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KidsWheels
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By BMWi8
#145895
This thread will review upgrades to the Avigo BMW i8 6V electric powered car. Note that a 12V version does exist, but I am not familiar with it.

PHASE 1 - BATTERY RUN TIME UPGRADE
The first thing I noticed was insufficient "run-time". After about 20 minutes of use, the i8 sounded different and was visually slower. Sure enough, checking the LED "power meter" showed only the red LED illuminated. There are 2 main factors which affect this run-time, that being load on the motor and battery capacity (amp hour rating). I cannot easily change the load on the motor, as this is determined by weight of the operator and resistance (both slope and rolling resistance). I can however change the battery to a higher Ah rating!

The battery tray appears to be designed for several different sizes. After taking some measurements I went with the 6VDC 12Ah sealed lead-acid battery by Keyko Japan.

Supplies
1. Wire stripper & terminal crimp tool
2. 2x 1/4" female spade connectors (for 12 gauge wire)
3. 6VDC 12Ah replacement battery by Keyko
4. Phillips screwdriver
5. Rubber bumpers
6. Electrical tape (optional)

Procedure:
1. Remove original battery, 2x phillips screws and black battery cap
2. Cut off red (positive) and black (negative) terminals as close as possible to their ends
3. Strip 1/4" of insulation off each wire and crimp on 1/4" female spade connectors
4. Add rubber bumpers as needed to reduce battery vibration (vibration can shorten battery life). I did the underside of the hold down bar and one end of the battery
5. Install, cover terminals with electrical tape, charge and enjoy over 50% more runtime!

PHASE 2 will be upgrading from 1WD (the motor drives only the right rear wheel) to 2WD.
Attachments
Battery Upgrade 1.jpg
Battery Upgrade 2.jpg
Battery Upgrade 3.jpg
Battery Upgrade 4.jpg
Battery Upgrade 5.jpg
Battery Upgrade 6.jpg
Last edited by BMWi8 on Sun Jun 11, 2017 4:45 pm, edited 1 time in total.
User avatar
By BMWi8
#145901
PHASE 2 - UPGRADE FROM 1WD TO 2WD

If the BMW i8 attempts to climb the valley between the street and driveway at an angle, the single drive wheel can loose traction and the car gets "stuck". The ability to go through grass is a struggle and use in light snow or ice is non-existant. Time to upgrade to 2WD!

You can purchase replacement motors ($15) from http://rollplay.net/products/view/6v-bmw-i8-silver
I chose to wire the 2nd motor in parallel with the existing motor. As such, the 6VDC battery will see half the resistance and output twice the current. There is risk the relays (HF3FF) on the original control board will not be able to handle this additional current, and overheat. The relay data sheet says version "1C" is rated to 10 Amps at 28VDC or 280W. If I divide 280W by the battery voltage of 6 VDC that gives me almost 47 amps... using a DC clamp meter I did record a very brief spike of up to 36 amps from the battery when stalling both motors, so maybe it will be fine?

Supplies
1. Wire stripper & terminal crimp tool
2. male and female connectors and / or solder
3. stranded wire
4. replacement drive motor and gearbox
5. Pry tool & needle nose pliers

Procedure:
1. Cut the majority of wire harness off from new motor, strip and crimp connectors to wire ends
2. Pry off center BMW cap, use pliers to remove cotter pin, remove outer washer and wheel
3. Remove black 1.5" long plastic spacer, ensure inner washer is in place, install new motor and gearbox assembly, re-install wheel, outer washer and cotter pin
4. Use several zip ties (or one long one) to secure gearbox in same manner as original gearbox
5. Depress metal tabs inside original motor harness connector, remove both contacts, solder stranded wire and re-insert contacts
5. Connect wires, noting that the white wire from the new motor needs to connect to the blue wire of the original motor to allow both motors to operate in the same direction (otherwise you'll spin in a circle)

Observations:
The extra torque handles "heavier" riders easier. Runs through the grass better. Does make a louder noise during turns, as the outside wheel needs to spin faster than the inside... which the motors aren't set up to do.

PHASE 3 will be upgrading to a 12 VDC ESC system... in about a month
Attachments
2WD 1.jpg
2WD 2.jpg
2WD 3.jpg
2WD 4.jpg
2WD 5.jpg
2WD 6.jpg
2WD 7.jpg
User avatar
By Masterjosh
#147654
was just curious if u had any update on your project. I have a 6v Rollplay chevy police truck and the inside guts looks insanely close. everything looks identical, so i went on a whim and just ordered the gearbox as i believe its prob the same, however its odd that on the parts page for the truck my son has it doesn't list the motor/gearbox as a part you can purchase..so i went to the 6v truck non police version and it was there. also curious in what the difference would be if u wired the motors in series instead of parallel as you did? was just curious how things were holding up for you.
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