DIY Electric Car Forums banner

21 - 40 of 50 Posts

·
Registered
Joined
·
162 Posts
Discussion Starter #22
I got some work done on the hardware for the fuses. It is very slow and fiddly, but I think I am getting there. I am reusing some of the flat bar from the original configuration - I thought it seemed too heavy to be aluminum, and it is indeed copper with some sort of silver plating. Nickel, maybe? Anyway, it was fused for 400amps, so I think it will be sufficient for my needs.

There is not space to put an isolating contactor between the strings, so my plan is charge each string individually and then connect them. The BMS will monitor both parallel strings, so I do not forsee problems with eddy currents as long as the BMS balancing works as advertised. I need to finish up the main leads, which means a trip to the store to get bigger heat-shrink insulation. After that, all that remains to do in the battery box is to make a mounting rack for the BMS modules and run the wiring.

And thankfully I am about a 2 hours drive from the coast, remy_martian. We do get quite a lot of rain, of course, so I am going to be treating all the lumber with a couple coats of deck stain.
 

·
Registered
Joined
·
479 Posts
You're probably 2 doors down from me, lol.

Fingers crossed, after a solid month of this crap (even cardboard boxes in a roofed breezeway are soaked by the damp, then the mold grows on them) it looks like we may get a lull and some sunshine. Tossup whether I liked the wildfire a mile from the house or this.

F.Y. 2020 (not "fiscal year")
 

·
Registered
Joined
·
162 Posts
Discussion Starter #24
Unseasonably nice weather has kept me busy outside, but the forecast is now looking like some shop time will be forthcoming. I got the new signal lamps mounted, and put all the wiring back in split-loom in the back.


I am bummed about having to redo my frame, but better to fix it now. Its a little hard to see, but i need to trim some of the battery box, and move the support for the box closer to the original frame. Once that is fixed, I can hopefully get my modules permanently mounted, which will be exciting.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #25
Well, It turns out there is one thing that I hate more than painting: Stripping paint that you just painted, and then repainting it the next day! It was not actually as painful as I had thought it would be to make adjustments to the frame, and I think I have made enough clearance for the tires now that I can rest easy.

Trimming down the aluminum box was tougher than I thought it would be, as it turned out to be quite thick material. Once the paint is dry, It can all start going back together, and I can get the modules into place.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #26
Those Tesla engineers sure did love screws. Each module has 4 holding it down, 1 holding it from below, and then 3 more connecting it to the various cross-members inside the box.

Also, the first 4 bolts are deep, so they need to be dangled in with a magnetic holder. Anyway, long story short, putting this thing back together is proving to be a big job.

The modules are in now (I am really hoping I didnt forget something stupid that makes me have to take them all out again). It dawned on me that I may need to do another modification to the box lid to allow all the BMS wires through; it ends up being quite a thick bundle of wires. The black wires at the bottom left are just the thermistors, there will be another 84 wires for all the cell taps.

Next day I can get into the shop I will put the bus bars back on the modules to build my 2 strings. I can then work on plugging in all those wires and getting the BMS system working.

Goal #3: Check all the cell voltages with a functioning BMS.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #27
Well, I had a moment of panic as I went to install the plumbing manifolds, and I remembered that they came out after the modules, and should have gone in before them... It took a lot of wiggling, but I managed to get them in without taking out all those damn bolts.

I got a couple sections of hose and some aluminum tubing with the batteries, and that gets my coolant system plumbed to the bottom of the cab. I will maybe run some aluminum tubes along the frame, and then switch to 3/4" radiator hose to connect to the pump and radiator.

I also made the module connections today. I cleaned up the terminals, and put some dielectric grease on them. I dont really have much experience with using it, but the modules had some sore of goop on them when I got them, so I figured that was what it called for.

I was paranoid that I was going to short something out and cause a real mess (you can see my improvised "600v" wrench at the bottom right :)). The included insulators for the busbars were quite thorough, though, and put me at ease.

It appears there was at one point a service disconnect or something in the middle, but it must not have made it into my box of extras.

One of my modules has dropped more than the others - but it stopped falling - possibly after I disconnected the BMS board? Anyway, my two strings are at 158.35 and 158.60. I swapped the position of 2 of the modules to get the original voltages and resistance values to line up as well as possible. I will probably try and charge each string on its own once the charger is online, and try and bring them up to the same voltage before the final hookup. If my math is right, I think the higher string would try and push about 5 amps into the lower string if I connected them right now.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #28
Well, F#@&. Time to pull out all the modules. I started checking voltages in the harnesses as I was getting ready to start wiring the BMS, and I got really weird readings on some of the pins. Turns out the wires were coming loose from the bus bars.

It looks to me like the connections were made with some sort of spot-welding process. I am not sure if the storage conditions have made things worse, or if handling the modules was the problem, but it is not an isolated problem.

All the connections seem to be corroding, and simply scraping at them causes them to separate. I only have a 25w soldering iron, but I was able to tin a corner of one of the aluminum tabs. I am going to try ordering a bigger soldering iron and see if I can get the connections back in shape that way.

It might be possible to only remove every other module, but it is still a pretty aggravating setback.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #29
Now that I know the drill, taking everything apart was not actually that bad. I checked all the BMS harnesses, and found failures on 11 of the 12 modules. The blue wires were the worst, 8 of 12 were bad. None of the black or yellow wires had failures. I will probably add solder to all of them, and then cover them with dielectric grease to prevent any more corrosion.

I am still waiting on my new soldering iron, so I got a little work done on the charger today.

I mounted the J1772 plug and got a start on the wiring. I will need to install my HV junction box soon so that I can start routing the wires from the dash.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #30
Well, turns out more power was not enough. The solder just forms a bead on the surface, and will not wick. I poked at the one connection that I thought I had made, and it just popped off too.

I am loathe to try applying more heat with a torch, so I have decided to try and go the mechanical route. I ordered a set of M2 taps, and 100 tiny bolts and tiny ring terminals. This means I will need to drill and tap 84 holes in 2mm aluminum without bridging any of the plates, breaking any cell-level fuses, or over penetrating the bus bar and damaging a cell or the coolant ribbon... It does not sound fun to me either...

I am going to try and make some some sort of jig for the drill bit that only lets it protrude ~2mm, and hopefully there will be enough space behind the bars to start my threads with a plug tap. At least the aluminum will be easy to work with, I guess.
 

·
Registered
Joined
·
54 Posts
Hi Carl,
I recommend to observe that connector:
121206

it happened to me (and a friend) that it produces a lot (!) of heat until failing some day.
By the way, I like your conversion.
Markus
 

·
Registered
Joined
·
162 Posts
Discussion Starter #32
Thanks for the heads up. The charger should only be pulling about 10 or so amps, right? What size of wire did you use? If you zoom in on the picture you can see that I clearly did not have the right sort of crimping tool... I was going to solder the wires in before assembly. I used 10 gauge wire, which should be good for 30 amps, and will hopefully pull enough heat out of those spade connectors.
 

·
Registered
Joined
·
5,256 Posts
... Turns out the wires were coming loose from the bus bars.

It looks to me like the connections were made with some sort of spot-welding process.
Presumably ultrasonically welded: the wire is pressed to the bus bar and vibrated rapidly to friction-weld it in place. The cell wires are similarly welded to the cells and to the bus plates; no one solders or electrically welds wires like this in production applications.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #34
Presumably ultrasonically welded: the wire is pressed to the bus bar and vibrated rapidly to friction-weld it in place. The cell wires are similarly welded to the cells and to the bus plates; no one solders or electrically welds wires like this in production applications.
I looked at the wires under 80x magnification and they look like they have been hit with some sort of tiny, futuristic panini press :) Any thoughts as to why these connections would fail like this? It seems like the fact that they have been stored outside their sealed, moisture controlled enclosure for 10 months could be the root cause of the corrosion... Do you know what material is used to make the cell level fuses? Those connections do not show any signs of being a problem, but they also look like they could be made of the same material as the bus bars. I wonder if simply getting condensation on the copper-aluminum junction was enough to wreck them, and if that is the case, why they didnt just use aluminum wires...
 

·
Registered
Joined
·
162 Posts
Discussion Starter #35
I found the time to get a little bit of work done on the batteries today, and while going through all the modules, I did find evidence that the process they were using was not foolproof.

Seeing all the marks inside here makes me wonder how many man-hours go into assembling a module like this, even with all the state of the art machines I am sure they are using. I am glad I am not trying to build my own modules...

I had thought I was going to have to replace all the BMS wires, but some appear to still be very firmly attached. I sand each connection, and if it seems sounds I am just covering it with grease and moving on. The ones that are loose are pretty obvious.

I drill a 1/16 hole, start a couple of threads with a tiny m2 tap, and then solder on a small flattened ring terminal. I am using a little dab of locktight, and the connections feel nice and secure. I have been covering the adjacent plates with cardboard as I work, and have not had any major mishaps. A little shaving from the drilling did bridge two plates momentarily, but the resultant (tiny) explosion broke the circuit very quickly. :)

I got 5 of 12 modules repaired today, so hopefully I will be back on track pretty soon.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #36
Okay, I finally got everything back together, and verified that I see each cell voltage on the BMS taps. Now, I can finally start making forward progress again. I reconnected the strings, and started working on the thermistor wiring today.

I do not have whatever sort of crimper is used to make the connection on the little pins, so I am soldering each one... I got 20 wires in today, and have another 104 to do :). I have not quite finalized how I am going to route the wiring from the dash and engine bay back to the battery box, so that will have to get sorted out at some point. I want to keep things orderly and workmanlike, and also keep the HV wires as separate as possible from the 12v stuff. I have orange split loom, and will probably also paint any of the gray conduit I use. More to follow
 

·
Registered
Joined
·
162 Posts
Discussion Starter #37
I got the thermistors wired for the second string today, and also soldered the terminals on the first BMS wiring harness.

All that remains for the first string is to plug in all the terminals in the right order and it should be good to go. Another morning's work, and it should be possible to fire up the BMS!
 

·
Registered
Joined
·
162 Posts
Discussion Starter #38
Well, I got the first half of the cell taps done today.

I advise anyone using this system: buy a couple of extra plastic harness parts... turns out once you cram the pins in there, they do not want to come out. Anyway, it is moving along. I put in temporary power wires and managed to connect to the BMS, but it did not display any data. The string I am wiring is connected to the tail end of my daisy-chain of BMS boxes, so I think without power at the first box it is simply not sending messages on down the line.

Hopefully I can wrap up the next string soon and give it a test.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #39
Okay, string 2 is wired.

I hit a few snags, but it went a lot faster than the first one. I applied power to my BMS, and against all odds, the wiring was all correct!

I outlined in red the deviant module. I will have to consider my options for how to charge the strings up independently to get them balanced. It will probably just be a matter of reducing the size of the BMS and swapping around the harnesses...

Anyhow, this feels like a big milestone.
Goal #1 Mount batteries
Goal #3 Check voltages with BMS

Goal #2 wire main contactors to my power switch (which will mean routing some conduit and setting up my HV Box) - is up next
 

·
Registered
Joined
·
39 Posts
Okay, string 2 is wired.

I hit a few snags, but it went a lot faster than the first one. I applied power to my BMS, and against all odds, the wiring was all correct!

I outlined in red the deviant module. I will have to consider my options for how to charge the strings up independently to get them balanced. It will probably just be a matter of reducing the size of the BMS and swapping around the harnesses...

Anyhow, this feels like a big milestone.
Goal #1 Mount batteries
Goal #3 Check voltages with BMS

Goal #2 wire main contactors to my power switch (which will mean routing some conduit and setting up my HV Box) - is up next
Great progress! Assuming you have checked and the cell voltages and the bms agree. If so, why not turn on the balancing function on all the other cells so as to lower everything but the deviant module? It may take a while, since the balancing current is pretty low, but it should work over time and you can play with the BMS functionality and learn how fast things will change. Just an idea. ;)
Bill
 
21 - 40 of 50 Posts
Top