Is this design safe or dangerous?

[zedconnor]

I would like to know if this is a safe design for a 16s build or not.
Some are saying it is bad to stack batteries like this. This is a vertical box.
There are 8 cells per column.
Will this damage the bottom cells due to the weight of the top cells?

 

[hwy17]

It's about 100lbs on the bottom cells. If you are ok with no compression on the top cells then that weight is definitely fine. If you add compression, this limits how much you can add. They will always be unevenly compressed.

Some people subscribe to a theory that cells lying on their broad side is not ideal for electrolyte distribution and that sideways on the narrow side would be better. But generally it seems ok. Companies like EG4 will tell you it's fine to use their products with the cells laying on that side.

I don't remember seeing a teardown of the PowerPro yet, but those might be vertical like this too.

 

[Tulex]

If I remember, compression is something like 12 psi. Battery has about 56 si, so it would take 672 lbs to get that on the bottom battery. So weight is not an issue, and still leaves room for some decent compression if you still want to. Everyone says it depends on the cells. I used eve 304ah cells. Everything I found said orientation doesn't matter for those cells, so that's how I built my battery, just like your pictures. I didn't worry about compression, the more I read, the more I believe it was just hype. We aren't running the batteries to the extremes that they do in testing, and testing is where the compression number comes from if I remember correctly.

 

[BentleyJ]

I have a wall mounted YIYEN 150Ah battery with the cells stacked inside exactly** like your pic. No problems in 5 years yet.

**Its actually 2 stacks of 16 x 75Ah cells.

 

[OffGridInTheCity]

Everything written is consistent with overall comments I've read thru the years - but while we're on this, what's the latest on 'venting'.

The cells have vents at the top and I've seen comments that it might be good to have them vertical because of venting - any substance to this idea?

I bring it up because I'm interested and the OP might be interested as well to have an opinion in case they read about this later on.

 

[42OhmsPA]

Regardless what orientation you choose I would absolutely add insulators / separators between the cells.

 

[hwy17]

Yeah there seems to be a divide between people who want to prepare for a venting, or consider it so unlikely that it can be dismissed. I want to keep my cells upright for venting, although in that youtube video about the guy who had a cell vent, his vent cap apparently never actually popped.

I think if you are designing a pack without an exhaust path for vent gases, then you are already putting yourself in the camp of ignoring the rare possibility of venting. At that point, whether it squirts out electrolyte or boils it off probably doesn't make that much of a difference. Squirting it might even produce less gases overall.

 

[OffGridInTheCity]

Regardless what orientation you choose I would absolutely add insulators / separators between the cells.

@zedconner - I don't mean to presume but just in case you're not sure about this comment (and I can't tell in you're pic if you have insulators) it's because the metal cans are electrically active and if the thin wrapping rubs thru and the cans make contact - a large current short can occur. It's spot on advice.

 

[zedconnor]

@zedconner - I don't mean to presume but just in case you're not sure about this comment (and I can't tell in you're pic if you have insulators) it's because the metal cans are electrically active and if the thin wrapping rubs thru and the cans make contact - a large current short can occur. It's spot on advice.

I was just about to ask that. I have insulation between the cells. But not between the metal case and the cells.
The case is power-coated.

Would you advice to insulate everywhere the cells are touching the case as well?

Also I used a kind of rubber sheets (about 3mm thick, and they're not hard-type but soft bendy type like paper)

 

[OffGridInTheCity]

I was just about to ask that. I have insulation between the cells. But not between the metal case and the cells.
The case is power-coated.

Would you advice to insulate everywhere the cells are touching the case as well?

Yes

Also I used a kind of rubber sheets (about 3mm thick, and they're not hard-type but soft bendy type like paper)

Sounds reasonable to me

Perhaps others with more hands-on LifePo4 will comment. My powerwall is 18650 cells, and they have the same issue but I use standard cell holders that keep the cells apart.

 

[Alkaline]

The cell at the bottom as to bear all the weight of the cells at the top, mean while the top cell can just be a lazy fat ass, I personally think there should be a shelf between every 2 cells to isolate the weight.

 

[JJJJ]

There are videos which show server rack packs on their sides. Most consist of 100 amp cells which are smaller and lighter than most DIY cells.

I asked my Eve cell vendor about cell orientation. I included her response:

"For 16S, we do not suggest doing so, the bottom cell will bear much pressure;

For 8S, each column has only 4 cells, that should have little effect."