My question is about gracefully aging cells -> dendrites? --> fire???
Yes and no, as far as my knowledge reaches, if a cell ages gracefully it will consume itself.
To the point there is nothing left, in this case if that cell is "suicidal" your fusses must kick in.
A cell that will "self destruct" will consume a lot of power from his connecting cells in that pack up to the point of your fuse.
Thats why there is a "cell level fuse".....some use 5a fusses, some like to use 0.250a or even smaller fusses per cell
Some use a 5A fuse at 10 cells...( i am going to use 5a fuse at 10 cells at 2700mah a cell, i did 0.250A even 0.100a fuse per cell, still working)
Depending on the size of your power wall you must adjust your fuses to your feed and use and check them(cells/packs) once in a while.
Retest them.
Or a cell will not store more than 20% of its original capacity, you will find out when your bms is telling you there is something wrong.
Or after a year and you test the pack there is not much of the original capacity left....
However, I just don't understand the risk of dendrites. In particular, if a pack has degraded to <60% of original capacity is it more dangerous than when its at 90%? What about 40% etc. Could the pack be OK but 1 cell in the pack go up due to dendrites? I'd like to understand this aspect of risk better
Dendrites will cause the internal resistance to go up and thus the amount of power needed to charge a cell is also going up, the same for discharge.
You want to look at this as if it is a coffee filter(old fashion paper type(the best coffee btw)) if the smallest holes will clog the bigger holes will eventually do also, but you will taste it as your coffee is getting bitter..
So reusing a coffee filter is a no go for me because i would like to have no bitterness in my coffee...
(the best coffee btw is to boil 2 to 5 min!) it and let it sink, boil it AGAIN let it sink again, turn off the heat imminently after the water reaches the boiling point, stir in between and scope the edges))
Same as your cells, i like my coffee, thank you batrium.
Dendrites are just those small particals that are clogging up your filter, they dont allow movement between the anode and he cathode anymore, the filter is full and the resistance is gaining to get some charge into that cell.
Thus making them into heaters or very slow chargers or discharges, batrium will tell you if there is something going on.
But when they consume to much(cell level) the fuse will blow...
Spontaneous short circuits would seem to be the main risk source.
eg from a dent, careful builders discard any, but maybe accidental damage by handling a pack (but you're close by then)
or metal shaving/solder bead, etc in cap end, eg Sony laptop fires issue or fuse wire short (ironic right?)
Main origin of this problem is indeed careless builders.
THROW AWAY your dented cells OR heaters OR cells that wont take more/less than 1amp an hour when testing...
My testing is a fall out race
I test for Self dischargers
Heaters.
Time, they must take a certain amount of a in a certain amount of time.
IR
ect ect
I will rewrite a old topic soon, i have more good feelings for a fall out race(earn your place in the marine corps, my boy...)....than a survival of the fittest race
Spontaneity shortcut....(Johnny no5)
Spider, fly, leaking roof, rust on your cells not even(will get back to that one) branches what ever event...short circuit is YOUR FAULT...PERIOD...
Keep it clean no dust, no moister, no dogs/kids on the lose with saliva...make sure youre welds or your soldering are in good order....
Keep them(cells) in a good room, possible air tight, with a dehumidifier in it below 40% RH, you will be fine...even the ones that started rusting allready, but this i am not sure: no more moister...rust will not grow or eat further..again on this one i am not sure...
If rusted concrete iron bares are poured in and after 6 months you need to destruct it they are clean as the just came out of the oven.....oxygen did not reach the bars, rust did consume itself.
If there is some freezing over steel/iron will not rust because there is no moister/ thus the rust that was there will not gain in size or depth...but those are for steel concrete castings, but the rusted walls where CLEAN after 4 months of -10C...and lower temps...ake no moister.
Another material for fireproofing might be cement board (various names, eg hardiplank, villaboard, etc here in Australia)
Mine are in steel cases in shed separate from house but they are LiFePo4 not Li-ion so less risk there.
Those materials are very good but more expensive, in the NL DE and Pl i know for sure. dry wall will do the same for one hour if it is 1cm/half an inch thick.
Lifepo4 i would even stack them under my bed and go to sleep every night drunk without worrie's to not waking up....load one full...short circit him, shoot a bullet to him...hack with an ex if you want....with normal use and a bms on it(even the cheap ones) you have to do very difficult to let them catch a fire...put a stick of tnt in it or napalm or....i would even let my babies sleep on them....lifepo4 is very safe....sleep tight tonight.
www.bing.com
Li ion on the other hand...well read carefully what i was typing and how offgrid was testing....(like most of us are testing minimum!!)
With best regards Igor,
My two cents(my 2 dollars or perhaps 2 coins)
Comments are always welcome, chime in if you think to know more, learn me please, correct me please
