MUps charging voltage issue

Gaber Mohamed Boraey said:

attached the service manual, please look at smk3000 model, Qun807 circuit

Click to expand...

not attached.

1. Replace bad batteries with physical damage
They should be matched Voltage in series and share current in parallel. within acceptable tolerances.

Gaber Mohamed Boraey said:

Hello everyone
We have powrcom 3kva ups, with problem of charging issue
The batteries are 4 in series and parallel with another 4 , so total voltage is 48v

I’ve attached the service manual, please look at smk3000 model, Qun807 circuit

Look at page 35, this page for complete circuit
View attachment 188154
The charging voltage not stable, and the ups came with bad batteries , look like damaged , size became big as attached

Can you guide me which circuit is the charging circuit?

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I attach

D.A.(Tony)Stewart said:

not attached

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Now attached, sorry

I will

D.A.(Tony)Stewart said:

Replace bad batteries with physical damage
They should be matched Voltage in series and share current in parallel. within acceptable tolerances.

Click to expand...

I will replace, but when I checked the charging voltage it goes up until 61-62 v then down to 50-51v and so on, I think this not normal, as voltage should be little higher than battery voltages and stable

I think this is problem with charging circuit not give steady voltage for charge batteries, maybe over charge, that’s why batteries look like this

I agree with your findings. I could not see where Vcharge and Vfloat were set as the Theory of Operation was rather skimpy, but there are two pots. Nor did I see where battery current was sensed. Good Ruck. Nor did I see any battery voltages or any kind of BMS.

D.A.(Tony)Stewart said:

I agree with your findings. I could not see where Vcharge and Vfloat were set as the Theory of Operation was rather skimpy, but there are two pots. Nor did I see where battery current was sensed. Good Ruck. Nor did I see any battery voltages or any kind of BMS.

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The voltage go to battery via the terminal +b , can you see?
Do you think vr1 or vr2 related to charging volt?

Gaber Mohamed Boraey said:

The voltage go to battery via the terminal +b , can you see?
Do you think vr1 or vr2 related to charging volt?

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Yes but none of what I said


??



I like their use of transistors as a full wave diode bridge for ZCS pulses top left on p28 and there is another unknown pot bot. right on same page.


This manual doesn't want you to copy the design or repair battery errors.


Obfuscation by design.




Maybe now you can see the adjustments to reduce Vbat max using VR1.

My UPS had a battery pack which consisted of rechargeable gel cells. They're sealed so they don't leak. After a few years they decline (like all batteries). I measured their voltage and found one was worse than the others.

Articles told me gel cells cannot tolerate too fast charge rate. Not even one occurrence. It forms bubbles on the plates that never go away. Internal resistance goes up. Performance suffers permanently.
Having never seen new gel cells available in stores I replaced it with a small lead-acid battery purchased at a motorcycle shop. It worked along with the original cells.

Your cells appear swelled (possibly gel cells). If your cells increased internal resistance, then they need increased voltage applied to charge them. I think your charger tries to send a programmed level of current through them, thus it must apply increased voltage.

D.A.(Tony)Stewart said:

Maybe now you can see the adjustments to reduce Vbat max using VR1.

Click to expand...

What i understand, that this passage goes to inverter circuit “ mosfets part “ ,maybe control its output?, I still can not see the charging circuit

okay, why it fluctuate?, not steady?, this can be normal?

The FETS, drive the voltage into the batteries using pulse modulation. The logic and opAMPs control the pulse width, but I didn’t see how the battery voltage is regulated, except with VR1.

why don’t you scope it and find out

with key measurements maybe we can fix the overvoltage with protection.

With constant average current on cells with high ESR it , can produce unstable voltages. Add a BMS if you want to extend the life on new cells.

D.A.(Tony)Stewart said:

why don’t you scope it and find out

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I will, scope and see if 3843 ic generating right pwm or no

Gaber Mohamed Boraey said:

I will, scope and see if 3843 ic generating right pwm or no

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Scope and number test points affected by RV1 and the other pot. Markup schematic with a table of results. Use a spare battery with low ESR or a lab supply with a low series R or length of wire.

What is this circuit for?

Ho

D.A.(Tony)Stewart said:

Scope and number test points affected by RV1 and the other pot. Markup schematic with a table of results. Use a spare battery with low ESR or a lab supply with a low series R or length of wire.

Click to expand...

how you think of this circuit?

Did U do any tests yet?

D.A.(Tony)Stewart said:

Did U do any tests yet?

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No