WHAT SHOULD I DO IF IT DISPLAY DC BUS LOW SHUTDOWN

where did you find this old UPS> ? I'd bet cash it did not just fail 14 years online TODAY.!?
Redux1 this is way too long but there are many sub models of PULSAR and non told yet. by you.
nor if TOWER OR RACK MODEL is your? wow. that. ? not the same batteries at all in both ever.
did not read your manual first.

14 YEARS old it is, and now owned by APC.com (a 2007 event)wiki it.
The HIGH DC means the Charger output is too high
or the 36v 3 battery loop is broken (no load equals charge voltage is too high DC bus)
if you have rack UPS and use 12vdc batteries, in it (not 6vdc as it must) the DC bus will be too high.
UPS is complex and more so not telling full model numbers of it and photo of if.



the LIST OF what can be wrong, (besides bad PCB inside)
wrong batteries, used, or connected wrong.
battery terms rusty. or just loose.
EXB option was enabled before (14 years ago?) and not reconfigured now that it is gone. now.
battery breaker rear tripped. in inside batteries and if EXB option the outside battery breaker tripped. on it.
wire backwards is prevented with connector keys, but if hacked , any thing is possible wrong,.
no photos of yours, the DC bus is 36vdc on the tower. 3x12=36v


AC LINE IN CAN BE SET 100VAC TO 480VAC, (TO COVER WORLD POWER USED)
if not configured day1, correctly there is no hope, only smoke.
what AC voltage is your country, (at home are you) and freqency, 50 or 60HZ, (most are auto set for Hz)


MGE is nOT MEG. at all. sorry but typos like that make help super hard.


just one of many 1500, I can not guess what your REALLY is, Pulsar has many sub models.

https://www.manualslib.com/manual/821986/Mge-Ups-Systems-Pulsar-Extreme-1500.html?page=1#manual


MGE is now owned by APC for 14 years today, UPS company (a top maker)
and this model is not supported now it is too old,,, found in garage sail for $1 USD, I'd pass on that.

and APC does not support this very very old UPS now. they chose not to support it, but gee call them and ask.
Apc.com, click support , and contact them.

next time post photos of front and rear.
and full model number not just "Pulsar 1500," shortened like that. and MGE not MEG.
and what country you live and if at home or using commercial power , 100v or 480vac or what. LINE POWER.?
last , is , if you buy a used UPS outside of your country it will be wrong AC input line voltage. and must be cured first. by strapping or configuration settings,

I have never seen any UPS made that works in all countries, and the few that do many, must be strapped first.
how that is done is covered in every UPS MANUAL made, in the world.
if done wrong this test step, you will get smoke or worse fire. (only fuse can save you from that done wrong)
never bypass fuses OK
and if doing other hacks say so, tell the hacks , like using the wrong batteries.

How are you checking the batteries? If you are simply reading the voltage with a multimeter, then this is probably your issue. The batteries, when getting worn out, will often show full voltage in a static (non-loaded) state, but as soon as they are called on to produce load, their voltage will drop significantly, thus giving the DC bus low indication. Batteries in UPS's are similar to car batteries, they need to be tested under load to ensure they are good. If they are three years old or older, chances are they need to be replaced.

chck all your bus controller and also check DC capacitors.

If your batteries are ok a DC BUS fault and low o/p voltage means one of the componants inside is defective. An end user can not effect repair. You need to have it looked at.

Could you tell me what kind of UPS (brand/model) you have? DC BUS low is most likely caused due to DC-DC converter error or BUS error. If you can send me the brand and model I will look in to it.

Check your DC bus fuse. I have a manual if you need one. Email me at [email protected]

1 - Press the "0" button (28) more than 3s. The buzzer beeps once, and the load is no longer protected by the UPS. It is powered via the Normal AC source. If the UPS is set in frequency converter mode, the equipments will not be powered. If the Normal AC source is out of tolerance, the UPS will generate a 10ms output calibrated break. 2 - For a full shutdown of UPS and connected load, the upstream circuit breaker (notincluded) should be set to the "0" position.

Prag board(main board ) not working properly . Replace the board to solve the problem.

I removed the usb-card. Things work perfectly again.

Buy a CB10 10 ohm ceramic resistor (10%)

Alagator clips on (+) (-) and on the resister. If the battery can not hold the charge after one minute above 12V DC, but drops very quickly that battery is due to be replaced. Very simple test and cost hardly nothing.