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Introduction Marine Rated Battery Fuses (MRBFs) are sometimes used to replace Class T fuses due to supply chain issues, ease of installation, space constraints, and cost. However, the breaking capacity of MRBF fuses is significanly lower than that of Class T fuses as shown in Figure 1. Figure...

Thanks everybody a lot for the input. Feature requests so far: Create current versus time plot, e.g. using an oscilloscope / clamp meter with inrush (the latter has too low max current). Test more fuse types: Class T (example); bs88; NH; 300A MEGA; CNL; South Bend. Test breakers - cheap amazon...

Per request of @Pi Curio, 10 Heschen fuses (sourced on Amazon; HSPV-30; 32A; 1000VDC; I1 = 33kA) were blown while mounted in their DIN-rail fuse holders (sourced on Amazon) in the vertical position. These fuses are filled with sand, similar to Class T fuses. The resulting current versus time...

Today two more 22 AWG copper fuse wires were blown, similar to the previous black curve. The 22AWG copper wire fusing current is approx 41Adc (Preece), so this is a relatively small fuse having a clearing (blowing) time that is at the lower end of what I expect to be used in practise. Goal...

Triggered by @April's tip, I felt like making a drawing today just like in kindergarten, probably reinventing the wheel because the cell manufacturers have better drawings.. April suggested case D to avoid case C (if I am correct). However, initially I would prefer case B, provided that I have...

The following video shows how EVE compresses 10 cells using a spindle. Next, they laser weld the case while under pressure. Random note: see those rulers mounted on the table. Also note that no electrical insulators *seem* to be added between the cells, apart from of the blue (or yellow?) foil...

Calculation model description This thread focuses on the calculation of an approximate estimation of the maximum C-rate for a given battery and/or the cell temperature (increase) at full (dis)charge for a given C-rate. It is conservatively assumed that heat cannot escape from the battery...

Problem It's very annoying when yet another expensive and hard to source class T fuse blows. So how can we visualize why they blow? The graph below may explain why Class T fuses blow due to the inrush current from a (for example) LFP battery to an inverter. It may also explain why taking a fuse...

Here are two teardown videos of prismatic LFP cells. This can (or not?) be useful when accidentally stripping the terminal threads and considering strategies for repair (or not). Feel free to add more, especially for the "blueys". 1) CA180FI (I think - specs). Screenshot of the aluminium...

@krby Do you use a BMS? If so, which one? This may open some additional options. Also, you may not need to break the precharge circuit at all before making the main circuit, because as soon as you connect the main circuit, the resistance of the main circuit is nearly zero, so nearly all current...

From [1]: "When questioned, Sinopoly indicated that installing the cell in any other position than upright would cause some of the plates to run dry after a while, damaging it. Installing them flat on their side is out of the question in all cases." "I queried the matter directly both with...

I am trying to balance first. See below the LEDs that may indicate balancing cells, this was yesterday, 7 of the 16 are on. This morning only 3 were on. The PCB is 10-20F warmer around those LEDs where the balancing resistors likely are. I manually keep a cell-level voltage log in Excel to...

@Aussiecroc: This seems not to be a hoax, but part of an epic "roadmap": https://pushevs.com/2019/08/16/the-comeback-of-lfp-batteries/ See also on this forum here and here.

The following "Compression Lug Connector" no longer requires dedicated crimp tools: I just stumbled over these here - includes a video of assembly. However: What will a cross-section look like after grinding it open? As done here for example. Will they operate as "cool" as the traditionally...

@gnubie: You probably refer to this thread? See also some prismatic LFP cell teardown videos here on the forum.

This post shows how I opened the case of the EG4-WP 48V 100Ah (5.12kWh) battery without damaging any cells or other electrical components. This voids your warranty. First try to contact Signature Solar to see if a less invasive solution exists. In my experience they do their best to help you...

A bit more about the "blueys" specifically: Some stills from ETC's marketing video (published Feb 19, 2019, accessed Dec 30, 2019): Electrode winding or "coiling". Electrode pack compacting Pairing of two to-be-paralleled sub-cells (?) Tab laser cutting (?) or welding (?) Assembly of...

Below are some approximate BLS 105Ah cell terminal dimensions derived from the same J5GURU Youtube channel. Source: https://youtu.be/6d89tgUMEbI?t=280 (4:40min) For M6 bolts, assuming a coarse thread, the pitch is 1mm, so a max of 5 3/4 turns would correspond to 5.75mm. It is tempting to apply...

Do you want someone else to read a bunch of those time-consuming battery research papers and summarize them for you, for free in a smooth video with fancy animations? Then the following Youtube channel may be something you like: The Limiting Factor See for example this excellent video: CATL...

Update: Only done a couple dozen cycles so far. Always kept SoC between 50% and 90% SoC while stored in climate-controled space. I still have the version with the 1st gen (?) BMS. Result: Extremely out of balance, only 3.6 out of 5.1 kWh available. 🤨 Replaced with JK BMS 200A 2A active...

Another data point: I just dead-shorted a 150A MRBF fuse using 330Ah 48V LFP and 4/0AWG cable. Results are here.

Also you can check out this: https://diysolarforum.com/resources/youlovesolar-wire-size-calculator-highly-customizable.387/

Update: The BMS increased* the imbalance (wtf) instead of decreasing it, so I decided to take the cells out of the case and manually balance them individually using two parallel 3 Ohm (actually measured less 1.8 Ohm) resistors. Took me a whole bunch of manual actions spread out over a couple of...

Here is the female version of @Will Prowse: Sarah Chrisp Same kind of facial expression, and to the point. Too bad she probably lives far away otherwise Will and her should go have a coffee ;) This kind of posts is what you get when you become a public figure ?

I have very little experience with BMSs and I may misunderstand the problem, but recently I fully read some BMS manuals. So what is your budget? What about a €159 TinyBMS in dual port mode? From the manual, p31 (Revision A, 2018-07-30): Condition If one or both external temperature sensor...

@electric Interesting. This made me wonder what exactly is inside an LFP cell, so an example of a prismatic LFP cell is shown in [1]: It seems to show a stack of copper sheets and aluminium sheets, wrapped between a zig-zagging plastic sheet. The thermal conductivity is roughly a factor 100...

@alanlaing: Before throwing them away: Can you experimentally determine the maximum torque of a bolt into the terminal at the state where the aluminium thread strips, without the tip of the bolt touching the hole bottom? Preferably using a well-specified stainless steel bolt at known engagement...

When the cell specsheet only mentions an "impedance", then you could simply multiply that impedance by a factor 2 to obtain a rough conservative estimation of the DC internal resistance for most (?)(not all) cells. I loosely base this statement on the following graph...

This battery was picked up today (20191011) by me, I feel very lucky! Thank you @electric: thank you so much!

@Maast Great work! I agree: Dump that electrical energy in water, having one of the highest heat capacities available and dirt cheap. Oh, and you are not alone with tedious non-automated cell measurements - The famous Jack Rickard does it too. Here is (a tiny fraction of?) blue prismatic cell...

[1] suggests that 4 hours may be way too long for LFP, shortening cycle life. At the relatively low 0.2C charge rate, my first guess would be that you do not need any absorption at all because it's already nearly full. 14.2V for the bank = 3.55VPC (Volt Per Cell). You could even go a bit lower...

Thanks, solved: The image had a transparent background, changed to white. Also this forum compresses images, rendering the small print unreadable, so I attached PDF versions of the diagrams with infinite sharpness :) for those who like to view the devil's details.

Another data point: I just dead-shorted a 150A MRBF fuse using 330Ah 48V LFP and 4/0AWG cable. Results are here.

@chrisski @RCinFLA: Related to this, see also: https://liionbms.com/php/wp_resistance_vs_impedance.php

That is $1926 / (20 cells * 3.2Vnom * 0.280 kAh) = $107/kWh. Wow, good deal - iff they meet the specs - keep us posted :). Far cheaper & safer than for example salvage Tesla Model X 100D modules on Ebay @ ~$225/kWh. Less than half that price.

In the diagram, the 30A breaker does not disconnect the autotransformer from the Growatt. Was that the initial plan?

@electric, @grizzzman, see also my related new post about the maximum C-rate here.

Update: The roadshow is almost ending. This week at this Costco: 7981 E Stockton Blvd, Sacramento, CA 95823 Starting Fri Oct 23 for 7 days at this Costco: 1600 Expo Pkwy, Sacramento, CA 95815

@TJ Tom, @April, @boboxx Related to the visible aluminium damage (I have no idea whether the damage could be a problem), just as a reference I wanted to share: NordkynDesign - lithium battery banks fundamentals, in turn referring to (search for "edge", e.g. p32): Lithium-Ion Batteries...

I added some terminal bolt torque info here.

Yes! Nice! Seems an excellent charming solution to me! Thank you!

In his most recent use with the ATF, David Poz, like you, also correctly left out the dedicated breakers for the ATF. It's difficult to see in the video, but the ATF is directly (i.e. no breaker) connected into the wire nuts (instead of bus bars) as shown in this still: I think this makes...

@Steve_S and @ghostwriter66: I had a positive experience with Cotek recently (last 6 months), consisting of fast tech support (reply in 1-2 working days), one fast warranty exchange on a 3500W 48V inverter and another fast exchange on the same model. I am not affiliated with them, I just needed...

For me, charging 24h with the EG4 charger did not revive the BMS. I should recreate the problem and then try it with my bench top power supply. Other "solution" to get the BMS out of protect mode: https://diysolarforum.com/threads/signature-solar-eg4-wp-teardown.39768/

@grizzzman, @electric: Thanks for the replies. @electric: Yes the datasheets show the (lower) 45-55°C, yet the reason that I picked a higher value is that my guess was that those lower values correspond to the temperature probe values as measured on the outside top or terminal of the cell. The...

@sed6: What is the maximum balancing current that you used? 5A? Also, what wire gauge are your Tesla module balance leads?

Wanted: Damaged or discarded 280Ah EVE cell, preferably one that was sold to you as "new". Goal: Detailed teardown after full discharge for cell parameter estimation as input for analytical cell model. Offer: USD 10 (+ shipping if feasible) Destination: Sacramento, CA, USA. I may be able to pick...

Another idea (I have no experience with this battery nor supplier): https://www.electriccarpartscompany.com/Fortune-60Ah-Aluminum-Encased-Battery