Nov 3, 2009
On oct 1st, I ordered via http://www.evcomponents.com :
http://www.evcomponents.com/ProductDeta ... Code=H4810
On Oct 3rd i got my invoice, paid immediately..
- 48v 10ah Headway pack with BMS 349$
- Shipping 95 $
- Paypal + 2.5%
- Duties and Brokerage 29$
- + Exchange rate to canada
Total : 520 Canadian $
No charger !
I requested a tracking number on Oct 20, my customer getting anxious to ride his new to him e-BMX, yes, we have had snow already !!, i was then advised that the container had just landed and it would ship by end of the week.. . Had i known this i would have advised accordingly and avoided pissing off my customer.. Doh !
Last night, Nov 2nd, FedEx left it on my doorstep ( they attempted on previous friday but i was at work and they required their duties and brokerage.. ). I had requested USPS on my order as the online calculator does not yet determine shipping to canada, but i arrived Fedex...... all in all.. that's fine by me.
These cells are as fresh as possible = bonus !
Box was in relatively good condition, no holes .. good.. ( I always take pictures of anything i get shipped, i work for a shipping company and nothing says proof like a picture )
So, i anxiously opened the box, I was expecting exactly what was in the picture on EVC, ie:
To my VERY pleasant surprise !!!!
I like ! No cracks, but a shake reveals indication of something moving inside..
Headway molded into the box, nice touch.. + and - also there ( a colorfull sticker would be a nice added touch for those of us with less than 20/20 vision.. but i'm happy with the box ! this will save me a wad of time and efford.. A+ ! )
Voltage as delivered : 53.3v ! ( good ! )
Under the hood we go !
Simple 4 screw, pop the top.
- BMS is loosely held on the pack with tape
- Pack is not secured to the black box and loosely moves in there
- Broken red plastic tab on bottom left corner
All in all, not too bad, easy fix, Tipped the box sideways and the pack came right out, i see on the bottom of the black box some glue residue and melted red plastic in it, so an attempt was made to stick the pack to the box, however not good enough.
A quick check of the Positive+ and Negative- wires from the BMS to the pack reveals that the + wire is not tight, the cable spins around easily, the negative wire is solidly attached, the bus bars seem ok, sense/ballance wires connected with copper rings instead of being soldered to tabs is one thing i like..
Imo, The pack wires need to be secured to the pack itself, and the terminals need to be coated in either hot-glue or equivalent to prevent vibration loosening, hollow spaces inside the box need to be occupied with foam or other matarial to prevent movement of any sorts, WHEN not IF i crash, i want this thing to stay together..
Outside measurements of the plastic box:
15.4 Lbs ( 48v 10ah )
20 cm Tall
22 cm Wide
16 cm Deep
All cells from 3.321v to 3.328v
And picture of the glue results..
Time to start testing the cells and BMS:
1st cycle 2ah ( 3amps )
2nd cycle 5ah ( 10 amps )
3rd cycle 10ah ( 9.95ah at 10 amps )
The BMS shuts down the charger at 55.7v when cell No.2 hits 3.8~3.9v . The remaining 15 cells are all in the 3.4~3.5v range, no heat detectable from the BMS.. Once the charger goes green, cell no.2 slowly drops back down to 3.7v and the BMS lets the charger come on again for a few seconds, over and over..
BMS shut down the pack at 44v from cell No.3 at lvc.
After resting for a few minutes, 15 cells bounced back to 3.2v.except No.3 that sits at 2.7v
Pack slightly warm, room temp 22 celcius, pack 33 celcius .
Nov 5, 2009
For the price, this is so far very good, there are a few critical things missing imo, for example :
- Documentation !!! Safety warnings, Charging Instructions, spec sheet, BMS information ... ( should be printed and included inside the box imo )
- Terminal screws for the posts, i had to scavenge from the garage, I have all sorts of nuts and bolts but i'm sure not everyone is as much of a pack rat as i am..
- Insides of the box needs improvements, filler pieces, cable support and protection for the ballance leads ( some ballance leads are wedged between the box and the plastic studs on the lego blocks, this would lead to ballance wire failures early in life imo ) . BMS needs to be protected and supported better.
this box is perfect for a backpack, too wide to fit between pedal cranks so won't fit in bicycle trangle, could hang 2 packs saddle bag style for 20ah !..
Ok, so it's 9pm and COLD, but can't resist a road test..
Open up new " swiss " backpack, put pack back into black box, hook up a power wire ( 12 gauge with 45amp powerpoles.. ) .. Bundle up with toque and winter gloves, get BMX outside..
Above, Notice Sandy in the background sticking her tonge out at the camera !
And well.. test ride 1 kinda sucked......
Quote EVC :
" Built in BMS with max continuous discharge of 60a Max cutoff discharge current 100A "
Well, this is an e-bikekit.com hub motor in a 20" wheel with a crystalyte 35 amp analogue controller, shunt soldered for 45~50 amps on the Cycle Analyst meter..
This BMS does not automatically reset, it requires disconecting the wires and reconnecting.. 1st overcurrent cutout i reset and checked the MaxA value on the CA and it says 36 amps.
I then used up 0.3ah more and managed to cut out on command at low speed ( less than 20 km/h ), if i ginger the throttle to 25+ i can slam the throttle and peak at 50 amps for a moment and then * bzzt.. cutout.
Next step.. solder up the shunt !
So i opened the lid again and this is the shunt before solder
And After :
The reason i did this, the BMS detects the voltage drop across this " shunt " and this determines how many amps are flowing, by adding solder the resistance value goes down and tricks the BMS into allowing more amps than it was was originally calibrated for.
But, in this case,
Nope.. not gonna work.
I can manage to get 2000w from it ( voltage on the CA 46.5v, but i'm sure the BMS is contributing to this sag ) .. this BMS is gonna have to go !
I see extra spots for more fets on the aluminum chunk, from the digital camera closup i can see that there used to be fets in there.... leaves me wondering what's up with that...
After pondering my options a bit more, decided to have a look at the back side of the BMS...
Gotta love how the heat sink screws are stripped out, and that solder blob on one pad on the right seems suspicious, then the surface mount resistors between the fet legs on the left...
The Thermistor is inside a plastic sleeve, then on top of a G10 board, by the time this thing trips the cells are already in melt-down territory lol.. but the BMS won't allow that much juice to flow anyways so i guess it's a non-issue
Nov 6, 2009
BMS problem.. uhm..... Fixed !
46v at 46 amps ! and No cutouts this time !
Used the rear brake on the BMX to test.
Waiting for the rim to cool off so i can do this with my PSI pack for comparison
None of my personal packs have BMS's, but i monitor with care .. and accept the risks.. problem is that this pack was not meant for me, it was supposed to go into the hands of someone with zero E-knowhow...
With BMS removed, after my road tests and bms tweak testing, all 16 cells read 3.330v at rest.. all exactly 3.330 , i like !
edit : Oh !! and the PSI pack will hold 47v on the same 46 amps ! ( full 7 second count under load ), the psi are larger and have slightly more capacity than the headway cells so given C rate at capacity they are pretty much on par with eachother at almost 5C rate.
Nov 7, 2009
I've been saving these for another project, but oh well.. here goes !
These are 8 cell BMS's i got from a trade for my VMS ( PSI provided bms ), and they have been Rickified with better fets and doubled up resistors for better ballancing.....
I have 3 of these, was going to use it on a 72v setup, but they just happen to fit so perfectly in there........
So i'm removing a bus bar and making this 2 x 24v packs in series inside the box..
These 2 BMS's came with no instructions, aparently some competent poeple know how to hook them up, unfortunately i'm not that competent lol..
So i went with the logic given 7 wires and 7 junction points in the pack... starting from the negative side at B1...
Crossed my fingers, quick metal game plan involving fire extinguisher in the kitchen near by.. small prayer....
Wooot !! no smoke no fire !
And nice bright LED's !
Ok.. so now that the 1st test was a go, i soldered up the 2nd set of ballance wires to the other 8 cells, and soldered some 10g wire to the 2 BMS's i'm going to use.
Now i have to figure out how the hell to wire this up to the black box...
I can either remove the brass lugs on the box cover and install a gromet, then run 2 wires each side for 24v each, one charger per side and connect in series to run the bike
Or, i can have 2 charge wires exit the cover and use the main brass lugs for 48v connected in series inside the box..
Routed all ballance wires away from the bus bars, i found that using the holes in the red blocks i can zip tie the wires in a bundle, a drop of hot glue on the tail of the zip tie and shove it into the holes for easy removal in the future..
Made some lift straps to pull the pack out of the box i ever had to in the future.. ( recycled ratchet straps from the garage ! )
Getting more crowded, hooked up both BMS's.. and onto the e-BMX with the rear brake firmly planted.... 46 amps, 45.5v ( 1v drop with BMS ) and NO CUTOUTS !!!!!!!! Success !
( now to stuff all that into the box..... ! )
Nov 8, 2009
Cut some G10 fiberglass sheet to protect the BMS from the cells ( also should keep the heat from the BMS resistors away from the cells to an extent )..
Soldered all the ring terminals and heat shrink added, cut some pieces of Lexan (polycarbonate ) and shimmed all 4 corners of the pack, used industrial hot glue to keep them in place, if i ever need to remove the pack from the box, i can grab these with needle nose pliers and yank them out, but this will keep the pack from shifting inside the box !!!!
Took 10 minutes to get the lid on.. but i got it on !!..
pair of charge wires for each 24v pack, going to cut them short to prevent anyone from hooking them up together.....
Back in the backpack, out for a test ride.. I love that feeling of going for a test ride, dark as all hell out there at 6pm but temps are nice at +2 celcius..
Plugged in, CA powered up, and away i go...
Project Complete !
Used up 2.5ah as fast as i could, 46 amps sustained and voltage drops to 46.x , no cutouts, no smoke ( yet ).
Nov 9, 2009
The pack got my ass to work this morning, cranked the throttle full on all the way 5kms, managed to dip to 45v out of the driveway but pack averaged 46~47v at 1000 to 1500w, no drama and all went well..
Depends on your application, the stock BMS imo would be ok with a 20~30 amp controller, my bike needs 46 ..
Getting a pre-built unit is a good starting point, for the price you get the lego blocks, bus bars etc, tweak to your hearts content and giv'er !
I'm pretty sure there is enough room in that box for a 60v !!!
Trip back home went well, total capaciy used 5.666 ah
Was dipping into the 44.x volts at this point at 30+ amps, roughly a dozen cycles on them so far, a few lbs lighter in the backpack is nice, the PSI hold voltage better however, more test results as the week goes by...
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