Extending UPS runtime

[Crowley]

One of my clients has a 3KVA Mecer UPS and is looking to extend the running time. The external battery packs for this range of UPS's only work on the 6KVA and 10KVA units.

Any suggestions on how to do this short of buying a bigger UPS?

 

[GoneWithTheWindows]

You are asking for headaches, rather just advise them to upgrade the UPS.

 

[bigboy529]

Bigger batteries plus decent battery charger plus bypass battery alarms will do the trick for DIY.. If for a client, just advise them to get a bigger UPS, preferably one which can be expanded in future.

 

[The_Ogre]

Why do they want to extend the running time? Recent hardware upgrade? If they're using more power hungry hardware, they'll need to upgrade to a beefier UPS. Perhaps you should also explain to them what the actual purpose of a computer UPS is

 

[sajunky]

+1, considering poor efficiency of a standard UPS.

On the other side:
Models accepting external battery packs have a separate charging units. Your model do not. The only way to extend runtime is to remove internal batteries and connect external motorcycle/car battery (or two/three/four - if batteries are wired in series).

There are two problems with such solution:

1. Charging big batteries will take forever. It is because such cheap UPS's only use one (floating) charging stage. It will take two days for charging a large car battery. Next power cut can happen before batteries are fully charged. You will need a separate fast charger and be present on the site to do maintenance.

2. Most of UPS's are not designed for prolonged use. They use two forms of protection: thermal sensor and run-time timer which will switch off UPS after 10 minutes, a nasty things for such attempts.

I have 850VA Mecer UPS cutting-off after 10 minutes irrespectively of the battery voltage. I managed to disable timer, but it is getting hot, as power conversion is inefficient. Had another 2kVA Mecer with the same cut-off behaviour, but it died in a blast when I connected a fast charger (failed disconnecting both leads from the UPS, only a single one).

 

[oober]

Install a bigger pure sinewave UPS in front of the first one?