just a thought ! 18650 single wall ( 14s320p)

wim said:
320s ... 1184v...just one question .... Why ? :s

sorry i didnt explail well : 14p 320s ( 56 packs 80p 3.7v in 14 s ) : 48v system
i mean 56packs all in single structure !
 
So you mean 4 sets of 14 packs in series and one pack is 80 cells in parallel... correct? ( 4x80p14s )

i would say, if no specific question, go for it :)
 
That is 14S320P, not 320S14P :)

There is no real difference apart from handling the packs. 14S320P is 14 packs in series with 320 parallel cells each. 320 cell packs are a bit difficult to handle. You could make one big pack 14S320P, 4480 cells. Weighs about 200 kg, have fun moving it around :)
4x 14S80P is the same as 14S320P as you would put these modules in parallel anyway, you are just splitting the 320P packs. This is how Tesla builds its batteries for the cars, only they put their modules, as they call it, in series for higher voltage.
You can also build smaller packs like 7S40P and put these in series and in parallel. This only effects handling and, to a certain extent, cabling.

14S320P is just the electrical specification of a battery and doesn't dictate its physical shape.
 
Well explained darkraven!
 
Aren'tthe advantages of small packs around the modularity?

-you can add an extra (one more parallel)set of packs with fewer cells, so you can increase total storage capacity in more frequent smaller steps
-removing a singlepack is no big deal
-having a spare pack for immediate replacement is a smaller investment
-for swap-in, a small pack can be more quickly/easily charged or discharged to the matching voltage (instant re-balancing on connection to its parallel fellows is a very bad idea!)
-if you find a warm cell or otherwise need to rework a pack, you have less to dismantle and rebuild for the sake of perhaps just one cell
-the smaller pack is a lower current item, so has lesser requirements of pack busbars and connectors (they can be smaller, so soldering doesn't need blowtorches...) You shouldn't need to use bolted connections to the pack, which have the risk of dropping nuts and washers into awkward even dangerous (short circuit!) places.
-any 'problems' should be smaller
... But more small packs does mean more packconnectors! And you are going to take up more space.
One other disadvantage of small spread-outparallel packs is that you'd probably want multiple temperature sensor positions rather than just one (longmon) per serial step. (Straightforward Arduino or Pi project that you might want to do anyway, but likely more sensors and connectors with more smaller packs.)

I do like the idea of keeping the pack size small... :p
 
DarkRaven said:
4x 14S80P is the same as 14S320P as you would put these modules in parallel anyway, you are just splitting the 320P packs. This is how Tesla builds its batteries for the cars, only they put their modules, as they call it, in series for higher voltage.
You can also build smaller packs like 7S40P and put these in series and in parallel. This only effects handling and, to a certain extent, cabling.

14S320P is just the electrical specification of a battery and doesn't dictate its physical shape.

I do have to disagree a little bit ;)

4x 14s80p is different to 14s320p, even if all the packs are made of 80p cells...
The voltage at the end is the same, but the physical shape is different...


image_yxemcl.jpg


I leave in the middle what the bestright way is... both have thempro's and con's.
 
This is just what you imagine it to be, based on some assumptions that aren't set in stone ;)
There is no reason why they have to have a different shape.
 
HI, I am just starting and found a source to get a nice stream of cells. I build a 7S20P pack to be portable. And finalizing my first stationary 7S40P. Both are made of the lower capacity cells (586 cells) I have and have have each a 7S BMS 60A, both pack run their own inverter, they are charged by a solar panel. I want after I got more cells extend the stationary pack. What is the best way to add the 40P packs to it. And how do you connect higher capacity packs. Any advice for connectors?

For the higher capacity cells I get to build a large 14SPXXX pack. I have currently 434 (Samsung 25R and LGHGE2) cells tested and 660 to go. For the real power wall I will go to 48V, I will connected to the grid. My question for building of this wall is do I go for 80P packs 14S and add later to this or is it better to start with 40P packs and start adding when I got more? My Aim is to build at least a 50 kWh pack and upper target is 100 kWh. All idea's of the setup are welcome.

The I have also some (90+) Samsung 30Q which I am testing by Charging, de-charging (measure capacity they give) and charging them again. After a month I will check them how much they will fall. Love to start using them for an electrical motor bike. For which I need a ten fold. Here also the same issue: do I start with single 1kWh (7S14P) packs with each their own BMS, or do I build one big pack with one large BMS?


Most cells (with the exception of the 30Q) I just test by fully charging them and after a coupe of weeks test for voltage drop and their internal resistance. This will not give me exact the capacity. Is this good or should I discharge all cells and measure what they can deliver?

All advice is welcome.
 
paraskevas said:
in one single pack !!!!!!!!! . ( all together ) ( 14s320sp) .... your opinions please !

That's a interesting discussion I think.

As I can see it there are several pro's and con's to having large 320P blocks and then 14 of the in series obviously.

First and foremost a 320P cell pack would weigh in at around 16kg not including busbars and cell holders, and it would be quite large at say 8x40 /10x32/ 16x20 depending on layout and size restrictions.

Then there's the issue with finding and replacing broken cells and heaters, how do you identify those easily?

What about having a spare cell pack so you can replace a cell pack while you service it as above?


I think that having smaller cell packs, f.ex. 8x15 cell packs in parallel would be a better option as you could then have smaller and easier manageable cell packs that could be serviced individually a lot easier as long as you make them easy to remove from the 14S busbars connectors.

One issue with having large packs is that it would be a lot harder to identify underperforming cells / cell packs as you have no easy way to detect is a smaller cell-pack is on the way out unless you put shunts in each pack and then measure the current / power delivered by each individual cell pack. Each cell-pack would also need it's own temperature sensors and while you're at it you could even fan cool them and make a cell-pack management module (call it a CPMS) and have each cell pack monitor itself via a isolated I2C bus f.ex. Essentially cooking your own Batrium but with higher balancing capacity and more temperature sensors per cell pack.

I kind of like that idea, having individually managed cell packs with shuntsthat you then connect in parallel / series to get the capacity you need. They can be easily expanded, just add another cell-pack in parallel, as long as their individual CPMS have individual addresses they can be added to the same I2C bus with a simple connector. You could use Anderson connectors for each cell-pack and a smaller connector, say a DB9 connector for I2C bus andcentral power / cell voltage / currentmeasurements.

What do you think, am I overcomplicating things again? :p
 
mormor1971 said:
paraskevas said:
in one single pack !!!!!!!!! . ( all together ) ( 14s320sp) .... your opinions please !

That's a interesting discussion I think.

As I can see it there are several pro's and con's to having large 320P blocks and then 14 of the in series obviously.

First and foremost a 320P cell pack would weigh in at around 16kg not including busbars and cell holders, and it would be quite large at say 8x40 /10x32/ 16x20 depending on layout and size restrictions.

Then there's the issue with finding and replacing broken cells and heaters, how do you identify those easily?

What about having a spare cell pack so you can replace a cell pack while you service it as above?


I think that having smaller cell packs, f.ex. 8x15 cell packs in parallel would be a better option as you could then have smaller and easier manageable cell packs that could be serviced individually a lot easier as long as you make them easy to remove from the 14S busbars connectors.

One issue with having large packs is that it would be a lot harder to identify underperforming cells / cell packs as you have no easy way to detect is a smaller cell-pack is on the way out unless you put shunts in each pack and then measure the current / power delivered by each individual cell pack. Each cell-pack would also need it's own temperature sensors and while you're at it you could even fan cool them and make a cell-pack management module (call it a CPMS) and have each cell pack monitor itself via a isolated I2C bus f.ex. Essentially cooking your own Batrium but with higher balancing capacity and more temperature sensors per cell pack.

I kind of like that idea, having individually managed cell packs with shuntsthat you then connect in parallel / series to get the capacity you need. They can be easily expanded, just add another cell-pack in parallel, as long as their individual CPMS have individual addresses they can be added to the same I2C bus with a simple connector. You could use Anderson connectors for each cell-pack and a smaller connector, say a DB9 connector for I2C bus andcentral power / cell voltage / currentmeasurements.

What do you think, am I overcomplicating things again? :p

As an engineer myself. There is no better design then one you can service. But idea's are nice.
 
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