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400W UPS Modification to supply 3 computers

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Oct 28, 2009
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UPS Modification


I would like ask about UPS modification...

For example,
I have a 400 watt UPS, but I have to supply 3 computer/ some unit use electricity more than 600 watt.

What components i have to change beside the battery.

I need your advice... :idea::idea:


UPS Modification

change transformer for the requird power.
add one or two pair mosfets
if using overload cut off correct it to your required level

Re: UPS Modification

I see...

but this UPS using overload cut off, but I do not know, what kind of overload cut off component (model or specification).

For your information, my UPS now is 400 watt, but I want to upgrade my UPS until 1200 watt.


Re: UPS Modification

I suggest you to not try to make such modifications!
In general small UPSs like the one you are referring were developed to be really cheap.
Just some of the parts you will have to modify:
1) the transformer is by default designed for intermittent use (non continue), so its temperature will skyrocket if you use it with higher ratings than the default one. You will need a new transformer.
2) the inverter power devices (by default MOSFETs) will require more devices put in parallel to the default ones. How will you dissipate the heat from the new ones?
3) EVERY connections (cables, PCB traces, ...) will have to be changed to support the much higher current. This is valid for the battery power and for the line (mains) power.
4) every device used for filtering the mains will have to be modified accordingly (filters/inductors/...)
5) the same will be for the TA used to identify the load: you will have to modify it or using a new one.
6) I think your UPS is using a single 12V/7.2Ah battery: don't believe it is possible to put several more in parallel: your battery charger will not be able to keep the new batteries charged and it is almost impossible to get a good efficiency of the UPS when you try to "juice" more power. You will have to use at least 24V (2 batteries) when working with 1200W; even better 4 batteries (48V).
7) you will have to override the security checks (overload, ...) of the microprocessor inside the UPS. Unfortunately for you, I don't think you have the source code of the firmware... How will you be able to change the lots of internal parameters of the "new" UPS?
8) How will you be able to use the same case for the UPS?
9) How will you cool it?
10) even if you will succeed to create a such "Frankenstein" UPS, its will be really UNSAFE to use it! I will keep it VERY FAR AWAY from me!!!

My simple suggestion is to buy another one UPS! It is safer and cheaper then your proposition.

modification of old ups is a big task. even you have to change the casing also ( to keep big transformer ). if you want to modify a battery build in UPS. most of all the companies now making ups are using small transformer ( 60w to 150w ) for 600va ups. and again for ups for 3 computers can use 12v battery better go for 24v to reduce battery current

Thanks for all your advice.... I need that.

I'll buy new one for better and safer.


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