20Ah battery (sealed lead acid) and 1500w generic inverter

BB. said:

For lead acid batteries, their output voltage is difficult to estimate the state of charge by the battery voltage. There are lots of variables (state of charge, amount of discharge/charge current, temperature, age, etc.).

Lead acid batteries, if you can discharge to 50% state of charge, and recharge the next sunny day--That will give you a longer battery life. Generally, like to suggest discharging to 75% SoC for daily/normal cycling. And down to 50% SoC during bad weather/occasional heavy loads (running tools a couple days a week, etc.).

For a first approximation, with "average loads" (max ~1/8 or 12.5% rate of discharge) use 11.5 volts as your max discharge voltage for normal usage. For surge current (starting a motor, you might see 10.5 Volts for a few seconds).

Which brings us to your battery/battery bank... A 20 AH @ 12 volt battery is pretty small... A typical "automotive" battery is around 50-80 AH @ 12 volts. And in the USA, we suggest a pair of 6 volt @ 200 AH "golf cart" batteries in series for a 12 volt @ 200 AH battery bank for a first try. They are (at least here) relatively inexpensive and pretty rugged/forgiving.

As an example, using a maximum of 8 hour discharge rate:

• 20 AH / 8 hour discharge rate = 2.5 Amps max suggested continuous discharge rate
• 2.5 Amps * 12 volts = 30 Watts
• 20 AH * 0.50 max suggested/planned discharge = 10 AH "usable" capacity
• 10 AH * 12 volts = 120 Watt*Hours of useful power

A 1,500 Watt AC inverter is a pretty heavy load for a 20 AH battery... Normally, suggest a 100 AH battery for every 250 Watt rated inverter--Or for your 1,500 Watt inverter:

• 1,500 Watts * 1/250 Watts per 100 AH (at 12 volts) = 600 AH @ 12 volt battery bank to use a "fully loaded" 1,500 Watt AC inverter

Note your AC inverter might draw 10-20 Watts "tare losses" (using that much power "just turned on". 20 Watt tare + 20 Watt LED loads--Your inverter is only 50% efficient.

Highly suggest a much smaller AC inverter (maybe 6 Watts or less Tare losses) for your LED lightning.

Or, a better option. See if you can purchase 12 (or 12/24 volt) LED lights. No inverter losses. And there are lots of options. I believe you are in the Philippines... So, what is available in your region may be different. Some Amazon examples:

https://www.amazon.com/12-volt-led-lights/s?k=12-volt+led+lights (12 volt fixtures and even "light bulbs")
https://www.amazon.com/s?k=12+24+volt+led+lights (12/24 volt compatible LED lights)

For example, if you are using 3x 7 Watt 12 VDC LED Lamps:

• 3 * 7 Watts = 21 Watts LED lighting load
• 21 Watts / 12 volts = 1.75 Amp draw
• 10 AH (50% capacity) / 1.75 Amp draw = 5.7 hour run time @ 20 Hour Lead Acid battery (suggested)

Your thoughts?

-Bill