Tech specs for HV battery?

I posted something about an amateur Prius documentary a while back, but that thread got lost when the forum had problems.

I've decided to try to help teach myself the art of video production. Since I've been obsessed with the Prius for the past several months (just can't afford one yet), I'm trying to plan and shoot a documentary about the Prius. This will be low-budget, and I'll distribute it for free on the Internet.

So anyway... one of the segments I'm putting together involves the HV battery. I'm going to show why the HV battery lasts as long as it does, and why conventional wisdom about rechargable batteries doesn't apply here. That is, people already know how rechargable batteries last if you beat them to death: overcharge them a little bit, or leave them on a float charge long-term; discharge them until they're unusable, then leave them sit for a while and then quick-charge them again. On the other hand, if you have several thousand dollars worth of battery management systems on a vehicle, and you carefully control charge current, discharge current, and state of charge, you get much more life out of your batteries.

We know this -- first generation Prius owners already know this is true first-hand. But why is this true? I'm going to try to establish this in a rather technical video segment. Because it's distributed over the Internet, people can skip this part if they want.

I'm looking for some details about the HV battery, to help with this video.

First, what do we know about the individual cells in the 2004/2005 Prius battery pack? I believe they're NiMH D-cells, but do we know what manufacturer and what model? I'd like to try to find the data sheet for just those battery cells.

Second, for the 2004/2005 Prius, what do we know about how the battery pack is treated? I think Graham's Prius page says he measured something like 50 or 60 A of charge current during regenerative braking, but is that MG1-side current or battery-side current? What were those maximum and minimum states-of-charge the Prius considers empty and full, again?

Currently I'm planning three parts for this HV battery life segment. For part 1 I'd like to interview someone with Toyota (maybe a Prius tech on his day off, or something) and establish how the Prius treats its batteries. We might even show viewers sections of the repair manuals for confirmation, if that information is available there. Or in a pinch, maybe I can just get permission to show sections of the manual and talk about them myself.

For part 2, I'm interviewing Dr. Tisko at the Chemistry department of the University of Nebraska at Omaha. I think we're planning on shooting this next Tuesday. He'll give us a lesson on how rechargable batteries work, and what mechanisms cause a battery to break down over time. He said he can't get too specific, because battery design is still an area of active research and it's not his specialty. He's pretty sure he can get us "up to speed" enough that we can talk to a professional and understand what they're saying.

And then for part 3, I'm hoping to find someone "in industry" to interview to connect everything together: why will a battery treated the way a Prius treats its batteries last a long time, but a battery treated the way little Timmy's RC car treats its batteries needs to be replaced after a couple of years.

(Dr. Tisko surprised me. I was just hoping for a few minutes of on-camera interview, but it sounds like he's planning on showing us a demonstration or two. This could be cool. )

Because this is non-profit and amateur and all that, and because I really don't know what I'm doing yet, I'll definitely share these video segments with the community as soon as they're finished.

Thanks ahead of time for the information, guys.

 

Whew -- you guys saved me from looking like an idiot in front of potential interviewees then. *reads more* (The professor at UNO already knows I'm an idiot -- I'm not worried about him. )

I googled for Panasonic NHW-20 and didn't find much. It looks like these Prismatic modules are self-contained sets of 6 cells with some battery-management electronics inside. It sounds like it'll be even harder to get information about the contents of those modules... but I'll try anyway. Do we know what kinds of cells are inside those modules? If those cells are available as separate products, they might have data sheets.

Maybe I should try to email Panasonic customer support and find out.

I have a bunch of 9000 mAh NiMH D cells I was going to use as a visual aid. I guess I can put those away... X__X

Hmm...on even further analysis, it seems NHW20 is the model name for the current generation of Prius. Previous models were NHW10 and NHW11. http://www.autospeed.com/cms/A_2357/article.html

So "Panasonic Prismatic NHW20" just means the battery in the current-generation Prius. Hmm...

 

Hmm... New Car Features... it sounds like I need to sign up for access to Toyota's technical document library for a day. I can do that. Do they make it difficult to download entire documents for future reference?

I just spoke with the parts department at Old Mill Toyota. He said the entire HV battery pack is listed at $4823.41, and he doesn't show any items for one of the 28 individual batteries by themselves. Basic math tells me an individual battery costs $172.26. This makes sense: my fancy industrial 9000 mAh NiMH D cells cost $15.00 each, and I don't think they can tolerate anywhere near 100 A of charge/discharge current.

This is interesting stuff. I wonder if that flat-plate design has anything to do with the battery's higher current capacity, in much the same way as an automotive lead-acid battery with lots of thin, flat plates is capable of such huge current for cranking the engine.

(Or maybe I just don't know what I'm talking about, and my normal NiMH D cells would take that much of a beating just fine, as long as I didn't use wimpy little wires to connect the battery to power.)

So my targets for Dr. Tisko's interview should be:
* see the basic chemical mechanisms that make a rechargable battery work
* talk about which parts of that process can degrade, and how those are affected by overcharging, leaving a battery flat, charging too fast, discharging too fast, etc.
* talk about how the battery's structure (thin flat plates instead of cylinder-shaped plates) allows the battery to tolerate faster charging and discharging

--Spence

 

Thanks Xevious. Hopefully a .torrent should be forthcoming in the next couple of weeks. (You might want to edit your earlier post, by the way, and add asp to the end of your link.)

From what it sounds like, this won't be a pure interview. I'll introduce him, establish his position and expertise, and then things will be teacher/student from then on. You're right, though: I should learn as much as I can about this before wasting someone's time.

I think I already have the basics down, though: http://www.valence.com/BatteryEducation.asp

Apparently there's some kind of barrier material which keeps the postiively and negatively charged portions of electrolyte separated. I think he mentioned something about dramatic things happening when the negatively and positively charged portions of electrolyte combine all at once, so I don't know. I think there's some magic happening in that little orange tube in the flash animation on that site, though, and that things aren't nearly as simple as that tube makes it seem.

(So I think it's not so much that he's agreed to an interview, I think it's that he agreed to teach a mini battery chemistry class for me. That makes me extra worried about wasting this man's time.)

--Spence