Street legal Cafe Racer build.
- Thread starter PK2000
- Start date
Houston, we have a problem!
I carefully inspected the spot welds (pro tip, you can get a sharp probe in the little slit in the nickel tab and measure the difference between the bus plate and the cell), and spent a day or so in denial, fantasizing about easy fixes.... Then had at it.
I used a rotary bur to trim the tabs where they were welded to the copper. A trim removal tool and a hammer actually did a good job of splitting the pack.
In one way this was a good thing, it gave me confidence in the mechanical strength of the assembly. It was mostly the kapton tape that let go.. +1 for the Sikaflex..
Eventually got to this point
All the spot welds are good. Another little confidence booster.. The cells (unsurprisingly) measure the same at this point. So I'll test them individually and find the dud....
Gotta say, those big LFP cells look pretty bloody good at this point..... :-(
I carefully inspected the spot welds (pro tip, you can get a sharp probe in the little slit in the nickel tab and measure the difference between the bus plate and the cell), and spent a day or so in denial, fantasizing about easy fixes.... Then had at it.
I used a rotary bur to trim the tabs where they were welded to the copper. A trim removal tool and a hammer actually did a good job of splitting the pack.
In one way this was a good thing, it gave me confidence in the mechanical strength of the assembly. It was mostly the kapton tape that let go.. +1 for the Sikaflex..
Eventually got to this point
All the spot welds are good. Another little confidence booster.. The cells (unsurprisingly) measure the same at this point. So I'll test them individually and find the dud....
Gotta say, those big LFP cells look pretty bloody good at this point..... :-(
- Joined
- Aug 8, 2022
- Messages
- 1,210
I'm so sorry about that, it must be really frustrating. Did you get the cells brand new?
Yep, they were new.. I have enogh spare cells to rebuild that group, but I'd like to find proof that we have a bad one first.
Disassembly wasn't actually that bad, I'll probably solder them back in.....
j bjork
1 MW
Ouch, that didnt look too encouraging 
I mean, there are a few that are worse than the others. But a lot of them are all over the place.
Is this after a balance charge, discharge and charge? Or is it several cycles?
Do you think you punctured any cells when welding?
I mean, there are a few that are worse than the others. But a lot of them are all over the place.
Is this after a balance charge, discharge and charge? Or is it several cycles?
Do you think you punctured any cells when welding?
The other groups are fine. Charge it up and they all come back up to ÷- 0.025V. But 27 is definitely not fine! I'm working through it cell by cell. Unfortunately, I have another week away.. gonna get one of my guys to keep the testing going. Should have it back together by next weekend...
Battery testing is just about finished. Going to make a decision on what cells to swap this afternoon and aim to get the thing back together over the weekend.
Whilst all that's been happening, I've got the anodising tanks up and running.
Whilst all that's been happening, I've got the anodising tanks up and running.
That turned out great!
Some more pics. I got the oil seals installed and the last step is pressing the output drive flange onto the output shaft.
Its an 8 degree taper, so:
A little bit of heat.
A little bit of MDS grease on the threads.
A tiny drop of green Loctite
Some custom tooling (the thing on the right is a puller that I made up front expecting the worst),
And all the torque she'll take....
Done:
OK, not quite. I still have to do the fill and drain plugs...
I put the first part through the blue dye. It's the motor baseplate, so it's not very visible.
I'm going for that BMW grey/blue. The colour depth is very dependent on surface finish, and time in the bath... Hmm..
I've got one of the battery box sections in the tank now, I'll see how it comes out and make a call..
But what about the battery you say?
After about 10 days of testing each cell there was only one that exhibited some self discharge. It's hard to imagine that it was soely responsible for the results we saw in the whole pack test.
What I decided to do is build a new P group (I had spare cells).
I had some nickel strip, but there was no way known my battery setup was going to spot weld that onto the 2mm copper. So I soldered them in with braided copper:
Not pretty but it went well, a bit of preheat on the copper and <1 second per cell.
I'm waiting for some glue to dry and manually balancing the pack, then I'll repeat the discharge test...
Its an 8 degree taper, so:
A little bit of heat.
A little bit of MDS grease on the threads.
A tiny drop of green Loctite
Some custom tooling (the thing on the right is a puller that I made up front expecting the worst),
And all the torque she'll take....
Done:
OK, not quite. I still have to do the fill and drain plugs...
I put the first part through the blue dye. It's the motor baseplate, so it's not very visible.
I'm going for that BMW grey/blue. The colour depth is very dependent on surface finish, and time in the bath... Hmm..
I've got one of the battery box sections in the tank now, I'll see how it comes out and make a call..
But what about the battery you say?
After about 10 days of testing each cell there was only one that exhibited some self discharge. It's hard to imagine that it was soely responsible for the results we saw in the whole pack test.
What I decided to do is build a new P group (I had spare cells).
I had some nickel strip, but there was no way known my battery setup was going to spot weld that onto the 2mm copper. So I soldered them in with braided copper:
Not pretty but it went well, a bit of preheat on the copper and <1 second per cell.
I'm waiting for some glue to dry and manually balancing the pack, then I'll repeat the discharge test...
j bjork
1 MW
Cool, I havent got around to try anodizing. It would be interesting if you described the steps a little more, and maybe some pictures of the equipment you are using
I've held off posting pics of the anodising tanks because... well.. I've been anodising small parts with some success for many years. I'm confident enough to just lash up what I need for these bigger pieces. That lash up is not something I'm gonna post pics off. Many 30+L tanks of chemicals squeezed into too small an area, with all sorts of nastiness going on.Cool, I havent got around to try anodizing. It would be interesting if you described the steps a little more, and maybe some pictures of the equipment you are using
The internet has many good how to's on anoidzing, go find one.
My tips.
- In the same way that painting should just be called sanding, because that's what you spend most of your time doing, anodising should just be called cleaning. Getting the part ABSOLUTEY SPOTLESS is the single most important step. I have anodised may parts over the years that ended up with one of my fingerprints imortalised in the finish...
- It's easy to get a good result. For most colours, it's hard to get a consistent result. You need to be meticulous for the Blues/reds/yellows.
The exception here is black. Too much black is still black.
- Acid from the pool shop. Use lead flashing for cathodes. Nothing but Aluminium or Titanium in the tank.
- Keep everything cool. I freeze 2L milk jugs and drop them in the tank before I start. Adding 5g/L Oxallic acid makes a big difference, you can get a good result up to a tank temp of 25C.
- Seal in Nickel Acetate, it does a good job.
- Lastly. The alloy you use is important. 6061 anodises nice, 2000 series is hard to get a good result with. You can fix this with a nitric/phosphoric acid dip to dissolve the surface copper/magnesium away, but it's not as good as just using the right grades of Al to start with.
