Leaking Electrolyte from Bigbattery Powerblock
- Thread starter Will Prowse
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I don't know, it would appear not to be.
Until your post, that was about the only part of the design I actually liked. My interest being primarily marine, I am concerned about motion, vibration and shock loading. I wonder what needs to be done for a circuit board to perform satisfactorily as part of the mechanical structure like this, or if it really is just a design dead end.
I don't think this one is quite done yet, just a hunch
From what I've seen, there will never ever be a Bigbattery on board my boat, they just haven't been engineered or tested for that environment. And fabricating a large circuit board is well out of the DIY zone, I think, but I would still like to do an armchair analysis. What would you have to do to make that circuit board not the weakest link in a marine battery system?
Chris-Bishop
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Apologies for the delayed response, John. The original order came fromDo you have a link where you purchased those?
My google-fu is lacking, can't find them on the big battery site.
Eco-worthy seems to sell them on aliexpress. Apparently I can't get them unless I'm in the UK.
280.7US $ |Eco-worthy Portable Power Station Solar Power Generator 750wh Ac Input Lifepo4 Battery High Efficiency For Outdoor Camping Rv - Storage Batteries - AliExpress
Smarter Shopping, Better Living! Aliexpress.comwww.aliexpress.com
And yes, the electrolyte is quite toxic.
Amazon for $557 or £330 ... The unit comes with a built in inverter, external mains charger, and various solar panel linking cables - also a multi jack for the six 12v outs. The original unit has no issues hence me buying another. One full charge gives me five to six hours of camera's, LED lighting, three high resolution monitors, phone charging etc all without a noisy generator.
Hopefully the replacement will be as good as the original.
I must admit it's a bit scary when things go wrong. In this case poor handling/shipping looks the likely cause.
My experience (dated, but does consist of a few million motherboards, along with additional power supply test sets, MRI circuit boards, etc.) says a circuit board is not designed to handle holding LiFePO4 cells in place. A mechanical strap would be much more cost effective and easy to design. I might be biased towards circuit board approach since I spent 5 years working as a tech in a factory that manufactured (among many others) IBM and Compaq motherboards. I did work half of that time in the test engineering lab designing/programming test sets for the various products. Obviously in the 1980s before they first moved it to Taiwan, then mainland China.
Certainly placing it so 8 cells are supported by it is not a well thought out design, if during shipping the box happened to be placed so it was face down.
That said, current capacity is easy, now worries about it adsorbing anything (circuit boards are routinely washed, de-fluxed, soldered, etc.)
Certainly they do a good job of supporting massive heatsinks, and massive video cards with not a lot of additional reinforcement. Some video card slots are reinforced, but I haven't noticed any additional CPU support other than backplates.
Then you get to the welded busbars are much better, but good luck replacing a cell. Crimping cables takes training and will still have the occasional badly done event, even when mostly automated. Using regular busbars is labor intensive and all that entails with problems.
Circuit boards mean very good and easily made connections for voltage and temperature sensors. It does require precision cell physical specs, but wouldn't be difficult to automate for smaller designs.
Yes, looked like some pretty beefy support brackets were bent, although they could have been designed that way.
We were just wanting to see if was related to a current issue with Big Battery in the USA that have had leaking cells.
I saw that listing on the Amazon UK web site, it's not a big battery product and appears to contain 60AH cells rather than the 170AH cells we are concerned with. That electrolyte is nasty stuff, keep it outside.
Thanks!
Recall for sure If this were the auto industry instead of batteries, probably sharp teethed lawyers circling around also. But it isn't the auto industry, it's the wild west.
It's related in the sense that it removes all doubt about whether leaking electrolyte is caustic and dangerous.
Well, I already knew that, I was trying to see if it was the same Lishen 170AH cells.
I would say you are exceptionally well qualified to comment on the question. What I got from your detailed reply is, mechanical stability is the only real issue and even a beefy circuit board is not enough. So next question: what would be enough, if one insisted on using a circuit board? I recall the photo of stabilizer attached to top of circuit board, I think it was you who posted it, but I can't find it again just now. I was toying with an idea that the studs could be bolted through a non-conducting stabilizer lying on top of the circuit board, but that would seriously reduce the electrical contact.
The circuit board isn't the only worry, there will also be large forces and vibration on the terminals. The cells themselves need to be fixed firmly in place, but still with flexibility for normal expansion under load. How on earth do you do that, with or without a circuit board?
Chris-Bishop
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Hi John
Just had a call from Eco Worthy (strange name) they said this UK version has 100ah cells earlier versions had less - probably 60ah you mentioned.
They were very kind with a cash reduction and a new unit on the way via a different courier this time.
Wow, sounds like good customer service!
Most designs just use a metal bar placed across the top in between the terminals.
Then you come up with who will pay?
The manufacturer of the faulty cells based in China?
Hedges
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I would want to hold the cells under compression and avoid mechanical stress on the terminals. Flexible busbars would seem the way to do that, although possibly holding cells under compression would mean the terminals don't move.
Alternative if compression isn't needed is to let them float and have rigid busbars. That would work with cells vertical and enough space between them for whatever pillowing is going to occur, but busbars couldn't attached during shipping.
I've seen some pictures of welded busbars that had bends, allowing flex as cells expand.
I can't speak with authority for how these cells are actually used in China, but my understanding is the large ones are used in vehicles like a bus.
They are compressed in a fixture (limiting movement of terminals in 3 directions), and welded busbars are used. All that is really needed for a more demanding marine application would be to limit movement in the fourth direction (up) with a metal bar across the top between the cell terminals. I have seen this approach used on large batteries (like 48v rackmount). Of course then it would be difficult (not impossible) to use welded busbars. While braided busbars make sense, preventing the terminals from moving also makes sense, especially in a marine application that indeed will get a lot of up and down movement.
Now, for big battery, first they need to have more than one shelf (currently a stack of 4 cells presses on the bottom one). Due to variances in cells, they should probably put each cell on its own shelf, and perhaps use thin high density foam on the sides to make it stay in place, perhaps with a thin plastic membrane on the exterior to facilitate putting/shoving it in the "pocket". Then put a bar across the front of the stack, thus holding it in the last direction. Of course that still doesn't fix the problem if the cell is manufactured with a leaking vent cap. It also costs additional money to design and implement the changes to the sheet metal. To me, the better and cheaper fix is the bar across the top, and then just make the battery a horizontal one rather than vertical so the cells stand upright.
good questions, do most businesses selling items buy some sorta insurance for liability???
Curved busbars are pretty common but it looks to me like they will still transfer plenty of load to the terminals. Some have used braided copper cable, but there are concerns about less reliable electrical contact and increased corrosion.
Firmly fixing the top and bottom of the cell while leaving the sides some expansion room would seem to be a promising approach, but harder to design and fabricate.
I would say there's still lots of room for progress in the art of prismatic cell mounting for mobile/marine, both on the DIY side and commercial. And I will equally say that it's clear BigBattery is far from an acceptable solution at the moment.
Don't know if you noticed earlier in thread or not, but it turned out it was not even a Bigbattery product that leaked on that poor person but something from another vendor entirely.
Not trying to defend Bigbattery or anything but its not fair to blame them for this leaky competitors unit.
I did notice it wasn't BigBattery, but it just bumped that whole sad story back to life. Plus there was a link in this thread to the "banned" post by MrGreen, which triggered me and reminded me among other things of how unsuitable those products are for marine use, in spite of claims.
Thanks. Understood, just didnt know if you were aware of it or not.
Wow it said about 60% of products on scAmazon are from foreign sources.
Checking back in to say that the replacement renogy CC and Big Battery Hawk have both been 100% rock solid. I just placed an order for 2 more of the hawks (which would give me 6 total). I'll be sure to report in if there are any problems getting the 2 new ones added in.
I would eventually love to have 8 of them but I'm starting to wonder if anyone has hooked 8 (the max listed on specs sheet) of them up? Whats the largest non-diy off grid LifePo battery bank you all have seen?
I would eventually love to have 8 of them but I'm starting to wonder if anyone has hooked 8 (the max listed on specs sheet) of them up? Whats the largest non-diy off grid LifePo battery bank you all have seen?
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