Bamboo GT AT 50km Range Project

All tested .wrapped in foam and heat shrunk ready to fit in new enclosure

 

I don't think there will be much current at all. From my understanding BMS only monitors voltage of each cell. Charge goes directly to series connection. But just in case I've matched gauge of stock wires 22awg on mine.

 

Eugene
Thanks for that

As I understand it , all charging current is through full series battery cells but when near full charge, the BMS bleeds a very small current (50 mA or so) on individual cells through resistors on the BMS in an attempt to lower voltage of any cells that are too high compared to total battery voltage /10.

If so , no chance of the BMS doing any balancing on a 4P or 8P set up as it would take many days to decease cell volts with such a small current!

Still concerned that a BMS fault has full cell potential feeding it via balance wires.

What do think of idea of putting some 1A PTC fuses in balance leads ?

Also -If you cant buy Evolve BMS - what purpose does 11pin balance lead plug serve.?

Am thinking about soldering balance leads directly to BMS board as you did .

Cheers

 

Going to solder non resettable 2.5A fuses directly to BMS board and join balance leads to other end of fuse. ( Fuses are 38c each)

 

That is very good idea!

 

Just a plug here for Psychotiller.com for excellent customer service .
Have had a few issues with new enclosure depth to accommodate double row of cells - but Dave from Psychotiller has been great.

The enclosure outside looks great.


25" Monolith Low Pro • Psychotiller | Electric Longboard Components | California

 

Completed a bit more on balance and BMS connections.Have decided to directly solder balance leads to BMS board and put a 11 pin connector for final power up.

I dont fancy soldering to BMS with full cell voltage present☺️

So the cell balance wires go to a plug (From Altronics) with a screw terminal.

The other part of the connector has a solder connection so this is where I solder the 2.5A fuse with heat shrink and hot glue to hold wires in place. then solder final balance wires to other end of fuse.these wires will soldered on BMS after removing stock socket.

photos tell the story

Still waiting on some switches and sockets and a low voltage (30V) cut off module for cell discharge protection for auxiliaries supply .
Evolve BMS has this cut-off for ESC main supply
Cheers

 

Wiring Diagram for enclosure here - happy for any comments or suggestions
Cheers

 

Dave from Psychotiller.com has just finished forming enclosure with deeper sides ( 55mm) to accommodate depth of battery - looks great !

Now waiting for shipping USA to WA to finish off changover

 

Looks good!
Just a question:
Why 40A Fuse? I would go with 80A. I've recently took mine for a ride and on AT wheels I was getting up to 65A in GT during take off uphill.

 

Also, I kind of new that but just recently came across a very good article stating you can at least double a life of Li-Ion battery if you only charge it to 4.1V.
And you need cut A in half if you charge it below 10 degrees.

Tesla does it by default on their cars.. Computerized charger ex:iCharger have default setting on Li-Ion is 4.1V

That article says battery manufactures are trying to compete, pushing capacity and performance up. AS long as it's stable they will claim 3000mah 4.2V > 2.5V but realistically it harms battery cells.
Of course capacity drops quite badly in 4.1V > 3.3V leaving approx 2100mah out of 3000mah to play with but it will allow cell last and perform much longer.

 

Also just curious - how thick are your main wires?
You've used very solid cable between cells but main looks a bit slim to me. I've used 12AWG with 90A connectors.

 

Eugene
As I understand it the ESC has current limiting to 30A per motor and at that motor current there is approx 5A in ESC losses so yeah 65A in total.
I have tried going up a steep hill in GT mode but could only get to 25A per motor- could be something to do with having AT wheels.

I rarely use GT as the only time I have had a major stack was braking going downhill in GT mode and it started to fishtail.
You would think that the braking torque could be capped at fast mode level even in GT mode but maybe that is too logical for Evolve!

My plan is start with 40A fuse and if it blows move to 50A and then 60A
Cheers

 

Eugene
Yeah cell life is considerably extended by only charging to 4.1V or even better only charging to 4.0 volts
With the Ah that my battery has I decided to extend cell life by having the "normal" charge at 4.0 volt by having the two diodes in series with +ve of charging socket (this also prevents the battery voltage being on the charge socket)
and adding another socket for full 42V charge for very long rides etc.
Cheers

 

12AWG silicon flexible for main power leads
the evolve main power cables look about 14 awg (2.5 sq mm) and I would think these would be a volt drop source for currents >20A but if the ESC is current limited, maybe this is not such a problem
I would think that with 14 awg and 65A continuous these would warm up a bit!
Cheers

Correction Evolve main power leads are 16awg or 1.3 sq mm
Astounded that this size wire is used for main battery supply to ESC

 

Interesting... when i was doing tests before battery mode I could never get more than 40A even on AT..
now with bigger battery and 12awg (I could be wrong maybe it's even 10awg) I'm getting 65A.
I've used wire gage calculator to aim for 80a

 

I see, fair enough..,

 

That is cool.. I may ended up getting it as well..

I need to come up with enclosure for carbon GT.
I'm thinking of using 2 x 4p packs- one integrated and one under the deck in slim enclosure.
Do you think he can mold thonething to fit carbon gt profile?

 

Probably the volt drop through thin evolve stock wires not able to supply enough volts to ESC to get to 60A!

 

Eugene
He can do custom sizes using vacuum forming in a baking oven.
The enclosure material is 1/8 inch ABS which is quite strong yet still has a bit of flex.
Check out the website -he has a lot of standard enclosures
Cheers