Bamboo GT AT 50km Range Project

I agree with Nickelberry - it's not worth it. Just sell it as it is on Ebay or something- including BMS.
I've purchased 2 x new BMS from Evolve separately - they are smaller and from memory were around $30-35AUD

 

Yep, I've realized I was wrong about the dimensions and that 10s4P will fit - I did correct myself later in the thread.
LG HG2 curve looks much better that other high discharge 18650 cells. I could be wrong - but from what I've noticed from specs - one downside of HG2 is a shorter life : 170-200 cycles. It could be incorrect but these is what I've noticed going through different website trying to compare batteries.

 

I only have spacers between packs of 4 not between each cell. Yeah I have seen people use braid I used high strand 10 AWG wire as I could not find any rated braid. Also I dont think you ever want your nickel flexing, it would break over time if it did. You realize if you are connecting each bank of 4 cells to your stock pack you don't actually need to wire your new cells in series, you could just use the series connections in the stock pack.

 

I just did a quick search and found this on the LG GH2

Cycle Life @ 10A: 300 cycles at 10 A
Cycle Life @ 20A: 200 cycles at 20 A

18650 Battery Review, Test, Specs 2017: LG HG2 Battery Review 18650 Test 20A 3000mAh Part 1

So I'm thinking I should be getting around 300 cycles as most of the time I'm pulling under 5 A per battery and never over 17.5 A

 

Can you please share a link to source latest LG HG2 3400Mah? Having problem finding it.
Cheers mate!

 

Excellent, thank you. I'm pretty much placing an order on everything to start building it now. Have found same spot welder in AU for $199AUD
HG2 3000Mah Cells just under $10AUD per cell. But I'll wait for SkaterBoy's reply re: 3400Mah version.

I don't have 3D printer to make spacers, but I'll try to come up with some alternatives.

What material have you used to make gasket between deck and enclosure?

Thank you mate

 

I picked up some adhesive foam from Bunnings, like this stuff but wider, should be arround $5
Whites 50 x 5mm x 1m Adhesive Rubber Foam

Also make sure you get genuine nickel, test it with a rust and spark test. I used this
Pure Nickel Strip for Scientific research,18650 battery welding Size:0.15*10mm-in Welding Wires from Home Improvement on Aliexpress.com | Alibaba Group

 

Thank you for that - I'll get genuine as you've suggested.

 

I've just spent some time on the phone with a supplier who sells 18650 cells. here in Sydney.
He suggested Sony VTC6 instead of LG HG2. He said it will be better choice for high current applications.
Basically he showed me graphs where Sony VTC6 holds slightly better past 5A discharge. For example: Under 10A load: HG2 will reach 3.4V in approx 8m50sec while VTC6 cell in 10m10sec.
He suggests I'll be using more capacity from Sony cells considering BMS cuts off around 3.4V and they will have more life cycles as well.
But as usual - they are more expensive. So... now I'm puzzling again.
Do you have any thoughts on that?
Cheers

I've also asked 2 suppliers about LG HG2 2017 with 3400Mah - both said nope - they all 3000Mah.

 

Looks like the Sony cells are only rated to 15A continuous which isn't quite enough for a 10s4p. You need them to do 17.5A plus a little overhead for power loss.

 

Sorry - I'm my rush earlier today I quoted the wrong cells I intend to use!

I am intending using LG MJ1 rated at 3.500 mAh ( ideal discharge scenario of course )

See link below

Test of LG 18650 MJ1 3500mAh (Green)


and revised discharge curve for 5A

Do you have a voltage % curve for the GT ?

Cheers

 

He claims VTC6 them to be 20A. He showed me graphs in 5,10,15,20A for both cells.
This is why I considered those instead of HG2... I wouldn't use cells rated less than 20A..

But after you've mentioned they are 15A - quick research on google shows you are right.

Thank you! I'll stick to HG2..

 

Makes sense now. Thank you for clarifying that. However I wouldn't go for anything less than 20A. MJ1 rated to 10A.

 

I've done these tests a while ago and I remember on AT 8" set up max peak current was around 40A. Start on the grass or uphill.

I remember that once battery was reaching 3.5V per cell remote was showing 25% or something. Once voltage drops closer to 3.4V from memory it will show around 10%. Which is not usable as remote switches to ECO mode.

 

Thanks for that

I will run down to 0% on next ride and do a voltage check

So in a 4P arrangement - LG MJ1 should provide 40A peak OK

Cheers

 

Nick

you are right about only needing the series connection in stock battery .

The stock battery series connections should be rated for max demand ( ~40A?) so all good .

I guess having the additional series connections in the aux battery pack is a bit of redundancy for some of the series current - but not really required.

Maybe better to leave them out for flexibility reasons.

Cheers

 

Theoretically yes, but you would be pushing batteries to it's limit. I thinks you will have big voltage sags and you remote will be switching itself to eco each time you draw high current for a few seconds.
I'm uploading video on you tube... you will see what happens with battery under load. In the end of the video you will see remote shows 10% when voltage drops close to 3.4V

 

For above test I've connected power analyser in line on my Carbon GT. Run a few test.
I could feel about 10% power loss because I had analyzer sitting inline. So to be more accurate I would add 10% extra to actual readings.

End of the video shows CGT on the bench, full throttle, wheels are spinning freely - remote displays battery %.
Basically it's in ECO mode pass 34.5V

 

Did the battery rundown test this afternoon
Eco mode only below 34.5
0% on remote =32.5v
battery drain indicated on remote and battery cut out at 31.5V

I kept going for about 5 minutes at 23km/hr after remote started to indicate 0%.

Thinking that cut-out at 31.5 V is a bit conservative and leaving a bit of fuel in the tank but probably cant be changed with stock BMS with uart comms to remote.

So aux battery capacity can only be utilised down to 31.5V

Cheers