Last week the kit including the BMS arrived. No circuit or wiring diagrams, just a pile of parts. Hmmm...
The BMS consists of a module for each battery cell and a "control unit" if you can call it that.
The BMS components are from EV-Power. Here is a link: EV Power cell module.
The "control unit" seems to consist of a few relays and a butchered plugpack which floats around in the box. It seems that I am supposed to connect the mains to the Vectrix charger through this box. As far as I can determine without tracing the tracks on the PCB, it is supposed to switch off the mains when the battery is charged.
BMS Module Testing
Since I am not going to entrust a $4000 battery to a pile of components which I don't understand, I started by testing the BMS modules. I hooked up the modules to a Lab power supply. A Fluke multimeter was connected via separate leads directly to the module and a second multimeter was used to indicate the state of the Solid State Relay (SSR) on the module. Like this:
It took about 2 hours to measure all 42 modules. Here is the data:
- VLL is the cell voltage lower limit (LL). Below this voltage, the SSR goes open circuit.
- Vth is the threshold at which the module starts to shunt some of the charging current through itself. I measured the voltage at which the module starts to draw more than 10mA.
- VUL is the cell voltage upper limit (UL). Above this voltage, the SSR goes open circuit as well.
- IUL is the shunt current drawn by the module at VUL.
In retrospect, I should have also recorded the shunt current at maximum allowable battery voltage which is 3.65V for the CALB CA66Fi cells. However, the current rises rapidly from Vth and reaches around 0.5A at Vth+10mV.
The only parameter which approaches a normal distribution is Vth. For the other parameters the production process seems to be less well controlled.
A significant worry is VUL. As can be seen from the measured values, VUL is 3.965V (average). This is 0.315V higher than the maximum allowed as per the battery datasheet. This is also the voltage at which the SSR switches to open circuit (OC).
However, the real worry is that the control unit does not know when the first cell has reached it's maximum voltage and the BMS module starts shunting current. By the time the SSR switches to open circuit, at least one cell will have been cooked for a while.
The maximum shunt current achieved by the BMS modules is 0.8A, some only get to 0.73A.
I don't think that shunting 0.8A when charging with 10A or 15A is going to make much of a difference to a cell.
How it ought to work
To properly manage the battery and to be able to equalize the pack, the charging system needs to have at least 3 states:
- Nominal charging, e.g. C/4 until the first cell reaches the maximum allowable charging voltage and the BMS module starts to shunt current. The chain of SSRs must go open circuit at this time.
- Equalization phase. The battery charger reduces the charging current to a value not much higher than what the BMS modules can shunt, in this case 0.8A or maybe 1A.
- Charge complete. When the battery pack reaches VBatt = N × 3.65V, all BMS modules should be shunting current and all cells should be at SOC = 100%. The charger reduces the current to 0A.
A "real" charger should of course also have a state for the case where the initial VBatt is below the lower limit, timeouts, alarms, etc...
I have the wrong BMS modules. They might be designed for cells which have a Vmax=4.0V (maybe Thundersky?). They also switch at the wrong time.
The modules don't seem to be suitable for the cells I have because:
- The modules don't indicate when the first cell has reached Vmax and shunting starts.
- The SSR switches at the wrong woltage for my cells.
- By the time the module's SSR switches, at least one cell (but probably many) will have been cooked for a while with nominal charging current minus 0.8A
I am trying to figure out how to fit the battery. The original plan was to put 32 cells arranged as 2 rows of 16 in the bottom of the battery compartment. However, they don't fit.
At the rear, welding lugs from the frame's rear casting are protruding. I am prepared to grind some of that away to make the cells fit side by side.
The interference at the front is more problematic:
I am not going to attack the frame with a big hammer or a hydraulic jack and I won't grind away material from the frame's tubing.
Well, adversity is the mother of all innovation... So now I will be able to fit 33 cells instead of 32! See:
The whole pack will probably be arranged like this:
Received the battery. 42 CALB CA66Fi cells, 66Ah. 32 of them go into the battery compartment standing up as 2 rows of 16 and the remaining 10 will be stacked flat on top, most of them where the impellers used to be. Unfortunately the supplier forgot to send the interconnects. Next week then...
I have satisfied myself that forced cooling will no be necessary with the cells I bought. As a contingency however, I have a plan B which will use conduction instead of forced convection. 2mm aluminium sheets between the cells would serve as the heat conductors. They would be thermally coupled to the bottom of the battery compartment. For the cells stacked horizontally, I would have to come up with a heatsink – maybe the plastic sides of the battery compartment could be replaced with aluminium sheet...
Battery mechanical fitting
I could not fit the cells side by side where the frame welds are. Some of the protruding welds will therefore have to be ground down by about 1 mm. Also interfering is the bracket for the rear temperature monitoring board and a rivet in the front center of the battery compartment. While I am at it, the big ventilation holes will also need to be covered – this will stop the battery from getting a shower when I ride in the rain.
After having been convinced by Matt Lacey's Li conversion videos that a Li conversion is quite managable, I started looking for a 2nd hand VX1.
By good fortune, I ended up with a VX1 from the former Australian Vectrix importer and distributor. The bike is ex-demo/showroom and I have been told it has done less than 500km. It has a few marks and the chrome plated surfaces have brown corrosion spots. The battery could find a new application as a zero-volt reference if it were not so heavy, and since the plan always was to convert to Lithium, I did not even attempt to revive it.
My choice was to go for the largest capacity battery possible. Partly because I don't want to have to worry about making it to the next charging point and partly because the disacharge capability of the battery is proportional to the capacity. At the same discharge current, a larger capacity battery will be stressed less.
A local distributor still had stock of CALB 66Ah cells so I ordered 42 of them. As of July 2013. CALB does not make any 66Ah cells, only the 60Ah ones. The datasheet states a max discharge current of 2*C (132A) so a peak discharge with up to 200A for a few seconds should be well within the battery's capability. Internal resistance (Ri) is quoted as < 1 mOhm. At that Ri, drawing 50A would dissipate 2.5W of heat per cell or 105W for the entire pack, at 100A that would rise to 10W and 420W respectively. Average power dissipation of the battery will probably be closer to 105W than to 420W, depending on how I use the bike. In any case, with the LiFePO4 cells, I am not too concerned about battery cooling and the 2 battery compartment impellers will be permanently removed to make room for more cells.
Hello... I own a 2005 E-max EP 2000 Sport and would like to remove the speed restriction on the controller as discussed many times in the Forum. The controller, located in the battery compartment, that is now on the scooter does not appear like any of the images I have seen in the V articles and archives- this is possibly an early model or replacement. I'd like to know if there is a way to change or adjust this controller to remove the speed restriction.
The scooter has 48 volts with SLA batteries in buddy packs and runs well. I have not got around to making it 60 volts. The rearrangement of the batteries increased the range to about 33 miles. When I checked the operation of the relay switches, the compartment appeared to be modified- does the controller belong in this compartment, rather than in the battery area?
Any help would be appreciated.
CHRIS V Rockport, USA
Last month my charger packed up and attempts to fix it failed as everyone knows that this charger is made in such a manner it's impossible to repair it.
I just managed to built a basic charger of course with a help from this forum to keep me going while I'm trying to accumulate money for the new charger ,the problem I'm facing is that my fuel gauge works like a revolution counter while riding ,displays full bar( 17 bars)if bike is motionless ,range estimator shows zero all the time it does not matter even if the battery pack is full and only way to know if I still have enough power is to measure voltage of the pack with a multimeter.
I need to know where could be a good spot to source 12V for battery cooling fans since the stock charger is no longer in the bike.
Are there any connections that I need to do to get the fuel gauge and range estimator working again?
i was hopeing that gmouchawar could send me a copy of the ev global service manual. thank you
How do I repair/adjust or remove E bike rear brake shoes and where to buy parts, im in VictoriaBC firstname.lastname@example.orgSubmitted by rutherfordservi... on Sun, 10/14/2012 - 23:08
I purchased a used 2008 Zapino in May, 2012. I've had problems with the battery. First, the switch went out. (It no longer turns off charger) Now, when I charge the bike, the red light stays on. After 12 hours charge, I unplug charger and the light goes green for about 5 seconds, then of course both lights go out (power and charge indicator). Has anyone had this problem? Will I ruin the battery charging 12 hours (overnight?) Would a new batter charger help?
I bought with only 78 miles on it and have just reached 1400. I want to get my money out of this thing as long as I can, especially with the price of gas.
Is there anyone in central coast of Calif. who works on these things? Where can I got a good education on charging batteries for this electric bike?
I have a xb 610.
Was wondering if anyone has put a windshield on this bike?
This might be an old topic; but: what mods can be done and can lithion ion batteries be used?
I have only had the scooter for two weeks.