Bamboo GT AT 50km Range Project

My stock Evolve battery is rapidly loosing all punch . I am on 90 charge cycles since new and very noticeable reduction in km to get down to 50% and then into Eco only mode. ( with AT tyres at 50 psi)

This is behind the change in plan from adding a separate battery in parallel with stock battery to current plan which is to totally replace stock battery with a 10S 8P set up in a new battery enclosure.

It is a pity that Evolve put such a crappy prismatic low capacity battery in to start with but I guess it has been done for cost reasons or maybe they want a steady stream of on-going business to sell replacement batteries every 6/12 months !

Cheers

 

+1
Mine boards also loosing punch. I'm not sure how many cycles I've done on "Bamboo" - maybe 20 but on AT wheels I hardly gets 8km range now. (Used to be around 16Km on the same roads). And I'd say last 2km would keep switching into Eco.
Similar scenario with Carbon - 12.5Km ride until it started to drop to Eco., And I used to get 23Km before.. So once I finish building Bamboo battery carbon will be the next..
I'm sure if I would be constantly in Eco my total range would be better but common! Usable punch definitely degraded by half.

I'm glad you've decided to go away from your original plan to add battery on top - I don't think it would work efficiently.

 

Good job! I think with these wires you can power up 2 boards at the same time!

 

Arrived yesterday - not good. A correct pitch - it's definitely 2.0 but the evolve plug is much slimmer with connections right in the center of the plug. While those are 1.5 times thicker with holes offset to one side. With some modification it should fit if it's flipped up side down.
Plus gage of the wires so tiny..
I'm not real happy will be keep looking..

 

Mine is almost ready, just need to sort a harness for balancing port.

 

I've decided to solder balancing wires directly to the back of BMS board and will have 2.54 JST sitting externally.
Clear epoxy applied to seal and reinforce contacts

 

I like your very official looking battery pack serial numbers!

 

Did a bit of calculation for range today - a number of forum and DIY guys quote typical ESk8 board power consumption of 10Wh per km.

Checking this against Evolve quoted battery Ah and range correlates pretty well as shown below

Looks like 7 Wh per km for Street and 10 Wh per km for AT is about right.




So for my 10S 8P set up using MJ1s should be about 85km for AT and over 100km for Street ( would be very happy if this is achieved)

I have dropped Ah of MJ1 cell down from specified 3.4 to 3.0 to allow for Evolve BMS cut-off at 3.0V.
The 36V comes from averaging max volts of 42 and min volts ( cut-off) of 30V

Using my calculation a 10S 6P with GT with 3Ah cells ( very best cells) would give 65km range
and with 10S 6 P with 2.5Ah cells would give 54km range

and 10S 4P with 3Ah cells would give 43km

Interested if anyone who has replaced Evolve battery with 18650s can benchmark above calculations with actual obtained range.

The Evolve Battery Ah would be that when new and Ah would decrease as the crappy battery deteriorates- hence reduced range. over time

Cheers

 

Hurray!!! I've finished.
Everything is appears to be working. Will test the range this Sunday if weather is fine. I will be testing it on the same route where my Carbon used to give me 23km range on AT setup. (When it was new)
Will give update on that.
I've made gasket to raise enclosure and allow more room for batteries. I had to put balance cables in the middle. They are moving freely.
Main power cables and plugs are rated to 90a.
Almost none changes was done to enclosure itself. I think it's still looks clean- like stock. However It was a very tight fit.

And I've still managed to keep it as 5 separate packs which can be easily swapped or removed for air travel.

Very happy!
Cheers

Eugene

 

Nice!
On stock battery I could never achieve claimed range neither on Bamboo or Carbon. On AT - it was 23/16km till pretty much "0".
However when I was charging batteries back using iChargers I would always get pretty much close to 10000mah reading (charged capacity) on Carbon and 6500mah on Bamboo. I'm 72kg and was just cruising. So I was either riding to aggressive or I don't know how else do you need to ride to achieve claimed 30Km range on stock setup.

Anyway real world test will show improvement pretty soon. While when I've discharged my 12Ah 18650 pack to 34V and fully charged it back iCharged showed 9800mah capacity. So I think my mod battery bamboo should give me at least the same range as Carbon but with less voltage sags and should last longer than 6 month.

I stick to 3.4V per cell as when I was testing BMS a while ago below 3.4V remote was showing "you are almost done" and throwing it to ECO.. So to me below that it's not really usable.

I could be wrong, but I think Evolve stock battery could be LiPo. They feel and behave exactly as LiPo. Even BMS settings set as typical BMS for Lipo not LiIon. But they say it's Custom Li-Ion so ...

 

Finished both battery packs now
added liquid tape and rubber insulation on inside series braid connections .

Hooked up a temp 10S BMS for initial charge to 41V with a 2A charger

Next step is discharge test with load resistors to test Ah capacity

When this is OK will fit packs in new enclosure and then start to think how BMS and motor controller boards can be mounted

 

Good job!

 

I've done a real world test today. Happy with result. However as I expected after 20Km on AT 7' I reached 25-30%
Pass that point each acceleration dipped remote to ECO.
20% translates as 34.3V
18% - 34V
15% 33.7V
and I stopped riding after that - Just hate ECO - I can't ride that, I'm falling a sleep on ECO with 33.7V battery.

Anyways - from 33.7 to full charge to 42V on iCharger showed 9369mah. Close enough.

So.. Overall: Big improvement from stock Bamboo GT battery. Better performance and range - similar to brand new Carbon GT. Which is the way it should've been from day one.

 

I don't know if you saw, but evolve is doing f/w upgrades for remotes and moving the ECO cutoff down to 10%.

 

Thanks mate, I didn't know. I'll contact them tomorrow. That would definitely improve the range.

 

Guys - Completed first discharge test yesterday .
Complete battery pack was charged to 41.6V . Load was a 8 ohm 100W resistor with a fan blowing over it for heat dissipation.( at start of test power was 200W !)

This provided around a 5A load ( of course decreasing as volts decreased.) 5A is what my GT AT draws at steady speed approx. 25km/hour on flat ground. (The total load of 5A provides a 0.625A load per MJ1 cell)

Measured at approx. 10 minute intervals overall volts, current, power, Wh with a digital meter ( see photo) and calculated mAh based on average current over the 10 minute interval. Individual cell volts were also measured

The discharge test ran for five hours with battery voltage from 41.6 to 32.1 ( approx. Evolve remote 100% to 0%)

Graphed discharge data and compared mAh curve to MJ1 specs

All up the pack provided 851 Wh and 23,000 mAh for the discharge test .

There is additional capacity available in pack for discharge down to Evolve remote cut-off which I think is around 30V but unlikely that this will ever be needed with a pack of this capacity.

Quite happy with the result and it compares favourable to MJ1 specs


Cheers


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Very good mate!

 

Anyone know the maximum balance current through the Evolve BMS?

Looking to make the final BMS connection wires as small as possible to act as a fuse if fault in BMS

People dont seem to fuse the BMS balance wires at all yet they connect directly to cells.!

Cheers