Desi UPS, 500 watts circuit

I bought this 500 watt desi UPS from a shop nearby. I adjusted the charging cuttoff at 14.05V to be precise. It took around 2 hours from 13v to 14.05v, the battery is ancient, am I good at this cuttoff limit? I'm posting the picture, please explain the other trimpots.

Regards,

Asrar.

If your battery is old, and it gets heated up while reaching upto 14.05V, then you should adjust the charging cut-off voltage to a lower value. Otherwise the battery will start losing water quickly and cause mere wastage of electricity.

Regarding other trim pots, these are probably functioning as below:

Mains Low: This sets the value of AC input at which the inverter should start to save the load.

Batt Low: The low battery cut-off voltage value.

Batt Full: The charging cut-off voltage

Amp Set: Ampere setting for ??? No idea (probably related to battery)

Overload: Sets the load limit at which inverter should trip to save the inverter from overload.

Fix Volt: To fix the output voltage while on inverter, basically changes the PWM generated by the circuit.

I hope this helps

1 Like

The battery is AGS CNG-45. The battery even being old is working fine. In 2 hours it gets charged to 14.05v, I touched the battery carefully at 14.05v and it was very normal.

Also please tell me, it has two markers, Upper limit and Lower limit. It was completely dry when I discovered it, I took it to the battery guy and he filled it up with acid right to the cap ring in 70 Rs.

what's the proper electrolyte level limit for AGS ? the cap ring or markers ?

The upper and lower markers.

Ijaz,

Which desi UPS circuit is designed around a microcontroller. My preference is PICs. Have you seen a circuit which has some kind of monitoring of charge and discharge current of the battery even if it is not displayed. It should have its circuit diagram also available.

Please tell me where to buy one.

Asrar,

I am not sure about the battery's construction but if you overfill it, the electrolyte in the adjacent cells would mix thus shorting the cell.

Aurangzeb

Almost all desi ups kits are designed around a microcontroller and are essentially a copy of each other with not much difference. In the above picture, the IC in the middle and near the crystal is a microcontroller.

Unfortunately there is no such kit to my knowledge which actually measures the charging current. All these kits just start uncontrolled charging process which is unregulated DC from the transformer , these kits just watch the battery voltage using a comparator to see if battery has reached a certain voltage level or not.

Want to make your own?

@ijaz Thank you for clarification of electrolyte level!! Yeah I guess the Amp Set is for battery charging amperes. Currently its around 15 amps. I'll check if it charges at constant amp and volts or its variable according to battery charge condition.

@aurangzeb Its AGS CNG45, ancient battery. I suppose the electrolyte compartments are constructed up to the top, so it didn't mix.

[quote=", post:6, topic:18538"]

Want to make your own?
[/quote]

Ijaz,

Yes infact I have been thinking of making one which has a proper battery charge management system. At one time I was interested in it as a commercial project. However now I think it would be 'sadqaa jariyah' if it is placed in the public domain. The reason is that a huge amount of money is spent on replacing batteries by the common citizen because these batteries get damaged due to overcharging, deep discharging etc. S I think it would be nice if some work was done on these lines in this forum.

Asrar,

Have you actually measured the current.

The photo you have pasted in your post shows two small transformers with CT written over one of them. Now CT or current transformers are for measuring current. But it has to be AC. However even if the circuit measures AC on the primary side of the transformer, it is just a matter of adding a formula in the firmware to calculate the DC current. If the transformer has been manufactured using a standardized manufacturing process, theoretically the circuit should be able to measure both charge and discharge rate of the battery. Coupled with some temp. measurement of the battery we can have an excellent battery management system which should help to significantly prolong the life of the battery thus saving costs.

Try to monitor the battery charge and discharge current. If you do and contain discharging the battery below C/10, before the next re-charge, you should see significant financial gain in the form of increased battery life.

Aurangzeb

Sorry, I don't have any proper education in electronics as its not my field. I do it for fun. Excuse me if I don't understand things the proper way. Feel free to educate me.

I don't know how to check the charging current, the terminals only start charging process when they sense battery, so I have no idea how to measure transformer charging volts. I just know that its charging at 14.5 to 15 amperes.

The Batt Full trimpot cuttsoff the charging at 14.1 v
The Batt Low trimpot shuts down the UPS at 10v, after I adjusted it. By default it was draining battery at like 7volts. 10v is good ?

I don't know if it gradually increase the volts while charging, Initial or final current.

The kit has this microcontroller IC, the one in the middle.
http://eu.mouser.com/ProductDetail/Microchip-Technology/PIC16F72-I-SP/?qs=sGAEpiMZZMsUzhEcHltCuTdgPb2UOSsg


Here's the mammoth transformer.

The IC with the heatsink is BAT16-600B, couln't find datasheet. I suppose you can explain it.

It seems to be related to battery charge control or something.

2012102416475679246.jpg

The component is BTA16. You probably googled BAT16 and couldn't find the data sheet. By the way BTA16 is a triac

Presence of triacs in your UPS makes me very very curious to say the least. In fact the system that I have in my mind uses triacs. By the looks of the topology, these triacs seem to replace the high current diodes for charging the battery. Interesting. The designer may be using using all these triacs in parallel, with some kind of synchronized switching arrangement to make these work as rectifiers, allowing current to flow only for half a cycle through one bank of triacs and then through the other bank during the second half of the AC wave. Ingenious and very clever. I bet even 4 or five of them in parallel still cost less than a 50 Amp diode. Great trick. I am really impressed. My compliments to the chef, if he happens to read this.

Now for measuring the current. If you have a clamp on meter just clamp it to the first and then the second wire, coming from the transformer and connected to the two heat sinks. Note down the values displayed, for both the wires seperately. Ideally both readings should be the same or +/- 5% of each other. Meanwhile I'll post an Excel sheet in which you you can plug in these values and calculate the DC charging current.

Aurangzeb

[quote=“aurangzebhaque, post:8, topic:18538”]

Ijaz,

Yes infact I have been thinking of making one which has a proper battery charge management system. At one time I was interested in it as a commercial project. However now I think it would be 'sadqaa jariyah' if it is placed in the public domain. The reason is that a huge amount of money is spent on replacing batteries by the common citizen because these batteries get damaged due to overcharging, deep discharging etc. S I think it would be nice if some work was done on these lines in this forum.

[/quote]

That seems a good idea though I doubt that there will not be many people able to benefit from this because most users can't make circuits from the diagrams.

[quote=", post:, topic:"]

Presence of triacs in your UPS makes me very very curious to say the least. In fact the system that I have in my mind uses triacs. By the looks of the topology, these triacs seem to replace the high current diodes for charging the battery. Interesting. The designer may be using using all these triacs in parallel, with some kind of synchronized switching arrangement to make these work as rectifiers, allowing current to flow only for half a cycle through one bank of triacs and then through the other bank during the second half of the AC wave. Ingenious and very clever. I bet even 4 or five of them in parallel still cost less than a 50 Amp diode. Great trick. I am really impressed. My compliments to the chef, if he happens to read this.

[/quote]

I am wondering where the triacs came into discussion or may be I missed something. As per OP, the BTA16 is on heatsink (presumably on the UPS kit ?)

Anyway if there is a triac somewhere in the UPS, it is for switching transformer taps and not for rectification. The UPS kit designer might have used the triac to switch the AC input to a different winding on the input side of the transformer intending to change the output voltage which will result in higher / lower charging current.

Sorry, I don't have a clamp multimeter, I'll buy it in a day or two. There's only one BAT16 on the kit, its on the kit with silver heat sink, with large screw, see the first picture.

The guy who sold me this UPS, told me that imran brothers ( now known as imran & CO ) makes the best local UPS kits.

check this out, their kits with LCD display.

The LCD display:

Sorry, BTA16, I keep referring to it as BAT16 lol my mistake.

The LCD, one more pic.

[quote=", post:12, topic:18538"]

I am wondering where the triacs came into discussion or may be I missed something. As per OP, the BTA16 is on heatsink (presumably on the UPS kit ?)

Anyway if there is a triac somewhere in the UPS, it is for switching transformer taps and not for rectification. The UPS kit designer might have used the triac to switch the AC input to a different winding on the input side of the transformer intending to change the output voltage which will result in higher / lower charging current.

[/quote]

Ijaz,

That is what I thought initially. However if you look at the first set of pics posted by Asrar, you would see (although these are in the dark in that pic) that all the triacs seem to be wired in parallal with their tabs tied to the heatsink. The heat sinks are quite obviously connected to the secondary, of which the center tap wire is clearly visible in the photograph. So I have my doubts that these are being used to control voltage on the primary side.

Asrar,

Many thanks for this info and the pics. I just came back from Lahore. Had I known this, I would have certainly paid Imran & Co. a visit.

While the second set of photos is excellent, my heart goes out to the first kit. The CTs and the opto-couplers and the 6-pinned white IC (probably MOC series with zero-crossing detector triac control) and a microcontroller make this kit very interesting. One can play with the firmware to improve the system without having to get into PCB designing and all that.

Regarding your battery charging, if you have a Digital VOM then don't buy a clamp meter. Instead buy a shunt. Here is a photo of it in the link given below

http://www.reuk.co.uk/What-is-a-Shunt.htm

This will be added in-line by cutting the red wire going to the battery and inserting it there. By measuring the voltage between the two terminals you can accurately determine the current going to or coming from the battery. Should cost you around PakRs. 400/-.

Aurangzeb

How do you assume that those are triacs on the two big heatsinks while OP is tellingus that there is only one BTA16 on the UPS kit PCB?

The one you are referring to, could be MOSFETs connected in parallel in the dark picture.

Ijaz,

From Asrar's assertion quoted above. Yes, could very much be mosfets.

Nevertheless, Asrar can you please confirm the name/number of the semiconductors attached to the heatsink in the photo that you titled 'mammoth transformer'.

Aurangzeb

There you go.

Updated the image.
I can see it, even in your message. why can't you ? try to refresh.

[quote=", post:18, topic:18538"]

There you go.

[/quote]

Asrar,

Can't see the pic. Pls. re-load. Thanks.