Can I salvage a (slightly tipsy) eBay buy and turn it into a fully working unit? More importantly, is it worth the hassle?
So, in my spare time, (because I obviously need a better hobby) I spend a lot of time on various auction sites looking for cheap ways to expand my battery storage. I have a Givenergy system at home and over the years I’ve tried a few things – add an extra inverter? – Check…. Shove some DC Coupled Pylontech’s into the Givenergy Hybrids PV strings? – Check….
You get the idea…
However, it’s always been a bit of a fudge to get around the closed nature of the Givenergy ecosystem. You really want the real thing! Thus I keep an eye on auctions for “bargains” that may be had.
Occasionally, you do stumble across Givenergy equipment (I’ve picked up several inverters, a AIO Gateway & a BMS in the past) and so when this rather sad looking 2.6kWh pack popped up I thought ” I’ll throw an offer in and see what happens… “
The Purchase
The description was honest enough. The item was listed as:
“faulty. It looks like it may have some water ingress. Fully tested, the battery cells and are charging and holding at over 50v.”
From the pics it didn’t look that wet inside. I had a spare BMS kicking around to copy readings from, so that shouldn’t be a problem & if it was truly beyond repair I could just fit that and bin the old BMS. Finally, as if I needed to convince my self further, as something interesting to play around with to keep me out of trouble, I thought why not…
Well I should have known better as unlike every other sane person on eBay, nobody else must have given it a second thought, so along with being £100 lighter, I ended up with it.
Hey, atleast it holds voltage right?…right…?
Such Potential Arrives
Fast forward a week or so and I had hold of it. It’s boxy shape cunningly hiding it’s surprising heft, I quickly “peeled” it to see what it was like inside.
It’s a 2022 model & it had clearly spent it’s life outside – owing to it’s sun-bleached appearance & well… having had water in it previously.
Externally, other than the weirdly missing handle on one side it seemed “reasonable” and on first glance inside, it didn’t look like it had, at one time, had standing pools of water in it – more of a look of moisture ingress (there were no obvious tide marks inside for instance.)
So, first things first – lets take a look at the BMS itself in more detail. On face value, there looks to be nothing untoward? It’s not excessively corroded or with obviously failed components, scorched or melted anywhere. I think I might try and boot it up and see what (if anything) it does, but first I need to confirm what the pack voltage is standing at right now? I don’t know how long this has been stood & If it’s too low, then the BMS won’t switch on, so I might need to boost charge it in that case.
Alright, that’s not brilliant (a healthy pack should be somewhere around 50V but as we don’t know it’s history, how long it’s been stood or if it was even turned off while it’s been sat around.)
Power On
Let’s try switching it on – Success! the BMS powers up still, so the cells must be at least above the Low Voltage cut off threshold, and the indicator LED’s show an alarm (understandable) – OK, fine, lets talk to the BMS and look at what it thinks is wrong then?
Interrogating the BMS directly (which I won’t go into here, as I’ll no doubt upset the OEM (again)) I can start to build up a picture of what it believes the issues are – so here is what it has stored in it’s log, handily put into a spreadsheet for ease of display, rather than a series of command line screenshots:
Oh dear, well that’s not good at all.
Panic?
Well maybe let’s not panic just yet. Sure the dates are all nonsense, the BMS is fully in protect mode & none of those are the sign of a healthy battery: To be simultaneously massively undervoltage & over voltage is not a good position to be in.
Surely that can’t be true??? Maybe the moisture is screwing with it’s voltage sensing wiring and it’s all just a false reading. After all, the total voltage I measured earlier was 43V? So that’s roughly 2.6V per cell (as there’s 16 of them) which even though a far cry from normal can’t mean it’s in too bad of a shape. Let’s look at the BMS wiring and check for corrosion – starting with it’s cell voltage sensing & balance wiring:
Ah! there we go, that’s certainly not normal but is some good news as it’s the likely source of some very worrying cell voltages. So it looks like moisture has got in this socket here and caused a short. Not a massive one as nothing has melted and the corresponding plug looks a like it would clean up ok.
So let’s remove the BMS entirely and put that to one side – we can test the BMS components later and replace any that this short may have damaged.
While the BMS is removed I can get a better look at the cells and check the connections for corrosion as the moisture may also be causing funny readings at that end also.
Hmm, that’s not looking too good, it’s the connection from the positive side of the cells to the battery outgoing terminals and although it’s hard to see on the image it is showing signs of having been wet / starting to rust.
Sinking Feelings
For clarity, this battery contains 2 distinct cell modules: each module should have 8 cells each, with each cell rated for 3.2V nominal, we should see each module around 25.6V, with the total of 16 cells giving us the 51.2V nominal battery voltage. So lets measure these ones:
OK, so 26V for the lower module, that’s kind of what I’d expect for a healthy pack – it means the cells are roughly sat at 3.25V each. But we only measured 43V for both packs combined when they should be broadly balanced? Maybe the connections between packs are more corroded more than I thought. Lets measure the upper module to check:
18V? Oh no! That means those 8 cells are roughly 2.25V each. That’s getting dangerously low and not healthy at all. For reference, anything below 2.5V or above 3.65V is considered outside of specification and likely damaged (often irreparably.) I think I need to pull this module out and check it over more thoroughly:
Well that won’t be helping, but it’s more the stud than the crimp, it’s not visually rusty between the connections – but as the module is now out, might as well confirm the cells are ok.
Sinking Even Lower
Oh NO (again!) That’s catastrophically bad. Cell 1 is sat at only 1V. Starting to think that the BMS was right all along. But surely it must have been lying about that cell being at high voltage?
OH NO!!! (Number 3!) – Gingerly places cell module down & steps away…
This pretty much puts this module in the scrap bin – there’s no way I’m risking any of those cells being put back into service, so these need to be safely stabilised through careful discharging and then responsibly disposed of.
I think this is the end of the line for this one.
Game OVER!
So it looks like this time I’ve been unlucky & it’s the end of the road BUT I’m not giving up just yet… ultimately I still have a module of 8 cells that appears to be healthy. I also have a BMS that seems to be healthy too (it was certainly correct about the cell voltages in the end) so maybe I can still turn this around?
The next steps are seeing what I can salvage out the bottom module (after carefully testing them!)
There may be an option to split them into two 12V batteries which could be used for caravan/motorhomes or even just selling them individually to people who have a single faulty cell. The proceeds could then go towards re-celling this entire unit (with either reclaimed or new cells.)
I could also just go a bit over the top and see just how much capacity can be crammed into a 2.6kWh shell!
I’ll mull over some ideas (& AliExpress) and see where this goes for part 2…
Warning
Disassembling electrical items is dangerous, lithium batteries even more so. The above should not be used as a teardown guide at all – there are many, many steps I’ve omitted where I’ve isolated, insulated and generally taken precautions around shorting things out for my own safety. It was also carried out in a large, well ventilated space, with fume extraction and clear exit routes if things went wrong.
Don’t simply read this and start taking these things apart, as you’ll at best end up with a broken battery…
Consider yourselves warned!
No responses yet