Maintaining UPS/car batteries

[siraj_7]

@nasirjavaid

bro tell me first that 2kva 200amp truck battery is fine for the load shedding schedule and load I mentioned?

[shabantarif]

@nasirjavaid

bro tell me first that 2kva 200amp truck battery is fine for the load shedding schedule and load I mentioned?

3fans and 3 lights provided the lights are energy savers would make your load 400W. Don't know about the fridge wattage. Add that and you would get watts. Divide that by 24V and you would get ampere hours for 1 hour.

Ampere hour is the battery requirement

[shabantarif]

24V is Liya because I feel your wattage is going to exceed 1000W and you would need more than 1kv ups and 24V is the nominal value for bugger ups than 1k

[Zyrak]

Do you mean the current inside the source is equal to the current in the series circuit? That's what you mean by this statement. I agree with your diagram. What you are doing here is installing ammeter inside the battery as a matter of fact when you install it between the batteries.
Chalo. Try it. Will see where it goes.
But I don't believe that the current inside the source is equal to the current in the circuit. Reason is that the potential difference inside the source is equal. Except for the far terminals. In this case the far terminals are aik battery ka positive aur dusri ka negative.

mere bhai it is not inside the sources, its like that the 2 sources are joined in series. ap khud check kr lijie apne ya kisi b ups ya is trah k setup mien, there will not be the difference.

[siraj_7]

dividing load with battery wattage will give me amp hours for the battery? Experts please approve the calculation below:

3 Savers = 25x3 = 75 Watts
3 Fans = 80x3 = 240 Watts
1 Fridge = 400 Watts (1200 Watts drawn at starting)

Total Wattage = 715

Efficiency = 70%

715/70% = 1022 Watts

1022 / 24Volts = 43Amps

and 200 AMP Truck battery can only be discharged safely to 80% which means I can draw a total of 40 amps out of it.

So that means I will get 1 hour backup ?

[siraj_7]

yaar whats happened to pakwheelers.. nobody replied since 2 days... ?

[shabantarif]

I will check it. But two batteries in series make it one battery with increased voltage.
Still I'll see if I am wrong. Could be my bad. :).

[murtaza.ajmi.3]

Anybody want APC UPS for home or office ... dry cell batteries in lahore ... sale n service. .. do contact me
0321 499 70 60

[zalamng]

Anybody want APC UPS for home or office ... dry cell batteries in lahore ... sale n service. .. do contact me
0321 499 70 60

Dear Murtaza
Salaams
We have a disconnected UPS System with inverter and exide batteries that were used for 1 year.
We have upgraded to solar system hybrid with solid state.
I was wondering if you could help us by taking our old system and letting us get more back up by adding extra solid state batteries to existing solar system back up or possibly convert this into a standby solar UPS?
Please advise me what is the best solution.
I will appreciate any help and advise if possible.
Best regards

Sent from my iPhone using Tapatalk

[whiteangel]

dividing load with battery wattage will give me amp hours for the battery? Experts please approve the calculation below:

3 Savers = 25x3 = 75 Watts
3 Fans = 80x3 = 240 Watts
1 Fridge = 400 Watts (1200 Watts drawn at starting)

Total Wattage = 715

Efficiency = 70%

715/70% = 1022 Watts

1022 / 24Volts = 43Amps

and 200 AMP Truck battery can only be discharged safely to 80% which means I can draw a total of 40 amps out of it.

So that means I will get 1 hour backup ?

200AH capacity means battery can provide 10A for 20 hours @12V
With a two battery (400AH) configuration in series you can get 20A for 20 hours @24V

Now your load is 1022W @ 24V = 43A

Now you are trying to pull 43A from a battery that is most efficient at 20A. In theory you should get a little less than 9 hours of backup from the battery @43 amps assuming you discharge battery to 100%. But in reality, the faster you discharge a battery, the less power you get out of it. Ideally you should not discharge conventional lead acid to more than 50%. Only deepcycle lead acid batteries are designed for 80% depth of discharge. If you keep discharging locally made lead acid battery at 80% you will seriously shorten its life. Other factors such as high battery temperature (over 25C) also reduce capacity.

So I would say you should get 3 hours or more at 50% DOD.

[murtaza.ajmi.3]

[murtaza.ajmi.3]

Dear Murtaza
Salaams
We have a disconnected UPS System with inverter and exide batteries that were used for 1 year.
We have upgraded to solar system hybrid with solid state.
I was wondering if you could help us by taking our old system and letting us get more back up by adding extra solid state batteries to existing solar system back up or possibly convert this into a standby solar UPS?
Please advise me what is the best solution.
I will appreciate any help and advise if possible.
Best regards

Sent from my iPhone using Tapatalk

Above is solar setup with APC UPS and dry cell batteries ............ for dry cell batteries go for NARADA BRAND GEL BATTERIES ..... comes in 100 Ah , 155 Ah and 200 Ah .......

[siraj_7]

@whiteangel

Dear Thanks, first I would request you to check that have I calculated 43 amps per hour load correctly in my post?

Secondly, I did not mean to say to discharge truck battery to 80%, what I meant was that I can only let it discharge such that it remains at 80% charge. Which means that out of 200AMPs I can discharge it to 160AMPS only and draw 40 Amps out of it and it should remain at 80% level. Only deep cycle batteries can be discharged uptill 50% and no battery can be discharged to 20% as it will fail imminently.

So considering the above will I get a back of 1 hour if I discharge 200AMP 24volt battery setup such the UPS cutoff is that the battery remains at 80% capacity.

200AH capacity means battery can provide 10A for 20 hours @12V
With a two battery (400AH) configuration in series you can get 20A for 20 hours @24V

Now your load is 1022W @ 24V = 43A

Now you are trying to pull 43A from a battery that is most efficient at 20A. In theory you should get a little less than 9 hours of backup from the battery @43 amps assuming you discharge battery to 100%. But in reality, the faster you discharge a battery, the less power you get out of it. Ideally you should not discharge conventional lead acid to more than 50%. Only deepcycle lead acid batteries are designed for 80% depth of discharge. If you keep discharging locally made lead acid battery at 80% you will seriously shorten its life. Other factors such as high battery temperature (over 25C) also reduce capacity.

So I would say you should get 3 hours or more at 50% DOD.

[siraj_7]

Also I was thinking of selling my generator and buy a hybrid inverter with built in MPPT charger and use it as UPS only for a while with 200AMP Hour battery before slowly and gradually adding solar panels to it as pocket allows. I have googled and Olxed a bit but not able to find the price of 3KVA Infini inverter. What is its exact price (brand new item) with warranty?

[siraj_7]

yaar thread response is very slow, I need to make a decision in this load shedding...

[whiteangel]

@whiteangel

Dear Thanks, first I would request you to check that have I calculated 43 amps per hour load correctly in my post?

Secondly, I did not mean to say to discharge truck battery to 80%, what I meant was that I can only let it discharge such that it remains at 80% charge. Which means that out of 200AMPs I can discharge it to 160AMPS only and draw 40 Amps out of it and it should remain at 80% level. Only deep cycle batteries can be discharged uptill 50% and no battery can be discharged to 20% as it will fail imminently.

So considering the above will I get a back of 1 hour if I discharge 200AMP 24volt battery setup such the UPS cutoff is that the battery remains at 80% capacity.

The load calculation is correct. Ideally, truck batteries should should remain at 80% charge to get maximum life out of them. But most solar installers set their inverters to maintain charge level at 50%. This is less than optimal but it helps reduce initial investment on batteries at the cost of battery life.

I think you will get at least 1 hour if you maintain charge level at 80%. But it depends on what is the optimal discharge current of the battery. (C-rate). For lead acid, the optimal C-rate is about 0.05 which in your case works out to be 400AH x 0.05 = 20AH. If the optimal C-rate is 20amp and you are putting a load of 40 amp then the battery will discharge sooner and not be able to provide the maximum duration of backup. In the graph below you can see that a discharge rate of 1C lasts less than 1 hour while a slower discharge rate of 0.2C the same battery lasts more than 5 hours.

Regarding the Infini, you should get Infini plus it will cost you about 125,000 for the 3KW model with 1 year warranty.

[jehlumi]

[jehlumi]

[siraj_7]

@whiteangel Thanks for the detailed reply. Clearly at the moment I cannot invest so much so hybrid solar inverter is out of question. I have seen couple of prodigy 2nd hand pure sinewave UPS 2-3KVA on OLX (24volt)

Is it a good investment? Does Prodigy last? is it better than Aurora? Cost is between 10 to 15 K for 2nd hand.

Also 200AMP battery would be 12 volt and UPS is 24 volt. To make 24 volt I would have to connect 2 100 amp batteries in series to get 24Volts but amps would remain 100. My question is will the backup reduce or remain the same?

PS: I can't buy 2x200 AMP hour batteries its going to cost 34-40K which is not in budget. Max I want to spend on battery is 15 to 17K in which I think I can buy 1x215 or 2x132 AMP hour batteries

Edit: Also let me know if prodigy or aurora are easy and cheap to repair or not...

[murtaza.ajmi.3]

Both prodigy and aurora are pak cheen dosti ups n nothin else ... go for pure sinewave ups like apc .. u ll find 100 of dealers there in karachi ... 1.5 kva works with 2 batteries n shud cost u 12000 without batteries ... prodigy n aurora or homage ... these all r 3rd class upss ... our local transformer based ups r much much better than these chinese ups ... once thy get faulty thn kiss ur ups goodbye ....