I'm using a miniBMS system in my batteries, and the loop is connected to
a Thunderstruck motors EVCC unit, which fires off a buzzer if the loop
drops (indicating a low voltage event) while driving or turns off the
charger if it's charging (indicating a high voltage event).
A few days ago I was driving around (short trip, pack no where near
discharged, but not super close to fully charged either...) and the
buzzer started to sound in a very regular pattern (about 1 second on,
one second off).
I have never experienced this pattern of sounds before.
Sometimes at the end of a long trip I've gotten a low voltage event and
the buzzer will sound briefly if I am drawing a lot of amps, but the
buzzer would always stop as soon as I let up on the throttle.
This buzzing on/off/on/off continued while driving for another mile and
when I was parked at home. I switched everything off and started it back
up again (resetting power to the EVCC) and the pulsed buzzing continued.
I have a physical switch in my BMS loop for testing purposes, and when I
opened it, the buzzer went from intermittent pulsing to solid on, so the
EVCC was definitely still monitoring the loop.
I have a parallel pack trackr system that monitors the voltage of (every
pair of) cells and everything looked normal on it, no pair of cells was
low enough to be triggering a low voltage alarm.
I left the truck sitting for a few hours, and when I tried it again the
intermittent buzzing had cleared and gone away. I've driven it a good
100 miles since then with multiple charge cycles and haven't heard it again.
The other option is that the EVCC was signaling the buzzer in it's own
pattern for some other type of fault (and then honoring the dropped loop
signal to turn it on continuously), but the support staff at TSM felt
that the pulsed signal was coming from the BMS loop, and the EVCC manual
doesn't mention the buzzer sounding for anything other than a BMS loop
I'm just wondering if anybody has experienced this type of on/off/on/off
loop signal with the miniBMS boards before, and if so, what it indicates?
Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)