# Off Grid Power

I was wondering what I could run off grid and wanted to start with an off-grid phone experiment, not really that radical, but more something for me to test the latest technology and to do the calculations around batteries, solar panels and power consumption – does it really add up?

### 2nd December 2017:

• Samsung Phone and BERNET Solar PowerBank fully charged off mains, the experiment starts now.
• How many days can I go before I have to resort to an alternative form of charging?

PowerBank:

• Battery Capacity:24000mAh
• Output:5V/2.4A
• Input:5V/2.1A
• Solar Panel:5V/200mAh 1W

The solar panel is just meant to be a top-up, but lets have a go. 5 hours of input from the sun every day should be enough to top-up what I remove with my phone.

Phone:

• Samsung J5
• 3000mAh battery
• Estimated battery life from full charge is 52h 48m based on last 7 days of use
• This means power demand from the phone on average is 3000/52.8=56.8mA
• Nominal voltage of the battery is 3.6V
• 6×0.0568=0.204W on average

The average numbers suggest that I’m going to be ok with running my phone on solar power acquired by the powerbank whilst I’m away from base.

### 10th December 2017:

• I’ve charged the phone at least twice in the last week and still going strong.
• Battery bank shows white light still and so either I’ve not used much or the solar is keeping up.

### 21st December 2017

• Could only charge phone to 26% and stopped
• So, this has worked for 19 days
• 0.204 x 24 x 19 = 88Wh used over 19 days = 93.02Wh
• Battery bachup + phone = 24Ah x 3.6V + 3Ah x 3.6V = 86.4Wh + 10.8Wh = 97.2Wh available in both devices
• This implies:
• energy used = energy in both batteries at the start
• zero solar power…..

### Conclusion

This is a fine power bank, but the solar panel is next to useless in the UK in December.