[drsingh]

For mainstream use in India, lithium ion is still very expensive. More expensive than the Tesla Powerall. Buy a good inverter like APC that is good at charging /discharging the battery. Go for Exide invatubular of the highest capacity you can afford. I would recommend the 200 Ah as it is good value. As calculated by R2D2 above kwh backup should be your consideration. 200ah *12 =2.4 kwh. For best battery performance /life, this system should be used upto 30% discharge. That is 800 watt hours which is 2*7w bulb+2*40watt fan running for 10 hours. If you add a 80 watt lcd +20 watt dth/WiFi etc, backup will be 5 hours. This is for optimal battery life. But make sure your battery capacity and load does not discharge the battery >50% of its rated capacity. I hope that was clear explanation and I didn't confuse the issue further.

[R2D2]

Originally Posted by su_madness

I would like to respectfully differ on the deep discharge cycle characteristics, and I could be wrong here. My father who has some experience with lead batteries tells me that if the voltage of a lead battery cell goes below 1.8V (from 2.2V), it used to get sulphated & damaged.

From whatever I have experienced and read sulphation starts when the battery's SOC falls below 80% which requires batteries to be kept on a float charge.

For certain there are advantages to lithium including high energy density, faster response to power demand, light weight, etc etc but matching disadvantages too. For e.g. this page makes for interesting reading:

http://batteryuniversity.com/learn/a...ased_batteries


IMHO using very expensive Li batteries in a deep & frequent charge/discharge environment would not be advisable in a hot country like ours. Thing is, I put safety above everything else. Will I use Li some day with my inverter? Sure! When my concerns regarding cost, safety, longevity, ability to operate in hot temperatures are addressed.

As for which type handles depth of discharge better, for this particular application (UPS/Inverter) you will need to compare the Li to a Lead acid specifically designed for this purpose. For e.g. Exide says it's Inva-Red Tubular battery models can be discharged up to 80% and provide 800+ cycles. That would be a more equal comparison IMO.

http://www.exideindustries.com/produ...batteries.aspx

I have been very happy with the performance of the Exide inverter batteries. This is the 2nd set of tubular batteries. The 1st was with a single battery inverter that lasted for 5 years and was still going strong before I upgraded the 800 VA inverter to a dual battery set-up.

[Aroy]

While calculating the hours that the battery can be used, make sure that you derate the capacity.

The stated capacity is for 10 hours discharge. For five hours the capacity is usually 60% and can drop to 25% for 1 hour. The exact capacity for different discharge rates are usually found in the battery manufacturer's technical literature. Some have it on line while others do not.

[ptaneja]

Guys, need a bit of help.

I have an old (14 year old to be precise! ) Su Kam Trendy 1400 VA Inverter - and I suppose it is still working fine. The double batteries last for about 2.5 years on average.

Question is, the batteries died again - can I install just a single battery ( maybe tobular, 150 or more ) , or is it by design, that I need to install two batteries ?

Any known good inverter mechanics in Gurgaon who can check the input/output and other parameters of inverter to see if it is working fine ? (i am afraid that overcharging/undercharging or something else may be causing an early death of batteries ...or maybe everything is working fine - dont know ! )

[R2D2]

Originally Posted by ptaneja

Question is, the batteries died again - can I install just a single battery ( maybe tobular, 150 or more ) , or is it by design, that I need to install two batteries ?

It is a dual battery inverter by design. If you need to increase/decrease the number of batteries you need to buy a new inverter.

Any known good inverter mechanics in Gurgaon who can check the input/output and other parameters of inverter to see if it is working fine ? (i am afraid that overcharging/undercharging or something else may be causing an early death of batteries ...or maybe everything is working fine - dont know ! )

Can't help you about inverter technicians in Gurgaon but T-BHPians based in that city may be help. A 14 year old machine may need a general check up to verify its charging parameters. Also, newer inverters are more efficient plus offer features like temperature sensitive charging and low ripple which extends the life of batteries.

So, coming to your problem of batteries not lasting long (assuming they're branded batteries AND meant for inverter use), it is probably because of high or low charging voltages. For a dual battery set-up the inverter should have a float voltage set to 27.6-27.8 VDC. Check your battery's instructions for the correct float charge voltage. Also, hope the distilled water is regularly topped off. Never let batteries water level drop too low. The plates should always be submerged in electrolyte.

[bhp_maniac]

Originally Posted by ptaneja

Guys, need a bit of help.

I have an old (14 year old to be precise! ) Su Kam Trendy 1400 VA Inverter - and I suppose it is still working fine. The double batteries last for about 2.5 years on average.

Question is, the batteries died again - can I install just a single battery ( maybe tobular, 150 or more ) , or is it by design, that I need to install two batteries ?

Any known good inverter mechanics in Gurgaon who can check the input/output and other parameters of inverter to see if it is working fine ? (i am afraid that overcharging/undercharging or something else may be causing an early death of batteries ...or maybe everything is working fine - dont know ! )

You will require two of them. It's designed to run on 24V which requires two 12V batteries connected in a series connection.

[ptaneja]

Originally Posted by R2D2

It is a dual battery inverter by design. If you need to increase/decrease the number of batteries you need to buy a new inverter.

So, coming to your problem of batteries not lasting long (assuming they're branded batteries AND meant for inverter use), it is probably because of high or low charging voltages.

Thanks a lot for the response !
Batteries used were always branded - 135 or 150 - be it Exide, SF, Su Kam and what not. But irrespective of brand, I dont recollect any one of them reaching 3 year mark. Moreover, its not a gradual decline of backup power - say 10 hours > 7 hours > 4 Hours > 1 Hour etc. It's like yesterday the battery was working fine for even an hour cut, but suddenly it would beep off in 5 mins.

Originally Posted by bhp_maniac

You will require two of them. It's designed to run on 24V which requires two 12V batteries connected in a series connection.

Thanks for your confirmation as well !

To both of you - help me finalize.
Use this inverter still, and buy 2 regular batteries. (If yes, then which brand/model)

OR

Throw this off/Sell it off, exchange and buy a new inverter + single tobular battery. ( again, which brand for both )


Budget is about 20k - can be stretched to 25k max.

[Aroy]

I feel that your inverter needs to be changed. Normally the batteries should last quite some time and if it is battery problem the backup power reduces gradually.

Do you check the water level regularly, say once a month. If not then the water is slowly drying up and one fine day when it is very low the plates give up. Same thing happened to my battery it was fine till it suddenly gave up. Checked and found the water level extremely low. After that the battery did not recover, even after filling up water.

If you can do with less power, say 500-600VA, then get a single battery 800VA model. In Delhi Sukam 800VA is around 10-12K with 150AH Excide battery.

[R2D2]

Originally Posted by ptaneja

Thanks a lot for the response !
Batteries used were always branded - 135 or 150 - be it Exide, SF, Su Kam and what not. But irrespective of brand, I dont recollect any one of them reaching 3 year mark. Moreover, its not a gradual decline of backup power - say 10 hours > 7 hours > 4 Hours > 1 Hour etc. It's like yesterday the battery was working fine for even an hour cut, but suddenly it would beep off in 5 mins.

Looks like a battery problem caused by over/under charging and/or poor maintenance. Water level in any flooded battery is CRITICAL to its life.

Throw this off/Sell it off, exchange and buy a new inverter + single tobular battery. ( again, which brand for both ) Budget is about 20k - can be stretched to 25k max.

Since your current inverter is old get a new one. Dual or single battery is up to you. A 150 AH battery with a 800 VA sine wave converter would suffice for light loads. For medium loads go in for a 1000- 1500 KVA model but these will take 2 batteries. What type of inverter, how many batteries & how much battery capacity all depends on the load and expected run time. A dual battery setup will probably exceed your budget of 20-25K.

[ptaneja]

Originally Posted by R2D2

Looks like a battery problem caused by over/under charging and/or poor maintenance. Water level in any flooded battery is CRITICAL to its life.

What type of inverter, how many batteries & how much battery capacity all depends on the load and expected run time. A dual battery setup will probably exceed your budget of 20-25K.

I think first point is correct - I used to take a look at the batteries once in two/three months, and refill it with RO water - not sure if this is also a source of issue.

For selecting an inverter -

Load would be around -> 3 tube lights + 3 fans + 1 aquarium external filter (about 50/60 watts) + 3 * 15 watt CFL lights

Duration would be max 10 hours (very rare) - otherwise it's an ON-OFF situation - power goes off for a max couple/three hours, inverter charges for 4 hours or so, then again on battery for 1 hour etc etc.

With above, will you be able to suggest something ?

[bhp_maniac]

Originally Posted by ptaneja

For selecting an inverter -

Load would be around -> 3 tube lights + 3 fans + 1 aquarium external filter (about 50/60 watts) + 3 * 15 watt CFL lights

Duration would be max 10 hours (very rare) - otherwise it's an ON-OFF situation - power goes off for a max couple/three hours, inverter charges for 4 hours or so, then again on battery for 1 hour etc etc.

With above, will you be able to suggest something ?

For the mentioned load, a single battery 800 VA would suffice.

[Thad E Ginathom]

The expectation of being able to continue as normal during power cuts is nice... and can be had at the appropriate cost. For me, I have settled for turning off lights in unoccupied rooms and settling for a 3 - 8 watt LED bulb that I can read by and at least see my way around the room.

Of course... that's on top of the 150 watts that my computer uses!

Of course, I know that the requirement of a houseful of extended family is different to that of one middle-aged couple.

[R2D2]

Originally Posted by ptaneja

I think first point is correct - I used to take a look at the batteries once in two/three months, and refill it with RO water - not sure if this is also a source of issue.

Never fill RO or tap water. This will kill your batteries. Only distilled water should be used. There's a difference between the two.

For selecting an inverter - Load would be around -> 3 tube lights + 3 fans + 1 aquarium external filter (about 50/60 watts) + 3 * 15 watt CFL lights Duration would be max 10 hours (very rare) - otherwise it's an ON-OFF situation - power goes off for a max couple/three hours, inverter charges for 4 hours or so, then again on battery for 1 hour etc etc.

With above, will you be able to suggest something ?

That load is about 500W which is quite a bit. You may want to consider reducing the load or upgrading the inverter and/or batteries.

Assuming 80% inverter efficiency a 800 VA just about would do. But I'd suggest sticking to a setup similar to the the current 1400VA dual battery inverter but with 180 or 200 AH batteries. This time ensure you are regular with battery water top ups with distilled water and other required maintenance. Also, get a sine wave model.

You can also use this chart here to calculate for yourself.

http://www.su-kam.com/load-chart.aspx

Incidentally this sizing chart also recommends a 1400 VA.

[ptaneja]

Sounds good.
Which of these is better -

http://www.su-kam.com/power-solution...ps/falcon-plus
http://www.su-kam.com/power-solution...rk-digital-ups

Both are 1600.

With the above couple of exide instabrite 150, for 8500 approx with exchange.

Total would be 17000 + 7k to 10k for inverter.

[ptaneja]

Originally Posted by R2D2

That load is about 500W which is quite a bit. You may want to consider reducing the load or upgrading the inverter and/or batteries.

My known neighborhood battery wala is recommending a new exide gel based battery, for 14500 per battery. No water fillup, maintenance free.

Second option is exide SM 8500 ...this one ia for 11000.

Old batteries buy back is 2500 per piece.