reverse battery polarity

[Anonymous user]

I foolishly connected my battery reversed to my BK605MC. A spark later and the UPS is completely dead.
I see two paralleled 40 amp fuses between battery+ and the board but they are both good, and the unit breaker is set in/on. Next to both battery leads are board traces that say "F 5 amp" but they are copper strips on the circuit board and good anyway.
Any advice where to start? I know my way around with a schematic but Im blind... Thanks

[BillP]

unfortunately, APC cannot provide internal schematics as they are proprietary. i am not sure if anyone around here has any general useful information though..

[Anonymous user · Accepted solution]

Let me give APC a design idea - FUSE the DC outputs to the battery! Whats that cost - 30 cents?

[BillP]

Hi, am not sure that would provide your intended protection really.

It only takes 0.65V reverse to destroy a solid state junction {which is what may have happened} and providing some form of polarity protection is going to lead to DC losses along the way.

An alternative could be polarised connectors which some of the larger units have, I guess where the unit you are dealing with is using spade terminals.

Good luck and sorry I couldn't be more helpful.

[Anonymous user]

HWL wrote:
Let me give APC a design idea - FUSE the DC outputs to the battery! Whats that cost - 30 cents?

Some battery packs are designed that way, such as the RBC6 and RBC7, but the purpose of fuse isn't protect UPS against gross user error. The low-voltage side of the transformer has a very small resistance and the only thing standing in the way between it and the battery are MOSFETs. The MOSFETs chop the battery voltage and use the inductance of the transformer to limit current, however if one of the MOSFETs shorts out, you've got battery directly across the winding and pull a massive amount of current.

The fuse will blow in the event of an MOSFET failure to protect against battery explosion and fire. NOT against damage to UPS from incorrect batteries/incorrect installation thereof.

[Anonymous user · Accepted solution]

Very enlightening post from KVAr, thank you for that!