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ghoot

Measuring Voltage Using Adc

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Here's the deal. I have 6 - 12 volt batteries in series and want to charge them with a solar cell made for charging 12 volt batteries. To do that, I'll have to switch the cell to be connected to one battery at a time. I want to have my circuit/code, switch to each battery and read the voltage of each, then connect the solar cell to the lowest battery. Then repeat that about every hour.

 

I have 6 different ADC pins, and plan to connect each battery to one of the pins, but how? I can't connect all of the commons together and tie them into the circuits common, or the batteries would be shorting out. One idea I had was to have a separate chip that is powered by the batteries. So I switch the power to a different battery after measuring one. But then, I somehow have to send the info back to my main circuit. Am I way over thinking this?

Gary

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:D I got an electric car back Year before last when OK was offering the big tax breaks on them. It runs on 72 volts, 6-12Volt batteries in series. They are big batteries kinda like golf cart batteries. I measured across one battery and got 12 Volts, so assumed, in my ignorance, that I could directly connect the solar panels to one battery and it would charge them all. So, I rigged some solar cells on the roof and connected them to one battery. Well, to make a long story shorter, it didn't seem like it was working right, so did a quick Google search and learned that when batteries are connected in series, you either have to connect the charger to each end of the string, in this case I would need a 72 volt solar panel, or you have to charge each battery individually. That's what i found. The one the solar panels are hooked to is charged and the other are dead. Here's the dilemma, just showing 3 batteries for simplicity: :lol:

 

post-34-1313468353_thumb.jpg

 

Gary

Edited by ghoot

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Nope, that's the problem, just have 3. They all connect to a regulator, then the regulator connects to the battery. So I really only have one 12 volt source.

 

At first it seemed like a simple problem, just switch to each battery to see which is lowest and charge it for a while. But, to read the voltage, I know I'll need a voltage divider to reduce the voltage, and positive will connect there and to the ADC pin, but what do I do with the ground from the batteries? I can't tie them all together.

Gary

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Ya know, for measuring the voltage, I could connect the ground going to the car to the ground of my circuit. Then connect all 6 positives to my 6 ADC inputs. The 1st one would measure 12V, the 2nd 24V, the 3rd 36V etc. That would solve the voltage measuring problem if I can get the voltage dividers pretty close, then I can figure out the voltage of each battery pretty easily that way.

 

Now how to connect each battery to the Solar cell separately (only one at a time of course)? May need another chip to do that, but shouldn't be too bad :ph34r: . Hopefully can use the ADC pins to drive that.

Gary

Edited by ghoot

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Am I way over thinking this?

 

I think you are. I was trying to solve the question last night, then questioned why. If your car's system is working like it's supposed to, and the batteries are good, they should keep themselves pretty equalized. I suspect you will still need to plug the car in to charge it, and I bet all that complicated stuff is already being done, if it needs to be. I would be trying to charge the batteries as equally as I can though, and considering the sun goes in out of clouds, cause it rains occasionally up there, I wouldn't go an hour before switching, maybe 10 minutes at most...maybe even every 1 second. You can stick some LEDs in there so you have a cool looking display to impress people :lol:

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Since the batteries are in series, they aren't equal. That's what I thought at fist too. The car has a voltage gauge in it that goes up to 85V I think. Fully charged, it shows about 78, so each cell is about 13 volts. Right now, the display on the regulator for the battery connected to the solar cell shows a bout 13 volts. The cars gauge shows about 70. So the one battery is 13Volts, and that means the others are about 9.5 Volts. I'm afraid to plug it in right now because it may blow that battery up. I have some lights connected to it right now to bring it down before charging them all again.

 

After doing some reading, I found that you can connect batteries of all kinds of voltages together in series if you want. If you need 24 volts, you can connect 2 - 6 volts and a 12 volt battery.

Gary

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Gary so why not put some 24V batteries in it and do way with all the 12V batteries , I know its a added expense , I would think it would make your operation a little bit simpler to setup and charge , I know I have seen the 24V solar chargers some where before , just a thought

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Yeah, true, I could run 3-24 volt batteries and 3-24 volts panels and connect each one to a battery, but the batteries in there now are probably $200 or $300 each, plus I already have the 12 volt panels mounted on there and they were about $170. And then there would probably need to be some customization to make the 24 Volt batteries fit. It's a good idea, but Daddy's pockets ain't THAT deep. :lol:

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Interesting idea to do. If I remember right, all of the batteries are only as good as the weakest battery. That's why they recommend you change out all 6 when one goes bad if they have a couple years use out of them... but I have ran them with a used battery till I could get more.

 

Gary why do you need this system if you have a charger, just curious? They'll run a long ways with newer batteries. I'll have to keep up with this post will be useful to see how you come out with it.

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I can plug them in and charge it, but I'm trying to get to work and back for "free". :blink::D It's only 4 miles to work, so it won't take much. The panels put out about 3 Amps, so I may have to charge every once in a while. If I'm going to drive a girly electric car, called a "KANDI COCO" no less, that only goes 32 MPH and has no heat or AC, I better be getting some advantage. LOL :D

 

Here's what it looks like. this isn't mine, but I have the same one. I'll post a pic of mine with the panels when I get her all done. In this car, and with my magnifier glasses, I get all the chicks! :lol:

 

post-34-1313510916.jpg

 

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I can plug them in and charge it, but I'm trying to get to work and back for "free". :blink::D It's only 4 miles to work, so it won't take much. The panels put out about 3 Amps, so I may have to charge every once in a while. If I'm going to drive a girly electric car, called a "KANDI COCO" no less, that only goes 32 MPH and has no heat or AC, I better be getting some advantage. LOL :D

 

Here's what it looks like. this isn't mine, but I have the same one. I'll post a pic of mine with the panels when I get her all done. In this car, and with my magnifier glasses, I get all the chicks! :lol:

 

post-34-1313510916.jpg

Whats the deal with the bigger tires on the front and the smaller ones in the back ? 32MPH , WTH !!!!!!! I think your going to have a hard time catching the hotties in that thing , but one things for sure you got the glasses going for ya :)

i can understand not wanting to unload the batteries that alot of dough to throw out the window , how big are your solar panels ? I know you dont have much room on the roof if there really is one there but maybe you could fashion some of the solar panels in a offset double stack on the roof , it would help with aerodynamics and help keep all that power planted to the road and possibly pick up more speed if the wind was at your back with the sail effect . :roll2::roll2:

Edited by pure havoc

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