Introduction and advice on solar charged go kart

[curiouscarbon]

While that does look interesting, there isn't a lot of overlap in what they are doing to what we are doing.... I will show this to students just to see what they think of it though

I like speed as much as the next guy but 100 mph on a go kart??

I need advice on the solar part of this thing more than anything

thank you, i agree that it might not completely overlap. just sharing link, as finding the source was a bit of task, wishing you continued good luck with project!

 

[12VoltInstalls]

Don't see rule prohibiting building panels but they do have a specific rating they have to fall under...

So a basic VOC and amps at standard temperature (77*F?) with the math for the event marshal(s) should verify their rating criteria the day of the event.
A single or several manufactured panels would have the same testing criteria so that should not be a problem.
A vom would verify your printouts. Hard tires with as minimal as possible contact patch and perhaps a 10W oil or mineral oil (test it?) in the bearings instead of grease and there are two huge things - if kept top secret- that will give you an advantage.

I’d like to see the joyous report when you win

 

[florida cracker]

So a basic VOC and amps at standard temperature (77*F?) with the math for the event marshal(s) should verify their rating criteria the day of the event.
A single or several manufactured panels would have the same testing criteria so that should not be a problem.
A vom would verify your printouts. Hard tires with as minimal as possible contact patch and perhaps a 10W oil or mineral oil (test it?) in the bearings instead of grease and there are two huge things - if kept top secret- that will give you an advantage.

I’d like to see the joyous report when you win

I think they will want to see manufacturer numbers.... I believe we would be head and shoulders above the field if permitted to build equipment that was able to produce up to the limits of the rules vs buy equipment that will never actually produce what they are advertised to produce....

Assuming it didn't burst into flames and kill us all, lol

 

[12VoltInstalls]

think they will want to see manufacturer numbers

The individual cells will have a separate data sheet or sticker on them.

 

[florida cracker]

The individual cells will have a separate data sheet or sticker on them.

I don't know if this is something we could do for this year but I will definitely pass this on to Admin to see if this is something we can try for the future.

Doing the math tells me we would need 4,150 of these to get to the 1050 watt limit and I don't even want to think about how to set them up (series and parallel)

Keep in mind that none of us (myself as the teacher or any of the students) had any experience with any of this until March or so last year so building our own solar panels might be a bit much, lol

 

[12VoltInstalls]

believe we would be head and shoulders above the field if permitted to build equipment that was able to produce up to the limits of the rules vs buy equipment that will never actually produce what they are advertised to produce

The advantages are that the students will actually learn the surface of real-world engineering considerations and their minds will be opened.

building our own solar panels might be a bit much, lol

I don’t think you should sell yourself or your students short. It’s just solder and crimps instead of molded plugs and a bracket or two.

My opinion is that when you open the mind people (even teens) exceed themselves. So few students do fantastic things these days because they can get a “102” without doing anything special.
Present a kid with an achievable but challenging goal and they’ll come alive!

It hurts my head to think that the competition would be limited to entertaining kids with bolt-together manufactured components and hoping for the best, with performance expectations are limited to a strategy paralleling that of the narrow brain use in executing a multiplayer video game instead of the dynamics and considerations of preparedness in execution of the car’s performance where on-the-ground execution is merely allowing the wide universe of brain functions if every aspect is considered. That’s the difference between participating and inventiveness. Inventiveness lengthens attention span. Inventiveness develops capacity for delayed gratification and creates new nueropathways in the brain. Inventiveness is what’s been declining in youth since the 1960s.

Geesh, I just half convinced myself to go find a job at a junior high or high school just to teach the willing how to actually do something in engineering. The Jim Keller mindset.

 

[florida cracker]

The advantages are that the students will actually learn the surface of real-world engineering considerations and their minds will be opened.
It hurts my head to think that the competition would be limited to entertaining kids with bolt-together manufactured components and hoping for the best, with performance expectations are limited to a strategy paralleling that of the narrow brain use in executing a multiplayer video game instead of the dynamics and considerations of preparedness in execution of the car’s performance where on-the-ground execution is merely allowing the wide universe of brain functions if every aspect is considered. That’s the difference between participating and inventiveness. Inventiveness lengthens attention span. Inventiveness develops capacity for delayed gratification and creates new nueropathways in the brain. Inventiveness is what’s been declining in youth since the 1960s.

Geesh, I just half convinced myself to go find a job at a junior high or high school just to teach the willing how to actually do something in engineering. The Jim Keller mindset.

I did pass the link to those cells down to the engineering teacher to look into because it could be a really cool classroom project with applications all over the place.

I am a Social Studies guy in the Special Ed dept that was dumb enough to go take a look at this thing last year when kids started talking about giving it a wing. It looked interesting and I found myself a faculty sponsor for this thing

I am not an engineer by any stretch but I was a street racer back in the day so I do understand how and why things go fast

Could we build our own panels for next year or the following year?? I have no idea but it is worthy of the discussion and I believe we would win the presentation portion by doing that and describing how we did it, lol

The race is going to be won by the team that has the most testing time used wisely to program their speed controller to get the most out of their battery capacity

 

[florida cracker]

As much as I have posted on this I thought it might be helpful to just post a link to the actual contest

This is from last year and is all we have to go on for now: https://www.fgcu.edu/cas/centers/whitaker/k-12#SunChaseResources

I did post earlier the proposed changes to more solar and different battery types allowed

 

[florida cracker]

Time to revisit this thread, it seems that the rules changes I was expecting are what is going to happen. 1050 Watt in panels and same 720ah in battery.

I still have not seen anything that seems to be better in a flexible panel than the Renogy 175. I do understand that flexible panels don't put out as much power as solid but they also won't need as much power to mover them around either and the Kart will be safer with less weight up high. The district has already sent us Renogy Rover 60 amp SCC.

Would like to know how would be the most productive way to wire them together 6s or 3s2p (hope I got the terminology right).

Posting Specs for Panels:

View attachment 112853


Specs for SCC:

View attachment 112851

If I wire 6 of these in series, the controller should handle it and it would simplify my wiring. If I understand it correctly, the only real benefit to wiring 3s2p or ever 2s3p would be if there is shade on any of the panels correct?? Would this also give us any benefit on a cloudy day??

I'm all in on keeping this as simple but efficiency is important. Cable runs should be less than 5' maximum on charging side

 

[12VoltInstalls]

only real benefit to wiring 3s2p or ever 2s3p would be if there is shade on any of the panels correct??

No. Higher voltage lets you use less money on wiring. If one string is unshaded it can help there, too.

Would this also give us any benefit on a cloudy day??

No.

I have two 400W arrays- one SE and one SW. The SE array goes out of direct sun by noon and it still puts out 60-150W most of the afternoon if there’s good sun. Yes, facing away from the sun.
There is no gain under clouds.

 

[florida cracker]

No. Higher voltage lets you use less money on wiring. If one string is unshaded it can help there, too.

So the only reason to not have them all wired in series would be if the SCC can't handle that level voltage??

No.

I have two 400W arrays- one SE and one SW. The SE array goes out of direct sun by noon and it still puts out 60-150W most of the afternoon if there’s good sun. Yes, facing away from the sun.
There is no gain under clouds.

We can move the Kart around to avoid shadows to get it in as much sun as possible and should be able to to build in a way to point panels directly into the sun

 

[Charleswgibbs]

Higher string voltage reduces current and the associated losses for the same amount of power.

That charge controller has a limit of 150v and those panels have an open circuit voltage of 23.9 so you could run all 6 panels in series giving you 143.4v

The risk is that as temperature drops panel voltage increases so it's possible if you ran your system on a very cold day the voltage could exceed the 150v limit and fry your controller.

If it was me I would play it safe and run a 3s2p configuration, where you have two parallel strings of three panels in series. This would be well within the limits of the controller and should give you basically the same performance as a 6s configuration.

Good luck!

 

[florida cracker]

Higher string voltage reduces current and the associated losses for the same amount of power.

That charge controller has a limit of 150v and those panels have an open circuit voltage of 23.9 so you could run all 6 panels in series giving you 143.4v

The risk is that as temperature drops panel voltage increases so it's possible if you ran your system on a very cold day the voltage could exceed the 150v limit and fry your controller.

If it was me I would play it safe and run a 3s2p configuration, where you have two parallel strings of three panels in series. This would be well within the limits of the controller and should give you basically the same performance as a 6s configuration.

Good luck!

We're in South Florida so not too concerned with the cold but my initial thought was to wire them 3s2p as suggested just because I really did not know and that just sounded right. Wiring them all in series sounded more "right" the more I read about it and the idea that it would simplify the wiring just made it sound more "right"

 

[12VoltInstalls]

We're in South Florida so not too concerned with the cold but my initial thought was to wire them 3s2p as suggested just because I really did not know and that just sounded right

I’d still go to an online calculator and factor for your lowest temps. You’d be surprised at how even at 45*F the voltage goes up.

 

[florida cracker]

Rules change is official.... 1050 watts in panels is 6 175 watt or 3 350 watt panels....

I'm pretty sure we will be doing the 6 175 watt flex. Is there any benefit to wiring them all in series (if the math works out) other than easier wiring?? Shouldn't change how fast batteries will get charged??

 

[12VoltInstalls]

I'm pretty sure we will be doing the 6 175 watt flex. Is there any benefit to wiring them all in series (if the math works out) other than easier wiring?? Shouldn't change how fast batteries will get charged??

Except in low light and certain circumstances as long as you reliably and substantially hit voltages above the charge controller minimum requirements, and have full sun on all panels then, production-wise, no difference. But with 6 panels in parallel you will be using more and heavier wire. Plus if the vehicle does not have equal sun on all panels you’ll take a hit from that, too. I can envision 3S2P being necessary. Or perhaps 2S3P to insure sun production isn’t inhibited. But again wire weight can add up.

 

[florida cracker]

Except in low light and certain circumstances as long as you reliably and substantially hit voltages above the charge controller minimum requirements, and have full sun on all panels then, production-wise, no difference. But with 6 panels in parallel you will be using more and heavier wire. Plus if the vehicle does not have equal sun on all panels you’ll take a hit from that, too. I can envision 3S2P being necessary. Or perhaps 2S3P to insure sun production isn’t inhibited. But again wire weight can add up.

It was always going to be either 6s or 3s2p, shading shouldn't be a problem only possibility of clouds....

 

[12VoltInstalls]

shading shouldn't be a problem only possibility of clouds

Depending on whether the course is laid out parallel with the sun’s travel you could have “shadow:” indirect sun, not facing sun.
In that circumstance you may negate your production wattage. And lose.

 

[florida cracker]

Depending on whether the course is laid out parallel with the sun’s travel you could have “shadow:” indirect sun, not facing sun.
In that circumstance you may negate your production wattage. And lose.

There is a break between heats to allow karts to charge and course is laid out so that area is not shaded. Like I said, the only real concerns would be a cloudy day and I don't think is anything anyone can do about that, lol

We do plan on putting flexible panels on a PVC rack mounted to roof of Kart that can be pivoted up for best angle to catch sun

 

[florida cracker]

Had our race today, finished 4th and not unhappy about it.

Did have a few problems that we can work out with more time and testing but I have a question about battery capacity monitors. The Renogy SCC battery gauge is useless as it bases its SOC off of voltage and as soon as the kart stops and begins to charge with no draw on battery, it reads 100%.

Bought a smaller shunt based ammeter that is supposed to give us SOC reading also but it only gives us info while kart is running. I would like to find something that will give us real time SOC reading while it is charging. Someone has to make this