# Charging a battery from solar

1. Jul 6, 2011

### aussie101

Hi all,
If I have a battery bank 12V@1000A-
what size solar cell (kW) will recharge this battery bank (from flat to full) over a 8 hour period?

2. Jul 6, 2011

### Keyur

You need to calculate the full power stored in your battery bank.
Then you will have to estimate the amount required to generate that power in 8 hour.
Batteries do not charge at constant rate, rate slows when it gets charged more and more.
Solar intensity is not the same for full day, consider this too. You need to add the amount of power generated in 8 hours,it will not be same for every time of day. Consider this and then calculate what kWp- kilo Watts peak solar cell array you require.

3. Jul 6, 2011

### aussie101

like most things these days i'm out of my depth of knowledge.
let me pose the question another way-
how many days would a 1kw solar cell take to charge a battery rated at 12 volt @ 1000Ah estimate

4. Jul 6, 2011

### Keyur

Is it 1kw peak solar cell. That is does it produce a maximum power of 1kw at highest intensity of sunlight?

5. Jul 6, 2011

### aussie101

what ever will produce the most power

6. Jul 7, 2011

### Keyur

The more power it produces, the more it costs.
Why not use wind as energy source?

7. Jul 7, 2011

### aussie101

because a wave will rip it off the boat

8. Jul 7, 2011

### vk6kro

There isn't enough information to give a good estimate, but it is possible to make some assumptions.

Suppose the solar panel was giving 14 volts out and everything was 100 % efficient.

The solar panel maximum current would be 1000 watts / 14 volts or 71 amps.

If it was OK to to charge the batteries at 71 amps, then it would take 1000 amp-hours / 71 amps or 14 hours to charge the batteries.

If you had 5 hours a day of good sunlight, then this would be about 3 days.

9. Jul 9, 2011

### aussie101

thankyou vk6kro,