Are the heat pads AC or DC? And do they have a built in thermostat?
EVE 280Ah Lifepo4
- Thread starter boboxx
- Start date
Are the heat pads AC or DC? And do they have a built in thermostat?
Hi all,
can anyone tell me if I can mount the cells in other positions than upright? Due to space constraints I need to mount my cells on the sides with the terminals on top of each other. Would that be problematic due to the position of the pressure valve or for other reasons?
Cheers,
Marc
can anyone tell me if I can mount the cells in other positions than upright? Due to space constraints I need to mount my cells on the sides with the terminals on top of each other. Would that be problematic due to the position of the pressure valve or for other reasons?
Cheers,
Marc
good morning; there are two heat pads on each side of each battery. (8"x12" perfect size for the 280ah cells) they are AC, 7watts each. there isn't a thermostat but their spec sheet says they top out at a nominal temp of about 70-75degrees F. (the right temperature for a reptile). my plan is to just connect them to the output of the inverter either thru the night or in the morning to heat things up.
I guess theres really no need for a thermostat if they max out around that temp. Good failsafe having two pads per battery in case one were to crap out on you.
I’m planning to get some DC pads and run them directly off the charge controller load output on a timer setting. Also, thinking I may put my battery in one of those cheapo styrofoam coolers to make it easier to maintain temp for late fall/winter.
I felt that most of the DC heat pads were way too hot (around 80deg C). I put two heat pads with each battery as those 280ah cells are beefy. lots of mass to get warm. I also will look at insulating them but haven't dwelled on it as yet too much (looking forward to summer). I have victron charge controllers integrated with a BMV-712. they will not charge the batteries until the battery temp is detected at around 40deg. (I verified that this spring with some early morning temps) so a connection between the charge controllers and DC heating pads wouldn't work to heat up the batteries. But that's just my configuration in this instance.
sremick
Mostly competent. Knows enough to be dangerous
Did you ever get an answer to this or figure it out?
PScott
New Member
Can someone explain what "fixture" is referring to in the LF280 specification?
Refer to this thread:
diysolarforum.com
EVE-280 cells should these be clamped tight or spaced for expansion?
I working on my 4s 280ah battery plans. I thinking of my battery box. should these cells have a air space between them or be bonded tight together with a hose clamp or something similar.
diysolarforum.com
Refer to this thread:
EVE-280 cells should these be clamped tight or spaced for expansion?
I working on my 4s 280ah battery plans. I thinking of my battery box. should these cells have a air space between them or be bonded tight together with a hose clamp or something similar.
Start a bit further up the page, and continue reading beyond Steve's comment. My recollection is that his opinion (Snug but no pressure/force applied) was the minority opinion on this question, and did not appear to be supported by the manufacturer's specifications.
Like @sremick and @LukeVader I'm also hoping for clarity on the maker of these cells, OP states EVE, April thinks they are Ganfeng (based on the QR code?).
So what's the difference if one compresses the cells or keeps them snug enough to prevent the cells from expanding....lol. The aluminum around the cell isn't going to know any difference of the amount of compression unless one compresses the cell so much the aluminum is crushed.
The whole thing of compressing the cells per Eve's specifications with that much force never made any sense to me. However applying enough force to keep the cells from expanding does make sense. And that amount of force would be tiny, or snug.
I was looking at threaded rods and 3/4 inch plywood on home depots website. In my mind cutting two pieces of plywood to match the size of each end of the pack, then putting the plywood on each end of the pack and using the threaded rods to apply a snug amount of compression should suffice. Others have used this method and I think it's great.
Good question, some clarity from EVE would be helpful. In my eyes firmly snug and tight, and light compression are two ways of saying the same thing. However the linked comment states in the first sentence: "Compress does not mean put under pressure ! In this context, it means snug & tight but not under pressure or force." This statement is the only point that was questioned/received pushback from people as it appears out of step with the manufacturers recommendation of 300kgf compression. Beyond that I think everyone was on the same page that cells should be somewhere between snug and moderately/lightly compressed.
Setting that aside, I think the open questions are (1) do other cell manufacturers make similar recommendations (2) how is the 300kgf measured/derived and how specific is it (3) how best to accomplish it in our DIY designs.
I won't pretend to fully understand EVE's logic. But unless you are confident you do fully understand or have more info, it seems like a prudent default is to follow or at least approximate the manufacturers specifications as best we can.
Fully agree, I think this is a good method, and probably what I will do. I think its the best low tech, cheap, DIY friendly method that approximates the manufacturers guidance.
I'm wondering if tightening the threaded rods to the point of snugness at low SOC would achieve roughly the right amount of compression at mid and high SOC. I'm also wondering if I'm overthinking this
hard to say with so little info to go off of. Worst case scenario if you do nothing to compress your cells is your cells last a really long time (2500 cycles) as opposed to a really really long time (3500 cycles) If you dont want to overthink it I think using the method you referenced reccomended by MarineHowTo, Nordkyn and others and tightening to the point of firmly snug is a solid plan.
It's just my own common sense although I am not the brightest bulb around here. I don't know where they are coming up with 300kgf from. I had thought it might be a misprint and/or maybe they are referring to the aluminum casing. As you know there is a pouch contained within the casing. Or maybe they mean 300kgf is the required force to keep the cells from bulging when charging at the maximum C rate.
I'm wondering if tightening the threaded rods to the point of snugness at low SOC would achieve roughly the right amount of compression at mid and high SOC. I'm also wondering if I'm overthinking this
I have over thought about this too. If the cell has no bulge, which it shouldn't when new, then it shouldn't matter what the SOC is when mounting them snug.
hard to say with so little info to go off of. Worst case scenario if you do nothing to compress your cells is your cells last a really long time (2500 cycles) as opposed to a really really long time (3500 cycles)
And that is probably true. BUT.....if you do nothing to compress the cells and they never bulge, then why wouldn't you still be able to get 3500 cycles?
If I had to do an educated guess it's because it prevents the layers from delaminating.
1) I don't know. 2) Imagine you put something weighting 300 kg on the cell (you can convert it to a pressure if you divide it by the surface of the side of the cell if you prefer). 3) Use threaded rods, a torque wrench and a torque to traction/compression force table. +/- 10 % would be pretty good and probably good enough (and still better than nothing...)
They do bulge a little at high SoC, a few % at most but it's here.
The datasheet specified with and without "fixture" which was defined as 300kgf, and included graphs of cycle life for both, so I'm pretty positive its not referring to the alu casing, and suspect its not a misprint (well the value of 300kgf could be a misprint, but the concept is mentioned too explicltly and too many times to be included accidentally in my opinion). You could be right that the compression is designed for maximum C-rate, seems reasonably plausible, but again who knows. Without clarification we are just a low wattage bulbs speculating and educated-guessing
I believe (but am not positive) that the EVE datasheet specificies some normal and small amount of expansion.
Above my pay grade.
I'm not confident I can account for all the factors at play here. Particularly over 1000's of cycle / many years.
This seems to imply that you are saying it is ok to apply compression on the narrow side? I remember reading somewhere that you DO NOT want to apply compression on the narrow side only the wide side. Unfortunately I cannot find the source at the moment, but something about the way the pouch is constructed and you do not want to apply pressure to the pouch seams. I apologize if I misinterpreted your statement.
I would say that makes sense but only if the cell bulges and contracts which as you noted they are known to do under a high state of charge. It's the amount of force that EVE notes in their specs that is throwing me off. I simply do not understand what the difference is between applying the force they state to apply, or applying enough force to the cells to ensure they don't bulge. I am going to do the latter.
Without clarification we are just a low wattage bulbs speculating and educated-guessing
Nah, our bulbs are brighter than EVE's. I would be happy if someone could prove me wrong with my thinking....but with a detailed explanation
Well, I can tell you with another brand of aluminum-shell cells that no compression is applied. They are not even supposed to touch each other -- nor do they, using spacers.
And at sub-C charge I was unable to observe any bulging.
If these do bulge, I suppose I could see an argument for clamping them.
Either way, it probably doesn't matter very much for the energy storage use case.
And at sub-C charge I was unable to observe any bulging.
If these do bulge, I suppose I could see an argument for clamping them.
Either way, it probably doesn't matter very much for the energy storage use case.
I suspect these are Frey cells? (Aka Fortune, Overkill solar, etc). This is an interesting point. I wonder what role volume to surface area ratio plays. Frey cells top out at 100Ah I believe, and are supposedly pretty robust and well built. Furthermore, they are designed for high C-rates right (6C?) where cooling becomes a much bigger factor.
The EVE 280's have a much higher ratio of volume to surface area and lower C-rate. This may or may not be part of why EVE recommends compression. I would be curious to know whether other similar form factor aluminum cells (like CATL 202Ah, or ETC 277Ah) recommend compressions or 'fixture' and if their datasheets are any more clear on the method and the logic.
I may or may not be way off, but I have the impression that the bulge is the result of high state of charge more than c-rate. Can anyone confirm or correct my understanding on this point?
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