UPS battery testing

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mover85

29 posts

Geek

#2633111 10-Jan-2021 15:46

SomeoneSomewhere:

Oops, missed some of the comments above.

If you get a sparky who's willing to rewire the pack, you may be able to get a similar capacity with 1-2 strings of batteries, for about $3-4k. I would probably not go with 28Ah batteries as that's going to cost a lot more than strings of ~75Ah or 140Ah batteries.

I think smaller batteries would be good idea, we do have a generator and manual transfer switch. The load on the UPS is only 350w (that includes my network cabinet). The network cabinet is set to shutdown after 30mins to lower the load to 50w.

My father wants to replace 1-2 strings in stages, i'm just not sure if that's a good idea.

SomeoneSomewhere

1804 posts

Uber Geek

Lifetime subscriber

#2633117 10-Jan-2021 16:09

Replacing batteries in stages is probably not a good idea, though I'm not certain.

To confirm, your network cabinet is ~300W and the ventilator ~50W?

If so, your UPS is probably substantially oversized and the standing losses are going to be most of your load once the network is shut down. As others have noted, your UPS is approaching end of life and it may be worth considering moving to a 6-800VA one that is better sized for the load.

As you've got approximately 13kWh of batteries (when new), assuming you're using 100W at DC, your batteries would be good for ~130 hours when new, to empty. I'm guessing that's substantially more than you need.

I'd be looking at approx 2-3kWh of batteries with a small inverter, and a UPS just to cover switching between mains, generator, and inverter. Throw a big charger on your batteries so that they charge in a few hours off the generator - the charger built into a UPS typically takes 10 hours with the stock batteries, and could take days with large extended banks.

mover85

29 posts

Geek

#2633129 10-Jan-2021 17:13

SomeoneSomewhere:

Replacing batteries in stages is probably not a good idea, though I'm not certain.

To confirm, your network cabinet is ~300W and the ventilator ~50W?

If so, your UPS is probably substantially oversized and the standing losses are going to be most of your load once the network is shut down. As others have noted, your UPS is approaching end of life and it may be worth considering moving to a 6-800VA one that is better sized for the load.

As you've got approximately 13kWh of batteries (when new), assuming you're using 100W at DC, your batteries would be good for ~130 hours when new, to empty. I'm guessing that's substantially more than you need.

I'd be looking at approx 2-3kWh of batteries with a small inverter, and a UPS just to cover switching between mains, generator, and inverter. Throw a big charger on your batteries so that they charge in a few hours off the generator - the charger built into a UPS typically takes 10 hours with the stock batteries, and could take days with large extended banks.

The cabinet is 300w and my (and my brother's at night) ventilator uses ~50-90w. I forgot to mention that during an outage we have to run more equipment off the UPS but that is only in bursts (mealtimes).

Maximum load would be ~600w.

Your idea sounds good, though.

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