I really appreciate you making this video and sharing what you've learned.

Great catch on the spreadsheet talking about the aluminum casing. I never knew!

Ciao Andy, I'm the guy from Italy I wrote to you a couple of days ago (23rd Jan 2023). Thank you very much for answering. Let's put the compression/fixture topic in this way. Let's assume that 4 cells battery (for my Recreational vehicle, we call here Camper) 12Vdc 280Amp cost 800€, with BMS. If it stand for 7,5 year, it will cost 107€/year. If I will keep them under compression, they will last for 9,5 years, this means they will cost per year 84€- The difference is 23€ per year. Once more, as Andy says, in the next 7,5 year the technology will present us something new, and any way in the next 7,5 year I'll be 66+7,5=73 years old. So I'll have to buy, any way, another pack of battery ... I've been understandable ? By Andy and thank you so much for your great Job.

Thank you for your honest opinion about this stuff 👍 Me too, absolutely will not compress those lithium batteries and should more worry about the batteries temperature itself. Temperature is more important. Heat affects all type of batteries, whatever type of batteries.

I've found all this discussion around compressing LiFePO4 Batteries fascinating. For my purpose I decided to go halfway between the 2 options. I used some clamps to mildly compress the 4 cells using 2 fibreglass spacers between each cell for ventilation and the 4 cells bound with kapton polyimide tape. I live in a warm northern climate (Vancouver Canada) so my main concern will be the heat generation - especially with the record breaking heat we've had recently.

@bwilson948

5 ай бұрын

I am about to build my pair of 48 volt packs. How has you experiment come a along.. I do plan on using flex bus bars since this cells appear to love to breath. I have to retrain them as I do a car battery for they will be mobile.

I agree with you. Air cooled. No compression. No alluminium buz bars. No soldered joints. Mike

Good stuff! Great channel! Thanks!

Thanks again for your thoughts! Very helpful and nicely explained. 🙏🙏

@OffGridGarageAustralia

Жыл бұрын

Thanks, Lino.

Great video great channel thanks for you work Happy New Year

Great video, I just strap my battery pack together with tape, times and how you use the batteries will be the real test. If you look at the teardown of battery pack made for sale, you do not see the compression being applied at all. 5 ~10 years from now we will have new tech of batteries by then and these batteries will be obsoleted.

@Dirt-Diggler

3 жыл бұрын

Exactly, i'll probably be dead before that pack will :)

@monsieurd.6890

3 жыл бұрын

Even if they are obsoleted (they are already obsoleted by LTO, if I did not bought LTO it is because it is 2 times more pricy and I am not sure LTO will last 2 times longer at least, as advertised), if they still work, who will throw them away ? The more we can use them, the best.

Hi Andy, actually this Email exchange you posted at the end of your video is even more confirming my presumtion (posted in the comments of your last video - thx for mention it 😊) - you have only to "help" the aluminium casing, which is flexible, to avoid bending to much outside. Therefore a rigid/stiff enclosure should be enough. I was thinking about using marble tiles (about 2 cm thick) at the ends. Why marble - they are very plain and smooth, not flexible at all, and also can not catch fire. PS: about my name, don't worry, just think it in german and you are OK 😉

@OffGridGarageAustralia

3 жыл бұрын

Hahaha, thanks Alex 😂 Yeah, the only problem is the battery itself is not plain so you have the pressure on a few points of the side only. EVE has recommended metal strapping apparently...

@alexandergunda8916

3 жыл бұрын

@@OffGridGarageAustralia Nope, exactly that is the misunderstanding which happens here. When heating up, the battery get's from concave to convex - and only at the point when it starts to swell (from planar to convex) we have to keep it in shape. Meaning that only a reactive force will be exercised by the enclosure upon the battery casing, the actual force is created by the swelling itself. Therfore, imho, the manufacturer used "fixture" instead of "compression".

Well so far I like your work my man. Ok, so finally someone who can apply that rarest of of commodities to a problem LOGIC! Your application of logic re. Victron MPPT settings and "float" was right on the money, and your application of logic (which concurs with battery manufacturers advice) regarding the myth about the need for external compression was also spot on! There are so many armchair experts out there dishing out false and misleading information when it comes to Lithium batteries it is almost impossible for beginners to sort the facts from the fiction/rumours/opinions. Before I retired I ran a solar lighting business for 20 years, but that was before Lithium batteries came on the market, and comparing one to the other is like comparing a driver to a pilot. So for my two pence worth: 1. as a lot of these batteries go into RV applications, there seems to be a lot of angst about vibration such as on corrugated roads etc. This is complete nonsense, (as you yourself demonstrated when showing those cells in plastic cages in a vehicle application), just put then in a nice plastic or wooden box, use some foam tape as separators if you are concerned about heat, (QLD, NT etc.) and mount the box so it can't bounce around in the vehicle. Literally thousands of people have done the Gibb river road in a huge variety of vehicles with lithium cells on board, and I have never heard of a failure from vibration. I myself have done over 22,000 Klms outback with lithium with no (mechanical) issues. 2. In general Chinese manufacturers LIE! about everything, capacity, cost, freight, and warranty, so proceed by all means, but don't take everything they say as gospel. My system is 4 x 200 amp LiFePO4 cells, with a Daly 200 amp (separate port) BMS, a Victron 75/15 MPPT regulator, and a Victron BMV-712 Battery monitor (both devices networked together). And two 195 watt mono panels on a Pop top van. The first issue I had was my cells were supposed to be grade 1, but when i received them the QR codes were suspiciously damaged just enough to be unreadable. Questioning the supplier I received the usual obtuse response that is wasn't an issue and all the warranty details were recorded, not really satisfactory, and as I was still learning and building the system I had no way to discharge test them accurately. It now seems that they are performing at least adequately. 3. The first Daley BMS that (eventually turned up after two months) was DOA, eventually speaking directly to the factory on Skype they had me perform numerous (pointless tests and send them pictures and video to show the thing was just dead. During these conversations I actually sent them a photo asked them if the wiring of the balance leads in the plug looked correct, they replied yes it was. I then had to ship the BMS back to them, and send a picture of the shipping label before they would send a replacement, which I did. six weeks later I finally had a working BMS! Interestingly the wiring of the balance plug leads was not only logical (to me), but totally different to the original unit. Questioning the factory on this issue and pointing out their original response and providing two photos elicited nothing but a pure bullshit once again obtuse response, Oh well. My main beef with the Daley BMS is you have absolutely no idea whether it is working (or working correctly) at all, not even a lousy LED to tell you what is going on, and no App, (just keep your finger crossed). As for Victron I do like their gear, we used thousands of the regulators over the years and had very few issues even in very harsh conditions, (like in a steel pole in the middle of the NT, when the outside temp was well over 40C. or in heavy snow and freezing conditions. However, l do have a couple of issues with them. Firstly (like you) I don't like some of their default settings for LIFePO4, and I have used the Expert mode to change a few things to very close to what you calculated using logic. Secondly it is annoying that every damn time you want to connect with the App there is yet ANOTHER update! (which regularly crashes or does not install correctly) and quite often you have to reset using your save settings file. Secondly while I do like the (expensive) BMV-712 setting it up correctly is like Egyptian Algebra, (like your BMS)and watching their videos still leaves a heap of questions unanswered for a DIY guy. It seems to me that the biggest issue is to find a reliable quality BMS for these batteries in the 200 amp (typical RV) range, it was suggested to Victron that they should build such a unit as we know their quality and great warranty, however, apparently their response to this suggestion was "We will never build a product for other manufacturers batteries" meaning Prismatic cells. This seems a ridiculous attitude, what the hell do they think people are doing with their MPPT regulator and BMV units?, their mono block batteries are fine for industry, but far too expensive for DIY people. I was sad to see your outcome with your current BMS (bullshit management system)? It did seem to have some potential early on. I would be happy to send you my current Victron setting files for the MPPT and BMV for your consideration, just let me know how? Keep up the interesting videos. Cheers Tex

I would appreciate you going back to basics. Basically, I am very basic :-) Another great video. Thanks you

@OffGridGarageAustralia

3 жыл бұрын

Sure thing!

Nice enquiry dude, I am with you as far as conclusions go - rightly of wrongly !! :)

I have been off grid for over 50 years, you are over thinking this..

@dayleedwards3521

3 жыл бұрын

@Phil Ware . Any movement of the plates/layers due to expansion/contraction has already been allowed for in the packaging, in a similar way to the charge /discharge limits have been allowed for in the internal BMS if fitted. As our friend has alluded to in another video, even the BMS can be dispensed with if close care is given using human intervention. LiPo's are NOT as fiddly or fragile as some may think.

I have seen first hand the C-MAX cells expanded so much only the bus bars were holding them together however it is the only kind of cells I've seen actually expand. And I agree, though encasing your cells in epoxy is one way to ensure they never budge, at all I couldn't ever do that, heaven forbid I get more cells and want to adjust them. That'd be upsetting. So I think once again Andy, you've made the correct decision. 🤔 beside my garage and a few appliances in my house my main use for batteries is in car audio where FAAR more than 2c discharge occurs, my car audio batteries get heavily abused. But that's why I learn all I can to get the most life possible!

That's excellent point regarding the shape and force distribution Andy. Since my application will be mobile, I still need to ensure that they don't rub together and keep movement and vibration from exerting forces on the terminals. Flexible links are a great idea, but they are expensive and the cells are supplied with reasonable links already, so I need to find a way of holding them together under mobile conditions.

@MalkavianBilbao

2 жыл бұрын

Hey @Benny what did you do finally and how it goes?

@BenMitro

2 жыл бұрын

@@MalkavianBilbao Hi Malkavian. I have bolted the each set of 4 cells together under some compression with plastic dividers between the cells. I've elongated the holes on the links between the cells and joined the 4 packs of 4 together with heavy aluminium bar firmly secured to the compression plates so each pack is tied to its neighbours with 20x10mm aluminium bar. The bar is secured to the compression plates so relative movement between packs is not translating to the terminals of the cell. I have yet to use them like this in the "wild", so fingers crossed!

I think you are on the right way to put the cells uncompressed in the container. I would ignore the advises of compressing and store the cells on distance to perform cooling. And NEVER EVER fix the cells with exo glue: If one cell goes you cannot get it out.

Just FYI if you are going to tightly pack the cells together, make sure to add another insulation sheet between cell. I just check my LISHEN cell the Voltage between the case of the cell and the Negative terminal, it shows the same Voltage reading as when measure between Positive terminal and the Negative terminal, 0V between Positive terminal and the case. So I do the same test with the 90Ah Liitokola and get the same result. So the case is positive on my batteries. I put 100 Ohms resistor on Negative and the case, the Vdrops on the resistor is 1V, = 10mA. That is not low leakage.

It would be interesting if you got the all in one batch and ran them in series but compressed half and did not for the other half

As usual, very nice video I think it will be better not add epoxy, maybe one cell is dead then it will be a disaster to replace this cell. In my opinion there is no need to compres the cells. The battery will live for 7 years to reach 80 percent of capacity Then it will live for another 7 years performing more than the half capacity ( after 14 years there will be better technology coming like grafin and other stuff).

Andy, the issue is breaking the terminals from swelling. If the cell swells during use, the M6 screw could 'tear out' during charge/discharge. It's not a longevity issue, it's a terminal breakage issue. But, some sized plywood, held together with tape might be 'enough' to prevent the terminals from ripping the anode or cathode out each cell...

@MrSummitville

3 жыл бұрын

Then why don't they just sell terminal straps that are slightly wider to allow for a small air gap? That way, any swelling would never damage the terminals. Because it is so much more than just "damaging the teminals" ...

At the rates you intend on using the batteries, they will outlive every subscriber you will ever have and every tool in your garage--including the pink heat gun. Off-grid garage is not the International Space Station (Mark VII). Batteries are from China not Jupiter, if they required additional compression they would have added 1 mil of additional aluminum to the case and charged you six more dollars...

@OffGridGarageAustralia

3 жыл бұрын

Hahaha, great comment. And thanks for mentioning my pink heat gun ;)

I agree Andy. If you consider where a lot of these cells will end up, in large aluminium battery trays in cars, factory carts, forklifts, trolley trucks etc. etc. They will be tight enclosures. The engineers designing those enclosures need to know about battery expansion, how much room to leave, how strong a force, how hard to push back. You don't want your lovely new EV model to start being returned for the battery case splitting open.

Hello my friend I have to tell you that your channel is one of my favourite channels 👍👌on KZread. So a big bravo 👏 for all the efforts and ideas you are showing us . I have to admit that I am learning a lot from you.👨‍🎓. i am about to buy my very first mobilehome before my retirement as an Airline pilot and this is were I found your channel very very useful . I am thinking of using the same Lithium battries for my new Mobilehome made by Adria in Slovania (the Matrix Plus model). I was thinking of a good idea by compressIng the batteries individualy each with a High Spead Aluminium adhesive tape which we use in aviation . So if we wrap them each very tightly by this very strong and relable tape when they are half charged , so what do you think ? then we can wrap them tightly again with thermal adhesive tape also . I am not a DIY guy and will surely need your recommendation and valueable advise to be able to run my mobile home in the hot desert of Egypt and be able to run a 20000-24000 BTU aircondition on batteries only , for 3 -5 days , so how many batteries and solar do I need ? And what is the best value for money Solar panels you recommend ? I might ask the Manufacturer of Adria mobilehomes to intall th whole components for me as I am not a perfect DIY guy like you 🤗😉 You can contact me by email sheri330@hotmail.com i will wait for your recmmendations impatiently kindest regards and keep the good perfect job👍👌

do you have a link to the bms?

Springs or complex external mechanisms are not need to provide the desired pressure. It just takes a reasonably precisely built and pretty stiff box and stiff foam or soft rubber spacers between the cells. Compression can be adjusted by the screws holding the corners of the box to the sides/ends. To be sure that thermal expansion doesn't put too much tension on the bus bars, the top & bottom edges of the cells need hard plastic spacers rather than compressible material, or don't use straight bus bars.

Learning by doing 👍🥰

I watched someone else's video and he measured eight battery cells (unclamped) together both charged and uncharged. The length did have a difference 2mm. The reason he clamped them together was to avoid stress on the busbars. He used "nylon" chopping boards on the ends to spread the weight, and thin 0.5mm nylon sheet between each battery. If you are going to space the batteries apart there would not be any stress on the busbars. It's just another way of looking at it.!

@OffGridGarageAustralia

3 жыл бұрын

Yes, thank you. I could not measure any expansion but didn't spend too much time with this. The gap in between the cells allow for expansion without putting any force on the busbars. Expansion mostly occurs on high C rates which I don't have in my setup.

If you are intending to use the solar garage batteries to charge your EV then heat will be a bigger consideration than minor differences in battery life time cycles. I run a 24volt nominal system and have had it in place for approx 3 years. The important thing to realise is the current to charge your EV via a 24 volt inverter will be quiet high. My inverter is 24 volt to 240 volt and the cabling and batteries have to support around 65 amps to charge the car at 240volts/6amps. At 240volts/10 amps this rises to 110 amps, at 240volts/16 amps this rises to 170 amps (figures include losses in the inverter). I’ve not got a big enough inverter to attempt a 32 amp charge rate. So this amount of continuous current generates a lot of heat especially in cables, joints, and any switch gear or fuses you fit. Heat is your priority if you want to successfully draw large sustained loads.

@OffGridGarageAustralia

3 жыл бұрын

Thanks Harry. That's why I went for a 48V system with currents below 0.25C and 3kW of load. I will not charge the Teslander faster than 2kW, same rate I'm doing it right now from the grid. So this will be like 40A from the battery only.

i wouldn't worry about it too much. I would build an enclosure and put the batteries in just to keep them from expanding further down their lifecycle. the dip in the middle of each cell will allow the cell to breathe during its charge/discharge cycle.

Simple way of compressing batteries uniformly: Just build a little Hyperbaric Chamber. It can be rather inexpensive since it doesn't need to be transparent. Pump it up to 12psi and Bob's your uncle. Keep spacing between the cells to help them stay cooler (or put in a small radiator and run coolant to it if you have to). I would also pressurize it with Nitrogen to reduce corrosion and fire hazards.

It is not hard to build a container that provides some configurable, variable compression. I'm going to compress my 32kwh of these batteries. As 50$ of hardware to compress them for double the lifetime is the best investment I've ever made, by the simple numbers. Don't be lazy.

Yes,very good question,between compression and a fixture.correct me if im wrong but wouldn't both be the same?both hold together the cells together.

@edwardbyrd7667

3 жыл бұрын

You could certainly have a fixation device that includes compression, but you could also have a fixation device that is neutral in that regard, that is it holds the cells snugly, but doesn’t squeeze

I assume compression might help avoiding bending of the terminals connector. If you have flexible connector that should be fine.

If the battery needed fixture, they would not have given kgf, they would have advised kgf/cm or kgf/m, or even advise to use a torque spanner. I have seen perfect builds including spring coils. 5 mm EVE foam between each cell, (because this foam would need 25-30 nm to be compressed) etc. All great.... if you do not force the battery into its maximums, the battery will not bulge. (Low C charge, low C discharge)

I'm going to do what manufacturer recommend!

@golfish8589

3 жыл бұрын

People are reading the manufacturers instructions. But interpreting the differently. Some think the batteries are already compressed

Even though it would reduce packaging density, it would be nice if they could make some ~100-150AH cylindrical cells. With the terminals on one side of course. Then you really wouldn't have to worry about compression at all. And for solar storage, density isn't much of a concern. I almost thought about building my own pack with 32650 LFP cylindrical cells, but at only 5AH a piece, that would take a long time to build, and end up being a lot more expensive than the 16 LF280K's that I ended up getting. I just have them uncompressed. The max possible charge and discharge rate of my system is only 0.45C, and often much less than that.

It doesn't make sense to cast the cells in epoxy, when they "breathe". A fixation guarantees that every cell can breathe without building up pressure! Just use the packaging foam as a spacer. Who would cast bimetal in epoxy? - It doesn't make sense because it would lead to tension cracks! Keep the effort within limits to maximize profit.

He is Great, It is all about "The Viewers Understand!" and "The Basics." Because, some of us use these batteries for RV life (Boon-Docking) and off grid. Again some of us want a nice 12 volt system with enough 8 batteries connect for some Great Watt hours. 24 volts would require an adapter and that is one more thing that cold go wrong. They are not expensive, but, my converter in my fifth wheel is confusing enough for me. I'm looking to Build 2 packs of 4 in series, then put these two packs in parallel - called "4S2P" But I just can't visualize it. I'm Old, really Old. I know the Off-Grid Garage will help me and some many others. As for compressing, well I think once I have all my batteries and I'm ready, I'll use Gorilla Tape the top and bottom tightly and mount an old computer fan in my battery box hook to my MPPT solar charger to cool the batteries, I do live in Phoenix, AZ. and it's not the cold in the winter but the summers are HOT!

@Sylvan_dB

3 жыл бұрын

You have eight LiFePO4 cells that are not connected to anything. It is better to parallel cells, then connect the cell groups in series. You need a BMS for each series set. If you want to parallel these sets, make sure you use BMS that are okay to parallel. So to do it the better way, take two of those cells that are not connected to anything: * Connect Plus(+) on cell 1 to Plus(+) on cell 2 * Connect Minus(-) on cell 1 to Minus(-) on cell 2 Do that 3 more times so now you have 4 pair of cells with each pair connected to only itself. Now pretend each pair is a single cell, because electrically that is effectively what they are. That is 2P. To get the 4S: * Connect Minus(-) on cell (pair) 1 to Plus(+) on cell (pair) 2. * Connect Minus(-) on cell (pair) 2 to Plus(+) on cell (pair) 3. * Connect Minus(-) on cell (pair) 3 to Plus(+) on cell (pair) 4. That is your 4S. Your BMS has 5 sense points: * Minus on cell (pair) 4 * Minus on cell (pair) 3 (same as plus on 4) * Minus on cell (pair) 2 (same as plus on 3) * Minus on cell (pair) 1 (same as plus on 2) * Plus on cell (pair) 1 Minus(-) on pair 4 is your Minus for 12 volt. Usually this connects to your BMS "B-" terminal and then your loads use BMS "P-" terminal as their Minus. Plus(+) on pair 1 is your Plus for 12 volt.

@guohuaye12

3 жыл бұрын

@@Sylvan_dB WoW! Thank You, I m trying to visualize this. I'm 72 yrs old nd Slow. But that makes sense. I think this would give me lots of power. Thank You.

@PablumMcDump

3 жыл бұрын

@@guohuaye12 cells wired in parallel are effectively the same as a cell with double the capacity -- a pair of cells in parallel will have the same voltage (if the voltages were to get out of balance, the higher voltage cell would "charge" the other one until they're equal), so to the BMS, they're identical to single cells.

@alexandergunda8916

3 жыл бұрын

here you can find a nice wiring diagram: blog.seidel-philipp.de/wp-content/uploads/2018/01/4S2P_li_ion_battery_wiring.jpg

@guohuaye12

3 жыл бұрын

@@Sylvan_dB Thank You. I bought a 100 amp 12V Charger BMS Protection Board with Balance For 14.8V 16.8V Lipo Cell.

The cells will naturally expand and contract with general use and temperature fluctuations. The issue is once the cells are joined together with busbars, the top is held together and the rest of the cell is able to naturally flex, this causes stress on the negative and positive posts which are tightly bolted together. A general compression throughout the bottom and middle of the cells will ensure the posts don’t get damaged while in use.

@OffGridGarageAustralia

3 жыл бұрын

Yes, that's correct, BUT, the expansion will only be 0.5mm per cell as per specs. So if I keep them 2mm apart, it won't put any tension on the busbars.

@codiecarroll735

3 жыл бұрын

@@OffGridGarageAustralia I was thinking the same, keep the cells busbars tight with just a small gap between cells and there should be no issues. I would design the pack to never use 1C discharge anyway, seems like if your pack is hitting 1C it would be poorly designed. I would however compress them if I had a mobile battery pack.

@w3bb0y

3 жыл бұрын

It seems you want something to go between the cells BUT something that allows cooling or airflow. Google '4mm twin wall polycarbonate sheet' Might be of use as its strong but would allow good air flow to cool.

An experiment. With an accurate rangefinder, can you determine SOC from the amount of bulge? Or measure the thickness of the cell on the centre-line during charge and discharge. Full scale would probably only in the order of 2mm.

@OffGridGarageAustralia

2 жыл бұрын

Now, that's not possible. It all depends on the current. With low currents, there is no bulging at all. It is a change of up to 1mm from 0-100% if used their test settings, 0.5C charge, 1C discharge.

An easy way to test it out for long term. See how much capacity is loss after one year with no compression. Than compress it, and see after the next year. If the progression is similar, than we'll have an answer, if the progression is different, we'll know as well. But nothing can be said definitely. Keeping track of cycles will be hard, I don't think there are off the shelf devices which keep track of cycles for us.

@MrSummitville

3 жыл бұрын

No, you cannot test for just 1 year ...

Compress half of your batteries and give us the results in 7 years :-)

"To be compressed or not to be compressed: that is the question" New Shakespeare 2021

@OffGridGarageAustralia

3 жыл бұрын

Yes, hehe.

I'm currently top balancing 4 202Ah lishen LFP , at 3.65v 10 ampere and the ampere already fallen to 0.1A in my bench power supply for 2 hours, do i really need to wait until it goes to zero ?

@OffGridGarageAustralia

3 жыл бұрын

No, you don't need to wait for 0A. 5-10% of the capacity is usually enough to wait for. So for 200Ah cell, that is 10-20A cut-off current. If you charge with 10A, as soon as the current drops below 10A, call it, the cells are then full. It's actually enough to top balance the cells with 3.5V or 3.6V only. 3.65V is putting unnecessary stress on the cells.

Hi mate can you send me a link for that Bms cant find that exact one , cheers mate .

I think this compression idea may only work if you do it to each individual cell. charging increases the pressure "X" amount in one cell. 4s is 4 times that pressure. And 8, 16, 32 cells the same effect. Also , the weak point gets the pressure. It seems the only correct way, would be improving the case of each cell , before use. Do we really want the combined charge pressure confined withing 4, 8, 16, cells ,looking for the weak spot? I think 2000 cycles will be just fine for my 1969 camper.

Can we put 8pcs 280ah vertically like powerwall?

@OffGridGarageAustralia

3 жыл бұрын

It's not recommended, they should be upright when in a permanent installation.

Just as in the picture you showed of an EV vehicle. Those plastic cages do provide compression... compression forces that might only be measurable when the battery begins to charge and swell, but you can Clearly see how those plastic cages prevent swelling of the battery. That is Technically Called Passive Compression and the Rigidity of said cage will be measured as compression force at various points during that battery's Life Span.

@OffGridGarageAustralia

2 жыл бұрын

Yeah, it makes sense in a vehicle with high charge and discharge currents. Not so much for solar applications where currents are usually rather small.

I would use shipping straps that rachet.

@OffGridGarageAustralia

3 жыл бұрын

I thought about that...

@hommerdalor6301

3 жыл бұрын

I thought the same, and intead of using flat plates between cells and straps, I suggest to use half round pressure "plates" like a half splitted wood log, the flat side against the end cells, the straps, around the curved side, or cut rounded channels in a bloc, and the left flat surface can be used to attach accessories.

@OffGridGarageAustralia

3 жыл бұрын

@@hommerdalor6301 I like this idea. That sounds ideal in terms of applying pressure to the whole area. Thanks for sharing your idea here.

Wouldn't compressing the cells also cause excess heat?

No way I'd glue the cells together with epoxy. Big advantage of individual cells is being able to replace one if needed, or for whatever reason break it down to individual cells again. How about filling the box with fine sand or even plaster? Unless you turn it upside down, that should provide nearly the same transfer of force to the container. You could even weigh it to see how much thermal mass you've added. As for me, I'm going to think more about clamping my cells in 12v nominal groups. I'm not so worried about the small concave depression on the flats. A bit of breathing room seems fine. I'm more worried about the bus bars and terminals being stressed by the cells moving relative to each other. Maybe pieces of unistrut across the flats, and threaded rod along the edges... Or 3/4 plywood panels? Or I have some meters of nice aluminum bar about 30cm wide and 6mm thick that would make nice end plates. Thinking... :)

@OffGridGarageAustralia

3 жыл бұрын

Yes, absolutely. I don't think the comment from this viewer was very serious 😉

1C for a 280 amp battery connected into a 48 volt system would be around 13kw of discharge, which is not going to happen connected to a 5kw inverter. So you are safe not too compress.

@OffGridGarageAustralia

3 жыл бұрын

And I will only use a 3kW inverter, so ~65A is the max current I will draw...

I think I will compress my 16 batteries. With 0 compression when discharged. Because I fear that if I do not compress them, it can have a trouble with the connectors on top. As batteries are connected one to another, I fear that if battery size change it can eventually broke electrodes.

I've ordered some "280ah grade A" cells from Alibaba i think its Jidian Seller or something, they are CATL brand and they say they do not need compression. Im not going to compress because mine wont be cycled everyday maybe not even every week so its irrelevant to me as 2000 if thats the case is plenty of cycles, and thats still only down to 80%.

That heat gun is ribbed for your pleasure 😂

The manufacturer sheets give a cycle life of the battery based upon no compression. They will state that if you compress, you will get more cycle life than is listed. Compression isn't 'required', it just will make the batteries last longer.

2nd. And I'm glad to be a low number subscriber because this mans channel will get biiiiiiggg!!

@guohuaye12

3 жыл бұрын

3rd and I agree with you, he's cares.

I am a photographer. Surprised? There's a lot of photographers, some well experienced. who blow hot air from time to time. I am not surprised to see the same problems amongst this crowd. I'm equipping my recently-acquired van with electricity, carefully stepping around the nonsense. I have a DC2DC, ordered a cheap Li-ion battery, an inverter capable of connecting to shore supply and recharging. I am sitting on the fence re solar, by DC2DC is suitable, but I will see how I go with alternator charging. I don't expect to sit stationary for very long, the alternator might be sufficient. Or a second battery, in parallel.

Many people writes something like "compress, compress, compress". And I'm curious. How many of these people had a problems because of that they didn't compress theirs cells?

Yes the work bench needs redesigning, definitely no space presently.

@petergoestohollywood382

3 жыл бұрын

Thats how workbenches work. You can have as much area you want but there will Never be sufficient space to work freely. :)

@OffGridGarageAustralia

3 жыл бұрын

I've got a 10m workbench and it's full all the time. Too much work? Maybe just too many ideas 😂

You are not actually compressing the cells per say, you are keeping them locked together so if they do expand, it won't damage your terminals by bending or twisting them.

@OffGridGarageAustralia

3 жыл бұрын

The same would happen if I keep them apart?

@offgridtruckerdude7133

3 жыл бұрын

If they have no chance of applying pressure against them selves, it shouldn't be an issue then. But any movement of the terminals while using solid buss bars can add undo stresses, "possibly" causing damage to a cell. Is it worth the chance. A strip of thin plywood vertically on the corners and a diy cut your own length hose clamp kit is a cheap, and space saving alternative to the steel bars and bolts you were showing.

Until someone does an actual lifecycle test comparing compressed vs uncompressed we are never going to know for sure.

Or also using epoxy, 2 flat surfaces could be created on each cell 🤔

@Gnagnie

3 жыл бұрын

only a good idea when delta theta from epoxy would be the same as the delta theta of the cell, in all conditions of the un-/loaded cell

What about the use of an air bladder

@OffGridGarageAustralia

3 жыл бұрын

What an effort would that be to apply a consistent pressure to the cells? I don't think it is worth it. I have installed the battery for 6 months now and had 7 full cycles, so what are we talking about in terms of cycle life of such batteries?

@urbanbeeman5402

3 жыл бұрын

@@OffGridGarageAustralia I would agree that it would be very hard to come up with a consistent 12 lbs. psi but I think if you could shoot for maybe 6 it would be worth it

It's beginning to sound like religion not science. Good video. I'm planning on getting some of these for my solar setup. I'll retain them to keep them together but not compress them.

@MrSummitville

3 жыл бұрын

The problem is converting the data from Chinese to English. Something important is being lost in translation. And some people have made up their own "facts"...

For a stationary battery I can see that one can get away without compression but for a mobile battery I would think some level of compression. Is required to prevent damage to the terminals.

I know how to apply pressure evenly....CLAY. like pottery clay before it is baked.

I would at least recomend some "compression" to fix the position of the cells with or without space between them, because if you do not have flexible busbars, it can create high force on the terminals and damage the structure of the cells.

@OffGridGarageAustralia

2 жыл бұрын

I leave 2-3mm space in between the cells so there is no force on the actual busbars or terminals.

if there is such a discussion to compress or it is not very easy to do the right thing just not to compress. why? because no matter what happens, nothing will get worse if they are not compressed.

Bloating is mostly from pushing to charge their batteries 100% all the time. I am not a fan of that kind of charging style. I'd rather buy a 280ah battery from Aliexpress and treat it as a 250ah and still be EXTREMELY happy for the price I paid. At this rate, I minimize the bloating and actually prolong the battery life.

OH! and I forgot to mention, as a result of watching Will Prowse I have now have an expensive Victron BP unit, and a brand new 250 amp solenoid I have absolutely no use for. :{

You should realize that your first spec sheet assumed your cells were compressed. You aren't done until you have some threaded rods on that cells.

@OffGridGarageAustralia

3 жыл бұрын

Does it say this anywhere in the spreadsheet?

@Zorlig

3 жыл бұрын

@@OffGridGarageAustralia No, it's expected and assumed to such a degree that they don't mention not doing it. The idea that you aren't is completely contrary to manufacturer expectations and specifications. You are blatantly ignoring the recommendations and I can't even figure out why, it's weird.

Wieso nicht einfach Budelkastensand in jede Ritze füllen wenn man das Setup so hat, so kann man immer noch was ändern. Wäre jetzt für mich die Logischere Idee als Epoxy.

Maybe put an air bladder between each cell, and one on each end. I wonder if hot water bottles would work...with rigid plates (plywood) as end caps, pulled together by threaded rods to get to 2-5 psi. Nice thing about an air bladder is that the curvature in the cell walls won't matter.

HOWdy O-G-G, So - what is the THEORY of compression ? WHO dreamed up COMPRESSING the Batteries ? the only time that I have experienced a BULGING Battery --- was when an old LEAD-ACID Battery discharged & FROZE ! COOP ...

Compress - Not compress ? It's not a bomb - it not big deal . Long life ? In 5 years they will be Old technology and Cheap . Here uncompressed to avoid extra heat would make sense as ambient temperature is Often over 95 for hours .

Well, think of it this way, wtf is the DOWNSIDE of keeping them compressed? However, they do need to release heat as heat will destroy them, so if you pack them together without airflow, it will be WORSE. I have not put my hands on these cells, but from what i've seen, they don't look like they are in solid aluminum boxes, more like big pouch cells, which DO need support.

@OffGridGarageAustralia

3 жыл бұрын

Yeah, well, I don't have any heat here around my cells. They stay cool with 20-30°. Heat is my last concern.

@murraymadness4674

3 жыл бұрын

@@OffGridGarageAustralia Cool, then why not strap them together? As I said, what is the downside? Someone else just told me the manufacture says 2500 cycles without straps, 3500 with them, which I find an odd statement, the issue is they can fail when they swell, so more like 2500 or 500.. So why would anyone NOT strap them, the 2500 is plenty argument is silly.

@OffGridGarageAustralia

3 жыл бұрын

@@murraymadness4674 This is in the specs of the cells, yes. But the test conditions are not met with our setup. We don't charge with 0.5C and discharge with 1C. We also cannot apply a different pressure at different SoC as they did during the testing to get these numbers. So whatever you do, the benefit will be far less than what their claims are. You also need some material in between the cells which is hard enough to distribute the pressure evenly but soft enough to compensate for expansion and contraction of individual cells. I could not see or measure any contraction or expansion of single cells when charging or discharging so far.

So, you've found the reason that Tesla uses cylindrical cells, not prismatic ones.

@OffGridGarageAustralia

3 жыл бұрын

That has other reasons though.

@Zorlig

3 жыл бұрын

Yeah, cylindrical cells are naturally compressed, unlike these pouch cells.

@Sylvan_dB

3 жыл бұрын

@@Zorlig Indeed. Anyone that has much experience with LiPos knows that pouch or prismatic cells will turn into cylinders if provoked!

Check this video how a professional case looks like: kzread.info/dash/bejne/dY1-s9qdlqfQaJc.html And yes, they use tape and they use metal to compress the cells. They do not make a case for 280Ah cells yes ...

don’t like the epoxy idea to fix your batteries (too hard like ciment).. silicone can do the job with capability of compression/expansion.. i understand that you want to avoid any damages by vibrations but i hope that the better solution will not to fix it with something like epoxy!!

Well, not only the compression. To maintain your batteries, you have to leave Australia. Why? Because all the specs clearly state constant 25 degree celcius for lifecycles, Ah, and so on. You have to build a climate room, or leave Australia. (Hope you get my sense of humor. :-D )

I agree with the no compression needed for these if you look at the fortune lifepo4 battery cells in this video by Will Prowse ( kzread.info/dash/bejne/lKmC2sWliszepbg.html&ab_channel=DIYSolarPowerwithWillProwse ) these have individual cell holders on each cell therefore these cells aren't compressed again each other 7 have gaps between & the holders are just there for convenience on bolting them together. It would be nice if someone started printing jus the plastic holders for these 280ah cells so they can easily be bolted together also if anyone knows someone who does let me know

That made no sense. In your previous video about compression.. you show the manual. The manual clearly state longer life with compression. Now.. it shows shorter life without compression.. how do you get that shorter life if the battery is factory compressed in an alu block? Opening it with a grinder? Ofc not. So.. by deducting that logic we must conclude compression is needed just as the manual say. There fore.. put them on the flat large surface side in stacks of 4.. on a metal wall shelf.. 4 next to 4 next to 4 ect.. then put a long flat rectangular metal plate on top for natural consistent downwards pressure.. then stack cases of beer on top untill desired pressure obtained.

The casing may in fact be self compressing The inward curvature would be pushed out to flat by the expanding cells Thus the case would increase force as the wall straightens just like arches in a bridge Well spotted

Ok, so what?, he thinks it s a heatgun.

Long time to see one topic please move forward next topic LOL

First

Silly intros are not appealing to me

@OffGridGarageAustralia

2 жыл бұрын

Not the right channel for you then.

Well it is your investment you need to do what you think is right then later tell us how it went. Same with the BMS discussion some people believe you don't need one.

@asderven

3 жыл бұрын

often times your chargeable devices don't have bms in them, having them would increase battery life by a portion that people would see it. Since they don't have it, it requires quicker repurchasing, so ones call for the longevity of the system.