[GizmoEV]

Originally Posted by Ziggythewiz

I don't recall what Jack was doing when the cell died, however he has driven a car to a halt on purpose before to prove how great bottom balancing is.

Didn't he say it took out his charger because the cell went open circuit? Maybe I'm miss remembering it.

[JRP3]

Yes, he said the cell "opened up while we were charging and took out the Manzanita."

[Coulomb]

Originally Posted by JRP3

Yes, he said the cell "opened up while we were charging and took out the Manzanita."

Took out as in damaged it? How does an open circuit cell damage a charger? Surely the charger just sees the current go to zero, and terminates the charge soon after.

The cell and its battery monitor / management system (if installed) has to deal with full charge voltage less rested pack voltage across the cell, which is a design challenge. But the charger I would not expect to be stressed at all.

[ Edit: maybe if it doesn't open circuit cleanly, it might open and close milliseconds apart for a while, which might cause current or voltage spikes that the charger isn't designed for. But it still seems like a stretch to me. ]

[Ziggythewiz]

I'm guessing it sees the open cell and thinks, hey! 0 voltage! This thing needs some serious charging!

And then it tries to dish out the juice.

[Coulomb]

Originally Posted by Ziggythewiz

I'm guessing it sees the open cell and thinks, hey! 0 voltage!

But the charger won't see zero volts, it will see a pack that is whatever voltage the charger is presently putting out, and won't take any current. An open circuit, in fact.

So maybe it will periodically stop charging, and measure the resting voltage; that will be zero volts. So then it "tries to dish out the juice", which means it will go to its CV setting, and no current will flow. It's not like it's going to try to go to infinite voltage to try to make some current flow.

[JRP3]

I don't remember the technical explanation but the Manzanita chargers cannot be turned on with no load, if they are they die. I guess the same thing happens if load is removed during charging.

[PStechPaul]

If there is inductance in the output, an open circuit (actually probably seen as a capacitance) might cause an inductive spike or even a resonant circuit where high voltages may be produced. Once it starts to break down components, things could go south in a hurry. But that would indicate a poor design or a component failure to start with. A battery charger should be able to tolerate anything from an open circuit to a short circuit, as well as some inductance and capacitance.

I just looked at the charger information at http://www.manzanitamicro.com/downlo...ry/15-chargers, and it seems that they can be used for anything from 12V to 450V output. So if they have an internal bus of 180 or 360 VDC, they must use some sort of buck/boost topology which involves an inductor and a high frequency PWM. But the "potential" is there for the full high voltage to be applied to the battery pack until the regulation kicks in. Apparently you can adjust the output over this wide range to match your battery pack, and there is always the chance that the voltage or current settings were incorrect. And a true current mode regulator will use all of its DC bus voltage in an attempt to get the charge current needed. The specs say it starts in current mode and then switches to voltage mode, so unless it also has a voltage limiter it would apply up to 450 V to the pack with an open cell. And that might be bad...

[palmer_md]

There is a clear warning right in their manual....page 8....

NOTICE! DO NOT unplug the gray SB-50 Anderson connectors (DC line) from
your charger while it is charging! If the battery pack is disconnected while the
charger is putting out power the charger can be damaged. Failure to heed these
warnings may result in significant internal damage to the charger which is not
covered under your warranty!

http://www.google.com/url?sa=t&rct=j...4-M_yTyjL6EG9Q

[JRP3]

From the Manzanita manual:

NOTICE! DO NOT unplug the gray SB-50 Anderson connectors (DC line) from
your charger while it is charging! If the battery pack is disconnected while the
charger is putting out power the charger can be damaged. Failure to heed these
warnings may result in significant internal damage to the charger which is not
covered under your warranty!

[JRP3]

Beat me to it As I remember there is a mod you can have them do to the charger if you know you don't need the max voltage possible. If there is a lower max voltage limit hard wired I guess things won't blow up if you open circuit it.