I have just reconnected my batteries after replacing damaged cells. Reconnecting the Anderson connector went without incident and I used a domestic light fitting on the connector itself as per the video on YouTube which I posted about. the bike is now back and running, with a 200a Bussmann fuse instead of the OEM 125a. I'm hoping that the range will be increased. the bike feels more powerful.
I have a question for the experts.. What exactly do the three capacitors do? Where do they fit into the picture on the MC board? they obviously store current and like to greedily suck until they blow the fuss or whatever, unless stopped from doing so by the ICL device. but what are they for??
Since there is inductance in the leads from the MC to the battery, the bus caps provide the initial burst of current when one of the transistors in the IGBT switches ON. w/o the caps there would be voltage fluctuations at the IGBTs.
here's a simplified explanation:
Think of the battery wires as an inductor - it takes time to change the current flowing through it
think of the motor controller as a big switch.
each time the motor controller switches the motor on (connects to the battery) the current needs to come from somewhere.
intially it can't come from the battery as there's an inductor in the way, so it comes from the capacitors instead, until the current from the battery ramps up.
without the capacitors, the voltage at the motorcontroller would fall
when the motor controller turns the switch off, there is already current flowing from the battery.
as the current can no longer go to the motor, it has to go into the capacitors, until the current ramps back down to 0 again.
if the capacitors weren't there, the voltage at the motor controller would keep increasing until the voltage rating of the switch (in this case IGBT) was exceeded.
The capacitors smooth out both the voltage and current fluctuations during switching.
This all happens several thousand times a second (I forgot what the actual frequency is, but between 11'000 and 17'000 Hz)
The caps don't have to store very much charge, but they have to charge and discharge rather quickly.
The voltage ripple may be around 5V, but the current is ~250A.
That is why when they are at 0v and you connect a 135v battery with low resistance, the current initially is very high
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
oops, beaten to it
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
yeah but more thorough...