -- Ranges good to bad safety. Depends on the exact cell, cell monitoring, and battery construction. Shitty batteries burn down houses. The steel cylinder adds a lot to the robustness. Despite the steel cylinder and plastic cases typically used the 18650s and bigger cylinders tend to have better energy density than hobby lipos if you are using modern high capacity cells. With power oriented 'tool' cells like the 25R or 30Q it probably does a good job rivaling lipos in terms of power density.


Lipos -- Bad safety, decent energy, awesome power. Everything is a trade off. Probably the majority of lipo problem's are user's error. Stuffing a nylon bag full of cells with dozens of xt90 connectors and spider's nest of wiring is a recipe for disaster. Fall over wrong or squish the corner of the cell hard against the bag and you are going to have a very bad day. And the relatively low 150 C thermal runaway temperature isn't a good thing either. But by properly designing a protective enclosure, finding a solution to monitor cells, and recharging solution that doesn't require the user to disassemble the packs all the time will bring hobby lipos roughly on par with 'OK' quality 18650-style setups.

18650 generally wins nowadays because you can go out and buy over the shelf high-quality batteries that are engineered well from companies like Em3ev. That way you can concentrate on having fun with your bike instead of engineering a safe solution for lipos.

 

[furcifer]

Next year I think you might be right:

https://japantoday.com/category/tech/kyocera-to-roll-out-new-li-ion-battery-in-2020

Or both wrong

 

[jimmyhackers]

i want those (clay type) batteries to be real....