Back-UPS RS 800 Not charging

[canadaboy25]

Hello guys I have a Back-UPS RS 800 that refuses to charge the batteries.

It used to work great but eventually it died. I took the batteries out to find they were at 0.1 volt (in series) so basically 0.05 volts per battery. I did the usual adding water and charging on a universal powersupply but there were shorted cells. I brought in a lawn tractor battery and a small atv battery and hooked them up in series. They didn't last very long under a pc load but they hadn't been charget forever. After a while of tinkering with it the batteries got too low and the backup started giving me the usual your batteries are screwed warning.

It doesn't put out any voltage and when the batteries are hooked up the voltage is less than when they are disconnected. http://www.heime.org/post/17 This post is for the 500 model and it shows that the issue is a bad cap but I was unable to locate such a capacitor on this board. If you guys could point me to this cap or the actual issue I'd be real happy.

Right now all it is is a surge protector.

[budm]

Re: Back-UPS RS 800 Not charging

That link shows bad start-up cap for that SMPS section. So we need to see your board to locate the SMPS in your model.

[canadaboy25]

Re: Back-UPS RS 800 Not charging

Here are the pictures of the board. Let me know if you need close ups of any particular part of the board.

[stj]

Re: Back-UPS RS 800 Not charging

SMD caps - bastards!
i hate those things!!

[canadaboy25]

Re: Back-UPS RS 800 Not charging

SMD caps - bastards!
i hate those things!!

Oh well, I "can" solder those.

I say can meaning I have but it wasn't the prettiest.

Which one would have most likely failed?

[stj]

Re: Back-UPS RS 800 Not charging

no idea, but i do have a trick.

heat each pin/pad with yur iron - if it smells like catpiss then it's leaked.

[canadaboy25]

Re: Back-UPS RS 800 Not charging

The original batteries are dust so I think I may set up an array of old refurbished batteries and charge them with my solar panels and have them feeding the main batteries wen it is on battery power then that way if the power is gone or I can just unplug it I will have free power.

But that is all in the distant future.

[canadaboy25]

Re: Back-UPS RS 800 Not charging

Would I be able to find the bad one if I just took them all off and checked the capacitance?

Help is apreciated

[stj]

Re: Back-UPS RS 800 Not charging

chances are you would damage them during removal.
i wouldnt use them again anyway.

[canadaboy25]

Re: Back-UPS RS 800 Not charging

chances are you would damage them during removal.
i wouldnt use them again anyway.

I removed 2 and they tested fine and I re-soldered them without a problem. The board is still working the way it was (useless).

[budm]

Re: Back-UPS RS 800 Not charging

Can you please get better focus pictures, I also need the pictures of the bottom side of the board. Check the red fuse and voltages on those caps.
BTW, does it use two 12V batteries? From the spec it looks like just one 12V battery. And those two 30A green fuses are good, right?

[canadaboy25]

Re: Back-UPS RS 800 Not charging

Here are the voltages of the three caps with the board running and one lead on each cap terminal.

1 - 23 vdc
2 - 5.8 vdc
3 - 1.1 vdc

The green beaver tooth fuses are also good. The round brown f3 was blown. I removed it from the board to be certan.

I am very sorry about the pics. Both of my good camera's were slightly knocked off a table. I hope these are better. If you need a picture of a very certain trace or something I will try my best.

And why were the ends of 2 doides to the right of the green fuses circled?

And the battey pack is 2 SLA's in series but they had shorted cells so now I just have some junker batteries with alligator clips on them

[budm]

Re: Back-UPS RS 800 Not charging

I believe that fuse is for powering the SMPS for that small yellow transformer (not 100% sure), the secondary side winding of that transformer is connected to those two diode and that #3 filter cap. So there may shorted circuit in that area.

[canadaboy25]

Re: Back-UPS RS 800 Not charging

I believe that fuse is for powering the SMPS for that small yellow transformer (not 100% sure), the secondary side winding of that transformer is connected to those two diode and that #3 filter cap. So there may shorted circuit in that area.

Would that mean that the transformer is shorted?

[budm]

Re: Back-UPS RS 800 Not charging

It can be that the fuse may have blown due to in rush current. What is the value of that fuse?
BTW, that yellow transformer is actually an inductor, L4.
Those two green fuses, one end is connected to the + of the batteries, the other end of the fuses should be connected to charging circuit, you will have to trace that connection out, it should be connected to the Cathode of the blocking (or rectifier diode of the charging circuit) diode of the charging circuit.

[canadaboy25]

Re: Back-UPS RS 800 Not charging

Here is a picture of the fuse.

The rest was about as clar as mud to me

Both fuses are connected to the + battery terminal and from what I see they are connected to the 2 blue capacitors beside them. It looks loke the trace goes under the big transformer but I can't see where it goes. If it is nesicary I can take the transformer off and see where the traces go.

[budm]

Re: Back-UPS RS 800 Not charging

That is 2A 250V rating fuse. I am not sure yet as to where the charger circuit is, some of them use the SMPS for charging circuit, some of them use one of the winding on the inverter transformer (the transformer that is used for converting the switching 24VDC to 120VAC). I would try another fuse to see what happen, normally we would have used Ohm meter to check the resistance of each leg of the fuse (since we do not know which end of the fuse is the feeding side) to circuit ground, but we do not even know at this point which ground point is.

[Agent24]

Re: Back-UPS RS 800 Not charging

Would I be able to find the bad one if I just took them all off and checked the capacitance?

Yes, but only IF the capacitance has dropped. The thing with electrolytic caapacitors is that most of the time they fail due to high ESR, so you really need an ESR meter to do a proper test.

[canadaboy25]

Re: Back-UPS RS 800 Not charging

Yes, but only IF the capacitance has dropped. The thing with electrolytic caapacitors is that most of the time they fail due to high ESR, so you really need an ESR meter to do a proper test.

Yes I am in the process of getting my hands on an ESR meter so that is why I was wondering if that would be a fair enough test.

[canadaboy25]

Re: Back-UPS RS 800 Not charging

That is 2A 250V rating fuse. I am not sure yet as to where the charger circuit is, some of them use the SMPS for charging circuit, some of them use one of the winding on the inverter transformer (the transformer that is used for converting the switching 24VDC to 120VAC). I would try another fuse to see what happen, normally we would have used Ohm meter to check the resistance of each leg of the fuse (since we do not know which end of the fuse is the feeding side) to circuit ground, but we do not even know at this point which ground point is.

So why is this fuse in such an odd formation? I haven't some across many fuses like this before.

Would I be able to replace it with a "beaver tooth" fuse or one of those common cylindrical fuses to test the circuit?

Thanks