Bamboo GT AT 50km Range Project

Undervoltage cut-off module arrived at last.
Connected it up with a variable supply and its works well. Have set disconnect to 30V and reconnect to 32.1V.

Looks like a fairly hefty 20A mosfet switch and cuts off voltage even at no load (multimeter only)-So all good.

I will make up a blank pcb 150mm by 50mm to mount the cut-off module and the 40V to 12V converter and mount this vertically across the enclosure.

 

Great job!
I've done ride with my five. I was on carbon gt and she was on bamboo with new battery. Both on AT 7"
I'm 73kg and she is 60kg.
17km my carbon showed 48% while bamboo 86%..
So, I'm pretty happy the result.
Can't wait when you finish yours and give us some field test figures

 

ABS Enclosure finally arrived from USA - have had a struggle laying out every thing in that I want .

ABS is very tough yet still flexible so ideal for an enclosure under a board. Battery packs fits very snuggly inside enclosure so should not move around. I will put a few velco strips from battery pack to enclosure bottom to make sure

Mounted ESC directly to bottom of enclosure with a cut-out for heat sink to be exposed to outside.
Then second ESC board on top of power board - then a new insulated layer for BMS to sit on ( with air gap for thermal insulation - but all of the mosfet heat is directed to heat sink on bottom layer View attachment 2640 View attachment 2641 View attachment 2640 View attachment 2641 )

Starting to fit all the bits in and wire it all up - taking it carefully and slowly to avoid any issues

 

This is the psychotiller enclosure that can be fit to suit different lengths? Looks good so far.

 

Finally finished fitting bits inside enclosure- a bit crammed ! - photos tell the story

For mounting enclosure to board - I used a 12mm x 10mm EPDM rubber seal ( from Clark Rubber ) - this has a dual function - first to provide weather-proofing and secondly to take up the slight concave nature of the deck though the seal. This was glued on the enclosure in a single strip - the rubber seal is very flexible and compressible. I glued it every 100mm or so with closer spacing on corners. You need to get a particular glue to stick EPDM to ABS. Most glues do not stick ABS at all. I used a two part plastic weld glue from Bunnings which provided a very strong bond

Next is the scary part - to drill mounting holes through the board. I drilled holes in the enclosure lip first (10 in total) then stuck rubber seal on - then continued holes through rubber strip - then put board upside down and put enclosure on top of the back of the board - then drilled though the enclosure holes and through the deck . I figure doing this would get the holes at the right angle for the concave sections of the deck. Countersink top of deck holes a bit and then used 5mm x 38mm countersunk stainless bolts with nyloc nuts.

For the motor leads - I used 8mm rubber grommets to provide weatherproofing

 

Next is the powering up stage - probably the most dangerous stage so had a fire extinguisher on hand just in case!.

Connected battery -ve and ESC plug to BMS - then plugged in BMS balance lead plug ( after triple checking that the right voltages were on the right pin)

Then put a 2A fuse in main ESC power +ve lead ( which would blow quickly if any fault) and gingerly plugged in main ESC power plug. No motors connected at this stage

No smoke -so turned on ESC via switch - red light flashed on switch so all good. Then grabbed remote to see if it would pair with board - all good with remote connection good and cell voltages indicated on remote OK via secret menu.

Then power down , remove power fuse and connected motors. Power up again- turn on switch , pair to remote and pulled trigger and wheels spun . bit of a relief as there are many possible points of failure .

Completed mounting enclosure to deck ready for street test. There is approx 70mm ground clearance for bottom of enclosure (with AT wheels)

Still waiting on a few auxiliary bits ( voltage display etc.) but main board drive system was complete and time for street test

Battery was at about 40.2V when started - did three legs on a ride total approx. 40km with final voltage 35.8V ( under load) . Voltage sag going up hills was 2-3 % only .

Will do a proper range test next weekend from fully charged.

 

update on range testing
Yesterday run from Burns beach to trigg and return 39km .At finish resting battery showed 64% with voltage sag on hills 2/3% max

Today -no rain again -so a run in late afternoon around river lap and a bit of exploring in Belmont ,East Perth and Applecross.
Speed around 25km/hr average .quite a bit of carving and a few hills.This run is with AT wheels.

Starting 41.5V 100%
5.3km 98%
9.8km 98%
14.6km 96%
19.7km 91%
29.2km 79%
32.9km 68%
37.8km 48%
44.6km 34%
47.9km 28%

All readings under load

So range much as expected.
I would think that AT range to fully discharged (32V on Evolve system) would be at least 60km and probably 80km with street wheels.

 

One last thing to do is to test Evolve battery as I intend to reconfigure it to a 3S 3P 12V battery for general use.

So- I fully charged Evolve Battery to 42V and used the 8 ohm 100W resistor as a load ( approx. 4.5A load) and recorded volts , amps , wh every five minutes. The test lasted 95 minutes from 42V to 32V ( Evolve cut-out) . Result was a bit surprising as it came on bang on 7Ah which is nameplate rating- but this is a very steady load equivalent to coasting on flat ground approx. 15km/hr.

Conclusion is that the Evolve cells are reasonable for steady loads but don't have the discharge current capacity for peak demand from board - subsequently the battery has large voltage sags .

 

So pulled the stock battery to bits and seperated the 10 pouch cells.I had another two pouch spare from another project so made up a 3S 4P battery pack with about 12.6V output.

This togther with my 12V/42V double charger will charge a standard board at 3.5A 36V.

I can carry this in backpack to either extend my range a further 15km or to charge another board.
( I can also charge another board from main battery pack 36V outlet)
Have ordered a 3S BMS from AliExpress($4)

Did a 10A discharge test and pack has minimum of 20Ah (at 12.6V)

So the stock battery lives on to serve a another purpose probably more suitable to its discharge capacity!

 

Would you be kind enough to do battery mods for those of us who are willing to pay?

 

Hi Yanzo

What board do you have and what are you trying to achieve?

Cheers

 

Photo of final auxiliary 12V battery.The $4 BMS works a treat.
This completes this project with objective well and truly acheived on ATs .
I have some 107mm ABEC Superflys strret wheels on order so will compare range with these.
Have also put new GTX looking grip tape on board

It is quite invigerating and satisfying to not have to worry about battery capacity even on long rides with added benefit of no sag on hills and acceleration.

Will not update this thread further but happy to answer any questions or queries.

There is a part 2 to my board upgrade to replace the stock motor controller and remote with higher quality replacements (Using VESC and smart remote) but will make new thread for this

Cheers

 

Vescs on their way from Torqueboards Roger, will let you know how they go

 

Yeah -mine arrived today -See my upgrade part 2 thread!
Cheers