[brian_]

That's a lot of rubber, and it looks like a solid car to work with.

Getting the suspension up to date...

View attachment 125807

By "up to date", do you mean "completely replaced with something unrelated to the Beetle", or just "new shocks and bushings", or something in between? I see CV joints (a good start ), but while detail is hard to see what is there looks like original Super Beetle semi-trailing arms (and struts in the front).

 

[brian_]

Don't understand how (or why) the Tesla LDU will play nicely here.

The classic Tesla Model S/X drive units are logical for conversion of original rear-engined vehicles, simply because they place the motor behind the axle line. It's still not a trivial fit.

 

[brian_]

So, I was curious to see what's needed, beyond rear lawn mower engine logically replaced with Tesla LDU, and confirmed my suspicions on what's needed to keep from shredding the sheet metal with the power levels:

Ah, that's the concern. People having been engine-swapping Beetles and multiplying their power for decades, so while this is a legitimate concern it's not specific to EV conversion or the Tesla components. I knew a guy in high school who built a Beetle that would (briefly) lift the front tires off the line on a drag strip. Still, a Tesla SDU would be a more rational match. If the Chevrolet Bolt drive unit isn't too wide, it would be even better (for packaging and mass distribution).

I suspect that the massive front battery pack is as much of a structural concern as the drive unit.

Most of the features shown in the video have nothing to do with handling increased power, and according to the description only minimal bracing of a subframe to the stock structure has been done; nothing forward of the frame horns. It even has the stock suspension design (with just springs and shocks changed).

 

[brian_]

Lifting the front wheels off on a stock bug (especially with the cantilever a small block Chevy creates, for instance) is very different than lifting all that front battery off with instantaneous full torque from a DU that I'm guessing weighs about the same as the original engine/transaxle. It's like hitting the chassis with a huge sledgehammer.

Absolutely... although this thing won't lift the front tires (and the high school Beetle had a 2.0L VW 4-cylinder boxer). The point is just that a non-rusty Beetle won't fold up just because you put in a lot of power and sticky rear tires. Be careful about structure, yes, but this isn't new territory or unworkable.

The handling of the resulting vehicle is going to be questionable, if only because the major masses (motor and battery) are beyond the axles. It's essentially the opposite of the optimal vehicle configuration, which is mid-engined.

 

[brian_]

What are your thoughts on a Tesla type pack in the floor? The seats are up on 4” pedestals as it is. Cut out the tunnel and box everything in.

The tunnel is the structure of a Beetle floor, acting as a backbone frame. Since a Beetle body shell is separately constructed from the backbone and floor, and can be separated from the floor, you could build an entirely different frame and floor, complete with suitable points to mount front and rear suspension, and put the Beetle body on that. The new frame could be designed to accommodate a battery under the floor, but then you have two choices:

1. the entire floor is too high, so you either lose headroom equal to the battery pack thickness or raise the whole car up by that thickness (which is what Tesla and some other EV manufacturers do, usually in "SUV" style vehicles so the height isn't so noticeable), or
2. the floor has steps in it so the front seat footwell remains and the battery is entirely behind that and shaped to fit where it can stick up (like a Nissan Leaf).

Alternatively, you just build some boxes under the seats, in which you can fit a fraction of a usable battery in small modules ("shoebox" sized, not Tesla-sized).

There's a reason that even the smallest Tesla model is so large - they need the space to carry enough battery in one layer of modules, even using the entire area between front and rear drive units.

 

[brian_]

Shoebox modules just tossed his 600HP out the window.

It would take a lot of shoebox modules; using 3P4S 2.5 kWh modules a 108S pack would be 36 modules and about 90 kWh (nominal), which is what a Jaguar I-Pace carries and could be pushed hard enough to burst at 600 hp (the I-Pace is rated at 400 hp).

What matters is the total capacity, not how many or few chunks it is split into, and the Beetle isn't going to carry enough battery for 600 horsepower anyway. The one in the video linked earlier has basically two Chrysler Pacifica Hybrid batteries worth of modules (32 kWh)... not 600 hp there, either.

 

[brian_]

Which makes my point that a performance LDU a waste of money and weight...the M3 performance seems like a better choice all around, including physical track width.

A smaller drive unit makes sense, but since the idea is to use the stock suspension, something with the motor behind the axle line fits better than one with the motor in front (like the Model 3 rear unit) - Tesla units with the motor behind the axle would be the small Model S/X induction unit, or the front (not rear) Model 3 drive unit (which has an induction motor), or the related newer Model S front unit. I don't know if there is any hobbyist or aftermarket support for use of these units outside of the OEM installation.

It should be possible to turn the Model 3 rear unit around to run in reverse, as has been done with the original Model S units, but I haven't looked into the details.

 

[brian_]

Thoughts on the lg chem super cells from ev west?

The term "super cells" is bizarre: they're modules (not individual cells) and there's nothing "super" about them. I assume that you are considering the JH3 modules (which LG Chem builds for standby power systems in buildings, not EVs), not the no-longer-available 16S1P modules.

My comments from another thread:

I had not heard of a "JH3" cell or module, so I did a quick search...

An LG Chem catalog suggests that JH3 is the "Energy" (rather than "High Energy" or "Power") variant in their range of cells for large energy storage systems. It may not be intended for use in a vehicle, as it is intended for discharge rates under 1C. Based on this catalog, the 7S 63 Ah JH3 module appears to be one of two used in LG Chem's smallest residential energy storage system, the "48 V" RESU3.3. The other RESU models may use more of the same modules in parallel. The catalog shows that stationary ESS and automotive applications are distinct.

Whether this is the same cell construction as used in EVs or not, the JH3 modules being sold by EV West at 3.22 Wh/USD (or USD $312/kWh) is a 7S (26 V) 63 Ah module; it is not the 16S (60 V) 43 Ah module used in the Chrysler Pacifica, and not even built of the same cells. The Pacifica module is designed to thermal management via a bottom plate, but it is not apparent whether or not there is any thermal management provision in the JH3 module, although the general construction is similar. The JH3 module is a recent addition to the EV West website.


At 63 AH, a 98S pack to run near the 360 V typical of current EVs (and thus suitable if using a Tesla or Nissan motor) would require 14 modules, adding up to 275 lb (125 kg) - plus structure, enclosure, wiring, etc - for 22 kWh. That's a relatively small but usable capacity in a relatively light pack, compared to a complete salvaged EV battery.

 

[brian_]

Old lg cells sure looked like an easy solution. What are people using now for high current draw? Not concerned with range at this point.

Among non-competition automotive applications, the place where high power output relative to battery size (or energy capacity) is needed is in hybrids: they need to put out enough power to drive the vehicle, despite being small.

When the energy capacity required is really small (a classic hybrid that can only move a few blocks on the battery alone) nickel metal-hydride (NiMH) is still viable - Toyota still uses it quite successfully.

When more energy is required, for plug-in hybrids (and the logic would apply to short-range EVs), lithium-ion is used, but in specific electrode chemistries for power density (at the expense of energy density) and with sufficient cooling that it survives. That is a reason for the popularity of Chevrolet Volt batteries in relatively high-performance DIY conversions: in addition to being plentiful, and having been around for a while, a 16 kWh Volt battery can put out 120 kW for at least 10 seconds at a time even by GM's conservative ratings. The LG Chem modules built for the Chrysler Pacifica have been popular as well: plug-in hybrid power capability, and while the Pacifica Hybrid is rare compared to the Volt, the modules (new) were sold by various suppliers. There are other plug-in hybrids, although none are as common as the Volt and none of their modules are as available as the Pacifica modules were.

When the supply of Pacifica modules was cut off, EV West apparently went looking for something else they can buy and found the JH3 modules. They have apparently found them suitable at high C-rates; my concern is that this is not endorsed by LG Chem and this isn't even the ideal choice from among the ESS product line for high discharge rate. Maybe they'll work at repeated sustained high discharge rate, but I'll bet EV West won't warranty them for that.


The other solution is simply to use a big battery. Any cell technology is limited in its discharge rate relative to its capacity, so if you double the battery size you get double the power capability, even though you don't need the energy and don't want the weight or bulk. It's not a coincidence that when two Tesla models have the same motors, if one has higher rated power it also has a bigger battery. You might hope for a Model 3 Performance with the less expensive and lighter standard-size battery, but they know that won't work so they won't sell it to you (and they have more mercenary reasons as well, of course).


There have also been companies offering high-power cells for drag racing applications. Maybe they are still operating; they're certainly not relevant to reasonable street-driven EVs.

 

[brian_]

Thought this was diy forum.

It is. Don't judge from one member's comments, but also keep in mind that it's a fundamentally technical hobby.