Bamboo GT AT 50km Range Project

Eugene

Interesting choice of cell. Agree that is superior to HG2 .
I found a 18650 comparison site and below are curves for both 5A and 10A discharge comparing VTC6 and HG2

Also a picture comparing VTC6 and MJ1

Both VTC6 and MJ1 leave a bit in the tank for a 3.1V cut off from an Evolve BMS. Even dropping cut off to 2.9V would improve things vastly and probably not affect battery life too much.

Cheers

 

Have ordered following bits and pieces from China

• Spot Welder
• Kapton hi temp tape
• Heat shrink covers for each 18650 cell ( to avoid shorts cell-cell if cell insulation fails due to vibration or stressing)
• Heat shrink for whole completed battery pack
• flux pen
• heat glue gun and sticks
• nickel strips 0.15mm x 10mm
• 12awg flexible hi temp wire
• 0-48V/12V adjustable DC converter ( for lights and remote operated bell)
• 18650 battery holders ( not sure if I will ultimately use these)
• 8 ohm 100W resistor ( for load discharge testing - approx. 5A which is my total current cruising on flat ground at 25km/hr)
• Panel meter showing DV V Current ( with a 100A shunt) , Power and Wh)
• In-line 40A fuse holders ( using auto micro fuse)
• 18650 cell tester

Probably take a few weeks for all to arrive

Still working on 18650 cells , final cell configuration and enclosure

 

Looking at best way to wire the ten cell packs up
Anyone have any thoughts on pros/cons for the two options ?
I am leaning to Option 2 primarily to go with " in-line" series connections between cells ( except end cells) and also it brings the 0V connection to same end of pack as +42V ( less wire resistance)

 

I went with option 1 because less flex points so less width. But if you building an enclosure that is less of an issue.

 

Oh and in regards to battery case width, you can fit 2 18650 cells end to end but I needed to trim the plastic around the bit inserts to make them fit

 

Hi mate,

The seller I purchased cells from has ebay store: supersports600
His name is Yass - 0411191352
keeppower@optusnet.com.au
He does all those battery tests and graphs himself and was very helpful.
Plus delivery was done pretty much next morning . I've purchased batteries a few times from him already.

Cheers

 

U can do option 2 with braided copper wire as the series connections between each pack if you are concerned about flex

 

Intend to use nickel strip spot welded for cell banks ( 4 cells) parallel connection but with solder connection mid cells- and use either soldered flexible braid or flexible wire as series connections. In other words no nickel strip series connections between cell banks. This should provide flex ability .

 

Eugene
Thanks for that - Will contact him and see what he can do
Cheers

 

There are people like me that we say nothing but support you. I have many faith in your work!

 

Thank you guys!
Cheers

 

No worries mate!

 

Spot Welder arrived yesterday (787A)
7 days from ordering to delivered to front door in Perth -not bad
tried in on the strips that came with it on a dud 18650 cell and it seems to work fine
Put current to 50 with 2 pulses
May need to crank the current up for 2 x 0.15 thick strips

 

That was quick. Did you order from CN?
I've ordered mine on 21st April- supposed to be shipped from AU - still hasn't arrived..

 

Eugene
Yeah from CN AliExpress
Cheers

 

Looking at a new battery enclosure from 25" Monolith Low Pro • Psychotiller | Electric Longboard Components | California
This will need to be 50mm deep to accommodate two battery rows height. Should be no issues with ground clearance
The enclosure length can be trimmed to suit after all gear is mounted.
I will get a new "proper" weatherproof , metal 2.1mm charging socket to replace the plastic junk that comes with the board.
Will reuse main power VESC board and mount heat sink plate on outside of enclosure for cooling.
Also will reuse Evolve BMS in new battery pack to ensure remote still works!

I noticed the stock battery does not have a main fuse in GT version- bit perplexed as to why not - they must be totally reliant on overcurrent shutdown through BMS for motor shorts or other faults. Think I will add one in new battery bank +42V lead as potential short circuit current from new battery bank will be substantially higher.

Also - have ordered dean connectors ( main battery power connectors ) from ebay for testing batteries discharge aH capacity.
I will measure the actual capacity of stock battery before removing to see how it stacks up to nameplate capacity of 6.5Ah

 

Have decided to go with an 10S 8P configuration in a double row arrangement - this will provide very low current demand per cell which should lead to maximising the cell Ah capacity above 31V Evolve BMS cut-off and long life on the cells.
The picture below shows what I am looking at for the cell series connection.

Any comments or suggestions?
The copper braid rating is 65A and double 10mm x .15 nickel strip should be 15A or so.

Going with MJ1 cells - should get approx. 3Ah from fully charged to 31V based on average demand of approx. 1.25A/cell (10A total motor demand for cruising at 25km/hr) so total battery capacity of 24Ah which should get me 50km range. Only downside will be extra weight of approx. 2.5kg above stock battery .

Battery enclosure on-route from California USA

 

Looks very good mate! - I would go 8p as well but didn't want to modify enclosure. So for this project I'll see how 4p vtc6 works.
Bamboo GT is my wife's board and she doesn't even understand why I am doing this upgrade at first place. She recons stock battery is fine for her )) which is clearly not.
I ride carbon gt which is kinda better- I get 22km on AT. Plus I came up with portable charger wich uses bunch of my lying around 6s - 5000-10000mah batteries from other hobbies I have. So 30 min stop for a brake- 3a charge gives me extra boost.

 

My welder arrived including 8 x 2 strips. Started to assemble packs... I'm going nuts with welding- doing like 16 double shots to each cell. Plus double everything up with stock strips (the once came with welder) on top of it ) just in case.
I've used epoxy glue to hold cells together- both sides- rock solid.

 

Here is my first portable charger box with 6000mah 6s lipo - has a 6s BNS for it then step down to 12v and back again to 42v by Icharger. Works great- I was even using it while I'm riding- pumping 3a .