HOW NOT TO REBUILD A PRIUS NHW10
On the 30th of July 2011 I repaired the battery on the 2nd Prius I had bought recently. This is what I found when I took it apart, someone had been there before! I urge caution when buying a NHW10, buying one with a battery that needs work can be ok, the ones I have worked on that were original have been fine after replacing a faulty string, but beware if it has been worked on!
The first sign that all was not well was when I took the seat out and exposed the sheet metal battery cover:
Figure 1: bottom centre battery mounting bolt loose and smaller bolt missing.
Figure 2: left one the same.
Figure 3: left top.
Figure 16: this is the strap from the battery to the side of the cat that covers the vent, bolt has been broken
I then opened it up, I had previously identified the bad string pair as being string number 20. I had also let the car stand for 3 weeks before checking, when I measured the 2 strings in that pair with a voltmeter I found one string 1.2 volts below the rest of the strings.
When I removed the low string I found this:
Figure 17: dented cell.
The heatsrink has been slit from one end to just before the other, a cell has had the spot welds drilled out and another welded in. this cell has a 10mm dent in the side! Amazing it ever worked….
Figure 18: here you can see most of the strings are like this!