Chevrolet Bolt EV Battery Reassembly

voltage and not the low voltage ones and the first one is this x6 connector so we're going to plug it in with its little connector position safety clip and then these next two in order from the middle one out oh come on there we go and then it's the top one on the other side or the front one on the other side and then the one right next to it and then the last one, all good, so those are the high voltage connectors and then we connect the low voltage ones oh, I didn't connect this one ground circuit here, let me do it real quick.

I don't think it will make any difference in this case, but I'm not going to risk it because it might. Okay, so the last two connectors, we have the low voltage one, one on this side is number seven to plug in and the one here is number eight. , it is the last. Now I have to admit that in my deep dive into the 2018 Chevrolet Volt

battery

. I didn't, I'm not sure I disconnected them in the correct order because in the service information I saw the warnings to disconnect the ECM B first when you're taking everything apart. and then disconnect the others, but I didn't see or apparently pay attention to the warning of the correct order in which they should be disconnected, so I'm not sure I disconnected them in the correct order and I went back and watched the video and I didn't.Go back to connect them in the correct order, so it will be interesting to see if I have damaged anything when reassembling that volt

battery

.

Either way, we'll fix it and get it working again here shortly, but I made sure in this case. that I unplugged it and plugged it back in the correct order, a very important thing that's not something I would have thought about and I'm wondering if that's true of anything other than General Motors' LG battery monitoring circuits or not, so Just walk in and smash things, you can actually cause damage and not even realize it. The last thing we need to install is the relay assembly, the contactors on the front of the battery before putting on the battery seal and the front or top cover, we also need to check the cooling system for leaks, I have tools and adapters specials to do that and then once we put the casing on, we have to use what's called a smoke machine, a smoke test to make sure there are no leaks throughout the whole casing assembly because I don't want any moisture getting in. , dust or anything in it for the life of the vehicle and that's one of the reasons I didn't put the Chevrolet Volt battery back together and put the case on it and put it back in the car. yet and I have a video on that because I was waiting for the proper adapters to come out and they have so they will be coming here real soon to put the volt battery cover back on and do smoke tests and check for coolant leaks and then Put it back in the car like this Bolt EV.

Alright, let's take a look at the contactor assembly, the relay assembly, or the battery disconnect unit, depending on whether you're looking in the service manual, training information, or parts manual. There can actually be three different names for the same part, which can be quite confusing, so I like to know how it works. I don't care what you call it, if we know how it works, that can help us. Diagnostics, well let's take a look at that, right on the front of this battery is the high voltage battery disconnect relay center, also known as the battery disconnect unit, unfortunately this whole assembly if something goes wrong with either from the four contactors inside or the resistor, the fuse or the current sensor, you have to replace everything, from what I can tell I could be wrong but I don't see any procedure in the GM service information to replace anything inside here , it's just the whole set, which is a bit strange. because on the Volt you can replace individual parts, it's actually pretty cool, but that's the way it is, but if you've seen any of my previous videos, you know that I like to take apart things that I'm not supposed to take apart. as long as I can still put them back together and make them functional so I've completely disassembled the battery disconnect relay center here or the battery disconnect unit as it's called and we're going to put it back together here looking at the individual pieces inside.

Of this battery disconnect unit there are some important parts that are common to any electric vehicle or even a hybrid electric vehicle. We have some people call them relays, some people call them contactors, but we have two big, heavy duty contactors, we have one. called a negative contactor one called a positive contactor and these are the devices that connect our high voltage battery positive and negative to those two big heavy orange wires that connect to the front of the battery. We have to have something that disconnects the physical contactor. battery, the high voltage of the turi from the outside of the battery, that's the job of these two pieces, we have one for the negative terminal of the battery and one for the positive terminal, so they just sit inside here, we have the one on the negative side which is right here and one for the positive side which is right here, then we have another smaller version of the same thing in a contactor, this one is called a precharge contactor and the precharge contactor always It has a companion preload resistance.

This particular resistor is rated at 80 watts and 70 ohms and is an 80 watt resistor. As cooling fans go, it can get quite hot, but it's only used during the initial power-up of the Bolt EV when you press the power button and it turns on. So before we can close the positive and negative contactors, here we don't just connect the battery to those cables, we have to do it in a specific way so that we don't create arcing or any damage inside these contactors or inside. of the inverter assembly inside or under the hood, so what we do is close the positive contactor first and instead of closing the negative contactor next, we close the precharge contactor which basically does the same thing as the negative contactor, but it does through this resistor, so it will create a low current path for current to enter the inverter assembly where there is a large smoothing capacitor that is used to smooth out the voltage pulsations during acceleration that the IGBTs create.

It's also used to Smooth out the voltage pulsations that the full wave bridge rectifier creates when you decelerate and you have regenerative braking or just power generation when you decelerate so this slowly charges that capacitor when that capacitor charges and when I say slowly I don't I mean more. In a couple of minutes or even a couple of seconds, it's so many milliseconds instead of instantly, but when the smoothing capacitor charges, the voltage level on each side of the negative contactor is zero and it won't be zero until that capacitor of smoothing charges fine if we have zero volts on each side of this contact or we can close it and there will be no arcing and the contactor will survive so the purpose of the precharge contactor and the resistor is to avoid damaging the negative contactor in this case. current, some electric or hybrid vehicles do the opposite, they close the negative and use the precharge on the positive, it doesn't matter which one you do, that's what it does, it charges that smoothing capacitor that they all have. on the inverter okay, so the precharge contactor goes here and the precharge resistor fits right into this slot here and locks it in place.

Now this electric vehicle, like many electric vehicles, will have a fourth contactor and this is called the charging system contactor, so basically what this does is when you plug in your vehicle using a level one charger or a level two charger, the J 1772 compatible charging connector, this contactor will close in place of the positive contactor and allow an alternative current path for DC current to enter and charge the battery at a lower rate than through the two large wires that connect on the front of the battery if you have the fast charger option on your Bolt EV and you connect the fast charger then this contactor is still here but it is not used.

Instead, we will close the positive contactor and let the two large, heavy orange wires pass larger amounts of current to the battery to charge it, so we will use the positive contactor from the charging system if we are using level 1. or level 2 charger we use the large positive contactor to charge the battery when you are using the fast charger then we also have a current sensor and this is on the negative side of the relay assembly, here it measures the current in the negative circuit which is the same as in the positive circuit it is a large series circuit this current sensor has a low resolution signal and a high resolution signal and it depends on the amount of current that passes, what increments they use and so there is a bus bar that passes over there for the negative current negative cable from the battery and that is located here on this other side of this big relay center, so we have four contactors and a resistor.

There is also a fuse that goes into the load. circuit for level 1 and level 2 charging, this is a 40 amp p 450 volt, if it blows apparently you have to replace the whole thing, but if it blows you have a problem so you better find out what's going on there. but that fuse is located here on the passenger side of the relay center, so those are the main components. Now the rest of the parts here are just the little wire harnesses and bus bars to connect all of that together, so let's get them. connected so we have a big bus bar here for the negative terminal so here on the passenger side of the relay center we have our current sensor and the bus bar that connects to the overall negative terminal of our high voltage battery and then he hooks it. to the negative contactor here then we have this harness that feeds current from our plug-in charger to the plug-in charger contactor and then we have another little harness that connects to our positive contactor and the charging system contactor now we can screw these in contactors.

There are no torque specifications for these

bolt

s as they are not really useful. I tried using a torque wrench to measure how much torque was needed to loosen them, but it was so low that I couldn't. I'm not getting a good reading so just hand tighten is all I'm tightening so you know, screw in our preachers contactor and our charging system contactor. You can connect its small wire harness to our charging system contactor. Connect our bus bars to our negative contactor via the preload resistor harness and we have a bus bar for our positive contactor. Well, next we have the general connection of the positive terminal of the battery to the contactors and this will connect the positive contactor to the positive terminal of our large high-voltage, goodbye, a fact that we just reassembled now.

I'll have to remove it before putting it back on the battery, but I just want to show you where everything connects. I think it will help you understand how it works. then we have our overall negative battery terminal here on the other side which connects through the negative contactor and is located here, so these two are the inputs, we have our positive and our negative, the negative goes through the sensor. current going to our negative contactor which then once that negative contactor closes, we have a negative terminal output right here that sticks out of the front of the battery and goes to the two big, heavy orange wires on the front of the battery and then we have our positive battery terminal. which connects to the positive contactor and once it closes, it feeds current to the positive terminal here which connects to our big, heavy orange wire under the vehicle, just like that, there are a couple of screws that hold the current sensor in its place and then I have four nuts for the whole diffuser and connect it to the positive of the charger and one that connects to the negative of the charger and the third or fourth one here takes the negative from the outside negative terminal that is on the big heavy orange wires, OK?

So those are all the components, but we have to control them somehow and the ECM B that we just installed on the battery is in control of these, so there is a low voltage harness right here that needs to be installed, we have a connection that we have to be able to read the current from the current sensor, we have to be able to control all four contactors, so we have this harness that powers up below, okay, we are completely reassembled, so let's look at the general operation one more time, we have the negative battery from the overall battery here, positive battery from the battery here, so that's our roughly 350 volts nominal.

This negative terminal must be able to connect to this negative output terminal and is an open circuit between those two points until we close the negative contactor. The positive terminal here needs to connect to the positive output terminal here and that is achieved through this positive contactor, but asI mentioned before, we can't just close both contactors and have everything work correctly, there is a surge of current that would go. in the inverter assembly capacitor which unrestricted without a resistor could damage it and therefore we need to slow down that current, furthermore that rush of current could cause these contactors to arc which can damage them , so we close the positive contactor. first, then we close the precharge contactor, which is just a mini negative contactor, through the precharge resistor here to step down the current, we wait for that capacitor to charge once it's charged, then we have zero volts on each side of this negative contactor.

Then we can close it and release the pre-charge contactor and we are ready to go now, when we connect the charger to the vehicle and remember that there are two ways to charge the vehicle, we have the level 1 and level 2 plug-in chargers which are relatively slow to charge the battery which could be a level 2 charger when i plugged it in it said it would take nine and a half hours to charge once we got this new vehicle those chargers send alternating current to a special box under the hood called a charging module or something then it has a special connector on the front of the battery that has a positive and a negative terminal that connect right here, the negative terminal here just has a wire that comes to this negative terminal of the battery that connects them through the negative contactor and establishes a connection to the battery modules, the positive terminal here through this fuse then has a wire that goes to our charger contactor which when closed bypasses the positive contactor through this wire and charges the battery but at a lower current rate and when we use a level one or level two charger we still use the contactor precharged in that entire sequence of events because these two terminals are still connected to the inverter and that capacitor still needs to charge every time you start the vehicle now that capacitor discharges when you turn off the vehicle because there is a resistance in parallel that will discharge it well and then the second way to charge the vehicle is with the fast charger and that is where we use these two terminals and the two positive and negative contactors and the contactor precharged precharged contactors are always used to supply larger amounts of current much larger terminals on the positive and negative contactors than on the precharged contactor this is for small amounts of current to charge the battery, this has a power rating of 40 amps and the charger contactors.

I don't know if you get 15 amps or 30 amps or whatever when you plug in a level one and/or level two charger. I forgot to look. That's above, but use these smaller terminals when you use the level one or the level for the larger terminals here are for the fast charging option and I haven't looked up what that current is either, so if any of you viewers know how much current is used. in any of those or any of those three charging options put it in the text box or comment box below let me know and I appreciate you ready to go back to the front of the battery and then we press or We try this is the cooling system to make sure there are no leaks and then we put the seal and the cover on and we smoke test the system to make sure there are no leaks in the case so let's put this back on next before putting the battery in .

Relay center back on I want to connect the cooling system pressure tester because it has to stay pressurized for several minutes to check for leaks so the cooling system pressure test procedure has this connection, same two adapters which we use when we use vacuum to pull. The coolant comes out of the cooling plates, except now we are going to use them to pressurize the system and it tells us to pressurize it to no more than the pressure at the reservoir cap which I looked at is 5 psi or 35 kPa Cape. connect these adapters to the coolant fittings here on the front of the battery there's one there's the other put the clip back on so we can pressure test it and it doesn't come off then we use a standard radiator pressure tester we're just going to get to five psi, but we need to be able to plug this into that little outlet there, so there's an adapter to test the radiator cap that's going to go on and then there's an adapter to go to the small size that's on the connector on the battery. we'll put that in next and then there's an adapter to connect this connector to the battery connector okay here we go now we pressurize it to five psi there's a lot of area here so it's going to take a lot of pumping to get us to five it's okay, we're sitting at five, right there, four and then we'll keep an eye on it and see if we have any leaks, okay, let's put this relay center up.

Okay, put the relay center back. I have to remove this bus bar if you remember from the battery disassembly video this bus bar is right in the way of removing a nut from the relay center here let me check again actually maybe not it could be ok so There are some

bolt

s holding the center of the relay through the bottom battery box here, oh I know why we have to remove that bus bar. We won't be able to put a torque wrench on the nut to hold it in place, so let's take that back part. Look how we are with our pressure here, it looks like it's holding up well, yeah we'll remove that bus bar and then our overall positive cable from the battery to the contactor, oh no we can't do that yet, we have to reduce the torque.

First, the center of the relay to the battery box, okay, so those are the three center bolts, the nuts, now we can put the bus bar back on, get it working well, now we can put the overall positive battery cable on , they connect our low voltage harness. We can put our general negative cable as if it were missing a bolt. We will find. Let's check that the cooling system pressure is still maintained. Okay, we're going to connect our negative terminal, which is our output and input here on the front of the battery. next we'll go back and squeeze all of these here in a minute and then our positive terminal output right there, okay.

I'm missing a bolt. I found the missing bolt for our negative strap here. I know the torque on these battery bus bars, but I don't know the torque on these contactors and our terminal outputs, let me look it up, okay, since it turns out they're all the same nine Newton meters or 80 inch-pounds. Okay, let's check the pressure test of our cooling system yet. Waiting and all the service information tells us is that they need to warm up for two minutes so we've been well over two minutes so I think we can safely say we don't have any leaks the next.

The part we put in is the large x three electrical connector on the front of the battery. Here I'll get our cooling system pressure tester out of here. Okay, we're almost done here. The last part we must place is our cargo. electrical connector when we use the level one or level two charger, so this comes here on the passenger side and it has four bolts that hold it in place to achieve this torque at the same nine Newton meters 80 inches pounds and then there's just A few of us have the two cables, the positive and negative DC of our charger, which we must connect inside the relay.

In the center, the orange wire with the black stripe is the DC ground, the orange wire without the stripe is the DC positive. nine Newton meters 80 inch-pounds, okay, what an adventure: completely disassemble this battery from the Bolt EV. research all parts. Find out what each piece does here. label everything. Discover electrical circuits. It's a lot of fun and the next thing we should do. What I do is I put the orange cap over the center of the relay and screw it on and then we have the seal around the entire outside side of the battery and then the cap, the top battery cap that goes next, but I'm just here. and there's no one to help me put that cover on, so you're going to have to imagine we're putting the cover on and I'll do a separate video on smoke testing the Bolt EV battery case for leaks using evaporative emissions. smoke test machine and we'll do the same thing with the 2018 Chevrolet Volt battery over there because that's what we're expecting, that's what we were expecting with that too, so let's just do a quick overview of the whole system. battery and then we'll finish well, starting here at battery module number one, overall negative of the entire battery.

I'm going to take my DC voltmeter and connect it directly to the negative terminal. So if I go over here to the positive terminal, I get forty point five seven volts and what I'm going to show you is that this whole battery is in series, so we have forty volts there if we go to the next battery; It is the positive terminal, now we are 40 volts higher, 81 points. and if we go to the next battery, which is battery module 3, then battery modules 1, 2 and 3 Israel are forty volts each, now we are at one hundred and twenty-one volts and then if we go to the battery module for two , is the positive terminal 162. volts, that is, four times forty volts approximately, then the battery module five: its positive terminal and this time we do not add forty volts, we add 32 more volts, that is, 194 195 volts approximately, for which is half the voltage of our battery and that's where our service disconnect lever and The connector is under the back seat and when we disconnect it we split the battery in two so we have 195 volt batteries in series between yes at that point so now if we plug it in and come over here to the positive terminal we now get the 235 volts that we would expect okay and then if we go down to the positive terminal of battery module 7 we'll add another 32 volts and now we have 267 volts and then we go to the battery module eight with another 40 volts, now we have We are at 308 volts on the positive terminal of the battery module, mine at another forty volts, now we are at 348 0.9 volts and finally in the module of battery 10 into another forty volts and the overall voltage of our fully charged system is three hundred and eighty-nine and a half volts. at this point and fully charged the battery before taking it out, which I shouldn't have done.

It's safer to leave it at a lower voltage, but it is what it is, so I hope it helps you see how these batteries are in series with each other. and then if we go to the contactors here now, if we connect our multimeter to the battery side of the contactors, then there is the negative, here is the positive, there is our 389 volts, just like we measured the battery, but now, if we go next to exit. from the contactors we have zero volts and that shows us that the contactors are open and that is the same as the zero volts that we would have here on the front of the zero volt battery because the contactors when they are in working condition should be open every time the 12 volt system is disconnected, but we have the positive contact or the negative contactor of the application, the recharge contactor and the charging system contactor, any of which do not open as they should when the 12 volt system is disconnected It could still give you full system voltage or half a connection to the battery that would still read zero, but it could be a little more dangerous, so I hope that helps you understand the function of the battery contactors, the relay center, whatever they want. call it in relation to the drums themselves, well this has been very interesting, it's been a lot of work, but I've really enjoyed it and I hope you do too, thanks for watching.