# How to use solar panels in a electric go kart?

I am entering a electric go kart competition. Below are the electrical specification of my go kart.

1hp DC Motor. Normal batteries used in motor bikes (48 volts in total) And solar panels

And i am totally new to this field So i wanted to ask what will be the rating of solar panels i should use that could charge my batteries fast and can also run the motor directly (cant exceed 48 volts or 2hp).

I am totally new to this so it will be very helpful if you can provide me with some resource to study about these.

• I'm no expert, but a quick Google suggests that a 1hp 48V DC motor consumes ~1kW. A second quick Google suggest that 1kW solar panels might be too large for your go-kart. Are you sure you want to run directly from solar power? – Roger Rowland Dec 10 '15 at 6:05
• A little web searching should show details of solar race cars that have been built - they typically aren't that much higher in power than you are contemplating, but likely a lot more efficient in how they use it. Unless solar power is an explicit part of your event, it will probably be a distraction from building an effective battery powered vehicle. – Chris Stratton Dec 10 '15 at 6:15

1hp DC Motor. Normal batteries used in motor bikes (48 volts in total) And solar panels

1 HP ~= 760 Watts input at 100% motor efficiency
Controller losses and motor losses mean you'll need more input than that to get 1 HP out - or will get under 1 HP for 760 Watts input.

Typical Solar crystalline silicon solar panels give about 15% at the system level - somewhat more for the best 'normal ones'.
Back contact Si PV cells may give a bit over 20%. The best you can get money-no-object may give 30%. Cost is very large.

At 15% overall efficiency you get about 150 Watts per square meter in full sun at noon with panel correctly aligned to sun. Less anywhere in China (smog all over) and up to about 20% more in some unusual locations. Say 150W max at noon.
If you want to run your vehicle directly from the panels and at 1 HP = 760 Watts IN you need 760W / (150 W/m^2) ~= 5 square metres of panels. eg
2.6m x 2.6m - square or
3.7m x 1.9m - 2:1 or 4.6m x 1.5m - 3:1
Rather large in any format.
If you want double the power you need double the area.

• thank you this was very useful, exactly what i was looking for as i have no prior knowledge in this. If you can suggest a resource to know a little bit more it will be very helpful – Dimensionless Dec 10 '15 at 6:56
• To make it a bit easier for others to understand, it might be worth changing "At 15% overall efficiency you get about 150 Watts in full sun at noon with panel correctly aligned to sun" to "At 15% overall efficiency you get about 150 Watts /square metre in full sun at noon with panel correctly aligned to sun" – gbulmer Dec 10 '15 at 7:11
• @gbulmer Thanks. Yes. The "per square meter" did not get from brain to page :-). It's in the calculations but not in the explanation. – Russell McMahon Dec 10 '15 at 8:07