Beyond our previous exploration of the Leaf drive unit, we’ve recently acquired a Smart ForTwo electric drive unit. This particular unit is quite rare – online resources offer minimal imagery and only sparse specifications, noting its Bosch SMG 180/120 motor and a 55KW power rating. It’s especially interesting due to the SMG 180/120 motor being readily available as an off-the-shelf component. This accessibility should simplify its integration into various vehicle projects. Furthermore, this motor boasts a notable pedigree, having been utilized in vehicles like the Fiat 500e and even powering the front axle of the Porsche 918.
However, the integration design of the Smart Car Electric Drive is notably… basic. This isn’t entirely surprising given that the Electric Drive variant was never intended for mass production. It likely served more as a compliance vehicle for Mercedes, aimed at meeting fleet mileage standards and heavily dependent on EV subsidies in environmentally conscious regions to achieve profitability. For future reference, here’s the donor vehicle’s identification tag:
Let’s take a quick detour to examine the air conditioning compressor within this smart car electric drive system:
This compressor is completely integrated, featuring both DC and CAN connectivity. Internally, it utilizes a scroll compressor mechanism:
and an internal Permanent Magnet (PM) motor:
along with a small inverter mounted at the rear. Is it a particularly useful component for EV conversions? Probably not, unless your specific project requires a 370VDC air conditioning system. Moving on to more substantial components, the integrated charger is a 6.6KW unit manufactured by Lear:
Similar to other components in this smart car electric drive, significant coolant draining was necessary before further disassembly could proceed:
Once the coolant was evacuated, the charger was easily detached with just a few bolts, revealing a neatly self-contained module:
We opted not to delve deeper into the charger’s internals, as our immediate focus wasn’t on activating it. However, getting it operational should be relatively straightforward. It’s worth noting that this charger is responsible for AC-DC conversion only; battery balancing is handled elsewhere within the Smart electric drive system. Next, let’s examine the inverter. Jackpot! A part number is visible! The inverter is identified as an EFP 2-3, manufactured by Continental and also marketed by Zytek.
Further investigation reveals this inverter to be a 235A continuous, 355A peak unit. A few bolts are all that secure the inverter to the rest of the drive unit:
It’s remarkably small and compact. The high voltage (HV) cables likely outweigh the power electronics within. At this stage, we had successfully separated the motor-gearbox assembly from the remaining components of the smart car electric drive. It’s already showing promise – the motor is nicely cylindrical and can be moved relatively easily by a single person.
| Hi Charles! |
After detaching the gearbox from the motor within this smart car electric drive…
…we were left with a truly adorable little traction motor:
The motor’s mounting pattern is quite convenient:
Although, suspending a 32kg motor from those mounting tabs might be pushing the limits of wisdom. The gearbox design closely mirrors that of the Leaf, only in a smaller form factor:
Internally, the gearbox exhibits a very similar construction to the Leaf’s unit:
Finally, we attempted to peek inside the inverter of this smart car electric drive. Initial signs were encouraging:
Notice the pin-style channels, presumably designed to minimize pressure drop in the cooling system. However, the high voltage cable harness is connected…
…using surprisingly large blade terminals! Unfortunately, our exploration reached a roadblock at this point. The inverter housing contained some delicate ribbon cables connecting to internal circuit boards, and it wasn’t clear how to safely separate the housing without risking damage to these cables.
In conclusion, this smart car electric drive unit presents itself as a highly promising option for conversions of smaller vehicles. Its somewhat rudimentary integration is actually advantageous, as all components feature practical mounting points. Furthermore, there’s a reasonable possibility of obtaining datasheets for both the inverter and motor directly from their respective original equipment manufacturers (OEMs). The main drawback is the 55/80KW power output (Bosch’s peak rating for the motor), coupled with 200Nm of torque. This level of power may be insufficient for converting a full-sized car, potentially necessitating the use of two of these units to achieve satisfactory performance.
