Monday, 17 October 2016

The solar system

Going on a bike tour one might think the bike itself would be my primary focus. But with a master's in electrical engineering and being environmentally concerned, I have been very focused on the electrical, ie solar, system.

The bike has a 250 W, 36 V Bosch engine with a 400 Wh battery.

The bike trailer can nicely fit two 50 W solar panels from SunBeam. They are connected through a Peak Power EP MPPT, 10 A solar controller to the system.

Just beacuse there would be electricity on the trip a cooler sounded like that piece of equipment that you just never can bring along but now could. So the Waeco beauty CoolFreeze CF-11 was tajen onboard. It is a very efficient piece of machinery and consumes only about 6-7 Ah a day, meaning about 80 Wh.

So, there are the outer boundaries - a cooler consuming about 80Wh a day and a bike wasting 400Wh and to our disposal are 100W solar panels. It sounds doable, with only half the day sunny, even with a phone and laptop and what not also to be charged.

A battery big enough to feed the cooler and fill up the bike battery would imply 400 + 80 Wh = 480 Wh that in a 12 V system would mean a 40 Ah battery. Lithium, of course, or LiFePO4 to be exact, which I found at Batteriexpressen.

Note that there is a 10% loss in the 12/230 V converter needed to charge the bike battery and the solar panels will not be able to deliver 100W. But not sure about what exactly the needs were and the fact already the 40Ah battery is bloody heavy, I leave the system as this for now.