Hi,
I wanted to share the summary of this thread:
ReInVolt PHEV Plan - Page 3 - PriusChat Forums
SUMMARY
ReInVolt Capacity - there is no evidence that NHW20 modules suffer similar degredation that is seen in the NHW11 modules. Independent measurements by the Dept. of Energy, 'oldnoah' and myself have documented the loss of original NHW11 module capacity. In contrast, the ReInVolt pack has double the Ahr capacity of my fully functional, 133,000 mile, NHW11 pack. Suggestion: we, the NHW11 community, need a better method of measuring traction battery health. (My conservative measurement based estimate is 6.46 Ahr but the data suggests on the high-side of 7-8 Ahr.)
ReInVolt Battery Electrical Quality - the module-pair balance at ~0.08 volts is less than half of my existing pack balance, ~0.20 volts even after sitting unused four weeks. (This is the advantage of a depot rebuild. With a large inventory of NHW20 modules, they have the ability to match module capacity that an individual buying just pairs of NHW20 salvage packs will lack.)
ReInVolt thermal characteristics - there is no evidence of any problem cooling the ReInVolt modules. The improved, lower internal resistance of the NHW20 modules significantly reduces the rate of heating compared to NHW11s under descending hill, forced charging. (The newer modules have two, welded tabs between the cells and this significantly reduces the I**R losses. They are also more firmly constructed.)
ReInVolt case - the first case had a bolt hole misalignment and the installer of my pack reported some evidence of 'bent as if once dropped.' I didn't see it but then I didn't install it either. Regardless, case fit remains a challenge when dealing with used parts and shipping on a pallet. There was never any question about whether or not it would fit.
* * * end summary * * *
To measure the pack capacity, I calculated the dV/minute at a near constant load, ~65 A. I then took the highest measured voltage under load, ~294 V., and a projected 19*6 ~= 114 V end at 1 V/cell. Dividing the dV/dt rate into the voltage difference gave me an estimated discharge time to 1 V/cell which I multiplied by the current, about 10C. Fixing the units, I came up with 6.46 Ahr as the lowest possible capacity of the ReInVolt traction battery. The data suggests it is closer to 7-8 Ahr leaning towards 8 Ahr.
FYI, using a similar approach for the original, NHW11 traction battery suggests ~3.5 Ahr capacity. There is nothing wrong with the original pack. Rather, I felt this was an excellent time and a reasonable price to take 'battery failure' off the table. I'll also get to resume my earlier, traction battery experiments. <grins>
I now have to race getting a sustaining charger on the old pack pending building out the frame to hold it over the ReInVolt pack. Then comes the more fun task, the full battery management and interface to the ReInVolt pack. Obviously, the project is only 25% done. Still, it has been a lot of fun.
FYI, feel free to comment on any of the postings over at PriusChat. Just include the URL to the specific page so I can understand the question.
Thanks,
Bob Wilson