Author Topic: Charging input ports:  (Read 1055 times)

siai47

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Re: Charging input ports:
« Reply #15 on: September 02, 2017, 02:59:02 PM »
I'd be careful with "quick charging" and Li-Ion batteries.  They don't self balance or equalize like a lead acid or NiMH battery.  In traditional batteries, the internal resistance is highest in the lowest voltage cells.  When in a series string, as they charge, the resistance drops and self equalizes the string.  Ii-Ion batteries work in the reverse.  The lowest voltage cell in the string receives the least of the charging power (charge current is constant in a series string but the highest resistance cell has the highest voltage therefore receiving the most power input and heating).  This causes higher charged cell to exceed its maximum voltage and destroy itself.  They need a balancing circuit to equalize the cells and make sure that no cell exceeds a specific voltage (usually around 4.2 volts per cell).  If you do, the excess charging current goes into the overvoltage cell which will quickly heat and destroy itself and possibly ignite the entire pack.  If you are supplying power with an external charger that doesn't allow the BMS to initialize the balancing phase, you run this risk.

To be safe, never use a quick charger to go to more than around 80% charge--this should keep an unbalanced cell pair still below the 4.2 volt threshold.  Finish the charge with the bikes internal charger and let the balancer do its job which occurs at the very end of the charge cycle with reduced current from the charger.  The balancers are basically resistors that are placed across the highest voltage cells by the BMS and shunt the charge current to the lower voltage cells.  These resistors cannot dissipate much heat so charging current is usually reduced to less than one amp during balancing---which is why the charger may appear to stay on for a long time at 100% charge if there are cells that are far out of balance.  It is also why the bike must be charged from time to time to full charge so that balancing can take place.

It can be done, just play it safe with quick charging.  A pack doesn't go out of balance quickly unless there is a faulty cell pair (or in our case a faulty cell in one of the ten that are paralleled).  Just bring up the balancing screen on the instrument cluster when using the bikes internal charger to finish the charge and be aware of any segment that appears to be constantly the "low" group.  One last point and that is about the bike being aware that external charging is taking place.  In EV cars that I have hooked an external charger to, the only way the battery management system knows that a charge is taking place is if it is on.  In addition, it needs to think that the power is actually being regenerated from the drive system so that it can look at the amount of power you are adding to the battery for range and percent of charge calculations.  In the cars, if the external charge source was between the drive inverter and the battery pack, with the vehicle in the run position, the BMS would just think you were coasting down Pike's peak and regenerating the power--not using an external source.  I don't know how the system would react with the Brammo components as I haven't looked at the wiring diagrams to see where the best connection point would be.

nunux59

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Re: Charging input ports:
« Reply #16 on: September 02, 2017, 03:18:15 PM »
I am aware of the unbalancing problems and safety concerns. In any case I would not charge the bike without the BMS being in function. I will either hook the "fast charger" in parallel of the onboard charger but I still need to fully understand the consequences on the onboard charger. The other possibility is to "fake" regen but it means that the bike needs to be powered on while charging.

siai47

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Re: Charging input ports:
« Reply #17 on: September 02, 2017, 04:34:14 PM »
Be aware that some vehicles monitor the amount of input power going into the pack.  If it exceeds the nominal output of the onboard charger, it thinks something is wrong and shuts the onboard charger down.  Case in point was a Mitsubishi I-Miev with a 3.3 KW onboard charger.  I paralleled a 11 KW variable output charger (Manzanita Micro PFC-50B) with the onboard charger.  As soon as the output reached a combined 6 KW, the onboard charger shut down.  No big deal but needed to forget the onboard and supply all power with the offboard charger until final charge.

nunux59

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Re: Charging input ports:
« Reply #18 on: September 03, 2017, 03:27:27 AM »
That is interesting to know. Did the onboard charger powered up by itself when the power was under 6kw again or did you have to reset the car?

siai47

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Re: Charging input ports:
« Reply #19 on: September 03, 2017, 12:08:43 PM »
In the case of the I-MiEV, it was just a power cycle to get everything back to normal.  I have no clue how the Empulse will respond, however, the simple workaround is to charge with the external charger and the Empulse in the "run" mode.  Power up your external charger and if you can vary its output, ramp up the output while watching your KW meter on the instrument panel.  If it starts going negative its showing the bike's systems think you are in regen.  Keep the power on until you reach 80% capacity then shut off the charger.  Connect the onboard charger and after the charge starts, look at the balance screens and see where your highest cell pair is.  This will determine to what extent you can safely charge with your external charger.  Also remember that if you are putting a lot of power into the pack, you can exceed the 4.2 volt limit with the charger on.  Be sure you never are near the maximum system voltage under charge.

I am going to put a Anderson connector on the bike at some time and hit it with the PFC-50.  Its 11KW output is still only 1C so it shouldn't stress the pack in any way.  I just don't want to do anything to damage the bike as I know it won't be repaired and I still like to drive it  8) !

nunux59

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Re: Charging input ports:
« Reply #20 on: September 03, 2017, 03:23:34 PM »
Charging the Empulse in the run mode seems to be the easiest and safest way to do it. I know that we can regen to at least 5kw so it should be no problem to charge at this rate in run mode. Moreover the balance screen is available in run mode so I can verify that no cell is going over 4.2V. When the input power decrease to 3000W I can switch to the internal charger. This option is almost guarantee to work but is not the most convenient. First because of the need to stay near the bike at the first phase of the charge. Second because of the need to switch the charger.

If you fit an Anderson connector, please, make pictures ! I am in the same situation than you, I would really like to improve my bike in order to make road trips with my friends but I don't want to damage anything as it is my daily commute vehicle !

shayan

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Re: Charging input ports:
« Reply #21 on: September 03, 2017, 09:02:48 PM »
In the case of the I-MiEV, it was just a power cycle to get everything back to normal.  I have no clue how the Empulse will respond, however, the simple workaround is to charge with the external charger and the Empulse in the "run" mode.  Power up your external charger and if you can vary its output, ramp up the output while watching your KW meter on the instrument panel.  If it starts going negative its showing the bike's systems think you are in regen.  Keep the power on until you reach 80% capacity then shut off the charger.  Connect the onboard charger and after the charge starts, look at the balance screens and see where your highest cell pair is.  This will determine to what extent you can safely charge with your external charger.  Also remember that if you are putting a lot of power into the pack, you can exceed the 4.2 volt limit with the charger on.  Be sure you never are near the maximum system voltage under charge.

I am going to put a Anderson connector on the bike at some time and hit it with the PFC-50.  Its 11KW output is still only 1C so it shouldn't stress the pack in any way.  I just don't want to do anything to damage the bike as I know it won't be repaired and I still like to drive it  8) !

Faking regen is certainly a safe "hack"! And How do you connect the external charger to fake the regen? As in where would the output of the external charger be connected to? Sorry for the "obvious" questions but i'm new to completely understanding battery charger systems :)
 
And yes, pictures please!
Also will u use the full 1C (11kW) power of the charger or are you planning to attempt to start to experiment at around 5kW and slowly bring it upto 1C?

Charging at 1C from 0-80% would take around 45 mins and then about another 45 mins from there to 100% with the onboard charger. So that would be ~1.5 hrs. For longer trips we can do away with balancing the cells for every charge!

nunux59

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Re: Charging input ports:
« Reply #22 on: September 04, 2017, 03:31:06 AM »
I think the bast place to hook an additional connector would be on batteries. Referring to the service manual GND DC VCC DC should be on battery #7 (just above motor controller) and the VCC DC GND DC should be on battery #4 (closest to handlebar) battery #1 (closest to the seat). Another potential spot would be on the motor controller but keeping everything waterproof here does not look as easy.
The service manual is full of pictures : http://www.brammoforum.com/wiki/index.php?title=Empulse_Service_Manual
It is a nice source of information before tearing apart your whole bike :)
« Last Edit: September 04, 2017, 03:44:44 AM by nunux59 »

siai47

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Re: Charging input ports:
« Reply #23 on: September 04, 2017, 07:59:52 AM »
When I do this mod (and not quite ready yet) the connection will be to the battery indirectly.  The most logical place would be to the battery terminals themselves.  However, the positive terminal (located on the upper rear of the top module) is almost impossible to get to without either removing the module or taking a lot of components off the tail of the bike to gain access.  The negative terminal (located on the lower rear of the bottom module) is pretty easy to get to after removing the rear bracket for the motor controller.  The place to access the positive side of the battery is the main fuse which is located above the motor controller.  The fuse is held in by the studs that connect the fuse to the battery wiring.  A simple ring terminal can be used for the connection.  Another benefit of connecting at this point is you now have a fuse between your Anderson connector and the main battery pack.  Another possibility would be connecting to the main contactor which would shut off power to the Anderson connector when not in the "run" mode.  This would be safer from an electrical standpoint but in my case the PFC-50 can be damaged if it is under power and the load it is charging is disconnected.  Neither one of these connection points are really "waterproofed" so just common sense when wiring is all that is needed.

Be aware that any time you are messing with the high voltage system, you need to disconnect the service plug before doing anything else.  This splits the two modules and prevents any voltage from appearing at the battery terminal at the rear of the modules.  The voltages in the high voltage system on the Empulse aren't really high enough to kill you (unless you are standing in a bucket of salt water  :o ) but you could get burns if you short something like a cable or tool while working.  Again, common sense.

nunux59

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Re: Charging input ports:
« Reply #24 on: September 04, 2017, 08:58:29 AM »
What Anderson connector do you plan to use ? 175A or 350A ? Do you have a crimp tool big enough for this kind of terminals ?

175A would be more than enough for charging at 11kw but since I am planning to add an external battery also it may be a good idea to be large enough.

siai47

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Re: Charging input ports:
« Reply #25 on: September 04, 2017, 06:38:35 PM »
The 175 would be plenty large for the task at hand.  My PFC-50B can only put out a max of 75 amps at the lower voltage the Empusle operates at.  I will be limited to about 8.5 KW because of that fact.  In your case you need to remember that if you parallel an additional pack, you are splitting the current between the packs so each is supplying half of the drive current.  In the I-MiEV I paralleled an additional 16 KWH pack with a 175 amp connector with no problems.  I would use #4 wire in your application and it should handle the loads just fine.  You order the Anderson with the pins for the size wire you are going to use.  I have a hydraulic crimp tool that works great with the connectors.  If you don't have a crimp tool you can put the pin in a vise and heat it with a torch to melt solder and fill the cavity where the wire goes.  When melted, plunge the wire into the connector, keep heating it until the solder wicks into the wire.  After the connectors cool, put a bit of shrink tubing over the wire and on to the connector before inserting the pins into the connector body.  Sometimes it does a better looking job than the crimp.

BTW--I still have the 88 LEV-50 cells from the I-MiEV.  That enough to add 15 KWH of extra capacity to the Empulse and crush the bike from the weight  ???

shayan

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Re: Charging input ports:
« Reply #26 on: September 21, 2017, 04:54:53 AM »
Would you guys please be kind enough to post details on doing this mod, once you complete doing it? I'm sure it would be of greta help to everyone on this forum who would like to try a fast charger mod  :)