Battery rebuild on a dead 2002 Prius (NHW11)--Mixing Gen 2 with Gen 1

I can order 36 of the cheaper cells @ $33 each ($1188 + tax = $1288.98) plus $6.14 shipping (not sure if they combine) = $221.04 (at most, probably cheaper) = $1510.02 total. I have about $800 on hand (and shouldn't/can't really spend all of it this month--can probably spend $500 now).

So with the roughly $700 I've already spent, I'm looking at about $2200 for the job... more than the cost of a shop replacement, but now at least I have the infrastructure needed to keep my battery healthy.

 

I'm currently checking into salvage yards in the area. I've ordered 10 G2 cells from eBay. I'm going to go ahead with the G2 upgrade, but now, since I have 10 cells (2 on-hand, awaiting the other 8), I can just buy a whole G2 battery when funds become available (I'm seeing prices from around $700) and then I'll have some spare parts (ECU, case, etc.) I can sell online to recoup some costs. I hear that's a popular route on here.

So much for optimism. Well, I guess on the plus side, I should have a pretty healthy car after this. I'll have to break in the car slowly and have the transmission checked when all is done (clean the sludge, magnet, filter, etc.) to be cautious. Don't want to follow bad money with bad.

Looking back, I could have been a bit more frugal with my expenses. Planning this out, though, I made a huge assumption that, based on some of the voltage readings (and my erroneous belief that V directly corresponded with SOC), I could save some cells and just pull a few. I hope someone attempting a battery rebuild may view this as a cautionary tale and assume all his/her cells need replacing, especially in a '01-'03 Prius, and double-especially when it has been sitting inoperative for a good length.

I know there's (almost) always a bright side, even if I prefer the shade. Thanks everyone, for the tips. I will post photos of progress/completion/results.

 

I don't have time to elaborate much, but I got it working, as of 10:41 am. July 16!

I bought a local salvage battery from a 2005 with 100K+ miles on it for $575. I pulled it apart, read voltages on all cells individually (they were pretty good), so I slapped them in my case and called it good.

I did not do the charge/discharge cycle, as recommended (I'm hard headed and have to figure many things out first-hand). I added the cells to my old battery case, plugged everything in, and I measured about 296v for the series. The next day, I installed it in my trunk, tightened down a few bolts, and clicked the ignition.

Ready light came on, engine was a bit coughy and shuddered a little. Warming up, there were no lights on, no triangle of death, just a tired old Prius waking up. I took it down the street to the gas station, got some air in the tires, and drove it back. So far, I've been about 16 miles, and there are no battery codes. Even my HV sensing wire fix seems to have worked (though I'm dubious it will hold indefinitely).

I will say, though, that the newer Gen 2 modules do provide a rough fit for the case, and I have not been able to snug it all down tight yet. One option I'm looking at is getting longer screws. The battery is attached firmly to the mount on the front side, but not on the rear. I'm thinking I may need to loosen the front to get the rear screws in.

I think I may have put in a total of around $1200 or $1300 for the fix, much of which was not really necessary (a cart to work on, for example), though I do like having the ability to resuscitate my battery if need be.

I still need to take pictures, but I can't really drive it out a whole lot because the registration has lapsed, and my insurance was placed on hold, pending the repairs. When I get some money next month, I'll have all that squared away and be off and running. My brakes need replacing next, and then probably my 12v, but it is lighting it up each time, so for now it is okay.

I've got 16 miles on it so far, and nothing is coding for stored codes. Pending codes are a P0300 (Multiple Engine Misfire Detected), though that may be from sitting inoperable for so long. I'll look into that more in the days to come. I will post photos, but I'm short on time at the moment.