Newbie- Any simple way of upgrading a 500VA line interactive UPS to 750VA or 1000VA ?

[cnc2]

Hi guys,

I will be upgrading my current old computer (350W PSU) to a better one with a 600W PSU.

As I have a nice 500VA line interactive UPS (powercom BNT-500A) that works fine (great response time...etc) I just want to upgrade it by adding a 2nd battery & upgrading a few parts, but I'm not sure it's doable & not sure how to do it, so my questions:

1) Is it enough to upgrade the FETs...etc (the ICs on the big heatsink) to higher power ones (higher amp rating) ?

2) What to look at when upgrading FETs ? (if applicable)

3) Will the stock transformer do the job or it will be the limiting factor preventing the upgrade ?

4) is it safe to keep the stock heatsink ?

I have another unit in here rated @700VA but it's lower quality, I think it isn't line interactive, it has a poor response time during very short voltage drops & it has a smaller transformer which vibrates the metal case it is bolted to...creating an annoying buzzing noise.

Thanks !
cnc2.

[mike_Kilroy]

OK, let me change my original post. NO, I cannot see anyone even remotely considering redesigning a UPS that runs on 120v wall socket power like this. I am an graduate electric engineer who designs circuits all the time but I would never consider such a mod to a UL listed thing that could easily burn my house down.

That said, what is wrong with the 500va unit you have grown to know and love on a 600va power supply? It just means if your new computer pulls full 600va (which it won't) your uptime will be just a tad shorter?

THAT said, if you really feel it is important to have more up time, I would consider adding another 12v gel cell battery in parallel to the internal one and not worry about it. I assume if you run it way down you will be onsite to monitor it recharging on power return and making sure it does not get too hot. failure mode of these ups things is the batteries die and wont charge. If u ever replaced the gel cells in ur ups's you probably know sometimes the bad ones get really really hot and the ups still does not catch fire. I replace my batts about every 2 years.

[cnc2]

Thanks for the reply Mike !

Well, mine runs on 230V & has a sticker on it marked 300W max...the new computer will have a 80 certified 600W PSU (80% efficiency), 600W is the output power of the PSU while its input (drawn) power should be 20% higher, around 720W.

I have already replaced a gel cell & I know that wiring two cells in parallel will double the up time but what really bothers me is the inverter circuit which can end up in smoke if the PSU draws up too much current.

I didn't think about it but it now seems obvious that the 500VA UPS might be designed with a headroom making it able to provide 600VA...BUT will it do 720VA without smoking the ICs ? (I have no idea of the usual circuit oversizing, design practices)

Is there a way to make sure it won't smoke ? (like checking ICs ratings...etc)

Thanks !
cnc2.

[cnc2]

Hi Mike !

I just saw your original post very funny

Thanks !
cnc2.

[mike_Kilroy]

crud! I thought that original was GONE..... I see one can track even the deleted stuff - dang! Anyway, I missed the idea of actual supplying watts from the batteries without power - I was just thinking of charging them only.... So your original question/comment had more merit that I thought! Anyway, it is my opinion you really don't want to be messing with the design of something like a UPS that can cause a fire if not right. Makes me feel better that UL tried to make it catch fire and was satisfied enough to put a UL sticker on it. Still think your best bet is to go to a larger one..... I will someday run 2pc #14 wire from my solar charged 12v battery bank in workshop to each UPS in my house/garage to have BIG storage capacity behind each individual UPS on each computer & big screen TV setup, but without concern over the inverter's local size.....I would have no concern disconnecting the charge side of the circuit locally in each UPS... so many ideas, so little time!

[cnc2]

Well, that original post was gone from the forum, but remember that when you post a reply it is instantly e-mailed to all the members subscribed to this/the thread...so I read your original post by checking my e-mail

The good thing about an UPS is that it's possible to test it after the mod to see if it gets too hot...etc. I wanted to save some cash, avoiding buying a UPS instead of few ICs...but if the testing frys my PSU the upgrade will cost twice as much......Well, I won't go this way unless I'm guided by a dardevil professional

Oh, solar/wind PC was a far thought I had...ah the no plug PC/home server
The only advice I can give you is: DO NOT FORGET TO VENT THE ROOM WHERE YOU HAVE THE BACKUP BATTERIES...or H2 (hydrogene gaz) switch BOOOOOOOOOOMMM

Thanks !
cnc2.

[george4657]

Don't forget the 600 watts is the peak rating for your power supply. It will only draw the power it needs which should be far less than the maximum.
Why not put a meter on it and measure its actual draw. I may not even be 500 watts.

George

[cnc2]

Thanks for the reply George !

Well, I can't because I don't have it yet, but I have found a review which shows its efficiency under different loads, check this link: OCZ ModXStream Pro 600 W Power Supply Review | Hardware Secrets

And you can see in the table that at full load it draws 733W from the outlet/UPS.

It's true that it won't be pulling 500W all the time but, if for exemple, the CPU, graphics card, hard drives & CD were at full load, it'll easily be pulling 733W, and in the case of a power outage at that moment...bang, 733W from a 500VA UPS.

With an upgraded UPS, I could even plug the display to the UPS, which is very useful.

Any ideas ?

Thanks !
cnc2.