12v 100ah battery on sale made from 18650 cells

[ers61]

i saw some cheap battery packs made from 18650 cells inside with 100ah

what is the reason they use 18650 instead of prismatic cells? to be cheaper ? they dont mention this on the box

what are the advantages/ disadvantages of using these 18650 in such batteries ?

 

[Vigo]

Im very curious what you saw. Could you link to an example or two? Interesting topic..

 

[ers61]

Im very curious what you saw. Could you link to an example or two? Interesting topic..

something like this

 

[Vigo]

Thanks for the followup. Those are definitely too wide to be 18650s (18mm diameter 65mm height). Hard for me to scale properly but they might be 26650 since 26mm is pretty close to an inch which would make that box about ~7" x ~9.5" or so which is plausible. I'm not thrilled by the inconsistency of the welds of the bus bars, looks done by hand.

Technically there's nothing majorly wrong with cylindrical vs prismatic other than space efficiency (circles don't stack well) but i don't know too much about the pros/cons of cylindrical vs prismatic vs pouch cell design other than the basics like cylindrical probably have the best production tolerances for large scale mass production, prismatic is probably overall best balance of durability vs energy density, and pouch cells probably have the best energy density (volume unit per watt-hour) but might have durability concerns due to how they are packaged.. even that is stretching what i know into maybe-land. Hopefully someone else has better info on that.

I'd still like to know specifically where you are seeing this? Got a link?

 

[ers61]

Thanks for the followup. Those are definitely too wide to be 18650s (18mm diameter 65mm height). Hard for me to scale properly but they might be 26650 since 26mm is pretty close to an inch which would make that box about ~7" x ~9.5" or so which is plausible. I'm not thrilled by the inconsistency of the welds of the bus bars, looks done by hand.

Technically there's nothing majorly wrong with cylindrical vs prismatic other than space efficiency (circles don't stack well) but i don't know too much about the pros/cons of cylindrical vs prismatic vs pouch cell design other than the basics like cylindrical probably have the best production tolerances for large scale mass production, prismatic is probably overall best balance of durability vs energy density, and pouch cells probably have the best energy density (volume unit per watt-hour) but might have durability concerns due to how they are packaged.. even that is stretching what i know into maybe-land. Hopefully someone else has better info on that.

I'd still like to know specifically where you are seeing this? Got a link?

dont't have a link for it, someone sent it to me. i was wondering what was the point of it. does it work out cheaper to produce with these cells? looks like labour is more complicated and time consuming on this there must be a business sense to produce it like this. also wondering if one cell fails i think risk of error is higher

 

[DJSmiley]

Maybe 21700 cells.

Plenty of batteries with cylindrical cells, including some 'more known' sellers (eg Liontron in mainland Europe)

Prismatic has better energy density, but many are limited to 1C discharge. So with a 100Ah battery that would workout to 100A.

Cylindrical cells can have 1.5-3C discharge, so that allows a 100Ah battery with 150A or 200A discharge. Usefull if you don't need much capacity, but still require occasional high currents.

Also, cylindrical cells can be used in all orientations, unlike prismatic which generally only can be used either right up, or on the flat side, not on its small side.

 

[Vigo]

Other than the C-rate issue Smiley mentioned i would guess the 'reason' would probably come down to whatever that 'builder' could get a good deal on a supply of. It definitely seems more labor intensive to build, and it definitely has more failure points. If it were someone building for themselves or small batches for friends etc i have no issue with it but if it were me buying for a 'storage' system such as for my house, i'd stick to regular prismatic cell builds that have less parallel connections and less connection points in general.

 

[Wakintx]

I wonder if those green cells might be some A123 cells...new or old