hehee cheers mate
I have been 'playing' with a few, 3 actually, of the 8 lipo
packs i took to 5v and puffed. After seeing
Lukes extremely informative battery destruction thread, and concluding lipos aren't what they
used to be ~4-5 years ago. Lithium Polymer have definitely
improved 100% in the area of tolerances to over charging.
This doesn't mean we should start getting complacent
about the care and handling of these puppies, they still have the ability to bite you, but we know now
with Turnigy cells anywayz) that the boundary levels of past are now
not so 'restrictive,' the Lipo cell is much more tolerant to over and under dis/charging.
At this point in time we seem to know over charging past 5v
is required to produce fireworks.
So...With this new 'wisdom' on board i have managed to get 3 packs from the 8
in a state where i can start to test their ability to hold a charge and stay in balance.
These were the only packs that didn't have multiple 0v cells in them, these packs howver
didn't have a cell voltage under ~4.5-7v most were topping 5v or close to it
and EXTREMELY puffed.
When new, these Turnigys/Zippy packs are extremely good at remaining balanced if you dont
discharge them too far, Hyena mentioned he has never needed to balance
one of his packs past the initial building stage as they have remained in balance since.
The 3 packs i salvaged i took to with a knife, compressing the pack in a bench vice between too
pieces of MDF i made a small slit on the edge of the individual cells seam to
release the gassess that caused the puffing, once all were 'de'-puffed
i increased the pressure on the packs slightly, I then noticed a slight increase in cell
voltage on the Battery Medic likley due to decreasing the ir of the cell?
and then I dolloped hot glue over the slit, the 'over-hang' of the cells seam was
then folded over the slit/hotglue to complete what should IMHO be a tight long lasting seal.
I then made 4 wraps around the cell using kevlar packing tape, this stuff is oober strong
and will keep nice pressure on the pack.
Unfortunately camera batteries were flat so i didn't photo document the de-puffing
process. The packs in picture are all now in the 3.7v area the battery medic is the only method i have
other than the bike to discharge the packs, no incandescent light bulbs or old motors
to use etc :-( So it has taken since Friday to get the 3 packs discharged
i am now in the process of balancing these cells to 3.70v. Why 3.70v i hear
some of your are wondering, simple, 3.70 was the lowest cell on the newly purchases lipo packs
so i have balanced all those to that state of charge. As i only have the meanwell PSU as a charger, i will be
bulk charging all the packs in one hit. I am actually heading to computronics on Tuesday (Easter long weekend)
and i shall pick up another 24v charger to series with the 48v i have so i can pump out
66v, in fact ~74v (for memory) and run a 66v setup. I have another 2 packs from HK sitting at
Australia Post Since Thursday so hopefully come Tuesday ill see those also. So i shall have 9 packs
which will be run in 18s 3p setup or 66v 15ah. How well the de-puffed packs will
remain in balance, accept charge and hold it and for how long and much life span has been
reduced due to the over charging etc is something only time will tell. I will
use the 3 packs in parallel with individual balance taps 'free' so i can monitor each individual cell
for the first dozen or so cycles, when i am happy (if they) remain in balance etc
at this point i can parallel the taps up and monitor the entire pack with the battery medic, this
will give me a read out of the 6 cells, in actual fact though obviously the reading we will get is
of 3 parallel cells being reported as one individual cell by the battery medic.
Shall report back on how things go, due to the time consuming discharging and balancing i haven't
been able to make up the packs i think this will happen Monday, again depending on the speed of the balancing.
ciao for now...
KiM