UPS - lower wattage but longer time ?

[wp100]

Hi,

Looking to provide backup power to a small aquarium, the average load would be 50w with a peak of 85w at 230v

Can readily buy some 480W UPS from the PC places relatively cheaply but they only use a 9ah battery so they would only give a 2hour backup at best.

Have seen some hack about adding a larger battery in parallel with the UPSs battery.

While I can see that would theoretically work, am a bit concerned about the safety in that from what I have read many of the parts used are designed to only handle full load for just a few minutes, so wonder if, even at a much lower wattage they will be ok for several hours ?

Perhaps just the addition of a cooling fan might be all thats needed at such a low wattage but having no practical experience of these UPS so do wonder if it will work reliably which is the most important factor.


Wonder if using a ready made 300w inverter that are used for long periods, eg in caravans etc, with a large battery and a diy switch over would be a better way ?

 

[kam1787]

Hi,

Looking to provide backup power to a small aquarium, the average load would be 50w with a peak of 85w at 230v

Have seen some hack about adding a larger battery in parallel with the UPSs battery.

1) While I can see that would theoretically work, am a bit concerned about the safety in that from what I have read many of the parts used are designed to only handle full load for just a few minutes, so wonder if, even at a much lower wattage they will be ok for several hours ?


2) Wonder if using a ready made 300w inverter that are used for long periods, eg in caravans etc, with a large battery and a diy switch over would be a better way ?

1) a larger battery will take longer to recharge. should be fine if the UPS is decently designed

2) sounds like a nuisance

What do you need to be on during a power outage? Just the pump? Maybe provide power to only the critical equipment.

 

[wp100]

1) a larger battery will take longer to recharge. should be fine if the UPS is decently designed

2) sounds like a nuisance

What do you need to be on during a power outage? Just the pump? Maybe provide power to only the critical equipment.

Hi,

Yes the wattage mentioned is to cover just the circulation pumps,the average current of a heater and the controllers temp sensor; things like the heavy current lights will be automatically turned off by the controller by a separate mains failure sensor.


As for a decent ups well this is where I do not have a clue, particularly in the cheaper end of the market, the smaller ones available locally are made by FSP, PowerWalker or PowerCool; names I have never heard of before.

From further reading seems you also have to consider the "low" demand they say you need a load of at least 10% of its rated output otherwise it becomes very inefficient, so I would have to go for the smallest available 360w UPS for my typical load of 50w

Thats why I was now thinking a simple 150w inverter and battery might be better ?

 

[FlapJack]

If you use an inverter then someone will have to be there to turn it on, or you will have to design your own start up circuit.

The 360W UPS with an extra battery attached to it sounds like the simplest way to go.