Tools for diagnosing Generation 2 ?

John, I have a bench set up just for testing and cycling these modules, I keep the modules compressed in the OEM racks. I have racks for 38 module, 28 module and 20 module setups. I have (3) HiTec X4 AC+ charge/dischargers and a TENMA 300W electronic programmable DC load tester.

First thing I do is record all the serial numbers and the voltage for each module.

My methodology:
1. I orient all the modules so the (+) terminals are on one side and all the (-) terminals are on the other. This helps prevent accidental reverse polarity connections and accidental short circuits between terminals. Safety First.
2. The rack is placed on spacers (3 sides) to lift it about an inch above the work bench. I have a 120v fan rig that blows air under the rack and the air then flows between each module to prevent any heat issues.
3. I currently have the HiTecs set up for 5 cycles. This is just personal preference based on experience.
4. I connect the Hitecs to every other module starting with 1,3,5,7,9,11,13,15,17,19,21,23
5. After those are complete, all data is recorded and I connect to 6,8,10,12,14,16,18,20,22,24,26,28
6. After those are complete, all data is recorded and I connect to 2,4,25,27 and any others if I want more info.
7. After all modules are done, I let it sit for two days to let voltages stabilize. I then disassemble the rack to move any failed/marginal modules to one end of the rack. Then clamp it back together. I install a heavy copper wire across the (+) terminals and another one across the (-) terminals to allow the voltages to equalize for a day. The failed/marginal modules are not connected to the copper wires.
8. After a day of equalization, the copper wires are removed and the modules are allowed to sit for a week or two. Voltages are checked again to look for any significant change. This is an easy way to check for abnormal self discharge.
9. Now they can be individually load tested using the TENMA.

For those of us who have a Gen 2 and need battery repairs, I am a BIG proponent of purchasing a battery from a wrecked GEN 3 and just doing a full swap of the modules. If you happen to get a 2014 or 2015 model, there's no need to even perform any significant testing or balancing. If you do end up just replacing the marginal modules, Gen 2 or 3 will work fine, as long as module quality has been verified.

A few years ago, I had a 2005 that had a failed battery at 235,000 miles. We swapped one obviously bad module with no further testing and put another 30,000 miles on it with no problems. We decided to let my son have the car, so I purchased (2) 2013 Prius C batteries from a salvage yard. We installed 28 of those modules into his battery and it's been going strong ever since. The old battery sat in the garage for over a year, untouched until I bought another 2005 with 260,000 miles and a failed battery. We took the one out of the garage and put it in with no testing. Fired right up. I bought a 2015 battery with intentions of eventually swapping those modules, but car got wrecked. Very recently bought a 2007 Touring model with a bad battery. Had a set of 2011 modules on the shelf, already cycled and tested, so I installed those and now the 2007 is killing it with a first tank average of 49.3 mpg.

With what I know now from the testing I've done on hundreds and hundreds of modules, I was extremely lucky with my early module swaps. An example is the 2007 battery I just replaced. The initial discharge values for each module were crazy. There were three modules that were obvious suspects with voltages less than 7.2 Their capacities measured 3, 109 and 300. The remaining 25 modules had voltages from 7.54 to 7.76 Sounds good, right? This is exactly why voltage cannot be used as a sole indicator of good or bad. Initial discharge capacity of those 25 modules ranged from 711 to 4172, with 10 less than 2000mah. The 711mah module measured 7.54 volts. Modules like that are sold every day on ebay. That was the condition of the battery within a week from being removed from the car. Following cycling/testing of the 28 modules, 5 were less than 6200 mah (lowest was 5974 mah) the rest were 6200-6545mah. The obvious bad module maxed at 2013 mah even after 5 cycles. Even the other 2 marginal ones recovered >6000, but probably have internal self discharge problems.

 

That is correct. The modules are identical except the Gen 3 supposedly has a slightly lower internal resistance which allows it to have a slightly higher max amperage discharge capacity. I'm pretty certain the max discharge is controlled by the CPU, so our Gen 2's wouldn't know the difference between Gen 2 or Gen 3 modules, but a Gen 3 may not like having a Gen 2 module.

The 28 modules are clamped between two fiberglass/plastic plates. The Gen 2 and Gen 3 use the same style clamps except the Gen 3 has an additional tab on top for holding wires. I removed the Gen 3 modules from the 2011 clamps and installed them into the 2007 clamps just to keep it OEM as much as possible.

Just take a bunch of photos as you're disassembling so you have something to reference during assembly. Definitely want to have the battery module polarities correct.

I've had excellent results from most Gen 3 batteries. I actually have (6) 2013 modules (manufactured in July 2013) that I'm cycling right now with some other random leftovers. I caught one of them during it's rest period between cycles and it was showing 6700+ mah from that discharge.

I'll look around at some of my previous sources and see if I can find something in GA that might interest you..

 

where do you buy your batteries? Junkyards?

 

I keep my eyes open to all opportunities. Salvage yards, people parting out wrecks, Craigslist, even ebay a few times. Not everybody recognizes a good deal, even when it's staring them in the face.

 

No, no, no..I'm referring to deals on ebay and CL that I run across here and there. Most people don't recognize what's for sale or how to look at the serial numbers to tell the manufacturing dates. There could be (2) Gen 1 batteries for sale on ebay, one built in 2002 and one built in 2012 or 2015, but someone always ends up buying the 2002 battery. In all seriousness, my comment had nothing to do with this conversation.
Jim

 

If it were me, I'd start looking for the salvaged, low-mileage NiMH Gen 3 pack, maybe around $1000? I'd also start shopping the dealers' parts depts in my area for new battery price. It sounds like some are selling them for around $2100, with a reduced warranty to DIYers. Factor sales tax in your decision.

I would steer clear of salvaged Gen 2 packs. Even the newest are approaching eight years of age, and in my mind ten years is a good maximum battery life, regardless of mileage.

Keep in mind, if it helps with the amortization thought process, that a healthy battery pack will be easily transferable, and has some salvage value per se if something happens to the car.

 

John, If you're wanting to go the full module replacement direction, I'm going to throw this offer out to you. I have a Gen 3 battery removed from a 2015 wrecked Prius with 14,000 miles. I've already tested all the modules and have them on the shelf. They are all date coded 04XP, which decodes to a manufacture date of November 4th, 2014. The capacity test results were between 6705 and 6942 mah. I can assemble these in a case, along with all the support electronics, install it in my car (also 2007), and drive it to you. I think its probably a 2-2.5 hour drive from Columbia to Savannah. We remove it from my car, install it in yours and make sure everything is good to go. (I'll bring my battery also, of course, so I can put it back in to drive home). $1200 plus your old battery.