2005 battery replacement from newpriusbattery.com

I ordered some cheaper electrical insulating gloves on Amazon and plan on wrapping my tools in electrical tape. I also watch lots of videos and prepare myself mentally for the risks. I plan on not reaching over an open battery, for an example, but having a way to go around it.

All that is probably overkill to most people. But I prefer to err on the safe side.

 

Many people don't use any protection at all. But the warnings are because it is dangerous if you (a) don't know what you're doing or (b) make a mistake. I have had lots of high voltage things explode next to me, and it is not fun. If you want to be safe, use gloves and goggles along with insulated tools.

 

The high voltage risk is real, at least until you have a crystal clear understanding of when there is no high voltage risk... Always better to start off as safe as possible... This post of yours is a good example of you figuring it out. As you get more comfortable with arming and disarming the high voltage nature of the pack, you'll better understand why more experienced people don't use the gloves. But be patient and keep being as cautious as possible until you're certain you can be safe without the gloves.

 

The HV cables shouldn't be getting any voltage, unless there's a problem (or you really didn't disconnect the 12V, you really didn't pull the safety plug, and you accidentally turned on the car all at the same time.) If they still get "half the voltage" with the plug removed then there would be a major problem. I would still treat the plug with respect, just because there's a very, very small chance they could carry battery power even with the 12V disconnected and the safety plug removed. And a chance is a chance no matter how small. But it is very very unlikely.

I'm the kind of guy that takes a Multimeter with me and will check those to make sure they don't have any power to them.

 

Think about it. You have three places where power is disconnected. The two main contactors (I believe Prii have two main contactors and one charge contactor) and the service plug. Interrupting the circuit in just one of those places makes 0V at the cable on the outside of the battery. To get full voltage you'd need both contactors closed and the service plug installed. To get half the voltage there would have to be a short from the middle of the battery to the case, which would be a major problem.

Yes, treat the battery always with care. There is always a very small chance a closed up battery could shock you. But the main danger is once you open up the battery.

 

All the modules, even with the safety disconnect disconnected, still have energy.

If you take out the safety plug, then go lick the bus-bars, you're gonna have a bad time...

 

¿Because of residual voltage left in the capacitors? Good point.

 

No because of the actual energy stored in the battery module themselves. And the bus bars are exposed. Between each module is 14.4v. That will give you a buzz, but won't hurt. But if you're using a torque wrench with a 12in handle, and short between modules far apart, it could be 100v+.

 

Oh. I read too fast and didn't see "bus bars." He was asking about the main cable coming out of the battery even before disassembly of the battery itself.

 

Yes for those main connectors, you do have cap charge in the inverter. Step 21 in our manual specifically says if you are a ninja and got to the point of removing the battery plate within 10 minutes of disconnecting the safety plug, then sit back and relax for the 10 minutes so that residual charge goes away. I am sure most people don't even read it, or just say "I don't need to do that".

 

Where did you order your batteries from? Where did you get the balance charger from?

 

Disclamer. I'm also new at this and haven't even seen the inside of a Prius battery in person. The drawings I made are not to scale and may be way off as far as orientation goes, not to mention colors and such. But this is what I understand. Maybe someone else with more experience can chip in and correct me please.

So let's see. A cell has around 1.8V. There are 6 cells in a module, or about 8.4V:

Two modules in series is a "block." That's what the car reads to see if part of the battery is failing.

Then you have 28 modules, or 14 blocks, bolted together in series producing around 235V, with the service plug installed of course. Not only that, but any place where one battery is connected to the other is a point that could short out if connected to any other connection, depending on how many modules or blocks you short one to the next. It could be 33V, 50V, 84, 168 or so on.

But not only along the battery could we have this problem of shorting out. There are high power cables that run back to the contactors and BMS stuff at the end of the battery. Now as long as the contactors aren't closed (either because the 12V is connected and the car is turned on or because they are stuck down) there shouldn't be any voltage past them into the place the main HV cables plug into the battery itself from the outside, except for 10 minutes or so after turing off the car due to capacitance, as @2k1Toaster brought out.

However, where ever the cables come in will have high voltages. (Pic from another PriusChat member.):
View attachment 59522
But the service plug (terribly drawn) should separate those components a bit. There still is a chance of shorting out on the cables connected to the contactors, service plug, battery, bus bars, etc. But the voltage is less now. Plus one half is now no longer in an electric circuit with the other half making some of things no longer shortable without making two shorts.

But you also should note that there are other wires going from each block back to the "BMS". Of course they are insulated, but any damage to them or if "unplugged" from whatever they are plugged into could open up a chance of a short or place to be electrocuted as well.

Once you unbolt and remove all the modules and keep the terminals separated (not touching), you won't have any more high voltages until you put it back together.

 

Hybrid Automotive installation instructions recommends you use a multi-tester to double check where those cables attach to ensure there's no voltage left in them after removing the orange safety plug. Once you see 0.0v from those two points it's safe to remove them. And while there's almost no way the pack can produce high voltage with the safety plug out, this double checking practice makes sense in terms of redundancy.