Power Supply

If the panel is rated for 24 Volts then why not to put 24 Volts battery directly on panel input?

isn't that enough?

It depends on the discharge time but roughly for a 3 to 5 hour discharge a lead acid battery of 12 cells will be exhausted when its terminals reach 21 Volts, much lower for short time reserves. Practically, you have to allow for cable voltage drop to the equipment from the battery at economic cost. A vented lead acid battery will reach 32 volts on a charge at a rate of about 7 amps per 100 A-hour of capacity which ensures full charge. A vital equipment is often powered in parallel with a battery which is maintained at 2.25 volts/cell +/- 1% "float" charge at which the battery will automatically stay fully charged for years - if AC mains fails the battery maintains power to equipment, without break, without any sensing or switching equipment. But to get FULL charge back you need to apply 32V for some hours before return to float. N.B. If batteries are sealed, the charging voltage limits must not be so high.

You have equipment with good limits for 24V battery operation (whether Acid or alkaline type). Rejoice! Many companies offer 24V +10%, -10% --- which makes life difficult for the battery/charger supplier or designer, and expensive for customer.

i am using 24v,7ah battery and want to operate it for two hours.will it be safer to give direct output from the battery to the p.c.? and if not what is the solution?

1. As I explained in post #2, if the limits of your panel are 18 - 32 volts DC, then there is no problem with having it permanently connected to a battery which is on float charge, discharging or even on maximum voltage "boost/equalize" charge.
2. But it is not clear if you just want to.......
3. a) Run the panel for two hours off a battery, because there is no AC mains, then take it away and re-charge the battery for the next time.
4. b) Have the panel on AC mains power for 24 hours a day and switch it manually to battery when mains fails.
5. c) Have a fully automatic system for 24 hour/day operation with automatic battery power to panel and re-charging.
6. A 7 A-h battery bank, e.g. Panasonic LC sealed type will give discharge 2 hours to 22 volts at 2 amps. It can be float-charged continuously at 27 volts wired in parallel with your panel.
7. Please clarify what you want.
   

hello sir I want to run the panel for one hour off a battery , because there is no AC mains, then take it away and re-charge the battery for the next time .

There is no problem with what you want to do with your panel and battery, provided the panel limits are 18 to 32 volts and you are using a 24 volt battery (accumulator or secondary cell). You must ensure the battery positive terminal connects to the panel positive terminal, and negative to negative else the panel could be damaged. A fuse of 5 amps rating is advised, close to battery. Insulated Cable of 1 or 1.5 square mm copper will be adequate for 5 metres run (about 1 volt drop at 2 amps and 5 metres.

Some hints :-

1. Always begin charge of the battery as soon as possible after the discharge and charge it fully. If it is standing open circuit unused for a month, give it a charge.
2. Mark polarity of cables very clearly to avoid error.
3. Ensure you have a charger which will not exceed the recommended charge rate when the battery is fully charged. Leaving part discharged or excessive charging current will shorten battery life.
   

ok.i think i can connect the p.c. directly to the battery source. if i connect 24v,7 ah battery for a 24v,2amp rated load, then how can i calculate for how long the battery will be able to deliver power to the load?

1. One cannot calculate a value without load, temperature and battery data.
2. The load of 2 amps is probably at 24 volts and is a maximum.
3. You do not know if the panel load is constant current or constant watts (volts x amperes). If constant watts, the current may be 2.2 amps at 0.9 x 24 = 21.6 volts.
4. Battery capacity at higher than the nominal rate [often name-plated as 5, 10 or 20 hour discharge] cannot be got by calculation - the higher the current the lower the useful amp-hours.
5. The Panasonic lead-acid 6 Volt sealed block battery type I mentioned (LC-R067R2 - obviously 3 cells per block), listed 7.2 A-h at 20 hour discharge is tabulated to give 11.9 watts for 3 hours to 4.8 volts (47.6 watts to 19.2 volts for 4 in series). So four would probably give you 3 hours panel operation ( 2 amps x 24 volts = 48 watts).
6. But batteries are different according to size and thickness of plates for same amp-hours at 20 hour discharge - some will only give C/3 amperes (where C = 20 hour capacity in amp-hours) for 1 hour to 1.8 volts/cell - which would be 2.3 amps to 21.6 volts for 12 lead acid 7 ampere-hour cells in series. Typically, a battery with good capacity at high rate has many thin plates, close packed, while a battery with lowest cost for low rate, long life has fewer, thicker, plates, spaced apart.
7. If you do a Google or other search on the internet, for the battery type you have, you will most likely find the makers website and detailed data sheets of capacity versus amps/watts/temperature and charging limits
   

Suck it and see

Cheers

Mark N

Really

What Is the question.

You have made a statement.

You have a 24 volt Battery to drive a 24vdc touch panel. This is right.

So, again, what is your question.

Cheers Mark N.

I am confused about battery work.As battery will be discharged with time, so as the power given to p.c. should be constant, will it be right to give direct voltage ? and one more thing i want to ask is that the battery rating is 24v,7 ah. as the current required by the touch panel is 2 amp, then how do the touch panel current rating is to be related with battery current rating ?

Yes battery will discharge with time, But that's why chargers are made, you need a charger that can recharge your battery on 10 to 15% discharge. 7 Ah is not a problem that is indicator of total charge stored in battery, and operating it at 2 Amp look ok but it would be better if you can use 10 to 15 AH battery, that will prolong battery life.

You can put a low battery alarm on it so that you can get alert if voltage goes below 15% of rated,

actually while supplying the load, the batteries will not recharged.once batteries are used, then only they will be set to charged.