Hot-rodding the Toyota MGR

[Astro]

Originally Posted by Cyruscosmo

...I like the idea of placing one small board on each battery and daisy chaining them together. Fewer wires, points of failure and less hassle all around. Plus if one board does not respond it is easy to change out.
...

The Low Cost BMS does that, there is a thread here on EcoModder all about it.
It's the one i am going to use.
Small board mounted on top of each cell, daisy chained comms using opto's for isolation. A master display for mounting in the cabin that shows high and low cell voltages and temperatures, also total pack voltage.
A charger output to control the charger to achieve a top balance on each full charge.
Load resistors on each cell top module to slow the rate of charge on individual cells to allow the lowest voltage cells time to catch up and achieve a top balanced pack.

There are several members using the set up in their cars with good results.
With a BMS reliability is the number one consideration, it being cheap is just a bonus.

[e*clipse]

First qualification: I haven't read the whole thread.

Issues that bother me:
1) Isolation. What is the rated voltage? Yes, there is one. Remember, we're talking about 650V here. Many isolators, etc have voltage limitations far below that.
2) GND is local - the cell's local ground, I assume. This is ok, BUT data must be completely isolated from GND. (see below)
3) Dout is near the cell's voltage. That is fine when we're talking about cell 1. how about cell XXX - the one near 650V??
4) Any safety for the balance resistor's control? If it locks on, any sensor or override? Lee Hart has some excellent suggestions about this.

In one of my basic "how to convert an EV" books, it makes the very wise suggestion that the ENTIRE drive train's HV system is completely isolated from the frame. This book was written for relatively simple 144V DC conversions. Any detection of a frame to battery/drivetrain connection shuts down the main contactor. This is kind of like ground fault detection, but helps prevent a "hot" chassis. It's imperative that the BMS doesn't form this connection.

I'll pass. I've gone through that learning curve.

I'm sorry I don't have any better suggestions or alternatives. I do like that it prevents the spaghetti wiring, which (believe it or not) is all over my Leaf battery pack.

- E*clipse

[Cyruscosmo]

Thank ya for the pics FreeBeard

Yes my friend is in the Duval area and I am in the Woodinville area, although he just got married a week ago so he is out of the tinkering game, for a while anyway. Gotta keep the wife happy. They are planning a new house with big shop so I got my fingers crossed for him.

Yes I seen an exploded view of those units and there was a cross piece bolted to the case and then a couple rubber mounts at the ends of the cross piece.

I got some ideas on how to mount that thing in place based on the pictures I have seen, but until I get one in my hands I am unsure just how the ideas would pan out.

You know... I could have sworn I read every page of this thread and I do not remember seeing those other pics the first time round...

I think my mind is leaking...

Cyruscosmo

[Cyruscosmo]

Originally Posted by Astro

The Low Cost BMS does that, there is a thread here on EcoModder all about it.
It's the one i am going to use.
Small board mounted on top of each cell, daisy chained comms using opto's for isolation. A master display for mounting in the cabin that shows high and low cell voltages and temperatures, also total pack voltage.
A charger output to control the charger to achieve a top balance on each full charge.
Load resistors on each cell top module to slow the rate of charge on individual cells to allow the lowest voltage cells time to catch up and achieve a top balanced pack.

There are several members using the set up in their cars with good results.
With a BMS reliability is the number one consideration, it being cheap is just a bonus.

Thank Ya Astro

I had not seen that thread yet. I am going to start reading that thread tonight. !

Cyruscosmo

[freebeard]

Yes I seen an exploded view of those units and there was a cross piece bolted to the case and then a couple rubber mounts at the ends of the cross piece.

You wouldn't have a link or picture for reference would you? I found a Lexus in a parking lot and tried lying on the ground and sticking my camera underneath but I didn't get a useable picture. If they saw me they probably thought I was bugging their car.

That cross-member sounds like just the ticket. I also need to pick up the three big orange cables.

[Cyruscosmo]

Originally Posted by e*clipse

First qualification: I haven't read the whole thread.

Issues that bother me:
1) Isolation. What is the rated voltage? Yes, there is one. Remember, we're talking about 650V here. Many isolators, etc have voltage limitations far below that.
2) GND is local - the cell's local ground, I assume. This is ok, BUT data must be completely isolated from GND. (see below)
3) Dout is near the cell's voltage. That is fine when we're talking about cell 1. how about cell XXX - the one near 650V??
4) Any safety for the balance resistor's control? If it locks on, any sensor or override? Lee Hart has some excellent suggestions about this.

In one of my basic "how to convert an EV" books, it makes the very wise suggestion that the ENTIRE drive train's HV system is completely isolated from the frame. This book was written for relatively simple 144V DC conversions. Any detection of a frame to battery/drivetrain connection shuts down the main contactor. This is kind of like ground fault detection, but helps prevent a "hot" chassis. It's imperative that the BMS doesn't form this connection.

I'll pass. I've gone through that learning curve.

I'm sorry I don't have any better suggestions or alternatives. I do like that it prevents the spaghetti wiring, which (believe it or not) is all over my Leaf battery pack.

- E*clipse

Isolating the main pack from vehicle ground is first on my list. I have been bit by a case grounded winding on a 480 motor and that is as close to flying as I ever wanna be again. Lucky for me it was from one hand to the same arm.

Just a curiosity question, why not link the individual BMS boards to a controller with a light fiber? The plastic ones are cheep and "Non" conductive spaghetti sounds much safer. The batteries already supply the power for the board and you can use the same fiber for communication both ways right?

Yes I know all the ends will have to go to one control box but the total bundle would not be much bigger than my finger. Or you could make a few smaller control boxes that handle say ten cells each.

Just thinking out loud...

I got an idea for your "One unit per wheel" setup.

Instead of paying for a solid spool to be made, you have access to a lath and mill right? Make a shaft with a drive line flange on it like what the unit has already.

Working in from the flange you make an area on the new shaft for the oil seal then an area that is a close fit to the inside diameter of the carrier bore at the outer bearing. Next you have a hole perpendicular through the shaft that is the same diameter as the spider shaft then another area that fits tight inside the opposite carrier bearing and maybe a bolt on cap that rides against the other seal.

So what you do is remove the drive line flanges and dismantle the case. Next you remove the ring gear and pull the spider gear shaft. Remove spider gears and bushings and the side gears and bushings.

Now you install the new shaft with single flange to whichever side you want to drive and slip the spider gear shaft back in place. The "differential" part is now removed for single drive axle connection to one wheel. And you don't have to mess with splines.

Cyruscosmo

[Astro]

Originally Posted by e*clipse

First qualification: I haven't read the whole thread.

Issues that bother me:
1) Isolation. What is the rated voltage? Yes, there is one. Remember, we're talking about 650V here. Many isolators, etc have voltage limitations far below that.

It uses opto isolators. So you would just have to ensure the electrical isolation of the one you use is appropriate to the pack voltage you are using.

Originally Posted by e*clipse

2) GND is local - the cell's local ground, I assume. This is ok, BUT data must be completely isolated from GND. (see below)

As with item above, uses opto isolator so no sharing of grounds etc. The two wires from the data out of one cell provides a voltage to drive the led in the next cells opto. So the opto's isolation rating is the cell to cell isolation rating providing the layout is appropriate and the opto pins are well separated from other components.

Originally Posted by e*clipse

3) Dout is near the cell's voltage. That is fine when we're talking about cell 1. how about cell XXX - the one near 650V??

With higher voltages would come an increased attention to layout. On large Ah cells there is more than enough room to keep things well separated. A 650V pack is probably less common than a 144v pack and so the builder would (i hope) be aware of the higher isolation requirements of anything they built.

Originally Posted by e*clipse

4) Any safety for the balance resistor's control? If it locks on, any sensor or override? Lee Hart has some excellent suggestions about this.

There was some discussion in the thread as to how best to implement this. Some were talking about adding fuses. I have the LED and resistor in parallel with the load resistors so i get a visual indication of when the cell is being loaded. Then there is the master module which monitors the each cells voltage and turns on the error led if there are any problems. If the car is unattended (charging) it wouldn't be difficult to wire up the error led output so that it sounded the car horn or something equally noticeable.

[Cyruscosmo]

Originally Posted by freebeard

You wouldn't have a link or picture for reference would you? I found a Lexus in a parking lot and tried lying on the ground and sticking my camera underneath but I didn't get a useable picture. If they saw me they probably thought I was bugging their car.

That cross-member sounds like just the ticket. I also need to pick up the three big orange cables.

It is one of the parts breakdown lists from Toyota. The search for the part number shows a bunch of other suspension parts as well. https://www.google.com/search?q=G105...w=1237&bih=875

I ran onto a picture from a salvage yard as well that still had it bolted on but I can not find that one at the moment. That particular one had already sold when I called them.

Cyruscosmo

[freebeard]

Thanks. The exploded drawing with part numbers is more useful anyway.

This is a comparison picture from post #75 that may interest your friend.



Edit:
e*clipse -- This may be of interest to you.

32910J COOLER ASSEMBLY, OIL, No.1. COOLER ASSY, OIL; KOREA SPEC; KOREA SPEC&TOWING PACKAGE-3500LBS; TOWING PACKAGE-3500LBS; TOWING PACKAGE-WITH(3500LBS)

http://www.lexussouthatlantaparts.co...rimLevel=19115

[Cyruscosmo]

Originally Posted by freebeard

Thanks. The exploded drawing with part numbers is more useful anyway.

This is a comparison picture from post #75 that may interest your friend.



Edit:
e*clipse -- This may be of interest to you.

TRANSAXLE ASSY, HYBRID VEHICLE. Fits: LEXUS RX400 WAGON, STANDARD | Lexus of South Atlanta Parts

Thank Ya FreeBeard

That gives me a better idea of the size of the gear box.

And as soon as I get my hands on one... I too will have one!

Um... Yeah

Cyruscosmo