300 Cells in Parallel

[size=small]300p14s / 2000mAh (2Ah) / 18650 cells. 14 in series for 48v nominal.[/size]

Anything wrong with these calculations?

2Ah x 300 = 600Ah
600Ah x 3.7v = 2200kW
2200kW x 14 = 31,080 wh = 31.08kWh

My monthly electric usage is 923kWh so around 923/30 = 30kWh each day.

I often see packs which have far less cells in parallel, anything wrong with 300 cells? Any downsides?

The Voltage is not quite correct in that cals. you take the capacity in Ah and multiply it by the Mid point of your voltage rage (entire pack) for 14s it would be 50.4V (if you used 3v to 4.2v) which would be 30240Wh or 30.24kWh

Okay, got it, use 3.6 instead of 3.7 because 4.2 - 3.0 = 1.2 / 2 = .6 4.2 - .6 = 3.6

[size=small]2Ah x 300 = 600Ah[/size]
[size=small]600Ah x 3.6v = 2200kW[/size]
[size=small]2160kW x 14 = 30,240wh = 30.24kWh[/size]

fenderbender said:

[size=small]300p14s / 2000mAh (2Ah) / 18650 cells. 14 in series for 48v nominal.[/size]

Anything wrong with these calculations?

2Ah x 300 = 600Ah
600Ah x 3.7v = 2200kW
2200kW x 14 = 31,080 wh = 31.08kWh

My monthly electric usage is 923kWh so around 923/30 = 30kWh each day.

I often see packs which have far less cells in parallel, anything wrong with 300 cells? Any downsides?

Click to expand...

Congratulations - a 30kwh DIY battery is on the larger side!

>Anything wrong with these calculations?
Close enough -600ah@48v ~30kwh battery.

>I often see packs which have far less cells in parallel, anything wrong with 300 cells? Any downsides?
My physical packs are 260ah (120p) and 14s. I have 3 of these in parallel. I chose 120p because:
1) This fits on my shelving
2) A good weight for me to manhandle into place on my rack
3) A good size for Batrium Longmon balancing - i.e. 300p is OK for Batrium as well, but I bought 3 times as many longmons so each pack will balance faster.
4) I plan 5 all together (1300ah) and with 5 I can take one out of service to repair it and still have 4 (1040ah) available - which I need for my power consumption plans which include a whole house heat pump.


>My monthly electric usage is 923kWh so around 923/30 = 30kWh each day.
This comment is interesting, but need more info (PV array size, inverter size, on or off grid, your plans) before a discussion on whether the size of your battery is well matched for your system.

Nothing wrong with having 300 cells in parallel. Most of the time, most builders are constructing several banks of smaller strings and then parallel the totals together. For example having 3 strings of 14s80p. Electrically this would be 14s240p, but maintenance is a lot easier as one string can be brought offline while the other 2 stay operational and not need to power down the whole system.

Charging the cells to 4.2 will drastically shorten the life cycle of standard lithium cells. You're looking at a few 100 cycles, maybe around 500. If they go through a full a cycle each day, that's about a year and a half before they start to drastically decrease in capacity.
Dropping to just 4.1V will greatly increase the life cycle to over 1000 cycles.
Same with the bottom voltage of only going to 3.2 instead of 3.0V. Overall, there isn't much capacity between 3.0 and 3.2V and 4.1 and 4.2V, maybe a few 100 mAh.

This is true for used and new cells alike.

A few moredownsides:
* ca 15kg / pack. More difficult to physically handle, accidental bumps, s[size=small][size=small]tructural[/size][/size][size=small][size=small]stability,[/size][/size]back injury, ...
* When some of your cells become defective, finding it/them will take much more time
* You'llneed a whopping4200 cells harvested and tested to get started.

Just a little unit error in your calculation:
2Ah x 300 = 600Ah
600Ah x 3.7v = 2200Wh
2200Whx 14 = 31,080 Wh = 31.08kWh

Also, taking into account losses in the cable+inverter, and alsoonly using 3.3V ~ 4.1V to make the cells last significantly longer, you'll likely get 60~70% (ca 20kWh) of usable AC power.
Incidentally, I have the same number of cells/capacity, but in 14s100p x3 in parallel configuration - 4th coming in a few weeks.

ajw22 said:

Incidentally, I have the same number of cells/capacity, but in 14s100p x3 in parallel configuration - 4th coming in a few weeks.

Click to expand...

Very cool.

My packs are120pmade up of 2x60p base units. I put 2 x 60p units together to make 1 x 120p. I have 42 120p packs which lead to3 'batteries' of 14s120p - pretty close to your own situation. So I have a 'base physical unit' of 60p - mostly by accident because in the beginning I thought 60p was a 'huge' amount of power

You mention a 4th (battery) coming in a few weeks... and I'm also working on a 4th batter (i.e. 14s120p). One of the reasons for keeping packs smaller / batteries smaller (than 300p) is that to do a 14s120p battery I need 1,680 cells for each new battery in the bank. If I had 14s300p that would be 4,200 cells just to add a 2nd battery - kind of a big jump in capacity / not very 'incremental'.

Bottom line - another reason to think about pack size is to think about what it takes to incrementally expand your battery bank as you ramp up your consumption.

Anything wrong.....?YES
Numbers are to low......you can do better
300kwh for a example.

But i agree, its better to split up in 100 cells a pack times 14, times 10 or even 30 strings, for a lot of reasons.
Heck, if you would do 3 x 100 in one 3.6v pack, you can take out one (100 cells)at the time.
IF you don't discharge to low or dorushand hurry up with testing.
Take a look at owitte'sbuild.

Use glass fuses also.
My humble opinion and two cents, best