Why the On-Board Charger Matters for Your Miata
You have selected the motor, battery, and controller for your Mazda Miata EV conversion. The last piece of the puzzle is the on-board charger (OBC) — the component that converts AC power from your wall outlet into DC power for the battery pack.
Without a properly matched charger, your Miata's 35 kWh battery pack will charge slowly or not at all. With the right one, you plug in when you get home and wake up to a full "tank" every morning.
How an OBC Works
The on-board charger takes AC electricity from a standard Level 1 (120V) or Level 2 (240V) outlet and converts it to DC at the voltage your battery pack requires.
Wall Outlet (120V/240V AC) → OBC → DC (350V for a 350V pack) → Battery Pack
The charger communicates with the battery BMS via CAN bus to optimize charging current, monitor temperature, and stop charging when the pack reaches full capacity.
Charging Speed: 3.3 kW vs 6.6 kW for Miata
| Charger Power | Charge Time (35 kWh pack from 20% to 100%) | Home Outlet Required | Best For |
|---|---|---|---|
| 3.3 kW | ~8.5 hours | 120V or 240V | Weekend toy, occasional use |
| 6.6 kW | ~4.5 hours | 240V (NEMA 14-50) | Daily driver, recommended |
| 10+ kW (dual OBC) | ~2.5 hours | 240V 50A+ circuit | Track car needing fast turnaround |
For a Miata used as a daily driver with a 35 kWh pack, 6.6 kW is the sweet spot. It fills the pack overnight on a standard 240V outlet and does not require expensive home electrical upgrades.
Matching Voltage to Your Battery Pack
The OBC must output the same voltage as your battery pack's nominal voltage:
| Battery Voltage | OBC Output Requirement | Common Miata Config |
|---|---|---|
| 96V (LFP: 32 cells) | 96V charger | Budget builds |
| 144V (LFP: 48 cells) | 144V charger | Mid-range conversions |
| 350–400V (LFP: 112–128 cells) | 350–400V charger | Performance Miata builds |
CMVTE offers on-board chargers compatible with all three voltage ranges. Confirm your battery pack voltage before selecting a charger — a mismatch will prevent charging entirely.
Physical Placement in the Miata
The Miata's engine bay is tight. The OBC should be mounted:
- On the firewall — common location, away from heat and moisture
- Under the false floor in the trunk — keeps weight in the rear, improves balance
- Alongside the motor controller — if using a common mounting tray
Average OBC dimensions: 300 × 200 × 80 mm, weight ~5 kg. Ensure adequate airflow around the unit — air-cooled chargers need ventilation, while liquid-cooled units can be sealed in a compartment.
FAQ
Can I use a Tesla or Nissan Leaf charger in my Miata?
Yes, with modifications. Tesla Model S chargers (6.6–10 kW) are popular for conversions but require CAN bus decoding. CMVTE chargers are plug-and-play with our battery packs and controllers, reducing integration work.
Do I need a 240V outlet at home?
For a 6.6 kW charger, yes. A 3.3 kW charger can run on 120V but will take ~8+ hours for a full charge. A 240V NEMA 14-50 outlet (same as an electric dryer or RV) is the standard for Level 2 EV charging.
Can I use public charging stations with a converted Miata?
Yes, if your OBC supports J1772 (the North American standard for Level 2 AC charging). Most CMVTE chargers are J1772 compatible. DC fast charging (CHAdeMO/CCS) requires a separate fast-charge port and is not standard on conversion OBCs.
Does the OBC need CAN bus communication with the BMS?
Yes — strongly recommended. CAN communication lets the BMS tell the charger to reduce current when cells are cold, stop charging when full, and log faults. CMVTE chargers are CAN-compatible with our BMS.
How does charging speed affect battery life?
Charging at 6.6 kW is gentle on a 35 kWh LFP pack (~0.2C charge rate). Faster charging (10+ kW) generates more heat. For maximum cycle life, 6.6 kW is ideal for daily charging.
Choose Your Miata Charger
Browse CMVTE's Chargers collection to find the right on-board charger for your Miata EV conversion.
Not sure which charger matches your battery voltage? Contact our team with your pack voltage and capacity — we will recommend the correct OBC.
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