Thursday, 22 May 2014

Battery testing begins

I began by removing the 2 remaining battery boxes that survived and getting them into my workshop, removed the lid from the first and removed all the buss-bars, LVC/HVC boards and all additional cabling until I had just the cells, attempted to pull one out, not budging, panicking a little as I was assuming they had all swollen due to the over charge I contacted Steve and asked how much force I could use on the banana leads after all I don’t want to start another fire in this box whilst I am trying to disassemble!

Steve was also assuming the batteries were probably swollen beyond use and this is the main reason I needed to get the whole lot apart to check for swelling and discard any swollen cells, after Steve’s reassurance that I could safely give them a good yank without puling the banana leads out of the cell packs, I went back for another try, this time I turned the whole box upside down and gave the end/edge of it a good whack on the bench in my workshop, flipped it back over and almost in despair grabbed a couple of banana leads and yanked!

To my surprise it popped out sweet as a nut, and of course once one was out the rest came easily, and to my great surprise and relief there was not a jot of swelling to be seen on any of them in fact they all looked good as new!

Borrowed a Powerlab8 from Steve and began testing batteries this weekend just gone 15th March. The powerlab8 is a cool little unit and does a lot of stuff but I was basically just using it to do a discharge from the overcharged state to an “Empty” state 3.5v whilst graphing the discharge on a PC that way you can see if any of the cells are out of balance or damaged in any way.

To achieve this is a little tricky though, the powerlab8 is best run from a 12v or 24v lead acid battery this allows you to do a fast charge/discharge at 20A, simulating actual usage discharge speeds, as I was not versed in the use of the powerlab8 Steve ran me through the basics via email, and after doing 4 discharges my 12V Lead acid battery hit its fully charged state (denoted by the voltage popping up to 14v, peukert effect!

As Steve explained) despite me attaching (what I thought were headlight) bulbs to the 12v to drain excess current, so after a little more fiddling around finding 12v devices that I could attach to drain the 12v and provide a load, I finally settled on the 4 bulbs I had initially, plus a 12v cooler box, plus a 12v car tyre pump, plus a single true headlight bulb wired so that it was on full beam i.e. both filaments lit, And at last this seemed to be enough, I was now able to continue testing and to my surprise at 4 x the speed as before for the first 4 tests I had only been dumping 5A rather than the 20A I had set because the 12v battery could not take any more.

So this greatly increased the speed at which I could test and by Sunday evening I had tested almost all of a single box worth of 5S1P cell packs, I think around 6 will need rebalancing for sure but I may just balance the whole lot and retest the ones that were out of balance to check there is no intrinsic issues.

This Still leaves me short the 36 cell pack’s I incinerated and 4 new LVC.HVC cut-off boards with extender boards (I had better make sure I use them this time eh! You f##!ng TWAT!)
And I am going to need to do some reworking of the buss-bars as well!

No comments:

Post a Comment