Replacing UPS 9Ah with 105Ah 1

[DaveOB1]

Hi all

Newbee here

I have a small home office and after 5 or 6 years, found the UPS lasting only a 2-3 minutes when the power died this afternoon. Previously it used to run 2 PCs for about 15 minutes. Last had to use it about 2 years ago, so I am assuming that the batteries have passed their prime.

I am looking to replace the batteries, but was thinking about 'upsizing' the existing batteries to something a lot larger, as I would like to add on the CCTV DVR and some emergency lighting to the system.

The existing specs are :

Model ME-1400-BK
Capacity 1400VA / 840W
Voltage 230VAC
Modified Sinewave
Batteries : 12V9Ah x 2

Now I understand that the circuitry in the UPS is probably not designed to charge a 105Ah deep cell battery, but what if I was to externally charge to 105Ah ( say, with an automotive battery charger ) and then connect it to the UPS to keep it topped up. A monthly exercise would be to remove the UPS mains power, use the batteries, connect to the charger and re-charge, reconnect to the UPS.

Can you foresee any drawbacks with this approach ?

My thinking is that, the 1400VA system can run 2 PCs ( 200W each = 400W ) for around 19 minutes ?

My understanding is :
12V9Ah x 2 batteries = 12V x 18Ah = 216W / 400W ( 2 PCs ) = 0.54hr x 60% pf = 0.324 hr ( 19 minutes )

If the calculation is correct, with the larger battery, I could run :
2 x PC @ 200W each = 400W
Router 20W ( guesstimate )
Hub 10W ( guesstimate )
Cordless Phone 10W ( guesstimate )
Backup Lighting 15W x 5 = 75W

Total required = 515W

Therefore, usage time should be :
12V105Ah = 12V x 105Ah = 1260W / 515W = 2.54hr x 60% pf = 1.47 hr ( 88 minutes )

comments please ..

 

[FredWagner]

Your numbers seem to work out, but the monthly drill of shutting everything down, disconnecting the big battery to charge it separately, then putting it back onto the UPS and restarting the whole setup, seems like it would get 'old' pretty fast.
Have you considered 'trading up' to a system which is designed to have expandable battery capability? If that doesn't make economic sense, then simply replacing the present batteries with similar-spec'd new ones, to get back to your original 15 minute runtime, might be your best course, particularly if you don't experience power failures all that often, and can afford to do a graceful shutdown when they do happen.
Some newer UPS's have an app that runs on your primary PC, and automatically exercises your UPS, and lets you know the current runtime without you having to discover it by experimentation. Are you using factory software with your current unit ?

Fred Wagner

 

[DaveOB1]

Hi Fred

Thanks for the reply.

After sleeping on the idea, I thought of a problem. If the power drops overnight ( or when not at home ) then the UPS charger is going to try charge the battery. I would need to be here when the power resumes so that I could take it off the UPS and connect to the mother charger.

Also, I think maybe the inverter part of the UPS is probably designed to run only for a certain time ( the max time it would run with the original batteries ).

I have changed my thinking to an Inverex 1000 charger / inverter ( has a 8amp charger ) and 2 x 105Ah batteries.

 

[FredWagner]

The inverex info I found says it will charge up to 100 Amp-hours of battery - so two 105Ah batteries might be exceeding the charger rating! for your original idea, the runtime for the inverter likely would not be an issue, but having to swap the charger for recharge vs float would be.
UPS software and a USB connection so the inverter can talk to the computer, and let the computer shut down gracefully before the batteries run down, if that happens, can be nice to have. I don't see that feature on the Inverex. If it will just be your router, TV and DVR running unattended, no big deal. But if it's computer equipment, or a non-technical operator who might not heed a shutdown warning, it could be an important factor

Fred Wagner