July 7, 2009
The 2008 Chopper ( Here ) with an X5305 and 48v 12ah prismatic cells was ok last year but the 12ah cells are fizzing out and they are dying one at a time making the chopper a sitting duck, so it's chopper upgrade time !
Since I have a stock of PSI cells on hand, I decided to put them to use on the chopper, but this time with a crystalyte X5304 ( higher RPM motor than the 5305 ). And to compliment that, a controller modified to push 80 amps !
1st step was to build the battery pack.
When I purchased the PSI cells from Taiwan they came as loose cells without any materials to assemble them into packs other than copper bars to link them and a " Voltage Monitoring System " in a seperate box. A few months later I was advised that there were now assembly blocks ie: lego's available to make pack assembly much easier.
An email and payment to :
http://www.rechargeablelithiumpower.com
I got my Lego blocks !
I've decided to build the pack in 12v blocks, given my history of relocating bits and pieces to different projects as i burn/blow things up
The blocks are incredibly well made, sturdy, strong, low flex, and they lock together very tightly
After lining up the notches, I used a block of nylon and a hammer to set them in place..
I dug thru my stash of carboard and found the template i made last year when building the 12ah pack.. as you can see, the 6 x 12v packs will fit in the frame perfectly with not much room to spare once i add sides to the packs..
One layer of electrical tape and the cells wedge right into the blocks..
I started the electrical tape between the white barcode sticker and the cell's shrink wrap stamp, this way the stickers and tape seams all point in the middle and out of sight ! ( Obsesive Ccompulsive Disorder ?? )
Up to this point, I have not been using any BMS's on my lithium packs, all the packs i've purchased so far that came with them have been problematic, causing charging problems and cutting out when they should not.. instead of doing what they are supposed to do.
This version of the " VMS " only monitors the voltage of all the cells, it does not have an Active Cut-Off to shut down the power if a condition occurs, but it does have allowance for a 5v signal that you can use to activate your own method of cut-off.
Each of the 6 circuit boards monitors 4 cells, they in turn connect to each other with ribbon cables, and all that goes into a main Data Board..
Now, imagine 24 cells, and a wire going to each connection, it gets messy and fast, managing all those wires is a must, making it look good is darn near impossible...
A few experiments later, I found that a dremel tool and a router bit on one corner of the block would allow me to run the wires all to one side of the 12v pack without having to pinch them on the outer edges of the blocks.
If i was going to build the whole 72v pack permanently into the chopper, i'd hook up all the blocks with the tabs, but i'm building 12v packs.. so off with their heads !
The hardest part in al this is making up your mind what to cut, where to run the wires and all the fine details, the rest is just a matter of copying the process over and over again, strangely, I like production work !
July 14, 2009
All 6 packs assembled, and stacked in a way I can bench test them. That's ALOT of wires !!!!
Back side, nice and clean !
Ok.. so here we go.. time to connect all the 12v into 72v.. I checked and rechecked my polarities a few more times and hooked it all up !
Next step.. connect the VMS and start cycling the pack using my lightbulbs...
Soldered all the wires to each 6pin connector, all ready to go.
Well, what's worth doing is worth doing in excess huh..
Got my hands on a full 4x8 sheet of 1/8" thick polycarbonate, the acrylic was cheaper at 80$ for a 3x8 ft sheet, the lexan was 200$ +tax, .. I like having extras, this stuff will be usefull in the future, no doubt..
I"ve had good sucess with heat guns and angle iron strips clamped in a bench vice, I am ordering a strip heater right now !!! seen some videos on youtube using those.. makes life alot .. ALOT easier..
It's a tight squeeze ! and i had to make sure none of the boards short out against each other.. tore strips of foam from the cell boxes and taped over them as insulators.. BMS condoms ?
I Individually charged each cell with single cell chargers to 100%, ready to hook up VMS for the 1st time !!! Each of the 6 boards has a tiny dip switch you turn on one at a time... and Voila !
Then we start testing the pack !
BRIGHT in here ! I get 5 amps from 4 bulbs, 6 more i can add later for aprox 12 amps !
And above, the 3 Soneil 24v chargers, charging at 5 amps on 10ah cells means I go from empty to full in 2 hours !
( Charging at 5 amps = 417 watts in !! You can't do that with cheap batteries ! )
July 19, 2009
When i plug in the charger, the LED"s wake up, but not always on all boards.. I know that if a cell or group of cells have below 8v( 4S ) the BMS will not wake up, but all cells are well above 3v so they should. Somestimes they do.. sometimes they dont.
I have not yet gotten the buzzer to kick in on Overvolt or Undervolt, I plan to drain a deep DOD tomorrow and confrm that it will trigger..
I'm not sold on this VMS thing yet, cell voltages are not ballanced with variance way wider than No BMS that I have been doing on a 48v pack.. but it's early still.. a bunch more cycles on the bench and I will either start to see a pattern or dump this VMS and bolt up a Gary and Richard unit !
July 21, 2009
On Sunday night I fully charged and let the pack sit overnight, last night I went for a deep discharge to confirm the buzzer works .. and it does !.. The VMS bleeds off a significant amount of juice, brings all cells to 3.33x volts. Got 8.8ah before i shut down the test
Well.. at this point in time.. i'm seriously considering my options
- Get 2 x 12 (edit: channel not V hehe) LVC boards from tppacks.com and charge via Single Cell chargers and the 5amp Soneil's ..
- Get Gary and Richard BMS and proper power supply
- Stick with VMS, tho after a 2nd deep discharge and a full recharge, the cell voltages are all over the place.... got the OVP ( Over Voltage Protection ) beep as one cell was a 3.9v and the lowest one was a 3.45v.. i'm not all that impressed with this thing right now.. needs more testing... but time for bed !
July 22, 2009
A Video I made to explain some of this :
July 31, 2009
Ok.. so after thinking about this whole VMS thing, ALOT, i'm ordering a 24 channel board from AndyH ( from the Endless Sphere forum ) the vms is not going on the chopper.. i'm not giving up on it but I want to get the chopper on the road NOW... and don't want to waste too much more time fiddling with the unknowns of the vms.
This weekend I start cutting lexan !
October 24, 2009 !
Ok, so the chopper sat for a while, the RC bike parts arrived and it took over my spare time.. but oct 24 and i'm back on the chopper project.
Cut panels for the 12v PSI packs, even tho this will be a 24S pack I want each 4 cells seperatly bundled.
Table saws rule, but Daaaaamn dangerous ! I'm past the " afraid " level, i'm now " extreemly cautious " .. had one piece nudge the side of the blade, go flying in the air, land back onto the blade and shoot across the garage catching the end of my middle finger, some nice blood spatter !
The white template is the opening inside the chopper frame, so far so good, the pack will be wide but since the chopper has no pedals or chain.. it will be just fine !
Some of the lexan panels installed, i'm leaving the middle vertical one's out so i can use the brass tabs between the packs 1/2 and 3/4/5, those 2 sections will be joined with big thick copper straps.
Brand new shiny BMS built by AndyH !!! THANKS ANDY !!!! looks great !
I plan to install anderson powerpoles on every wire and have them hidden behind the BMS..
Nov 16, 2009
Finished soldering wires and cut a piece of G10 fiberglass board to protect the wires from the back of the circuit board.. Hot glued the wires flat nice and neat..
This is serious stuff, when you work with this many batteries don't screw around, clean work space is a must and don't connect anything until you absolutely have to. By keeping each 12v block seperate I reduce the chance of a MAJOR short, a single cell can create enough spark to really scare the crap out of you so 24 cells would really light up a room !
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Nov 23, 2009
Today I finally made my bus bars to hook up the 12v packs for 72v.
I had some copper bars left over from my original PSI order , they don't fit the lego cubes so i made use of them.. Double thick copper on one end, double 12g wire on the other side..
Then crossed my fingers and plugged it all in ! No smoke, No Fire ! Woot !
Some observations, the 3x soneil 24v 5amp chargers I have plugged in series provide 83.7v peak ( / 24 = ~3.48v per cell ) just enough to make one channel blink orange for a split second before the current tappers off to nothing. The main LED stays red and never goes to green.
I added a single cell 2 amp charger in series with that and then I get a whole lot of blinking going on, very cool to look at ! and I get 87.6v, that gives 3.6x v per cell and almost all channels blink until 87.6v the current stops again and all the channels turn off with the main LED still on red.
Bottom line is that the pack is basically fully charged, and does ballance while the BMS prevents any single from going over 3.7v nicely..
So far so good !
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Nov 26, 2009
Over the weekend ( after painting the whole house.. man I hate painting!!! ) I cut the side panels... looks blurry because one of the peel away layers is still on there, removed the white side of the polycarbonate to see the lego block holes and pre-drill them.
Spray painted metalic black on the inside of the Right side panel to hide all the BMS wires, the Left side panel will be left transparent on the clean side.. Numbered my BMS wires with gold stickers between a piece of clear tape, once the panels go on it's impossible to know what wire came from where.. I've done this in the past, spend hours building the pack and completely forget to label my wires.... get to the end and realize...aww crap...
Doubled up on the 10 gauge wires and an extra + and - 14 gauge leads for the charger, soldered them to a copper tab, heat shrink and ready to go.
Sandy giving me that " are you done yet ? " look..
Fits in the frame perfectly !
Found a spot for the upgraded controller, bend a small piece of lexan and bolted it to the bike. Used a hose clamp up top with a piece of copper to secure it to the seat tube.
PSI Chopper !
http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=11410&start=0
