A project of 12 volt

alkhaleejsolar

hi,today i have a project of

200 amp,battery solid,

12 volt 800 watt ups,

total load 400 watt,

so,i wired 2 solars
of 120 watt in parrel
and get 12 volt 13.33333
ampare.i want to know,

for how much time this load will

work if battery is fully charged.

and is this solar panels is enough

for this 200 battery,or still need more panels,
for best result,,,thanks sir

Cariboocoot

Re: A project of 12 volt

Let's see if we've got the specifications right.

Load: 400 Watts (looking for maximum running time from the battery).
Battery: 200 Amp hours @ 12 Volts, or approximately 1200 Watt hours of stored power at 50% depth of discharge.

In simple math terms that would run the 400 Watt load for 3 hours. In practical application it may be more or less depending on the Peukart factor, system losses (power going to feed the inverter/UPS), and variations in the actual load.

You have two 120 Watt 12 Volt panels capable of 13 Amps output together (these numbers check out as correct by my math). This would be enough to recharge that battery with no or very light loads on it and good sun on the panels. It would not provide much extended run time for the full 400 Watt load, which would be around 34 Amps @ 12 VDC.

So expect somewhere around 3 hours for the full load on that battery.

BB.

Re: A project of 12 volt

alkhaleejsolar wrote: »

200 amp,battery solid,

Probably a translation error--I am not sure what this means? GEL or AGM type battery vs flooded cell?

12 volt 800 watt ups,
total load 400 watt,

We recommend for best battery life that you discharge the battery around 25% per day, and try to never discharge more than 50% per day in normal operation.

So, for a 25% discharge of a 200 AH battery @ 12 volt battery bank with a 400 watt load on an inverter, roughly:

• 400 Watt load * 1/0.85 inverter efficiency * 1/12 volt battery = 39 amps @ 12 volt load
• 200 AH battery * 50% usage * 1/39 amps = 2.6 hours of usage recommended per night

Note, battery capacity is affected by how fast you discharge it... The 200 AH may be defined as C/20 -- A 20 Hour discharge rate. The ~40 amp load on a 200 AH battery is more of a:

• 200 AH / 39 Amp load = 5.1 hours ~ C/5 discharge rate (5 Hour Rate)

So that is a C/5 discharge rate means that the battery will be closer to ~180 AH of usable capacity--Check the battery specifications for details or read about Peukert Factor. So, the more accurate number would be (for example):

• 180 AH * 0.50 capacity usage * 1/39 amps = 2.3 hours (instead of 2.6 hours)

So,i wired 2 solars panels of 120 watt in parallel and get 12 volt @ 13.33333 amperes.i want to know, for how much time this load will work if battery is fully charged.

If the solar panels have Vmp~17.5 volts, then the you should on a typical cool/good sun day/in the middle of the day a peak of:

• 2*120 watt panels * 1/17.5 Vmp * 0.77 panel+controller deratings = 10.56 amps on an "average good day" peak current

If you have a good sunny day with 5 hours of noon-time equivalent sun, and assuming you recharge during the day then use power at night, you could expect around:

• 2*120 watts * 0.52 system AC efficiency * 5 hours per day = 624 Watt*Hours per day
• 624 Watt*Hours per day / 400 watt load = 1.56 hours per "5 hour sun" per day

and is this solar panels enough for this 200 battery,or still need more panels, for best result

There are several ways to answer that question... First is we recommend around 5% to 13% as the rate of charge for a battery bank for long battery life and useful loads from a system. So for a 200 AH @ 12 volt battery bank, the recommended solar array would be:

• 200 AH * 14.5 volts battery charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 188 Watt minimum array
• 200 AH * 14.5 volts battery charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 377 Watt nominal array
• 200 AH * 14.5 volts battery charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 490 Watt maximum "cost effective" array

So, a 240 watt array is above the minimum we would suggest for charging the battery bank--A 377 watt to 490 watt array will recharge the battery bank faster and support more loads.

The other way to calculate loads is to figure out how much power you want to use during the day, and then calculate the array to support it...

For example, say 2.3 Hour @ 400 watt load, with 4 hours of sun per day, then:

• 400 watts * 2.3 hours * 1/0.52 inverter eff * 1/4 hours of sun per day = 442 Watt array minimum

Note I have used efficiency number of 52% here... That covers a wide range of issues (panel deratings, controller losses, battery losses, inverter losses, a reasonable amount of sun, etc.). We can go into more details (for example, if you leave the inverter on 24 hours per day, we have to add the "standby" power usage of the inverter which is usually around 6 to 20 watts or so, depending on the size and design of the inverter).

But, the above numbers are usually "good enough" to quickly size a system that will work for most people.

If you have "non-standard" usage/equipment, you still need to work out the detailed calculations. Also, solar power systems work on actual hours of sun per day (and if the panel is pointed at sun vs flat on roof, clean or dirty, etc.). If the loads are "fixed" (need the power rain or shine), then you should also look at adding a small generator for backup power.

Otherwise, people have to keep track of their power usage (current from battery and solar, battery voltage, etc.). And turn off the loads when they exceed the amount of sunlight available per day. Battery Monitors (Victron is another good European brand) can make that much easier. Battery Monitors measure Amperes*Time (AH) in and out of the battery bank. Sort of like measuring the fuel used from a car's gas tank and refilled back through the same fuel line to estimate how much fuel is left in the tank.

Or with flooded cell batteries, using a hydrometer to measure the specific gravity of the electrolyte is the way most people do it. For Sealed Batteries (AGM, GEL, VRLA), you cannot use a hydrometer and must use a battery monitor or battery voltage to ensure that everything is working well.

-Bill

alkhaleejsolar

Re: A project of 12 volt

nice ,experience ,thanks,sir,