Roll-out solar panels sound too good to be true for any remote location shoots. The crew on BBC Planet Primate put them through their paces in Ethiopia and trialled 2 x 124watt – 24 volt solar panels provided by BAE Systems. The panels were connected to a V-lock battery charger which required 12 volts to power two batteries simultaneously.
Jon Wellingham, BBC Engineer:
“The solar panels were very easy to operate in the field. Weather during trip was bad for many days and in overcast conditions the panels do not produce any usable power. However, when the sun came out, with both panels hooked up we did manage to recharge a V-lock battery from flat to fully charged in around 2-3 hours. Cameras used around 10 Vlock batteries per day.
The main time the panels were used was in the middle of the day between 12-2 as filming was 5-12 then from 2 until dark. We tended to recharge all of our batteries via generator ready for the next day’s filming.
The panels can take quite a while to get going so effectively need to ‘warm up’ in the sun before they really start to output any power. The green lights on the charge controller are also very difficult to see in direct sunlight and a different display panel might well be useful to let you know when it’s working properly. Overall though, it was quite an easy system to use. Further field tests would be needed to really see how they perform but overall I think my team were pretty impressed.”
Jon Wellingham, an Engineering for the BBC NHU helps us get to the bottom to the technicalities…
‘The charger uses a switched mode power supply to generate the charging supply of around 15 volts from the 12 volt input, and that has a typical efficiency of about 75%. The battery being charged requires approximately 30% overcharge, so its efficiency is about 70%. Multiplying the two efficiencies =52.5%, which means that overall the solar panel needs to generate approximately twice as much power as the camera uses. If the camera is rated 30W, your solar panel will need to provide 60W to replace that. To do that it will need to charge for an hour and a half for each hour of camera run time (solar panel=40W times 1.5=60W). If there are 12 hours of sunlight per day, you can run the camera for 8 hours. This assumes the solar panel actually produces 40W for the whole 12 hours, which may be a poor assumption. This also assumes one camera, one solar panel and two batteries. One battery charges all day and the other is in use. The next day the batteries swap over.’