panel for 130 amp battery

[jony lima]

hi,
i calculated my load which needs 130 amp lead-acid battery 12volt system. but i cant calculate the appropriate solar panel (watts) that can charge my battery in 6/7 hours.
can u tell me the watt of panel and the amp of charge controller i should buy?

thank to all

jony

[russ]

Hi jony - Welcome to Solar Panel Talk!

What is your approximate location - it is need for anyone to comment.

What will you be powering?

Russ

[Sunking]

Jony technically you cannot charge a FLA battery in 6 hours. Maximum rate is 8 to 10 hours. However if you sized the battery correctly so that no more than 20% discharge in any one day, charge rate is not an issue.

Since I have no idea of your location, if you based the battery discharge on 20% daily (300 watt hours), and what type of charge controller you have, all I can do is guess based on maximum size the battery can handle.

If you use a PWM controller and use a standard 12 volt solar panel, 240 watt panel.
If you use a MPPT controller, 170 watts.

[Sunking]

Thank u Russ for reply,
my location is Dhaka which is the capital Bangladesh. here we can get sun for 11 hrs approx a day in summer. a have a charge controller 10amp pwm.

Sorry but that does not mean anything. Just because you may get 16 hours of sun does not translate to 16 Sun Hours. 12 volts and 130 amps does not mean anything either as you expressed it. 12 volts x 30 amps = 1560 watts which is just a measurement of power at a specific moment in time and is not a measure of energy which is watt hours.

[jony lima]

Jony technically you cannot charge a FLA battery in 6 hours. Maximum rate is 8 to 10 hours. However if you sized the battery correctly so that no more than 20% discharge in any one day, charge rate is not an issue.

Since I have no idea of your location, if you based the battery discharge on 20% daily (300 watt hours), and what type of charge controller you have, all I can do is guess based on maximum size the battery can handle.

If you use a PWM controller and use a standard 12 volt solar panel, 240 watt panel.
If you use a MPPT controller, 170 watts.

Thanks a lot Sunking for ur response, my location is Dhaka, Bangladesh. i designed discharging battery 50% (approx 700 watts) everyday. somebody told me that a battery needs at least 10% of its total Amp. Is it true? i roughly desired to bye 260 watt panel. my charge controller type is PWM. can u tell me the accurate watts of panel sir?

regards
jony

[Sunking]

Thanks a lot Sunking for ur response, my location is Dhaka, Bangladesh. i designed discharging battery 50% (approx 700 watts) everyday.

Jony do you mean 700 watt hours? 700 watts is not a measurement of energy, just power. They are two different things.

[Sunking]

somebody told me that a battery needs at least 10% of its total Amp. Is it true? i roughly desired to bye 260 watt panel. my charge controller type is PWM. can u tell me the accurate watts of panel sir?

Well there is some fact and fiction with 10% charge current. PWM and MPPT charge controllers are very different animals.

With PWM CC the Input current = Output current so if you wanted to say run a 12 volt @ 130 Amp Hour battery with a C/10 charge current (10%), you would have to select a solar panel with a Imp (current maximum power) or 13 amps. 13 is 10% of 130 right? However what wattage is that panel. Who knows it is not specified. With most 12/24 volt PWM charge controllers the maximum Voc (voltage open circuit voltage) can be as high as 55 volts, which means the Vmp (voltage maximum power) is around 42 volts. On the low end if you were to use a panel made for 12 volt battery system the Vmp = 17 volts. So what size panel would one need to supply 13 amps to a 12 volt battery system. Answer is anywhere from 220 to 550 watts. Quite a range huh?

Here is where it gets educational. The panel size for a MPPT controller needed to supply 13 amps to a 12 volt battery is 170 watts period. Think about that for a while and what it means.

The key to the mystery is the current, for PWM the panel Imp determines the current. For MPPT the panel wattage and battery voltage determines the current.

So to answer your question would a 240 watt panel work with a PWM CC. Beats me, what is the Vmp & Imp of the panel? If the Vmp = 16 to 18 volts, and Imp = 13.3 to 15 amps it will work.

[russ]

From PV Watts - annual average insolation for Dhaka = 5.24 kW/m2

For a 1 kW DC system projections-
Low month July = 85 kWh AC
High month March = 122 kWh AC
Annual projection = 1264 kWh

Russ

[jockellis]

Jony, Sunking has often reminded people that they need to remember that you don't set your solar aspirations on the length of sunlight in the longest day but the shortest which would, of course, be in the winter.
Here in America, that time, Sunking points out, would be about four hours because the sun has to be pretty much overhead. I would bet your usable sunlight hours are not too far from ours which would mean way less sun than you anticipate.
Lead acid batteries cannot sustain a loss of over 1/3 their rated amperage and last every long. You may have a number like 95 on your battery. That is a US government, or was, regulation so that buyers would know how much electricity was in that battery. It means that discharging at 12.6 volts and 25 amps that the battery would last 95 minutes. But remember that you can't use but a third of that without killing your battery so it is more like 31 minutes that you could discharge electricity at that rate.

[Sunking]

thank u
can u give me a easy formula that i can calculate my panel for any amp of battery?

Charge amps = C/10

[jony lima]

Charge amps = C/10

hello Sunking,
u might know that i have no academic knowledge about the formula about solar or electrical engineering. but i have much interest to learn this. i like to build some projects. thank u all for helping me. pls make the formula more easy, i mean what is charge amps and c/10 or how can it help me to calculate measuring panel watts?

jony

[jony lima]

Well there is some fact and fiction with 10% charge current. PWM and MPPT charge controllers are very different animals.

With PWM CC the Input current = Output current so if you wanted to say run a 12 volt @ 130 Amp Hour battery with a C/10 charge current (10%), you would have to select a solar panel with a Imp (current maximum power) or 13 amps. 13 is 10% of 130 right? However what wattage is that panel. Who knows it is not specified. With most 12/24 volt PWM charge controllers the maximum Voc (voltage open circuit voltage) can be as high as 55 volts, which means the Vmp (voltage maximum power) is around 42 volts. On the low end if you were to use a panel made for 12 volt battery system the Vmp = 17 volts. So what size panel would one need to supply 13 amps to a 12 volt battery system. Answer is anywhere from 220 to 550 watts. Quite a range huh?

Here is where it gets educational. The panel size for a MPPT controller needed to supply 13 amps to a 12 volt battery is 170 watts period. Think about that for a while and what it means.

The key to the mystery is the current, for PWM the panel Imp determines the current. For MPPT the panel wattage and battery voltage determines the current.

So to answer your question would a 240 watt panel work with a PWM CC. Beats me, what is the Vmp & Imp of the panel? If the Vmp = 16 to 18 volts, and Imp = 13.3 to 15 amps it will work.

hello Russ
thanks a lot. first i felt difficult to understand ur lesson. i read it several times and now i think i got it.u told me that main thing is current. can u help me that how can i measure the current from a panel by using a digital meeter?

[jony lima]

need to know

hello all,
I like to build a solar system which will run 3 to 4 Hours. my load is a fan/80watts and 3 lights (23 watts*3) 70 watts. i will run it when electricity fails. here average load shedding is 2-4 hrs daily. can u tell me what would be my battery bank and panel watt?
my area is Dhaka, Bangladesh.

thanks
jony

[Mike90250]

Cost wise, you will fare better with just a battery, inverter and grid powered charger, solar will easily add 700 $ us to the cost, a battery charger from the auto parts store is $100 (for a good 3 stage charger)

[jony lima]

Cost wise, you will fare better with just a battery, inverter and grid powered charger, solar will easily add 700 $ us to the cost, a battery charger from the auto parts store is $100 (for a good 3 stage charger)

thank u Mike

but i like to build a solar system for load shedding. can u give me the configuration?

1 fan for 3 hours=80*3=240 watts.
3 CFLs=23*3=69 watts
total load=300 watts aprox. per day.

jony