The lead is out!

I finally took the big step and ordered 73, 100AH sinopoly lithium cells.
They arrived 6 weeks later all the way from china.
First impressions all the cells were packaged in quality steel framed wood case's, well protected for the journey they made.
opened up the case's to find quality looking cells.

 Started installing the cells in the car, 25 in the front and 48 in the rear box.
I decided after much reading and absorbing lots of advice to bottom balance all the cells.

Basically this means discharge all the cells to the point where they are all empty  at 2.7 volts.
Easier said than done! I decided to drive the car very carefully monitoring the cells to bring the voltage down a bit before discharging individual cells as they were all sitting at about 3.294volts.

After about 20 miles of stop start nervous driving, continually checking all the cell voltages I got them all to around 3 volts, after awhile you find a few cells going lower than the rest so you can just keep an eye on those cells with a volt meter. near the end of the driving I hooked the volt meter up to the weakest cell and monitored it while driving. During the drive no cell sagged lower than 2.9 volts. that was as low as I was going, so next step is to drain each cell individually to 2.7 volts.

After looking on youtube at various types of bottom balancers I made up a box with a JLD volt meter which has controllable relay outputs, a 20amp power resistor, along with power supply and cooling fan.
As you see from the photo below I connected my gismo to each cell in turn discharging 20 amps, the first lap around the 73 cells was 20 minutes each. the volt meter was set to turn the load on above 2.702volts and off when a cell hit 2.6volts.
At the end of the first lap sure enough they all bounced back up a bit, so around again for 5 minutes each cell.
 To cut along story short, 3 days later I had every cell within 2.702v to 2.705v resting overnight. good enough job done.

 

 

After the successful bottom balance it was time for the first charge, but I was having to many thoughts about spanners etc dropping on the cells and shorting! So I purchased some 5mm macralon sheet, cut it to size to fit over all the cells.
 To allow for voltage monitoring I drilled a small hole above each cell terminal as per photo below.
A lot happier now, should help to stop any silly accidents