DIY Electric Car Forums banner
1 - 6 of 6 Posts

·
Registered
Joined
·
12 Posts
Discussion Starter · #1 ·
Hello everyone.

Thought I should join up so i have somewhere to ask all my questions, maybe even get some answers lol.

I have a 260z 2 seater and i've just organised the large drive unit from a Tesla Model S P85, I should have it fairly soon. Then I get the fun challenge of fitting it into the chassis.
Fortunately for me, i've also found a post on HybridZ with another guy just up the road from me doing exactly the same into his zed. So I plan to follow his build to some degree.

Along with the motor, im getting the driveshafts and HV cables, Should I be asking for any other parts with the motor from the wreck? Wiring plugs? Coolant line fittings?
Im still researching the parts i'll need, But my plan atm is to use a drop in motor controller such as the one from ZeroEV. Im quite comfortable with the DIY side of things, but I definitely like the idea of plug and play parts to make this easier.

Pictures will come later, I now have the new task of pulling all the unneeded petrol bits out.
The chassis currently has a RB25 engine in it, So its not the first conversion in its life
 

·
Super Moderator
Joined
·
1,352 Posts
Perhaps the air conditioner.

All the valves, Teslas have a fairly complicated and useful valve system the redirects coolant/heat every which way.

All the contactors.

Whatever the Tesla uses for a brake booster perhaps.
 

·
Registered
Joined
·
6,222 Posts
Whatever the Tesla uses for a brake booster perhaps.
Tesla uses a Bosch iBooster; although it is just a brake booster attached to a conventional master cylinder, it's unlikely to be practical to bolt it to a random master cylinder so you would use the whole thing complete with master cylinder and electric assist motor and gear mechanism. If the Tesla one is available that could presumably work, but it doesn't need to be Tesla; they are used by various manufacturers (vacuum boost is becoming obsolete, even with a gas engine) and over 5 million have been made. EVcreate has a list of vehicles that use them, which is certainly not complete; for instance, there is no chance that Honda uses them in two specific models and no others. That list also shows a few other systems as alternative to the iBooster, but the iBooster is probably the best-documented due to people using them in conversions.

I noted this from EVcreate:
"Nowadays there are two versions available of the iBooster by Bosch, GEN1 and GEN2. The GEN1 is typically found in the Tesla Model S and the GEN2 in the Tesla Model 3."​
Anyone using one of these units might want to choose their preferred generation. The also have helpful information about wiring the iBooster.
 

·
Registered
Joined
·
12 Posts
Discussion Starter · #5 · (Edited)
Thanks people :)

So, Looking at batteries and im trying to understand the configuration of the tesla modules.
I know there are 16 modules in a S battery back, with each module being a 74P6S configuration and approx 24v nominal. Are all 16 packs then connected in series to bring the voltage up high?
I've figured out that increasing range is essentially just adding more cells in parallel, but my current understanding seems to say that if I want more range using tesla modules and a tesla drive unit, Id need to bring up the module count a lot, potentially to 32 total modules.
That obviously would be really heavy and take up a lot of space, so much in fact it wouldnt fit in the chassis.
My current estimate is that I can fit 10 modules in the engine bay in replacement of the old ICE engine.

Is there a minimum 'module in series' count thats needed to run a tesla drive unit? I understand that less volts essentially equals less power, less volts is less motor rpm yea?
Or is there some magic step up voltage trickery going on inside the inverter?
 

·
Registered
Joined
·
6,222 Posts
So, Looking at batteries and im trying to understand the configuration of the tesla modules.
I know there are 16 modules in a S battery back, with each module being a 74P6S configuration and approx 24v nominal. Are all 16 packs then connected in series to bring the voltage up high?
Early Model S packs had only 14 modules, while later packs have 16 modules. Regardless of the numbers of modules, all modules have a 6S configuration. The largest-capacity modules have 74 cells in each parallel group, but before that they had fewer cells in parallel; regardless of the number of cells, they all have the same external dimensions. Most of the modules that are offered for sale are from the 85 kWh or 100 kWh packs, which are the 6S74P configuration.

Yes, as with essentially all EVs, all modules are connected in series. In the 16-module Tesla Model S and X packs that means 96 cell groups in series, which is typical of modern EVs (e.g. Nissan Leaf, Chevrolet Bolt). Assuming a nominal voltage of 3.75 V per cell, that's 22.5 V per module and 360 volts for the pack.

I've figured out that increasing range is essentially just adding more cells in parallel, but my current understanding seems to say that if I want more range using tesla modules and a tesla drive unit, Id need to bring up the module count a lot, potentially to 32 total modules.
That obviously would be really heavy and take up a lot of space, so much in fact it wouldnt fit in the chassis.
Range depends on available energy, and if considering different packs using the same cells that simply means that range depends on the number of cells. It doesn't matter what the combination of series and parallel is, as long as there are enough in series for the inverter and motor to operate properly, and yet not so many in series that excessive voltage damages components.

Assuming modules from the 85 kWh pack, 32 modules would means 170 kWh of total stored energy... and yes, it would be an unreasonable amount of battery to carry in a 260Z. Even without a driver or passenger the vehicle would be over the chassis rated weight limit. Why would you need so much stored energy in a 260Z? I wouldn't choose a Z-car for long-range cruising, and extended race track sessions are just not reasonable to expect from a battery-electric car.

My current estimate is that I can fit 10 modules in the engine bay in replacement of the old ICE engine.

Is there a minimum 'module in series' count thats needed to run a tesla drive unit? I understand that less volts essentially equals less power, less volts is less motor rpm yea?
Or is there some magic step up voltage trickery going on inside the inverter?
The power output limit of a battery is in proportion to the energy stored; 10 Tesla Model S P85 modules would safely deliver only 63% of the power of the full 16-module set.
The torque output of a motor depends on the current through it, and the faster a motor turns, the more voltage is required to drive the same current. Since the inverter does not increase voltage, a lower battery voltage means a lower maximum motor speed and less power at high motor speeds, but doesn't matter at low motor speeds.

You don't have to worry about the battery delivering the current and voltage that the motor needs, as long as the battery voltage is high enough for high-speed requirements, because the combination of current and voltage at the motor are not the same as the combination of current and voltage out of the battery - the inverter handles that. The inverter only reduces the voltage from the battery, and increases current in proportion; the inverter does not step voltage up.

Yes, in addition to limited high-speed performance with lower voltage, there is some minimum voltage for the controller/inverter to operate properly. I don't know what that is for a P85, but earlier Model S variants came with only 14 modules and obviously worked with the resulting voltage.
 
1 - 6 of 6 Posts
Top