UPS 3 hour up time for 30W?

[Rroff]

I certainly wouldn't use Li batteries - i dont see the point. they dont last as long and also have a fire risk compared to the lead acid.
Lead acid batteries can be good for up to 10 years if you keep them at a good temp.

The kind of lead batteries used in UPS generally have around 200-300 full depth charge cycles before capacity starts dropping significantly, 6-9 years lifespan if maintained, li-ion usually 500-3000+ cycles and 10-20 years maintained - though Li-ion can potentially last much shorter under unmaintained conditions.

LiFePO4 and similar chemistry largely alleviate the potential fire risk with li-ion, though largely you have to be pretty unlucky unless a li-ion battery is subjected to impact damage or a serious charging fault causing overheating (usually due to poor design or abuse).

 

[aardvark]

The kind of lead batteries used in UPS generally have around 200-300 full depth charge cycles before capacity starts dropping significantly, 6-9 years lifespan if maintained, li-ion usually 500-3000+ cycles and 10-20 years maintained - though Li-ion can potentially last much shorter under unmaintained conditions.

LiFePO4 and similar chemistry largely alleviate the potential fire risk with li-ion, though largely you have to be pretty unlucky unless a li-ion battery is subjected to impact damage or a serious charging fault causing overheating (usually due to poor design or abuse).

i guess my opinion is coloured by our data centre.
we have maybe 2 megawatts of lead acid batteries and it all works fine.
meanwhile the first major data centre fire in 20 years happened a year or so ago and it was because they use lithium batteries.

 

[Rroff]

i guess my opinion is coloured by our data centre.
we have maybe 2 megawatts of lead acid batteries and it all works fine.
meanwhile the first major data centre fire in 20 years happened a year or so ago and it was because they use lithium batteries.

Data centres will often use gel deep cycle or AGM batteries, especially these days, which are another kettle of fish again to the lead acid batteries in your average consumer UPS.

I have a bigger scale backup system I use instead of a UPS with deep cycle gel batteries rated for minimum 1300 deep charge cycles and 12-16 years at normal room temperatures, probably near 20 if maintained in a temperature controlled data centre and only required occasionally. Using a Renogy inverter with UPS function. The only real disadvantage compared to li-ion is the power density and weight - the batteries are 33Kg each! the delivery guy was NOT amused with me.

 

[aardvark]

Yeah our batteries are a good 35kg.I made the mistake of saying 'sure, i'll give you hand' when we were replacing 50 of them.

 

[Meddling-Monk]

One thing that wasn't mentioned early on in this thread (and may help someone else) is if you got a pair of UPS you could run them in parallel and split the loads (if you manage to get a 50/50 split then you should get roughly the same runtime).

That does however need a bit of planning in terms of current when charging so I wouldn't personally do that unless there's a twin (or more) socket from the wall available.

Yeah, I did query if splitting it by two UPS (in parallel) and whether that would be able to hit the target 3 hour mark given the power requirements of the comms units in play. Unfortunately it's not a common topic is appears with many variables (especially from the UPS in question, particularly the battery and its uptime vs power needed). Also, as you correctly identified, would need another socket from the wall which I didn't have here available . But even then in my scenario, it probably would not have been viable, because it would need more space for the UPS units as well as more trailing lines for the power distribution, which would cause a hassle when my parent would waddle over with their frame and/or stick and being potentially a trip hazzard. So the less clutter option was the best choice (for me here).

Looking at the power graph of the 1500VA Cyberpower, it also appears to have a (relative) upper limit (minimum load) to battery time where it can't hold the power up longer. So being able to go from it's projected 120 minutes (2 hours) at 50W load to 180 minutes for around a 30W load (probably less given it was giving me 195+ minutes projection from the UPS), suggests that the normal halving of power required doesn't provide back double the up time available from the battery that they have in their runtime chart projections once below a 50W pull and there likely being a limit to the uptime vs power pulled.

Would absolutely go with a parallel setup if viable though, just it wasn't in this particular scenario.