Walmart Everstat 24DC 101AH for DIY Solar build (flooded lead acid)

[SunEagle]

Well Our budget is limit is 500 set by the school. Anything else would have to come from out of pocket. Right now and not including some circuits, our cost is at 457.11

Thats with 50W and 35AH.

I was convinced 35AH would be enough when you consider that most weeks we wont be using the motors on the battery. It just occured to me. We need to run everything off the battery just for presentation purposes. We would test everything on the battery but if planned properly it should occur in spaced out days.

As for when we are running expriments, it would be to test the motor programming which means running the motors maybe at most 40 mins (motor1) 20mins (motor 2). Show that our charging circuit works and that light sensors work to check position of sun.

When I calculated it, it seems 15 AH in a day at most is reasonable.

Based on your answer and some of your later posts you might be able to get your 50w panel and 35ah battery project to work long enough to get graded.

Although I believe you are now beginning to understand that it takes a lot more battery and solar panel wattage to do what you want. Also there really isn't any "break even" when talking about a solar tracking system. Yes you can get maybe 20% to 25% more out of your pv panel if it tracks the sun but tracking systems usually use more power then the extra % they can generate.

There is a small company up in Massachusetts that has developed a "low power" tracking system using air cylinders to move a 2 panel system that tracks the sun. The equipment works for a flat roof installation but the final determination if they will be commercially viable is still out for review.

Hopefully you will be able to pull it all together and at least shows some results for your professor.

[sensij]

No problem. Others who have posted in this thread are way more knowledgeable than I am. However, based on everything you've posted, I think I would give the 50 W / 35 Ah combination a shot. The charge current produced by that panel will be reasonably well matched to the battery... putting that panel on a 100 Ah battery would be a very low charge current, so bigger or more panels would probably be needed for it to work right. The 35 Ah battery may not last as long as you'd like, but as long as you can avoid it failing during the demo itself, it sounds like your goals could be met.

[edo101]

Sorry for not looking closer at the battery. Dumb on my part.

So basically, you want to track the sun with a solar panel, more or less breaking even on the amount of energy it takes to operate the tracker and the amount of energy you generate. Am I understanding right?

If you don't need to build your own MPPT charge controller and buying one is an option instead, you could check out these Genasun products. They look like legit MPPT, and the smallest is sized for a 50 W panel, with other models for 65 W or 140 W panels.

Thanks for sharing that. I have been wondering why there aren't more lower amp MPPT ones but i guess people typically don't use MPPTs for small scale.
I'll have to talk with my professor and TA once school starts again to see if they'd be okay with just buying it.

Yeah we want to track the sun, and draw energy from it in the best way possible. It would be nice to say we broke even but at our level and with the fact that we are undermanned (although the profs don't seem think so) it shouldn't be necessary. We just need to show that the basic functionality works

[sensij]

What we want to do is build a solar setup that can track the sun, and uses mppt to charge its load.

Sorry for not looking closer at the battery. Dumb on my part.

So basically, you want to track the sun with a solar panel, more or less breaking even on the amount of energy it takes to operate the tracker and the amount of energy you generate. Am I understanding right?

If you don't need to build your own MPPT charge controller and buying one is an option instead, you could check out these Genasun products. They look like legit MPPT, and the smallest is sized for a 50 W panel, with other models for 65 W or 140 W panels.

[edo101]

Ok, I'm still not following exactly what you want to do. I noticed you linked a charge controller earlier in the thread... despite the MPPT in the name, that is a PWM charger and will seriously hurt your conversion efficiency.

A bigger problem I don't think you've covered yet... the 24 V Walmart battery can not be charged by a 12 V panel. If you go with that battery, you will definitely need a different panel, or two of them in series.

Edit:
What do you mean when you use the term MPPT? I'm getting the idea that your definition and mine might be different.

Another edit: Is tracking the sun actually required for the project, or are you assuming that by tracking the sun you will get more power and therefore it is something you should do?

What we want to do is build a solar setup that can track the sun, and uses mppt to charge its load.

The battery is actually a 12V battery. The call it 24DC (24 being its size and DC meaning Deep Charge). Some people on amazon told me that it might not be a good choice....nobody really explained why. I have seen people on youtube hook up their own DIY systems to car batteries lol

MPPT, maximum power point tracking and yeah after checking youtube, it looks like all those cheap eBay ones are all PWMs. Would be cool if there was a way to make them MPPT because that would save me some time. I not only need to code the controller but I also need to design the HW to make the circuit charge battery and my time is ticking down.

Tracking the sun is part of the project so yes.

[sensij]

Yeah its essentially a demo to track the sun and produce solar power at the same time.

So yes I am trying, emphasis on trying to build an MPPT circuit that will draw power from panel and charge the battery. That's why the project is adding up but its just a project we need to do to graduate.

Thats why I now feel like 35AH and 50W panel is good enogh because most of the testing should be done with a constant source of electricity. And then some done with none to show that the MPPT works and the tracking.

I don't know how to do C/C++ prorgramming well so I am using National INstruments for now and their myRio controller.

Ok, I'm still not following exactly what you want to do. I noticed you linked a charge controller earlier in the thread... despite the MPPT in the name, that is a PWM charger and will seriously hurt your conversion efficiency.

A bigger problem I don't think you've covered yet... the 24 V Walmart battery can not be charged by a 12 V panel. If you go with that battery, you will definitely need a different panel, or two of them in series.

Edit:
What do you mean when you use the term MPPT? I'm getting the idea that your definition and mine might be different.

Another edit: Is tracking the sun actually required for the project, or are you assuming that by tracking the sun you will get more power and therefore it is something you should do?

[edo101]

Tell us more about the project. It sounds like you are building an MPPT circuit to get power from the panel... is it also a charge controller? That linear actuator is not cheap... is that to make the panel track? It is expensive to move a small panel to chase the sun, you might get more energy for your money by buying a bigger panel that is fixed.

Yeah its essentially a demo to track the sun and produce solar power at the same time.

So yes I am trying, emphasis on trying to build an MPPT circuit that will draw power from panel and charge the battery. That's why the project is adding up but its just a project we need to do to graduate.

Thats why I now feel like 35AH and 50W panel is good enogh because most of the testing should be done with a constant source of electricity. And then some done with none to show that the MPPT works and the tracking.

I don't know how to do C/C++ prorgramming well so I am using National INstruments for now and their myRio controller.

[edo101]

You have not factored in any system losses, like a panel with a 50 watt sticker on it, will only produce 80% of it's nameplate power, except in an air-conditioned lab with a 1 Sun reference arc lamp.
Now you have 40 watts. Batteries only convert 80% of the recharge into storage, the rest bubbles away as lost gas (why then need vents, and distilled water added once in a while). Take 100 watt hours out, must recharge with 120Wh.

The losses just add up, and pretty soon, you have a dead battery.

But you'd take the 100AH walmart flooded battery?

[sensij]

As for when we are running expriments, it would be to test the motor programming which means running the motors maybe at most 40 mins (motor1) 20mins (motor 2). Show that our charging circuit works and that light sensors work to check position of sun.

Tell us more about the project. It sounds like you are building an MPPT circuit to get power from the panel... is it also a charge controller? That linear actuator is not cheap... is that to make the panel track? It is expensive to move a small panel to chase the sun, you might get more energy for your money by buying a bigger panel that is fixed.

[Mike90250]

You have not factored in any system losses, like a panel with a 50 watt sticker on it, will only produce 80% of it's nameplate power, except in an air-conditioned lab with a 1 Sun reference arc lamp.
Now you have 40 watts. Batteries only convert 80% of the recharge into storage, the rest bubbles away as lost gas (why then need vents, and distilled water added once in a while). Take 100 watt hours out, must recharge with 120Wh.

The losses just add up, and pretty soon, you have a dead battery.

[edo101]

Your first mistake was using Amp Hours. You should have been using watt hours. If you had done that you would have came up with 320 watt hours per day. Assuming 50% discharge daily on the battery would require a battery capacity of 640 watt hours. At 12 volts is a 620 wh / 12 volts = 51.6 Amp Hour battery. If you have one single cloudy day, you have to shut down until after you have one full day of sun.

To generate 320 watt hours in Dallas TX in January would require a [320 watt hours x 1.5] / 3.8 Sun Hours = 126 watts using a MPPT controller. If you use PWM will require [320 wh x 2] / 3.8 Sun Hours = 168 watts. Either way generates the same 320 watt hour per day of 25.8 Amp Hours per day at 12 volts.

what is 1.5 and 2 and why do you multiply them into 310 Whrs. And if I am understanding you, you mean I would need like a 150W panel to make up that daily usage the same day?

Let's say we decide to spend more, would that Walmart battery be fine for this situation? (Asking everybody really). The only SLA 55AH battery I can find is around 120 bucks.

[Sunking]

Your first mistake was using Amp Hours. You should have been using watt hours. If you had done that you would have came up with 320 watt hours per day. Assuming 50% discharge daily on the battery would require a battery capacity of 640 watt hours. At 12 volts is a 620 wh / 12 volts = 51.6 Amp Hour battery. If you have one single cloudy day, you have to shut down until after you have one full day of sun.

To generate 320 watt hours in Dallas TX in January would require a [320 watt hours x 1.5] / 3.8 Sun Hours = 126 watts using a MPPT controller. If you use PWM will require [320 wh x 2] / 3.8 Sun Hours = 168 watts. Either way generates the same 320 watt hour per day of 25.8 Amp Hours per day at 12 volts.

[edo101]

The biggest mistake people make when it comes to a solar/battery system is the cost. To even run a couple of small motors in your experiment requires much more than 50watt panel and 35Ah battery.

If you set your "budget" you underestimated the cost for your test. If someone else set the "budget" and panel wattage then they either want you to fail or want you to discover the fact that running electrical loads from a battery which is charged with solar is an expensive project.

Well Our budget is limit is 500 set by the school. Anything else would have to come from out of pocket. Right now and not including some circuits, our cost is at 457.11

Thats with 50W and 35AH.

I was convinced 35AH would be enough when you consider that most weeks we wont be using the motors on the battery. It just occured to me. We need to run everything off the battery just for presentation purposes. We would test everything on the battery but if planned properly it should occur in spaced out days.

As for when we are running expriments, it would be to test the motor programming which means running the motors maybe at most 40 mins (motor1) 20mins (motor 2). Show that our charging circuit works and that light sensors work to check position of sun.

When I calculated it, it seems 15 AH in a day at most is reasonable.

[SunEagle]

Winter through Spring. School Spring Semester: Jan 20 to May.
I am in Texas. Hmm I have to only use 1 50W (we are under budget limits).
Panel I want to use: http://www.amazon.com/RENOGY%C2%AE-M...0W+solar+panel

So it looks like if I want to be able to use the setup multiple days a week, I can't use 10Ah a day?
How did you do that calculation and where did the efficiency calculation come from? I am new to all this and I do think I might be overcompensating for this cause I don't see us using the setup too much a week.

Since I can't go higher than 50W, you'd say go for the Walmart battery then? I found a 55Ah one on Amazon but its 110 dollars

The biggest mistake people make when it comes to a solar/battery system is the cost. To even run a couple of small motors in your experiment requires much more than 50watt panel and 35Ah battery.

If you set your "budget" you underestimated the cost for your test. If someone else set the "budget" and panel wattage then they either want you to fail or want you to discover the fact that running electrical loads from a battery which is charged with solar is an expensive project.

[edo101]

A 50W panel is rated for about 2.7A. If you are using 26.3Ah per day, 26.3ah / 2.7A / .67 inefficiencies = 14.5 hours. Sorry, won't work.

Are you doing this in winter? Where are you? I'll assume pretty bad sun conditions for winter for 2.5 sun hours. Depending on where you are and when you are doing this, you may be better. 26.3Ah / 2.5 sun hours / .67 inefficiencies = 15.7A. x 12V = 188W panels.

Winter through Spring. School Spring Semester: Jan 20 to May.
I am in Texas. Hmm I have to only use 1 50W (we are under budget limits).
Panel I want to use: http://www.amazon.com/RENOGY%C2%AE-M...0W+solar+panel

So it looks like if I want to be able to use the setup multiple days a week, I can't use 10Ah a day?
How did you do that calculation and where did the efficiency calculation come from? I am new to all this and I do think I might be overcompensating for this cause I don't see us using the setup too much a week.

Since I can't go higher than 50W, you'd say go for the Walmart battery then? I found a 55Ah one on Amazon but its 110 dollars