Is the GenII Prius Battery Really 5kWh?

[Artric]

I was chatting with a Prius fellow, and they mentioned that their battery pack holds about 5kWh where I believe ours only holds about 1kWh. I could have sworn from prior research that it was not nearly so much larger... So is that correct?

I remember Mike D mentioning about trying to get one of those in our cars, has anyone done it yet? Do we have a thread about that project?

[uhtrinity]

It still 6.5 Ah NiMH, at approximately 50% more voltage. So ~1.5kWh. There was supposed to be a Lion plugin model with the EV range of 15 miles, but I don't know if it was ever produced.

[MN Driver]

Mike D was shoehorning the cells into the standard IMA case and managed to do it, he has a picture up on his site about it. Like uhtinity said, they are the same capacity at 6.5Ah but have a very different form factor since they are prismatic cells. The japanese Gen 1(before the US Gen 1) had the same exact Panasonic cylindrical cells that we have except there were 240 of them in two seperate sub-packs so there was twice the capacity in that one. After that Panasonic and Toyota got into a legal agreement for the prismatic cells meaning that Honda is stuck using the older style cells.

The only disadvantage that I see to the prismatics is that the walls of the cells are plastic and they swell under overcharge as they aren't designed to contain much pressure. The advantage is that they have almost no self-discharge which is a major component to issues related to our packs. I'm not sure if the current setup for any of the Honda hybrids could be retrofit with these cells without swelling.

My idea would be to build in breakstrip fuses like consumer electronics do to disable lithium polymer batteries if any swelling occurs with the pouches. That way they could be implemented and no harm would likely happen if there was a failure. It would be a decent amount of work for fitment and trying to ensure that everything was safe but the issue of recals on the packs might occur less. ..but I'm not sure because it seems there are a fair amount of battery failures on the 1st US generation of the Prius from the Priuschat forums. The problem with the Prius when the battery fails is that the engine can't run without that battery so it could leave you completely stranded in place rather than just without the DC-DC like how the Honda's operate.

[Mike Dabrowski 2000]

The depth of discharge of the cells is not being considered.
The Insight 20-80%
The Prius 40-80%
Useable capacity to stay in the "safe" operating range according to the manufacturer.
Honda appears to have been a bit optimistic about real world "safe"
I never actually used the pack that you see in that blog, just confirmed that it was possible to do it the reqiured pressure plates to contain the swelling sides were going to make the thing dangerous.
I sent that cut out pack to a guy in NC who is hoping to put in some lithium cells similar to what Peter has done.

[Artric]

That's awesome. I hope one day I'll be able to reach that level and go Lithium. Until then, I'll have to leave it up to the pros like yourself and dream!

[Hybrid-Battery-Repair]

AFAIK, Gen I Prius's (Prii?) used 38 6.5Ah Prismatic "slices". Each one is comparable to a Gen I Honda "stick", so that puts the pack at about 1.5 KW (vs Honda's 0.75 KW). Of course, Honda uses more of the pack's capacity than Toyota, so the difference isn't as big as it sounds.

The Gen II Prius's use 28 slices, but ramp up the voltage electronically. This however still gives about a 1 KW pack because wattage is independent of voltage.

The Gen I Prius slices have a bad tendency to leak acid and corrode their terminals. Fortunately Gen II slices are only about 1/2" longer and will fit in a Gen I housing.

Pricing: a set of 28 new slices costs mechanics $1700.

1997-1999 Prius's (NHW10) used 40 Honda-style sticks.

Now HERE'S a battery that is worth using:



This is (a bad picture of) a NiMH pack out of a Toyota Rav4 EV. The bricks that look like motorcycle batteries are actually individual 1.2V NiMH cells. They are (I think) 95Ah each. These are the ones that Toyota got in trouble with Cobasys for building. That battery pack weighs 1500 lbs and lowers from the belly of the truck.

Originally Posted by Artric

I was chatting with a Prius fellow, and they mentioned that their battery pack holds about 5kWh where I believe ours only holds about 1kWh. I could have sworn from prior research that it was not nearly so much larger... So is that correct?

I remember Mike D mentioning about trying to get one of those in our cars, has anyone done it yet? Do we have a thread about that project?

[Artric]

Another thing I learned from the Prius guys - if they are charged over 80%, the car will just spin the motor, as it doesn't want to be up in that range at all.

If we grid charge, we can go above 80% (of course, this might bite one in the ass eventually if it wears the battery down), so the Insight could be more like 20%-95% versus 40-80%, nearly double the usable capacity.

Or am I missing something?

Originally Posted by Mike Dabrowski 2000

The depth of discharge of the cells is not being considered.
The Insight 20-80%
The Prius 40-80%
Useable capacity to stay in the "safe" operating range according to the manufacturer.
Honda appears to have been a bit optimistic about real world "safe"
I never actually used the pack that you see in that blog, just confirmed that it was possible to do it the reqiured pressure plates to contain the swelling sides were going to make the thing dangerous.
I sent that cut out pack to a guy in NC who is hoping to put in some lithium cells similar to what Peter has done.

[mikep_95133]

Originally Posted by Artric

I was chatting with a Prius fellow, and they mentioned that their battery pack holds about 5kWh where I believe ours only holds about 1kWh. I could have sworn from prior research that it was not nearly so much larger... So is that correct?

I remember Mike D mentioning about trying to get one of those in our cars, has anyone done it yet? Do we have a thread about that project?

A few years ago I bought 11 Gen 1 Prius packs. 38 modules each. I tested them in my US Electricar S10 truck. Acting as EV batteries the modules put out 0.9-1.0 kwh each. In my case I had 5 complete Prius batteries in parallel. This was consistent through out all of my testing. The next generation of cells might be something like 10-20% higher capacity but not 500%.

The total pack impedance was insanely low. My tires would almost skid during regen. The truck would come to a very abrupt complete stop due to such a low total pack impedance. But alas, hybrid cells are not heavy duty enough for EV work, especially a 4k lb truck. Having to design and build 5 temperature sensing fan assemblies was also a lot of work.

Mike

[mikep_95133]

This is (a bad picture of) a NiMH pack out of a Toyota Rav4 EV. The bricks that look like motorcycle batteries are actually individual 1.2V NiMH cells. They are (I think) 95Ah each. These are the ones that Toyota got in trouble with Cobasys for building. That battery pack weighs 1500 lbs and lowers from the belly of the truck.

What I wouldn't give for a pack of those 95ah NIMH modules for my truck. One guy did it. Not sure long term how he did. These are the best EV batteries ever manufactured. Southern California Edison has 300 Rav4's. Many of them are over 200k miles. Some are at 300k miles. Insane.

Mike

[Mesuge]

Originally Posted by Artric

If we grid charge, we can go above 80% (of course, this might bite one in the ass eventually if it wears the battery down), so the Insight could be more like 20%-95% versus 40-80%, nearly double the usable capacity. Or am I missing something?

Apart from different dis/charge algorithms, there are also the temperature variation considerations. These OEM cars have got some overhead in order no to get burned with premature warranty claims. However, if you go close enough these limits, you ought to babysit the batt. pack the whole day or involve some a bit complex protection/diagnostics schemes to get the job done for you.
The best write-up prolly here: blank