MGE Galaxy 3000 15kVA Battery CB open

[Anonymous user]

Hi guys, we have a 15kVA MGE Galaxy 3000 with an external battery rack with 24 X SW91W001 (M2B12-5-5X) batteries.

We checked individual batteries and at 100% charged the avg reading for each battery is voltage 13.5Vdc with 198Amps 10.8 mOhms (internal resistance) and 92 MHO (impedance)

Overall string voltage is 324Vdc with21C temp and 23 months service life. With a very minimal load of 0.7kVA the back-up is 2 hours 28 mins.

We are getting an alarm saying that the battery CB is open but when inspected the CB is still closed. When we reset the battery CB the UPS goes back to normal status but then in about 8 hours the same alarm appears - Battery CB open.

We know that there is a thermal switch at the battery CB. Is this the cause?

Thanks and appreciate any feedbacks.

[BillP]

Hi,

Did you check DC voltage to GND?

Hope I could help
M

[upsguy_apc · Accepted solution]

They UPS alarms for the battery CB off of a Normally Open contact in the batt CB. When the breaker is closed this contact is also closed. Most likely there is either a faulty contact in the breaker or the wiring is suspect. If the batteries were actually suspect you would get a rectifier/charger fault and not a battery CB fault.

I'd call APC support and have them tell you the terminal block location to check the wiring.

[Anonymous user · Accepted solution]

We did a few more trouble shooting and it is actually the secondary comms wires ( 4 nos) within the Merlin Gerlin Battery breaker was loose.

The breaker face cover was opened and the wires re-tightened. The UPS have been running fine now for some time. No more reoccurence of the Battery CB Open alarm.

Thanks all for the support.