HP R5500 runtime query

[operator_2]

We have a R5500 UPS with 1 ERM attached supplying battery backup for a HP EVA8400 in a 42u rack (rack completely full with 2 controllers, 20 disk shelves all of which are 2 thirds populated with drives). The UPS displays 25 - 50% load on its display but this only equates to 20 minutes runtime displayed within HP Power Manager. This can be roughly halfed in the event of a power loss (actually drops to 9 minutes)as the EVA has 2 power feeds, 1 straight mains the other via the UPS as all devices have 2 psu's.
I have already ran through the configuration on the front panel of the UPS and set it up so it knows it has 1 ERM connected.
I would have expected a bigger runtime than this, but not 100% sure?
I have tried disconnecting the ERM and configuring the UPS so it has no ERM connected and surprisingly enough the runtime displayed in HP Power Manager remains the same? Maybe the 9 minutes is correct? But I would have expected the runtime to change by removing the ERM and configuring UPS for none? I then replicated this on a spare 5500 with 1 ERM attached and couldn't get the runtime to change. Each time I cleared cache etc within IE when I accessed Power Manager and even went as as far as powering down the spare UPS once I had removed ERM and reconfigured still displays same runtime following this. Any ideas anyone?
(The UPS is at firmware level 2.08 and HP Power Manager ver 4.3.2)

[operator_2]

I did some more testing on this today on the spare 5500 and ERM we have. I observed the following:-

The UPS seems to have a runtime 'ceiling'. The test UPS we used to replicate the problem had no load on it and displayed a runtime of 455 minutes. When we configured and removed the ERM, so it had none the runtime dropped initially and then hovered around 449 /455 minutes. When we added a small load (2 servers) to the UPS it dropped to 110 minutes.
When we added the ERM back to the UPS still with load runtime went up to around 300mins.

So, it appears the UPS does need some kind of load to calculate its runtime (makes sense I suppose)
This doesnt however answer my original problem on the EVA8400 ups. We will do some more testing on this next week. I will try a 2nd ERM on it and see if the runtime increases as you would expect.

[operator_2]

Not sure what I did differently but worked first time when I tried again. Did everything as last time - but this time seemed to work, strange?
Mark.