# Prius Pack



## Guest (Mar 27, 2010)

As promised, here are the photos of the puked prius batteries. Be very careful. I could have lost the entire EV messing with this stuff. 

Messy car but it should clean up just fine. Stinks. 

Pete 


Go here for all the photos. 
http://greenev.zapto.org/prius


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## TheSGC (Nov 15, 2007)

WOW. I do know that Prius Packs need very special charging specs, and a lead acid charger will blow them up, I just expected maybe a little pop, not a BANG. 

Man that just sucks. Any pictures of the EV damage?


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## Salty9 (Jul 13, 2009)

What chemistry does Prius use now? I had heard they used NiMH.


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## Guest (Mar 27, 2010)

Actually the pack by it's self charges up just fine with my Quickcharger. It is when it's put into parallel that the pack will over charge. Yes I thought maybe just outgassing to relieve the pressure. But I was totally wrong. No damage to the EV except some crap from the batteries when they blew. Yes if you have a look on the web page I posted you can see some grey crap on the LA batteries and windows. I even got some stuff on my steering wheel. Damn crap sprayed everywhere. Hard to take good photos of the stuff in the car in the shade. 

Pete


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## TheSGC (Nov 15, 2007)

Salty9 said:


> What chemistry does Prius use now? I had heard they used NiMH.


Yep, all current Prius's use Ni-MH packs, and those need very special chargers. The Prius never fully charges or fully discharged the pack, so it lessens the change of a light and sound show.


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## Guest (Mar 27, 2010)

I will take a photo of the melted top of one of my LA batteries. It was melted by the cardboard burning. Got it out fast but not fast enough to save that one battery. Battery is still good but out of warranty. Not usable because of the hole in the top. Taking stuff out to clean here in a few. 


Pete


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## Salty9 (Jul 13, 2009)

You might try a quick-and-dirty patch job using hot glue to scab a resistant plastic over the hole. I would test both the hot glue and plastic using battery acid tho.


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## Guest (Mar 27, 2010)

I built the pack up so it will not fully charge when using my quickcharger. Works perfect by it's self. I do know that they need special charging but the larger sized pack insures tha the pack was not fully charged but the quickcharger would shut down when it thinks it's fully charged. Like I said, it worked perfect until I put the pack in parallel with the regular pack and at that point the charger over charged the tiny pack. Ooooop's. I will stick with what is known to work. 

Pete


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## Guest (Mar 27, 2010)

Salty9 said:


> You might try a quick-and-dirty patch job using hot glue to scab a resistant plastic over the hole. I would test both the hot glue and plastic using battery acid tho.



I will just replace the battery. Thanks for the tip.


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## MN Driver (Sep 29, 2009)

Every battery has its limits, sorry to see that you found the limits of your pack. The Prius packs(or any NiMh prismatic) will bulge at the beginning of an overcharge but it seems yours have gone far beyond the bulging stage and burst. NiMh cells do not charge well by voltage termination in a quick charge scenario or CC/CV like lead-acid and lithium and need dT or dV charge termination if charged quickly, or at the very least temperature monitoring. The problem with NiMh prismatics is they don't like overcharge at all which is something that cylindrical NiMhs can take just fine if they aren't allowed to overheat, so by the time any standard NiMh charger sees the dV it's overcharged and bulging already and same with monitoring temperature. The Prius uses a voltage reference when regenerating but it will never charge the pack completely and its reference voltage for end of charge occurs in a very safe point well before being fully charged which prevents overcharge.

Prismatic NiMhs are tough to manage if trying to get them charged to full SOC without the proper system in place to make sure there is nothing bad happening, it has been done successfully by someone in another forum but an Ah counting shunt with a PIC was used, typically with a current limited so that charge time takes about 16 hours cutting off at 236 volts(which at a low enough rate will top off the pack with enough time but must have a well capacity balanced pack or overcharging issues occur) with 8 fans blowing on it constantly and careful monitoring when the pack was first being used to make sure that the pack wouldn't get warm or have other issues.
I agree, don't play with batteries if you don't know how to work with them, Prius packs are very picky about how they are charged and charging them at lead-acid rates in the standard CC/CV method is asking for trouble unless things are done very conservatively.

Sorry to hear about your pack, good to hear lead-acid pack is ok, your car is okay, and that you are okay. Sucks to have a learning experience like this, it's a good thing you woke up and decided to investigate or things likely would have been much worse.


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## Guest (Mar 27, 2010)

> it's a good thing you woke up and decided to investigate or things likely would have been much worse.


Oh no, I was woken up by the popping of the pack. I can't imagine how loud it really was to sound like it was in the same room I was sleeping in. I bet I woke up some neighbors too with that noise. I always check around if I can't find something immediate. Always. I learned to check around a long time ago when I was real young. Folks smelled smoke but could not find a fire in the house anywhere. My dad and mom were persistent and my dad finally found a fire within the walls of the hot water heater room. It was still small but could have killed us all. This was long before fire alarms were mandated for new homes. Hell, they did not even exist back then. Just persistent hunting. They knew something was wrong. So did I but I did not know what. I found it fast. 

Pete


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## Guest (Mar 27, 2010)

I know that these batteries must be charged with special charging techniques but by building the pack larger than 96 volts I found that the quickcharger would charge up to the expected voltage of a 96 volt pack then shut down as soon as it saw the required full charge expected. It worked fine charging the pack by it's self. But not when inserted in parallel and charged. The pack alone must be higher than a LA battery pack and when the charger reaches it's expected voltage it will shut off. Since that was long before an over charge the pack along lived being charged with the quickcharger. But only in parallel did it go into over charge mode. It was seeing the LA pack too. 

Anyway I agree not to play with this sort of thing. It could have been far worse. But those batteries really let out a bang when under pressure like that. Had they not been held under pressure I am sure they would not have let out a bang but just caught fire and I would not have know till it was far too late. I am glad I was woken up. 

Saved my EV 

Removing batteries now and cleaning it up. 

Back later. 

Pete


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## Mesuge (Mar 6, 2008)

I think a year or two ago Nikki the podcast personality, has basically written off a whole Prius as her PHEV mod based on additional toyota NiMH packs went explosive, she even inhaled some of the toxic stuff and checked in hospital..


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## EVfun (Mar 14, 2010)

May I offer a little theory on this?

Nimh batteries won't accept a constant voltage float charge. Apparently, even the absorption phase of lead acid charging is to close to that for their liking. The issue is that Nimh batteries have a voltage drop when they get fully charged. A voltage drop when you are trying to maintain a constant voltage causes an increase in current. This little spiral gets out of control with the Nimh batteries taking almost all the current from the charger. They clearly aren't large enough for that!


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## Guest (Mar 27, 2010)

EVfun said:


> May I offer a little theory on this?
> 
> Nimh batteries won't accept a constant voltage float charge. Apparently, even the absorption phase of lead acid charging is to close to that for their liking. The issue is that Nimh batteries have a voltage drop when they get fully charged. A voltage drop when you are trying to maintain a constant voltage causes an increase in current. This little spiral gets out of control with the Nimh batteries taking almost all the current from the charger. They clearly aren't large enough for that!



I agree, it went into spiral mode and just went ballistic as you can see. I do see what your saying. When I charged the pack alone I never let it get into the float charge but the settings I have on my quickcharge are supposed to shut it off when the bulk charge shows CC. CC meaning charge complete. One of the settings I have is set to float when the main is done. So it should have stopped charging but did not get to the point where it should have done so. I guess it got into that destroying loop. Lessons learned. 

Pete


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## Guest (Mar 27, 2010)

Lost two batteries. Too much junk got into the battery so I will just replace them. I also found a few batteries that have low specific gravity.


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## Guest (Mar 30, 2010)

Back on the road again after a fair cleaning and I replaced three batteries. Two lost one bad. I think I may need to replace one more. We shall see. Anyway the drive went well and I had power for longer than with that one toasted battery. I am going to try to make it to work here in a few days. I may be able to but still need to do some distance checking. 

Pete


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## Bottomfeeder (Jun 13, 2008)

That's quite a charred battery! I'm glad the problems were relatively minor. You still have your EV!


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## Guest (Mar 30, 2010)

Bottomfeeder said:


> That's quite a charred battery! I'm glad the problems were relatively minor. You still have your EV!


Sure do! Took it for a spin yesterday. Doing another drive today to determine if I have another low battery. Maybe a few cycles will bring it up a bit. I don't drive it as much as I'd like so the batteries tend to be on the weaker side because of storage and a few cycles usually brings it up a bit better. 

Yeah that battery was toasted by the cardboard under from under the prius battery that I put there to keep them from touching. Damn thing caught on fire and I had to tear it out fast. But not fast enough to prevent damage on two batteries. Arrrrrg. Cars fine and so am I. Car runs fine too. 

Pete


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## Wirecutter (Jul 26, 2007)

gottdi said:


> MY MAIN PACK IS OK.
> MY EV IS OK.
> I AM OK.


Sorry for your loss, as they say, but kudos on the quick action that kept the situation from getting even worse. Looks like fear is a pretty powerful motivator, huh? Glad to hear that you're okay, and that the losses, while significant, aren't as bad as they could have been. Those photos tell a pretty scary story.

-Mark


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## Guest (Apr 2, 2010)

Thanks but the loss was not so bad. I did loose those prius batteries but it is not big deal on that. I did loose two main batteries but got them replaced and I replaced one other battery that was pretty much a dead one but not from the accident. I am glad I woke up and investigated rather than ignore the sounds. I did act quickly. Easy to do. I work good and calmly in situations that are emergent. It is a good aptitude to have in the emergency room. 

Pete 

Pete


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