Ideal load (watt) for 23ah lead acid battery for its long life (?)

[Willen]

Hi, Just now I bought a 'solar set' and it has-

- 20 watt solar panel
- 12V 23AH lead acid battery
- 3 LED bulbs, each bulb has 2 watt (total 6 watt)

I am using these bulbs almost 2 (sometime 3 hrs) hours at evening. Battery is charging whole day via 20 watt panel.

Aother company is distributing such solar system which has same powered battery and same powered panel but that has 5 LED bulbs (total 10 watt load.)

here, my main question is- Can I use 5 bulbs without any bad effect? Actually what is the ideal load for 12V 23AH battery for its ideal life? Any calculation? Any assumption?

 

[ronv]

To answer that question we need to know how many amps your leds take, So we need to know if they are in series with 1 resistor or in parallel each with its own resistor. Also need to know the forward voltage of the LED's if they are in series. We can kind of guess if you don't have the actual specs, but it would be good to know.
For long life on a deep discharge battery it should only be discharged about 40%. So if they are in parallel with their own resistor they would take 6 watts. Your battery has 276 watt hours X 40% or 110 watt hours /6 = 18.4 hours without sun. You can figure out what 5 would do.

 

[Willen]

Sorry I don't know about resistors inside LED bulbs. There are built-in modern LED bulbs (looks like ordinary filament bulb in shape) and it's rated 2 Watt, 12V DC. It's expensive than fluorescent tube light. And gives VERY brighter light like 20 watt CFL/tube light. Battery- 12V 23AH 10hour.

 

[MikeMl]

It not so much about your load, as it is about how much sun you have. To answer your question, put an ammeter in the system. Measure the solar panel current flowing into the battery the next morning. Note at what time of the day the charging current tapers to near zero. If that happens halfway through the solar day, then you could almost double the load current. If it happens late in the day, then you cannot add any load.

 

[dr pepper]

2 watts is about 170mA x 3 = 510mA, theoretically that would last a long time on a full charge, but as mentioned you may or may not get a full charge.
If you ran all 3 for 3 hours you'd use 1.5 aH or just over, so if you had say7 hours of sun midwinter you'd need a theorectical charging current of about 220mA, 350mA to overcome ineffeciencies.
A 20w panel if you believe the rating is over 1.5a, but I bet you never get that, measure the charging current on a bright day then a dull day, to be safe assume you will allways have a dull day.
A charging regulator would be required for a panel that size to be permanently connected to a 25ah battery.

 

[rumpfy]

I'll try to answer your question.
Your lead acid battery has a capacity of 23 Amp hour. If you discharge the battery at a current of 1 amp, it will discharge in 23 hours, theoretically. The actual capacity depends on how quickly you discharge it. Discharging it in say 1 hour (at 23 amps) it will not give 23 amp hour. The other problem with lead acid batteries is that as they are charged and discharged, their capacity is reduced.
Attached is a chart from an aussie battery maker. If you discharge your battery at a rate of one twentieth of the one hour rate (23 x 0.05 = 1.15 Amp), then according to the chart, the battery will maintain its terminal voltage for about 2 hours. If the discharge is kept to less than 15% of capacity, the battery should suffer no drop in capacity for at least 1600 cycles. (thats about 5 years.) After about 2500 cycles, the battery capacity could be reduced to 60 % of its capacity or about 14 AH. Thats after about 7 years.
Hope this helps.
In your case with 3 LED discharging at 0.5 amps, if you operate the leds for 4 hours per day, the discharge is 2 AH. ie 2/23 = 8.6 % per day. This is a very light loading and you should be able to run 5 lamps at 4 hours per day to give a 14.3 % discharge per day.

 

[ronv]

Sorry I don't know about resistors inside LED bulbs. There are built-in modern LED bulbs (looks like ordinary filament bulb in shape) and it's rated 2 Watt, 12V DC. It's expensive than fluorescent tube light. And gives VERY brighter light like 20 watt CFL/tube light. Battery- 12V 23AH 10hour.

Good, so they will be in parallel and each with its own resistor built in. So the example I gave above would be close.[/quote]