Does my SUA 1500I need to be calibrated battery cut-off voltage for new lead-acid batteries

Anonymous user · ‎2021-06-28

Hello, I have replaced new batteries to my APC SUA 1500I.

But I just realized the maximum charge voltage for my 12V 45Ah lead-acid batteries (I call them Water battery) is only ~12.4 V each

The UPS battery level shows only 40% even though the batteries are fully charged

So as far as I know, the original batteries were other types, they had higher maximum charge voltage, maybe 13.2 each.

the fact that if I go on using these new batteries, the UPS will automatically shut down even though the batteries still not running out.

My water batteries are available and I don't want to waste money buying other ones...

So my question is, can I change the cut-off voltage or change the operating voltage range, whatever it is called...?

Thanks for your understanding and your help.

Malvineous_apc · ‎2021-06-28

Do a bit of research on PROG mode. I have only just started reading about it, but it seems that it is possible to adjust some constants that are used to detect the battery voltage, so you can make the UPS think the battery voltage is higher than it really is.

In theory this will make the UPS stay on for longer, but it will likely make your batteries go really flat after a power outage (because the UPS shuts down too late) which could shorten their life. It also won't fix the problem with the float charge being too high, so this will slowly boil the water out of your battery and you'll need to top up the water much more regularly than normal.

Also bear in mind that the larger the battery the more current it will draw while it is charging. APC support advised me a number of years ago that the chargers in XL models (the ones with an external battery connector) are rated to provide more current (up to 10x the current of the internal batteries) however the non-XL models (no ability to connect external batteries) are only rated to provide enough current to handle the internal batteries. So if you use your wet lead acid batteries make sure they are equal or smaller capacity than what the charger is rated for or you might overload and burn out the battery charger inside the UPS.

See Answer In Context

BillP · ‎2021-06-28

Hi Pham -

We do not support the use of third party batteries with Smart-UPS and unfortunately there is no way to modify the float voltage on the charger for use with different battery types.

Liam

Malvineous_apc · ‎2021-06-28

Do a bit of research on PROG mode. I have only just started reading about it, but it seems that it is possible to adjust some constants that are used to detect the battery voltage, so you can make the UPS think the battery voltage is higher than it really is.

In theory this will make the UPS stay on for longer, but it will likely make your batteries go really flat after a power outage (because the UPS shuts down too late) which could shorten their life. It also won't fix the problem with the float charge being too high, so this will slowly boil the water out of your battery and you'll need to top up the water much more regularly than normal.

Also bear in mind that the larger the battery the more current it will draw while it is charging. APC support advised me a number of years ago that the chargers in XL models (the ones with an external battery connector) are rated to provide more current (up to 10x the current of the internal batteries) however the non-XL models (no ability to connect external batteries) are only rated to provide enough current to handle the internal batteries. So if you use your wet lead acid batteries make sure they are equal or smaller capacity than what the charger is rated for or you might overload and burn out the battery charger inside the UPS.