Broke ground on my new shop this week. Putting up a 26x37 shop with 16' ceilings, two 10' wide by 12' tall overhead doors, one 7'x7' overhead door on the side into the yard and a 8'x25' mezzanine at the back. It's a slightly miniaturized version of the 26x50' shop I had at my last place. My wife and I moved to a small community about 20 minutes away from where I work (as compared to being an hour away before) to save money on my commute and maximize my time with my family. The shop is supposed to be completed by the end of January. I can then move all my crap back in. My first priority is to get the Chevelle done. Then I'll start on the Tahoe.
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As far as the Tahoe goes - When I bought it I found that the 300V traction battery was really weak. I killed the thing while cranking the engine over to do a compression test to the point that I had to charge the 300V battery via the 12V battery using the internal jump start feature in the inverter module to get it to start again. I removed the modules from the battery and found that they were really weak. The Prius guys have devised a cheap at home testing option where you hook up a 12V 50W headlight to the module and depending on how long it takes to discharge from 8V down to 6V you can get a rough estimate on the capacity left. A new 6.5Ah module will last for hours. A decent one will last for an hour. A marginal one lasts for 30 minutes and anything less than that it was time to replace them. My best module lasted for about 10 minutes.
I went to GM to order a new battery pack and was told that they are sold out and while the part number is still valid, the manufacturer doesn't make them anymore and GM has stopped selling reconditioned modules. Same story with all the other brands that use the same modules to make their battery packs.
Without any real other options I bought a reconditioned set from a US based battery reconditioner who claimed that he only assembles batteries from sets of modules with at least 5Ah of capacity and that he matches blocks by internal resistance and ensures that all the modules have a recharge and discharge capacity within 5% of each other throughout the whole battery to ensure that the pack is balanced within factory specifications for the Prius (which is much more stringent than the GM factory specs). I put the batteries in and immediately noticed that the vehicle was performing worse than before. The transmission felt like it was slipping, the engine barely started (it is started by one of the drive motors in the transmission) and if I put the transmission into gear too fast after starting the vehicle wouldn't move. But, I was moving and didn't the time to further troubleshoot. I originally suspected the transmission to be at fault, but the more I thought about it I started to suspect that the new battery modules were junk. I finally broke down and bought a module tester from Prolong Battery Systems (which cost more than the reconditioned batteries did) and found that the pack of modules he sent me are worse than the factory originals. I've found internally shorted modules that cannot be charged to the full 8.6V of capacity, discharge capacities anywhere from 0.2Ah to 5.7Ah and internal resistances from 20 mOhms to 45 mOhms (above 30 is bad). Either dude doesn't test his modules beyond checking voltages and is selling randomly assembled used modules without any idea what he is selling or he knows perfectly well that his assemblies are crap and is selling junk intentionally. 1 year warranty my ass, he ghosted me as soon as I sent him my test data. Another $2000 down the drain. If it was just only or two bad modules as I'd originally suspected I figured I could replace them and carry on, but the whole pack needs to be replaced.
There were only two other options available on the market at the time for replacement modules. Both made by a Chinese battery firm Ceba and both with terrible reviews from the Prius guys. There is a guy running a business out of his garage who claims to have designed his own modules to sell but they look suspiciously identical to the Chinese modules, just a different color and three times the price so I really did not want to spend the money on a pack that may be no better than what I already have.
I was feeling pretty defeated and was considering hauling the thing to the scrap yard after parting it out when I discovered a 3rd option that recently became commerically available last year and has rave reviews with the Prius crowd. It is another guy selling modules out of his garage - But he is doing something really different. His modules are LiFePO4 instead of NiMH like the factory modules are. The Chinese aftermarket modules use cylindrical cells which totally ruins the cooling air flow within the battery, but these lithium modules are shaped like the factory prismatic modules so the cooling system works like factory. The modules are less than half the weight of the NiMH modules are, which will make the pack way easier to handle on my own. Each of his modules has a custom battery BMS inside that balances all of the lithium cells within the module to have the same voltage to make sure that individual cells don't get over charged / discharged or charged / discharged when the cells are too hot or cold. Something that the factory NiMH cells were incapable of. Since the inverter/charger is configured for NiMH chemistry, he has an interface module integrated with each module's BMS which accepts the NiMH charging and discharging voltages / amperages and modifies them for the lithium cells so they charge and discharge within their specifications. This corrects all of the issues with the OEM charging and discharging systems which degrades the NiMH modules (especially the GM battery energy module). The factory battery energy module is none the wiser that anything has changed. The NiMH cells are 6.5Ah new and the lithium cells are 7.7Ah within the NiMH voltage ranges. Really a clever design using the latest and most stable of lithium battery tech. They are good for -20 to 45C (the NiMH are rated for -10 to 30) but my truck generally sits inside so the temperature shouldn't matter much. I'll just make sure I don't drive the hybrid to work on the days we have where it is going to be colder than -20. The prius guys who are running them down in the US have collectively put millions of miles on these packs and have noticed zero degradation in capacity or internal resistance in that time, with some guys testing the modules on a regular basis with professional testing equipment to check capacities which remain at the name plate capacity, unlike the Chinese modules which often come at no better than 3Ah of capacity new. The Lithium cells are rated to sit for up to 3 months without use without losing any charge, while the NiMH batteries all self discharge due to differences in internal resistance and will be dead within a month of sitting. I've got a 300V battery maintainer I bought to keep the batteries topped up while the vehicle sits.
There is huge demand for the lithium modules so he sells out super fast. I happened to get the notification on FB that he had a shipment arriving and opened up a pre-sale today so I jumped on it and scored a set. They set me back $4500, but based on the 7 years of real life testing data that the guy provided in multiple different vehicles in all climate types I think they are going to work fine. An OEM set from GM would have been around $3000 if they were available and the reconditioned set was $2000. Should be shipping in about 2 weeks. I'm really happy to be putting in a high quality and North American made battery that I shouldn't have to even think about for the rest of the life of the vehicle. I'm really hoping that fresh cells of ample capacity will completely solve the driveability issues I've been having with the Tahoe and spare me from yet another transmission swap in it.
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