[Prowler]

Originally Posted by sagarpadaki

I will check the O/P voltage and battery voltage under load. What should be the ideal values for these?

The output of the Inverter (which can be adjusted within 10 % range if you gain access to the circuitry only when you a very valid reason I will explain later) should be within 220 - 240 V. Check with little load as well as under near full load. This will indicate the voltage regulation. For good inverters there should be no change.

The Lead Acid battery voltage has well established norms :This screenshot shows the volt relationship with the state of charge under 30 degree C ambient temperature.

Please note that the measured voltage is without load and without mains supply. For cars you measure when the engine is switched off .

Coming back to your original query, if your inverter puts out 220 V as output and the mains output is 240 V, you will notice a drop in fan speed with your inverter which is perfectly normal.

For UPS serving servers/computers, it is prudent to adjust the output voltage to 200-220 to avoid having a catastrophic failure.

In simple terms, it is better to have a small margin of safety in case the inverter voltage rises beyond 250V under light load.

[sagarpadaki]

Originally Posted by Prowler

The output of the Inverter (which can be adjusted within 10 % range if you gain access to the circuitry only when you a very valid reason I will explain later) should be within 220 - 240 V. Check with little load as well as under near full load. This will indicate the voltage regulation. For good inverters there should be no change.

I checked the voltage of an AC power socket and battery when running on Inverter

AC -> 208V [On Mains it is 230V]
Battery[Both] -> 12.08V

I will check the battery voltage once it charges by disconnecting the battery from inverter and compare it with chart you have shared. Currently, we had a 4 hour power cut and the battery is getting charged

[R2D2]

My inverter supplies 220v when the batteries are fully charged and it drops to about 215-217v after running for a few hours. But that's only because these are old 200 AH batteries, fresh batteries will provide more stable output while smaller batteries will discharge faster and cause a drop in voltage

@sagarpadaki - As Prowler correctly said older batteries consume more power to charge up (ask me ) I can save about Rs 600-700 a month if I keep my inverter off.

And BTW MSEB just hiked the electricity rates - highest slab which you hit if your consumption is >500 units a month is about Rs 15.57/unit.

[Prowler]

Originally Posted by sagarpadaki

AC -> 208V [On Mains it is 230V]
Battery[Both] -> 12.08V

I will check the battery voltage once it charges by disconnecting the battery from inverter and compare it with chart you have shared. Currently, we had a 4 hour power cut and the battery is getting charged

You don't need to disconnect the battery from the inverter. Just turn off the inverter and read the battery voltage after a couple of minutes.

From your readings it is obvious why your fans are running relatively slow on inverter compared with AC mains as the volt drop is about 22 V.

[sagarpadaki]

Originally Posted by R2D2

My inverter supplies 220v when the batteries are fully charged and it drops to about 215-217v after running for a few hours. But that's only because these are old 200 AH batteries, fresh batteries will provide more stable output while smaller batteries will discharge faster and cause a drop in voltage

@sagarpadaki - As Prowler correctly said older batteries consume more power to charge up (ask me ) I can save about Rs 600-700 a month if I keep my inverter off.

Which inverter do you have?

215-217V after a few hours even with old batteries sounds very good for me. Mine is at 208V after a couple of hours of power outage. I do not know if this is due to battery(7 years Old) or inverter. Only the fan is impacted due to the low voltage

BTW, after how many years do we say a battery is 'OLD'?

[R2D2]

Originally Posted by sagarpadaki

Which inverter do you have?

It's a Microtek 1.5 KVA sinewave model.

215-217V after a few hours even with old batteries sounds very good for me. Mine is at 208V after a couple of hours of power outage. I do not know if this is due to battery(7 years Old) or inverter. Only the fan is impacted due to the low voltage

My battery set is a little over 10 years old now...but maintaining output AC voltage not just depends on battery voltage it also depends on how good the inverter circuit is.

Also battery output can vary depending on factors like wear and tear on plates, construction quality etc. By and large go in for a tall tubular battery. They are longer lasting than the flat plate models though more expensive.

BTW, after how many years do we say a battery is 'OLD'?

Depends on what type of battery but my rule of the thumb is 4-5 years for inverter and car batteries. See the thing is how deep is the discharge on your battery each time the power is out. Deep discharge causes more damage. Most inverter batteries can take upto 50% DoD. Any lower can affect longevity.

[sagarpadaki]

Originally Posted by Prowler

You don't need to disconnect the battery from the inverter. Just turn off the inverter and read the battery voltage after a couple of minutes.

From your readings it is obvious why your fans are running relatively slow on inverter compared with AC mains as the volt drop is about 22 V.

I checked the voltage with a Multimeter after disconnecting the battery from inverter and letting it sit idle for 10 mins. Topped up DW as well

Battery1 - 12.50 volts
Battery2 - 12.36 volts

Does these values justify the low AC voltage output when running on the inverter?

[aim120]

Originally Posted by sagarpadaki

I checked the voltage with a Multimeter after disconnecting the battery from inverter and letting it sit idle for 10 mins. Topped up DW as well

Battery1 - 12.50 volts
Battery2 - 12.36 volts

Does these values justify the low AC voltage output when running on the inverter?

Rest voltage is not enough, you need to see the battery voltage under load with the mains input shutdown or during a power cut.

[Prowler]

Originally Posted by sagarpadaki

Battery1 - 12.50 volts
Battery2 - 12.36 volts

Do these values justify the low AC voltage output when running on the inverter?

We have already arrived at the reason why your fans run low in inverter as there is almost 10 % low voltage from inverter.

Your batteries are good as long as they provide reasonable back up time when there is a power cut.

Now your battery Volt readings are confusing : How come you have 2 different readings for 2 batteries? If they are connected in parallel (for 12 V inverter), they should show same Voltage unless you remove the connection.

[sagarpadaki]

Originally Posted by Prowler

We have already arrived at the reason why your fans run low in inverter as there is almost 10 % low voltage from inverter.

Your batteries are good as long as they provide reasonable back up time when there is a power cut.

Now your battery Volt readings are confusing : How come you have 2 different readings for 2 batteries? If they are connected in parallel (for 12 V inverter), they should show same Voltage unless you remove the connection.

Yes, batteries were disconnected from the inverter and sit idle for 30 mins before I took the readings. Hence the difference in voltage between the two batteries.

Question is, is this battery voltage the reason for 10% drop in inverter output voltage or is the fault with the inverter? On load, the batteries read 12.08V

[Prowler]

Originally Posted by sagarpadaki

Yes, batteries were disconnected from the inverter and sit idle for 30 mins before I took the readings. Hence the difference in voltage between the two batteries.

Obviously one battery appears to be better than the other one:
Battery1 - 12.50 volts
Battery2 - 12.36 volts

But the their charge level may not have reached the full level. Most inverters charge their batteries in about 5-10 hours depending upon the manufacturers.

Question is, is this battery voltage the reason for 10% drop in inverter output voltage or is the fault with the inverter? On load, the batteries read 12.08V

Your inverter puts out :
AC -> 208V [On Mains it is 230V]
So the inverter has been set to ~ 210 V (nothing unusual). Expect the fan speed to be low when compared with AC mains.

Even there the AC supplied by your utility is not a constant. There are many areas in Madras where the supply is 170 V (the main reason why many people buy the so called double Voltage stabilizer for their Airconditioners). In my street it hovers around 140- 155 V.

[Samfromindia]

Originally Posted by Gansan

I will remove the float caps and check/top up every four months even when they show good level of electrolyte. They may be struck in position sometimes, though all six getting struck is very very remote. But still, a battery not needing top up for three years is highly unlikely. So better remove the caps and ensure.

Originally Posted by R2D2

3 years and no top up? Something is wrong and you need to do a manual check.

Please check water levels manually and at regular intervals. Your floats are obviously inaccurate.

So I finally checked the float indicators by opening them. They are all working as intended and not stuck. Additionally I filled up water to the maximum allowed in all 6 cells, it took around 80% of the 1L distilled water I purchased earlier. Attached before and after pics. Ideally they should remain between the green and red levels.

Before


After

[R2D2]

Originally Posted by Samfromindia

So I finally checked the float indicators by opening them. They are all working as intended and not stuck. Additionally I filled up water to the maximum allowed in all 6 cells, it took around 80% of the 1L distilled water I purchased earlier. Attached before and after pics. Ideally they should remain between the green and red levels.

Goodness, <1 litre? Wow, your batteries hardly consume water that's very good. My Exide "guzzlers" take about 2-3 litres for a quarterly topup.

BTW did you check how water was remaining in the battery before topping up? As long as the plates were covered you're good.

[sagarpadaki]

Originally Posted by R2D2

Goodness, <1 litre? Wow, your batteries hardly consume water that's very good. My Exide "guzzlers" take about 2-3 litres for a quarterly topup.

BTW did you check how water was remaining in the battery before topping up? As long as the plates were covered you're good.

My Amaron 100Ah tubular battery takes about 1 litre every six months. There are two batteries, so 2 litres every time I topup.

What is your exide battery capacity? Maybe higher Ah batteries take more water

[R2D2]

Originally Posted by sagarpadaki

My Amaron 100Ah tubular battery takes about 1 litre every six months. There are two batteries, so 2 litres every time I topup.
What is your exide battery capacity? Maybe higher Ah batteries take more water

My set is a 200AH x 2, yes a larger battery will likely consume more water. But this one is more water (2-3L) but it's also more frequent ie every 3 months. The batteries are old now..over 10 and it may be due to the age. When tehy were new the consumption was about 2-2.5L every ~4 months IIRC

I am thinking of changing the bank in the near future. The inverter is consuming quite a bit of power keeping the old fellas charged up.