Back-UPS RS 800 Not charging

[canadaboy25]

Re: Back-UPS RS 800 Not charging

So I figured I'd post an update in case anyone else happens to have the same problem. Since one person already has, it's probably likely.

After using the UPS as a surge protector for the past 8 years and having my computer turn off after every little power flicker, I figured it was finally time to fix it.

After a quick google search, I was able to find the schematic for this exact UPS complete with proper component designators and values. I don't know if I just previously did not look, or if the schematic has been uploaded since I worked on it last time. I will attach the schematic in case anyone else needs it.

The 5th page of the schematic is conveniently labelled "Battery Charger Circuit". It didn't take long to trace the cause of the blown F3 fuse to a shorted MOSFET Q40. The part number of the MOSFET is 94-2358 which is some discontinued International Rectifier FET with no datasheet available. Since the schematic lists it as a 100V FET and the circuit runs through a 2A fuse, it shouldn't be too critical what replacement is used. I ended up using a 230V 25A FET that I had lying around from a salvaged plasma Y-Sus board. I'm sure this is overkill but it was handy and it had the correct footprint.

After replacing the MOSFET and the fuse, the unit now charges my batteries just fine. I am using two large batteries from a mobility scooter and they seem to be working well.

Hopefully this can help someone else out.

[vdubbus77]

Re: Back-UPS RS 800 Not charging

It seems one of the mosfets is shorted, Is there anyone that can tell me the value of the r145 resistor? Mine is a tad toasty and from the pictures I am coming up with .78 ohm which is proving difficult to source.

[Agent24]

Re: Back-UPS RS 800 Not charging

A resistor getting hot means it's passing too much current. Probably something downstream from that resistor is shorted - which makes sense considering the fuse blew.

If the resistor wasn't bad already, it likely is now, if it got that hot. You should replace the resistor and you also need to find out where the short is that blew the fuse in the first place.

[vdubbus77]

Re: Back-UPS RS 800 Not charging

There are some terrific pictures in this thread that can be used to help with my situation so I will bump this old thread. I also have a blown f3 fuse, when I removed the fuse I jumped the fuse terminals and my batteries started charging. However, the resistor (r145) right next to it got so hot it melted the solder holding it in place. Any Ideas? Is the resistor No good?

[kc8adu]

Re: Back-UPS RS 800 Not charging

its modded with an external truck battery.
if the date on the battery is what you are after its sometime mid 2013.
no date on the ups.

[stj]

Re: Back-UPS RS 800 Not charging

got a datecode stamped on them?
you normally do.

[kc8adu]

Re: Back-UPS RS 800 Not charging

just disconnected the anderson powerpole connector to the back of a connext(apc)700.
chirping and replace battery came on.
the battery probably could be totally worn out without tripping the warning.
its an exide d31 agm.

[budm]

Re: Back-UPS RS 800 Not charging

Since it does the self test when it is first turn on, now once it is on, disconnect the batteries to simulate fail batteries or fail charging circuit to see how smart the system really is to see what kind of warning you will get.

[brethin]

Re: Back-UPS RS 800 Not charging

all mine do.
when you hit the power button it turns on the connected loads to the line then about 10 seconds later it goes to battery for a test.tells you if the batteries will hold up the load.
if it fails you get an annoying beeping.

Then I would guess your units are not old. Like I said the old units I have don't care about the battery condition to work they just don't give much time when the unit inverts. I do have 7 newer units that do perform the self test and will not work with a degraded battery.

[kc8adu]

Re: Back-UPS RS 800 Not charging

all mine do.
when you hit the power button it turns on the connected loads to the line then about 10 seconds later it goes to battery for a test.tells you if the batteries will hold up the load.
if it fails you get an annoying beeping.

[brethin]

Re: Back-UPS RS 800 Not charging

All APC UPS always need fresh working batteries so the device to pass it self test (at boot up), and then it starts charging them.

Simple as that.

Not all APC UPS do a self test. I have a few old APC UPS (metal cases) that will function fine with worn batteries, they will just not provide the backup time a new battery would.

[Kiriakos GR]

Re: Back-UPS RS 800 Not charging

All APC UPS always need fresh working batteries so the device to pass it self test (at boot up), and then it starts charging them.

Simple as that.

[MarieShaw]

Re: Back-UPS RS 800 Not charging

Thanks For Solution.

[kc8adu]

Re: Back-UPS RS 800 Not charging

looks like something i would do.oh wait id did that about 7 times here.
the newer apc units are junk.
old metal cased ones i hang on to.
in the o.p's case the charger got killed by a shorted battery.
wish i had one like it here to autopsy.probably easy fix.

[ThePCDoctor]

Re: Back-UPS RS 800 Not charging

Many years ago now, I was given an APC brand, 600VA, UPS with dead and leaking batteries. (2x 6vdc gel-cells).

APC brand is the only one I've tested that WILL accept much larger batteries, like car batteries.

My own replacement batteries for the above mentioned UPS.



In case of a short circuit inside the UPS, the UPS and batteries are protected by a 30A quick blow fuse, in-line. (as seen in the photo).

In the case of the 800, mentioned above, I'd just replace all questionable parts.
The total bill would still be less than $5.

If those original batteries are 6vdc each, they CAN be replaced with a single 12VDC battery. That's basically what I'm doing.

Good Luck!

The Doctor

[canadaboy25]

Re: Back-UPS RS 800 Not charging

Well I fianally got the transformer removed and the main trace from the two fuses go straight to the large capacitor between the two heatsinks.

There are a few other small traces leading off to different places. If you need me to get pictures of those too let me know.

[canadaboy25]

Re: Back-UPS RS 800 Not charging

What I need is to be able to see real close up pictures that I can trace the connection from the two green fuses to see where it goes to.

Well the traces go under the transformer and through the board to the other side so I will try my best to get some good pictures of the traces.

I looked around at the computer recycling place and did not find any APC RS or CS 800.

I wish I had one of those places near me.

[budm]

Re: Back-UPS RS 800 Not charging

I do not think so, what I need is to be able to see real closed up pictures that I can trace the connection from the two green fuses to see where it goes to. I look around at the computer recycling place and did not find any APC RS or CS 800, I found CS350, CS500 but the boards are not the same as yours. I will keep an eye for it.

[canadaboy25]

Re: Back-UPS RS 800 Not charging

Would me removing the transformer and getting clear shots of the traces help at all?

[budm]

Re: Back-UPS RS 800 Not charging

So far we do not see any 28~29V dc power source for charging the batteries yet, the highest one is the 22VDC, and we also do not get the charging voltage all the way to the fuses to charge the batteries either. This is not easy to trace out the connection.