Short_Shot
Solar Addict
- Joined
- Jul 13, 2021
- Messages
- 1,823
Not necessary. In fact that would be bad.
Heating pads can just be stuck to the bottom or sides.
Last edited:
EVE-280 cells should these be clamped tight or spaced for expansion?
- Thread starter NEWYORKHILLBILLY
- Start date
Heating pads can just be stuck to the bottom or sides.
lance
New Member
- Joined
- Jul 29, 2020
- Messages
- 168
Ah, yes of course. I, out of my relative ignorance on the topic, was conflating voltage and SOC. I do understand the long flat curve in the middle....
I do not have an inverter yet, no. Curious though: even if I did, and followed these steps you suggest, how would I know the batteries' SOC using that method?
I also need to check the amperage of the charger I bought next time I'm downstairs where it is at.... if memory serves me right, it was one recommended by Will on this site somewhere.
Firstascent
Solar Enthusiast
- Joined
- Mar 7, 2020
- Messages
- 265
The most accurate way is using a shunt so you can accurately track how much you've used in aH. With that being said, voltage as we mentioned isn't the best measure of SOC, I'd think it'll at least get you close enough for storage. you just don't want them full.
good chance your charger is the same as mine haha. I got mine from amazon from one of Will's recommendations, I think it's a 30v/10a charger and was around $60 or so.
lance
New Member
- Joined
- Jul 29, 2020
- Messages
- 168
Yep. That's the one!
Interesting that the only way to know a battery's SOC is to monitor what's gone into it, and what's come out of it. I actually do have my shunt and bms (Shuntmon and Watchmon7) but, I'm nowhere close to prepared to take on setting them up. Hell, I don't even own the PC I'm going to need to run their software yet.... I'm a Mac guy here. I think I'll just sit on the batteries as they are....
Firstascent
Solar Enthusiast
- Joined
- Mar 7, 2020
- Messages
- 265
Oh that’s funny!
Very similar setup here, I’m using Batrium as well except I have the watchmon4 with blockmon’s and the shuntmon as well. I am also a Mac guy but have a pc I keep on the side for the rare instances such as this haha. Soon Batrium will have their cloud software and I can’t wait for that.
Johannlog
The sun shines even on cold days
- Joined
- Apr 28, 2021
- Messages
- 100
Is there a thread (or posts in this thread somewhere), that deal more specifically with how to compress cells to the desired 12 PSI? From what I have read so far there are a lot of assumptions on how/if it must be done and the effectiveness of compression. I am not sure what SOC my cells will be at when they arrive (I bought them from Amy) but apparently I won't really be able to determine precisely the SOC (using voltage) anyway, so should I just use tape and hope for the best?
Attachments
Bob B
Emperor Of Solar
- Joined
- Sep 21, 2019
- Messages
- 9,220
There is this one and also one about using a special foam, I don't have quick reference to the foam one, but you can probably find it with a search.
diysolarforum.com
Pack / Cell compression Optimized By Using Springs.
I am opening this thread to split it off from the general cell compression thread. That way those looking for info don't have to sort thru a thread that has many paths for pack compression. If you are new to this idea, it stemmed from an EVE cell specification that indicated a significant...
diysolarforum.com
Shawn Hayes
Learning Everyday
I’ve read a lot of posts/threads about compression. So many ideas and different ways to do it. I ended up using 5/16” aluminum plates with .20” hard rubber matting between plates/cells to give them a “firm” cushion when they expand and rebound when they contract. I used 1/4” threaded rods, 10 rods for each 16s pack, 4 packs of 4 cells, to apply pressure evenly as I could. I used the 12-psi (torque wrench) rule of thumb at 3.25 volts when clamping.
The one thing I never read was how much PSI was gained once you reached 3.65 volts? So tonight, I am charging up a my last 16s pack and had an idea.
When bolting together this pack, I inserted a blood pressure cuff between the middle cells on the end of the pack. I set the blood pressure cuff at 30 mmhg (millimeters of mercury) and started charging. Hopefully this will give me an idea of how much PSI is gained between 3.25v and 3.65v. So for every 1mm of mercury gained, I’ll divide by 51.715 to get the added PSI.
Now I I know this may not be scientific or the best idea ever. But since I was unable to find how much PSI would increase this was the best idea I could come up with to give me a good rule of thumb on the PSI gained.
Thoughts? Does anyone already know this? I assume each application may be different based on the materials used in the compression application.
The one thing I never read was how much PSI was gained once you reached 3.65 volts? So tonight, I am charging up a my last 16s pack and had an idea.
When bolting together this pack, I inserted a blood pressure cuff between the middle cells on the end of the pack. I set the blood pressure cuff at 30 mmhg (millimeters of mercury) and started charging. Hopefully this will give me an idea of how much PSI is gained between 3.25v and 3.65v. So for every 1mm of mercury gained, I’ll divide by 51.715 to get the added PSI.
Now I I know this may not be scientific or the best idea ever. But since I was unable to find how much PSI would increase this was the best idea I could come up with to give me a good rule of thumb on the PSI gained.
Thoughts? Does anyone already know this? I assume each application may be different based on the materials used in the compression application.
Attachments
Firstascent
Solar Enthusiast
- Joined
- Mar 7, 2020
- Messages
- 265
Cool setup and interested in your results.
Just one thought, you should at least use a washer in between the nut and the busbar
Daddy Tanuki
Solar Wizard
it ain't stupid if it works... and even if you cannot get an exact PSI figure, if you can get a percentage of pressure increase that could tell you a lot as well. there is no such thing as worthless data, it might not pertain directly to what you originally wanted, but it can still be used in one form or another.
Short_Shot
Solar Addict
- Joined
- Jul 13, 2021
- Messages
- 1,823
What is the "12psi rule of thumb"?
One does not make psi with torque without calculating the loading over the thread pitch.
Shawn Hayes
Learning Everyday
Maybe so. However there seems to be a hundred ways people are doing this compression idea. Springs, this pressure at this SOC/voltage etc....
So I’m using 12 inch pounds on a torque wrench to tighten down my threaded rods. Maybe I should have said 12 inch pounds on a torque wrench instead of PSI...
But it’s not perfect, but should achieve compression without over compression. Hence the blood pressure cuff to see how much increase I get at 3.65v.
Daddy Tanuki
Solar Wizard
to date I have only seen or heard of one member here actually taking the time and funds to build a pack with a pressure sensor. This is a poor mans way of at least getting an idea of what the delta is. if you see repeatedly that your pack experiences a 4 PSI inclrease then you know that you can tighten to xx without going over the 17PSI threshold (or whatever the current accepted value is). so good on you for trying. Do your thing and let us know the results. (not making fun of you I am serious).
Short_Shot
Solar Addict
- Joined
- Jul 13, 2021
- Messages
- 1,823
Oh. Yeah that makes more sense but does not readily convert to psi on the cell.
There's some simple math to do to figure that out but I'm neck deep in calc 2 homework
Thanks for the reminder from the very distant past. Now I'm going to have nightmares tonight.
12 inch pounds on a torque wrench is a VERY wrong interpretation of the 12 PSI of pressure required on the surface of the cells. You need to use the calculation tables and take into account the size of the threaded rod, the pitch, and the number of threaded rods, in order to derive the force that 12 inch pounds of torque on each nut is applying to the cells.
Shawn Hayes
Learning Everyday
I have not seen these tables, can you share a link? I would say I’m not looking for an exact 12 PSI, but enough compression without over compression. So, thinking 12 inch pounds would be good without over compression with the rubber matting in between each cell giving me some support both during expansion & contraction.
However I would like to see these tables you mentioned if you can share a link? This site has to many threads and opinions on this topic. I’m sure I’ve missed many....
Short_Shot
Solar Addict
- Joined
- Jul 13, 2021
- Messages
- 1,823
As I stated earlier. 12 inch pounds absolutely does not translate to 12 psi. That's not at all how that works.
The amount of force the nut is applying is a somewhat complex formula.
www.engineeringtoolbox.com/amp/bolt-torque-load-calculator-d_2065.html
Short_Shot
Solar Addict
- Joined
- Jul 13, 2021
- Messages
- 1,823
And keep in mind psi needs to be multiplied by the cell area. So you don't enter 12 for the load in pound force. It's whatever the surface area is in square inches * 12 psi.
The one thing I can't remember if you need to then divide that by the number of fasteners or they all get the full torque.
And as tired as I am I'm not even sure I have the right calculator in that link.
The one thing I can't remember if you need to then divide that by the number of fasteners or they all get the full torque.
And as tired as I am I'm not even sure I have the right calculator in that link.
Shawn Hayes
Learning Everyday
Thanks for the info. By reading the link that you posted to the DIY thread, it appears that 8 inch pounds on the torque wrench should be the desired number, not the 12 that I was using. I greatly appreciate the information.
Short_Shot
Solar Addict
- Joined
- Jul 13, 2021
- Messages
- 1,823
That one works too.
I just want to chime in here... I just recently built a 24v bank out of 80ah eve cells for a solar storage project. 15p8s. I used 1" boards on the ends of each parallel string with heavy duty 6" screws into 2x2's along the top and bottom to clamp them. I attempted to clamp them to the point that the assembled parallel string could be moved without cell movement. if I calculate 12psf for these cells it's something like 350 lbs of force on the face of the cells. I don't think I reached that amount of force before I noticed the cells shifting on their own during the tightening because the faces were compressing enough that the edges/corners were wanting to slide past each other. I stopped compressing at that point. I have fear that I've damaged the cells by overcompressing them but cant really find any info so far on what that looks like or what the effects might be other than 'possible punctures in the separating membrane and internal shorts'. but, so far they seem to be fine. I guess we'll have to wait either until they fail prematurely, or we have 20-something years of using them to report on the ultimate outcome.
Simi 60
New Member
- Joined
- Jul 10, 2021
- Messages
- 159
Interesting read but a bit above my pay grade doing the proper calculations even if using the links above.
Anyone got any further input as to what the "actual" torque wrench setting would be to get to the 12ft/lb in the eve280 specs?
I have started at 5 ft lbs (lowest click on torque wrench) over 6 X M10 threaded rod and that holds the batteries in place when lifting without a base.
Seems pretty tight for cranking on something as delicate as a battery cell.
17mm marine ply with plastic cutting board between cells
Garden hose over threaded rod.
This is one of three 24v batts.
Anyone got any further input as to what the "actual" torque wrench setting would be to get to the 12ft/lb in the eve280 specs?
I have started at 5 ft lbs (lowest click on torque wrench) over 6 X M10 threaded rod and that holds the batteries in place when lifting without a base.
Seems pretty tight for cranking on something as delicate as a battery cell.
17mm marine ply with plastic cutting board between cells
Garden hose over threaded rod.
This is one of three 24v batts.
Attachments
Last edited:
Similar threads
