Can I replace 1st generation battery cells with 2nd generation battery cells?

People have built out Gen 1 batteries using 38 modules from Gen 2 batteries (meaning you need more than one Gen 2 battery to pull from, because there are only 28 modules in a Gen 2 battery). Working at the level of modules turns out to be tidier than individual cells.

I don't think the modules are exactly the same size; they are a smidge longer, which might lead to some creativity in getting the cover back on.

 

This is what I know, about six months ago I had my mobile mechanic who specialists in hybrid batteries come out because I was having problems with my 2002 Prius. He told me that if enough of the cells (they were Gen 1 cells) were bad he would put in all Gen 2 cells and then charge me extra of course. Only one cell was bad so I didn't need the Gen 2 swap. So based on that experience I would say most likely you can use Gen 2 cells (hes been doing hybrid repair for many years, knows his stuff and my car is fixed again). I'm leaving a caveat that don't yell at me if its not the case, lol, just sharing my experience. Good luck.

 

David,

You and Chap are correct. The Gen 1 modules can be replaced by the Gen2/3/4 modules, but to do the job right, all 38 modules need to be replaced. Dimensionally, the modules are all the same thickness and height. The difference is the width(or length, depending on how you look at it). The bottom of the modules is the same, and they match bolt patterns for mounting on the steel base plate. Gen 1 uses 2 mounting bolts per module and the other Generations use only one. The upper portion, where the (+) and (-) terminal lugs are located is slightly wider on the Gen 2/3/4 modules. That's the main reason you cant mix Gen 1 with 2/3/4. The busbar harness will not sit flat and will not have the right spacing due to zig-zagging in and out. So, the upper portion of the Gen 2/3/4 modules are a bit wider, but they will fit under the steel top cover. There's just a bit less clearance between the black plastic terminal covers and the inside surface of the steel cover. The other issue that arises is that the interlocking "nubs" on the modules are different on the gen 1. This causes a problem only for the outer 2 modules, as they must mate to the steel clamp plates on each end of the Gen 1 case. The steel plates are made to match the Gen 1 modules, not the Gen2/3/4, so the "nubs" don't match and deform the Gen 2/3/4 modules a little.

 

Right. A cell is the smallest unit of a chemical battery, always producing a certain nominal voltage that's characteristic of the chemicals used. For NiMH chemistry, one cell is nominally 1.2 volts.

The modules in a Prius produce 7.2 volts nominal, so by simple division you know each module has six cells in it. You can see the six cells if you cut a module open, as seen here.

But no one cuts up the modules and replaces cells. Messy. And the stuff it's messy with is potassium hydroxide, which will eat you.

 

Be careful with Gen 4 modules. You can only use the NiMH modules from a Trim 1 or 2.
2 Eco and above use Li-Ion modules.

 

A grid charger is simplest, charging & balancing the whole pack. @jeff652 designed a good one. I do not see a discharger for the Gen 1 Prius though to totally recondition the pack.

Prolong® Battery Charger - Hybrid Automotive

 

see the battery rebuilding threads. they use hobby chargers and light bulbs to charge and discharge the individual modules.

 

I was babying my batteries at first and could not get results. The Dr. Prius app has a life estimate test. It hard charges the battery pack first: Park, foot on brake, Drive mode, full gas until fully charged. Takes about 5 minutes. Then they have a discharge process to follow for about 15 minutes. The charge process forces current into the pack hard stressing the batteries, that rejuvenates them. Not something you want to do a lot but maybe once or twice a year. MOST IMPORTANT is examine the pack. Humidity will collect and corrode the copper plates between the batteries and will drip into the battery ECU (orange connector). The water will corrode the sense pins shorting them together.
That at first will mess up the ECU ability to manage the pack and as the corrosion progresses, start a fire at the ECU connector....
Lots of youtube vids on removing the pack and examining the elements. good luck, be safe....