DIY Electric Car Forums banner
1 - 2 of 2 Posts

·
Registered
Joined
·
10 Posts
Discussion Starter · #1 ·
I recently got my hands on a set of modules from a 2019 e-tron, but due to some confusion at the dealer, I only got 31 of the 36 modules in the battery. The e-tron pack has two sections (see pic below) a 31 module main section and a 5 module upper blister. I bought a used/damaged pack and the dealer has either managed to throw away the upper blister of my pack or has been mixing and matching batteries during warranty repair (despite new packs only be supplied as a complete unit). At this point, I'm not sure I want to know the answer, but I'm only going to be able to get a 31 module pack either way.

Rectangle Slope Font Automotive tire Engineering


I still got a good enough deal that I'd like to keep the modules, but now I have a dilemma. I was planning on using two tesla SDUs, but I only have a 93s battery. With a 93s battery and 240v SDU cutoff, I'd hit the pack cutoff at a cell voltage of ~2.58v + sag. I think I could bump the minimum cell voltage from 2.5v to 2.6v (or higher) in the BMS, but I don't have a good feel for how much pack capacity I would lose. The pack would be 82.5 kwh nominal and I am trying to keep 240+ miles of range.

I'm trying to think through whether I should just stick with the 93s battery, or whether I should be looking for an extra e-tron or i-pace module. They are starting to show up on sites like second life ev and both use the same, or similar, 60AH cells in a 4P3S configuration. The only difference in the modules seems to be the BMS connector.
 

·
Registered
Joined
·
10 Posts
Discussion Starter · #4 ·
I just realized I was mixed up. I was thinking about LiFePO4 voltages (2.5v-3.7v), not Lithium-ion pouch cells. I realized I should be fine with a 3.5v lower cutoff and 4.1v upper cutoff. For a 93s pack that will give a pack voltage of 325v to 380v.

What BMS and controllers are you using? You should be able to set the minimum voltage if it is a custom controller or BMS. If you are using the Audi BMS then you probably need the full pack to keep it happy.
I am planning to use an Orion BMS. Nobody has cracked the Canbus for the Audi BMS.

That dealer sounds a bit shady...

You don't say what kind of vehicle has this 240 mile range target.

Keep your foot out of it at low SoC, stay inside the speed limit at low SoC, avoid mountain climbs at SoC, or limit power at low SoC, and you should be fine, right?
Sorry, I'm actually going to put the battery and motors into a kit car (Factory Five F9 or possibly an 818). The car should have good aerodynamics and weigh 2500-3000lbs. I think I should be able to keep the Wh/mils in the range of 250-300 with calm driving. I think I should be fine with a 93s battery.

The dealer has actually been great, but confused. The shadyness is my frustration coming through. They sold me the pack for $6K and offered a full refund if needed. They just don't have much experience with electric vehicles. What I think happened is that the tech replacing the battery assumed the lower pack and upper blister were two seperate parts because they are easy to separate. When they opened the new battery, which already had a blister (since it is only supplied as a single part), they set the old blister aside. Now, I'm talking to a manager who knows they took the old blister off and that the new battery was installed with a blister. He is assuming that they put the upper blister back in the car because he doesn't understand why that doesn't make sense.

I figure that they either disposed of the upper blister or that it is sitting forgotten in a corner of the shop. If they find it, I'll happily take it. However, I'm still happy with the deal I got for most of a pack.
 
1 - 2 of 2 Posts
Top