High cells count vs low cell count.

[Jestronix]

What is safer ? 1200whrs in 16 lipo pouch cells or 1200whrs in 110 cells of 18650.

I started thinking about the odds, almost 6.8 times the amount of cells and interconnects, then I thought about a thermal run away in a hot glue pack of 18650s. Are we all pushing our luck with hot glue packs ?

I have had both a HK lipo and a hot glue 18650 pack drop cells and go red hot. Both packs didn't catch fire or explode. On both occasions I only noticed by touching the packs while handling them at the end of a ride.

I know 18650 are inherently safer by design, but the cells we buy are not the protected type right ? They do have venting though ?

Lipo pouch cells are really only less safe by the fact they don't have a protective shell, same chem inside right.

I whitnessed a blower battery at work catch on fire and explode into flames when it got wet, it was just as fierce as the fire I saw from one of my lipo packs I punctured with a Stanley knife.
Either way both types get real angry when pissed off.

I'm actually now starting to think lower cell count and less interconnects could be safer if the pouch cells are protected physically.

Most new laptops etc don't run 18650 any more, they run pouch cells as they are thinner. So all they do is protect the cells from puncture and a few other electric smarts. So you have big business using pouch lipo, not lifepo4 either they are lipo.

I'm almost thinking some heat and fireproof layers between big 20ah pouch cells may be the go. Then each cells also protected from puncture.

 

[Matt Gruber]

i'd say tesla proves that 6900 18650 cells, is safe and reliable, done right.
the main thing is to avoid cheap china, any type.
i buy tool packs, makita, dewalt.
but would consider used Volt, Leaf, or tesla cells too.

 

[Jestronix]

Done right is the key, meaning fused and cell seperation. Hot glue packs have none of this.

 

[spinningmagnets]

Here's some info that might be helpful:

https://www.electricbike.com/inside-18650-cell/

 

[Overclocker]

a high number of interconnects isn't inherently less safe. actually this is something that is easy to get right

however a lot of things can and do go wrong w/ poorly designed 18650 packs. the metal can itself is one huge negative terminal covered by super thin PVC. have just a little chafing and you've got yourself a short. so yes it's also easy to get it wrong if you don't know what you're doing LOL

 

[Jestronix]

Good point, super thin barrier between cells, hot glue on a few of my packs came undone.

 

[d8veh]

Don't drop your lipos!

 

[marvak]

Apart from safety issue what are actual differences between battery with 18650 cells or bigger size 21700 size cells.

Some company claims they increased running time of electric bike by using bigger cell.

 

[atarijedi]

Don't forget about 26650s. Fasttech has a good deal on them, LiitoKala 3.6V 5000mAh. $40.46 for an 8 pack, $39.30 if you buy more than 5 packs.

 

[dogman dan]

FWIW, Lipo and most 18650 cells are not the same stuff inside.

But after my house burned, I'm not buying it that lipo is more dangerous anymore. Both chemistries CAN thermal runaway.